conlang: updated rustfmt

Plus it was more annoying than this is.

.cargo/config.toml

@@ -0,0 +1,2 @@
+[registries.soft-fish]
+index = "https://git.soft.fish/j/_cargo-index.git"

.gitea/issue_template/feature-proposal.md

@@ -7,7 +7,7 @@ labels:
 - enhancement
 ---
 # Feature Progress
-<!-- Describe the steps for implementing this feature in libconlang -->
+<!-- Describe the steps for implementing this feature -->
 - [ ] <!-- Step 1 of implementing a feature -->
 
 # Feature description
@@ -21,4 +21,4 @@ since it most closely matches what I'm currently aiming for
 -->
 ```rust
 
-```
+```

.gitignore

@@ -1,3 +1,13 @@
+
+# Visual Studio Code config
+.vscode
+
+# Rust
 **/Cargo.lock
 target
+
+# Symbol table dump?
+typeck-table.ron
+
+# Pest files generated by Grammatical
 *.p*st

Cargo.toml

@@ -1,11 +1,24 @@
 [workspace]
-members = ["libconlang", "cl-repl"]
+members = [
+    "compiler/cl-repl",
+    "compiler/cl-typeck",
+    "compiler/cl-embed",
+    "compiler/cl-interpret",
+    "compiler/cl-structures",
+    "compiler/cl-token",
+    "compiler/cl-ast",
+    "compiler/cl-parser",
+    "compiler/cl-lexer",
+]
 resolver = "2"
 
 [workspace.package]
 repository = "https://git.soft.fish/j/Conlang"
-version = "0.0.3"
+version = "0.0.10"
 authors = ["John Breaux <j@soft.fish>"]
-edition = "2021"
+edition = "2024"
 license = "MIT"
 publish = ["soft-fish"]
+
+[profile.dev]
+opt-level = 1

cl-repl/examples/collect-identifiers.rs

@@ -1,523 +0,0 @@
-//! Collects identifiers into a list
-
-use cl_repl::repline::Repline;
-use conlang::{common::Loc, lexer::Lexer, parser::Parser};
-use std::{
-    collections::HashMap,
-    error::Error,
-    fmt::Display,
-    ops::{Deref, DerefMut},
-};
-
-fn main() -> Result<(), Box<dyn Error>> {
-    let mut rl = Repline::new("\x1b[33m", "cl>", "? >");
-    while let Ok(line) = rl.read() {
-        let mut parser = Parser::new(Lexer::new(&line));
-        let code = match parser.stmt() {
-            Ok(code) => {
-                rl.accept();
-                code
-            }
-            Err(_) => {
-                continue;
-            }
-        };
-        let c = Collector::from(&code);
-        print!("\x1b[G\x1b[J{c}");
-    }
-    Ok(())
-}
-
-/// Ties the [Collector] location stack to the program stack
-pub struct CollectorLoc<'loc, 'code> {
-    inner: &'loc mut Collector<'code>,
-}
-impl<'l, 'c> CollectorLoc<'l, 'c> {
-    pub fn new(c: &'l mut Collector<'c>, loc: Loc) -> Self {
-        c.location.push(loc);
-        Self { inner: c }
-    }
-}
-impl<'l, 'c> Deref for CollectorLoc<'l, 'c> {
-    type Target = Collector<'c>;
-    fn deref(&self) -> &Self::Target {
-        self.inner
-    }
-}
-impl<'l, 'c> DerefMut for CollectorLoc<'l, 'c> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        self.inner
-    }
-}
-impl<'l, 'c> Drop for CollectorLoc<'l, 'c> {
-    fn drop(&mut self) {
-        let Self { inner: c } = self;
-        c.location.pop();
-    }
-}
-
-#[derive(Clone, Debug, Default)]
-pub struct Collector<'code> {
-    location: Vec<Loc>,
-    defs: HashMap<&'code str, Vec<Loc>>,
-    refs: HashMap<&'code str, Vec<Loc>>,
-}
-
-impl<'c> Collector<'c> {
-    pub fn new() -> Self {
-        Self::default()
-    }
-    pub fn location<'loc>(&'loc mut self, loc: Loc) -> CollectorLoc<'loc, 'c> {
-        CollectorLoc::new(self, loc)
-    }
-    pub fn collect(&mut self, collectible: &'c impl Collectible<'c>) -> &mut Self {
-        collectible.collect(self);
-        self
-    }
-    pub fn define(&mut self, name: &'c str) -> &mut Self {
-        // println!("Inserted definition of {name}");
-        let loc = self.location.last().copied().unwrap_or(Loc(0, 0));
-        self.defs
-            .entry(name)
-            .and_modify(|c| c.push(loc))
-            .or_insert_with(|| vec![loc]);
-        self
-    }
-    pub fn reference(&mut self, name: &'c str) -> &mut Self {
-        // println!("Inserted usage of {name}");
-        let loc = self.location.last().copied().unwrap_or(Loc(0, 0));
-        self.refs
-            .entry(name)
-            .and_modify(|c| c.push(loc))
-            .or_insert_with(|| vec![loc]);
-        self
-    }
-}
-impl<'c> Display for Collector<'c> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let Self { location: _, defs, refs } = self;
-        writeln!(f, "Definitions:")?;
-        for (name, locs) in defs {
-            for loc in locs {
-                writeln!(f, "{loc} {name}")?;
-            }
-        }
-        writeln!(f, "Usages:")?;
-        for (name, locs) in refs {
-            for loc in locs {
-                writeln!(f, "{loc} {name}")?;
-            }
-        }
-        Ok(())
-    }
-}
-
-impl<'c, C: Collectible<'c>> From<&'c C> for Collector<'c> {
-    fn from(value: &'c C) -> Self {
-        let mut c = Self::new();
-        c.collect(value);
-        c
-    }
-}
-
-use collectible::Collectible;
-pub mod collectible {
-
-    use super::Collector;
-    use conlang::ast::*;
-    pub trait Collectible<'code> {
-        fn collect(&'code self, c: &mut Collector<'code>);
-    }
-
-    impl<'c> Collectible<'c> for File {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let File { items } = self;
-            for item in items {
-                item.collect(c)
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Item {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { extents, attrs: _, vis: _, kind } = self;
-            kind.collect(&mut c.location(extents.head));
-        }
-    }
-    impl<'c> Collectible<'c> for ItemKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                ItemKind::Alias(f) => f.collect(c),
-                ItemKind::Const(f) => f.collect(c),
-                ItemKind::Static(f) => f.collect(c),
-                ItemKind::Module(f) => f.collect(c),
-                ItemKind::Function(f) => f.collect(c),
-                ItemKind::Struct(f) => f.collect(c),
-                ItemKind::Enum(f) => f.collect(c),
-                ItemKind::Impl(f) => f.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Alias {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { to, from } = self;
-            c.collect(to).collect(from);
-        }
-    }
-    impl<'c> Collectible<'c> for Const {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), ty, init } = self;
-            c.define(name).collect(init).collect(ty);
-        }
-    }
-    impl<'c> Collectible<'c> for Static {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { mutable: _, name: Identifier(name), ty, init } = self;
-            c.define(name).collect(init).collect(ty);
-        }
-    }
-    impl<'c> Collectible<'c> for Module {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), kind } = self;
-            c.define(name).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for ModuleKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                ModuleKind::Inline(f) => f.collect(c),
-                ModuleKind::Outline => {}
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Function {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), args, body, rety } = self;
-            c.define(name).collect(args).collect(body).collect(rety);
-        }
-    }
-    impl<'c> Collectible<'c> for Struct {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), kind } = self;
-            c.define(name).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for StructKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                StructKind::Empty => {}
-                StructKind::Tuple(k) => k.collect(c),
-                StructKind::Struct(k) => k.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for StructMember {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { vis: _, name: Identifier(name), ty } = self;
-            c.define(name).collect(ty);
-        }
-    }
-    impl<'c> Collectible<'c> for Enum {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), kind } = self;
-            c.define(name).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for EnumKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                EnumKind::NoVariants => {}
-                EnumKind::Variants(v) => v.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Variant {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { name: Identifier(name), kind } = self;
-            c.define(name).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for VariantKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                VariantKind::Plain => {}
-                VariantKind::CLike(_) => {}
-                VariantKind::Tuple(v) => v.collect(c),
-                VariantKind::Struct(v) => v.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Impl {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { target, body } = self;
-            c.collect(target).collect(body);
-        }
-    }
-    impl<'c> Collectible<'c> for Block {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { stmts } = self;
-            for stmt in stmts {
-                stmt.collect(c);
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Stmt {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { extents, kind, semi: _ } = self;
-            c.location(extents.head).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for StmtKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                StmtKind::Empty => {}
-                StmtKind::Local(s) => s.collect(c),
-                StmtKind::Item(s) => s.collect(c),
-                StmtKind::Expr(s) => s.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Let {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { mutable: _, name: Identifier(name), ty, init } = self;
-            c.collect(init).collect(ty).define(name);
-        }
-    }
-    impl<'c> Collectible<'c> for Expr {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { extents, kind } = self;
-            c.location(extents.head).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for ExprKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                ExprKind::Assign(k) => k.collect(c),
-                ExprKind::Binary(k) => k.collect(c),
-                ExprKind::Unary(k) => k.collect(c),
-                ExprKind::Member(k) => k.collect(c),
-                ExprKind::Call(k) => k.collect(c),
-                ExprKind::Index(k) => k.collect(c),
-                ExprKind::Path(k) => k.collect(c),
-                ExprKind::Literal(k) => k.collect(c),
-                ExprKind::Array(k) => k.collect(c),
-                ExprKind::ArrayRep(k) => k.collect(c),
-                ExprKind::AddrOf(k) => k.collect(c),
-                ExprKind::Block(k) => k.collect(c),
-                ExprKind::Empty => {}
-                ExprKind::Group(k) => k.collect(c),
-                ExprKind::Tuple(k) => k.collect(c),
-                ExprKind::While(k) => k.collect(c),
-                ExprKind::If(k) => k.collect(c),
-                ExprKind::For(k) => k.collect(c),
-                ExprKind::Break(k) => k.collect(c),
-                ExprKind::Return(k) => k.collect(c),
-                ExprKind::Continue(k) => k.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Assign {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { head, op: _, tail } = self;
-            c.collect(head).collect(tail);
-        }
-    }
-    impl<'c> Collectible<'c> for Binary {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { head, tail } = self;
-            c.collect(head);
-            for (_, tail) in tail {
-                c.collect(tail);
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Unary {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { ops: _, tail } = self;
-            c.collect(tail);
-        }
-    }
-    impl<'c> Collectible<'c> for Member {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { head, tail } = self;
-            c.collect(head).collect(tail);
-        }
-    }
-    impl<'c> Collectible<'c> for Call {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { callee, args } = self;
-            c.collect(callee).collect(args);
-        }
-    }
-    impl<'c> Collectible<'c> for Tuple {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { exprs } = self;
-            c.collect(exprs);
-        }
-    }
-    impl<'c> Collectible<'c> for Index {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { head, indices } = self;
-            c.collect(head).collect(indices);
-        }
-    }
-    impl<'c> Collectible<'c> for Indices {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { exprs } = self;
-            c.collect(exprs);
-        }
-    }
-    impl<'c> Collectible<'c> for Array {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { values } = self;
-            c.collect(values);
-        }
-    }
-    impl<'c> Collectible<'c> for ArrayRep {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { value, repeat } = self;
-            c.collect(value).collect(repeat);
-        }
-    }
-    impl<'c> Collectible<'c> for AddrOf {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { count: _, mutable: _, expr } = self;
-            c.collect(expr);
-        }
-    }
-    impl<'c> Collectible<'c> for Group {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { expr } = self;
-            c.collect(expr);
-        }
-    }
-    impl<'c> Collectible<'c> for While {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { cond, pass, fail } = self;
-            c.collect(cond).collect(pass).collect(fail);
-        }
-    }
-    impl<'c> Collectible<'c> for Else {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { body } = self;
-            c.collect(body);
-        }
-    }
-    impl<'c> Collectible<'c> for If {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { cond, pass, fail } = self;
-            c.collect(cond).collect(pass).collect(fail);
-        }
-    }
-    impl<'c> Collectible<'c> for For {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { bind: Identifier(name), cond, pass, fail } = self;
-            c.collect(cond).define(name).collect(pass).collect(fail);
-        }
-    }
-    impl<'c> Collectible<'c> for Break {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { body } = self;
-            c.collect(body);
-        }
-    }
-    impl<'c> Collectible<'c> for Return {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { body } = self;
-            c.collect(body);
-        }
-    }
-    impl<'c> Collectible<'c> for Continue {
-        fn collect(&'c self, _c: &mut Collector<'c>) {}
-    }
-    impl<'c> Collectible<'c> for Literal {
-        fn collect(&'c self, _c: &mut Collector<'c>) {}
-    }
-    impl<'c> Collectible<'c> for Identifier {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self(name) = self;
-            c.reference(name);
-        }
-    }
-    impl<'c> Collectible<'c> for Param {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { mutability: _, name, ty } = self;
-            c.collect(name).collect(ty);
-        }
-    }
-    impl<'c> Collectible<'c> for Ty {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { extents, kind } = self;
-            c.location(extents.head).collect(kind);
-        }
-    }
-    impl<'c> Collectible<'c> for TyKind {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                TyKind::Never => {}
-                TyKind::Empty => {}
-                TyKind::SelfTy => {}
-                TyKind::Path(t) => t.collect(c),
-                TyKind::Tuple(t) => t.collect(c),
-                TyKind::Ref(t) => t.collect(c),
-                TyKind::Fn(t) => t.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for Path {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { absolute: _, parts } = self;
-            for part in parts {
-                c.collect(part);
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for PathPart {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            match self {
-                PathPart::SuperKw => {}
-                PathPart::SelfKw => {}
-                PathPart::Ident(i) => i.collect(c),
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for TyTuple {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { types } = self;
-            for ty in types {
-                c.collect(ty);
-            }
-        }
-    }
-    impl<'c> Collectible<'c> for TyRef {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { count: _, to } = self;
-            c.collect(to);
-        }
-    }
-    impl<'c> Collectible<'c> for TyFn {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            let Self { args, rety } = self;
-            c.collect(args).collect(rety);
-        }
-    }
-
-    impl<'c, C: Collectible<'c> + Sized> Collectible<'c> for Vec<C> {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            for i in self {
-                c.collect(i);
-            }
-        }
-    }
-    impl<'c, C: Collectible<'c> + Sized> Collectible<'c> for Option<C> {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            if let Some(i) = self {
-                c.collect(i);
-            }
-        }
-    }
-    impl<'c, C: Collectible<'c>> Collectible<'c> for Box<C> {
-        fn collect(&'c self, c: &mut Collector<'c>) {
-            c.collect(self.as_ref());
-        }
-    }
-}

cl-repl/src/lib.rs

@@ -1,513 +0,0 @@
-//! Utilities for cl-frontend
-//!
-//! # TODO
-//! - [ ] Readline-like line editing
-//! - [ ] Raw mode?
-
-pub mod args {
-    use crate::cli::Mode;
-    use std::{
-        io::{stdin, IsTerminal},
-        ops::Deref,
-        path::{Path, PathBuf},
-    };
-
-    #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
-    pub struct Args {
-        pub path: Option<PathBuf>, // defaults None
-        pub repl: bool,            // defaults true if stdin is terminal
-        pub mode: Mode,            // defaults Interpret
-    }
-    const HELP: &str = "[( --repl | --no-repl )] [--mode (tokens | pretty | type | run)] [( -f | --file ) <filename>]";
-
-    impl Args {
-        pub fn new() -> Self {
-            Args { path: None, repl: stdin().is_terminal(), mode: Mode::Interpret }
-        }
-        pub fn parse(mut self) -> Option<Self> {
-            let mut args = std::env::args();
-            let name = args.next().unwrap_or_default();
-            let mut unknown = false;
-            while let Some(arg) = args.next() {
-                match arg.deref() {
-                    "--repl" => self.repl = true,
-                    "--no-repl" => self.repl = false,
-                    "-f" | "--file" => self.path = args.next().map(PathBuf::from),
-                    "-m" | "--mode" => {
-                        self.mode = args.next().unwrap_or_default().parse().unwrap_or_default()
-                    }
-                    arg => {
-                        eprintln!("Unknown argument: {arg}");
-                        unknown = true;
-                    }
-                }
-            }
-            if unknown {
-                println!("Usage: {name} {HELP}");
-                None?
-            }
-            Some(self)
-        }
-        /// Returns the path to a file, if one was specified
-        pub fn path(&self) -> Option<&Path> {
-            self.path.as_deref()
-        }
-        /// Returns whether to start a REPL session or not
-        pub fn repl(&self) -> bool {
-            self.repl
-        }
-        /// Returns the repl Mode
-        pub fn mode(&self) -> Mode {
-            self.mode
-        }
-    }
-    impl Default for Args {
-        fn default() -> Self {
-            Self::new()
-        }
-    }
-}
-
-pub mod program {
-    use std::{fmt::Display, io::Write};
-
-    use conlang::{
-        ast::{self, ast_impl::format::Pretty},
-        interpreter::{
-            env::Environment, error::IResult, interpret::Interpret, temp_type_impl::ConValue,
-        },
-        // pretty_printer::{PrettyPrintable, Printer},
-        lexer::Lexer,
-        parser::{error::PResult, Parser},
-        resolver::{error::TyResult, Resolver},
-    };
-
-    pub struct Parsable;
-
-    pub enum Parsed {
-        File(ast::File),
-        Stmt(ast::Stmt),
-        Expr(ast::Expr),
-    }
-
-    pub struct Program<'t, Variant> {
-        text: &'t str,
-        data: Variant,
-    }
-    impl<'t, V> Program<'t, V> {
-        pub fn lex(&self) -> Lexer {
-            Lexer::new(self.text)
-        }
-    }
-
-    impl<'t> Program<'t, Parsable> {
-        pub fn new(text: &'t str) -> Self {
-            Self { text, data: Parsable }
-        }
-        pub fn parse(self) -> PResult<Program<'t, Parsed>> {
-            self.parse_file().or_else(|_| self.parse_stmt())
-        }
-        pub fn parse_expr(&self) -> PResult<Program<'t, Parsed>> {
-            Ok(Program { data: Parsed::Expr(Parser::new(self.lex()).expr()?), text: self.text })
-        }
-        pub fn parse_stmt(&self) -> PResult<Program<'t, Parsed>> {
-            Ok(Program { data: Parsed::Stmt(Parser::new(self.lex()).stmt()?), text: self.text })
-        }
-        pub fn parse_file(&self) -> PResult<Program<'t, Parsed>> {
-            Ok(Program { data: Parsed::File(Parser::new(self.lex()).file()?), text: self.text })
-        }
-    }
-
-    impl<'t> Program<'t, Parsed> {
-        pub fn debug(&self) {
-            match &self.data {
-                Parsed::File(v) => eprintln!("{v:?}"),
-                Parsed::Stmt(v) => eprintln!("{v:?}"),
-                Parsed::Expr(v) => eprintln!("{v:?}"),
-            }
-        }
-        pub fn print(&self) {
-            let mut f = std::io::stdout().pretty();
-            let _ = match &self.data {
-                Parsed::File(v) => writeln!(f, "{v}"),
-                Parsed::Stmt(v) => writeln!(f, "{v}"),
-                Parsed::Expr(v) => writeln!(f, "{v}"),
-            };
-            // println!("{self}")
-        }
-
-        pub fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<()> {
-            todo!("Program::resolve(\n{self},\n{resolver:?}\n)")
-        }
-
-        pub fn run(&self, env: &mut Environment) -> IResult<ConValue> {
-            match &self.data {
-                Parsed::File(v) => v.interpret(env),
-                Parsed::Stmt(v) => v.interpret(env),
-                Parsed::Expr(v) => v.interpret(env),
-            }
-        }
-
-        // pub fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<()> {
-        //     match &mut self.data {
-        //         Parsed::Program(start) => start.resolve(resolver),
-        //         Parsed::Expr(expr) => expr.resolve(resolver),
-        //     }
-        //     .map(|ty| println!("{ty}"))
-        // }
-
-        // /// Runs the [Program] in the specified [Environment]
-        // pub fn run(&self, env: &mut Environment) -> IResult<()> {
-        //     println!(
-        //         "{}",
-        //         match &self.data {
-        //             Parsed::Program(start) => env.eval(start)?,
-        //             Parsed::Expr(expr) => env.eval(expr)?,
-        //         }
-        //     );
-        //     Ok(())
-        // }
-    }
-
-    impl<'t> Display for Program<'t, Parsed> {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            match &self.data {
-                Parsed::File(v) => write!(f, "{v}"),
-                Parsed::Stmt(v) => write!(f, "{v}"),
-                Parsed::Expr(v) => write!(f, "{v}"),
-            }
-        }
-    }
-
-    // impl PrettyPrintable for Program<Parsed> {
-    //     fn visit<W: Write>(&self, p: &mut Printer<W>) -> IOResult<()> {
-    //         match &self.data {
-    //             Parsed::Program(value) => value.visit(p),
-    //             Parsed::Expr(value) => value.visit(p),
-    //         }
-    //     }
-    // }
-}
-
-pub mod cli {
-    use conlang::{interpreter::env::Environment, resolver::Resolver, token::Token};
-
-    use crate::{
-        args::Args,
-        program::{Parsable, Parsed, Program},
-    };
-    use std::{
-        convert::Infallible,
-        error::Error,
-        path::{Path, PathBuf},
-        str::FromStr,
-    };
-
-    // ANSI color escape sequences
-    const ANSI_RED: &str = "\x1b[31m";
-    const ANSI_GREEN: &str = "\x1b[32m";
-    const ANSI_CYAN: &str = "\x1b[36m";
-    const ANSI_BRIGHT_BLUE: &str = "\x1b[94m";
-    const ANSI_BRIGHT_MAGENTA: &str = "\x1b[95m";
-    // const ANSI_BRIGHT_CYAN: &str = "\x1b[96m";
-    const ANSI_RESET: &str = "\x1b[0m";
-    const ANSI_OUTPUT: &str = "\x1b[38;5;117m";
-
-    const ANSI_CLEAR_LINES: &str = "\x1b[G\x1b[J";
-
-    #[derive(Clone, Debug)]
-    pub enum CLI {
-        Repl(Repl),
-        File { mode: Mode, path: PathBuf },
-        Stdin { mode: Mode },
-    }
-    impl From<Args> for CLI {
-        fn from(value: Args) -> Self {
-            let Args { path, repl, mode } = value;
-            match (repl, path) {
-                (true, Some(path)) => {
-                    let prog = std::fs::read_to_string(path).unwrap();
-                    let code = conlang::parser::Parser::new(conlang::lexer::Lexer::new(&prog))
-                        .file()
-                        .unwrap();
-                    let mut env = conlang::interpreter::env::Environment::new();
-                    env.eval(&code).unwrap();
-                    env.call("dump", &[])
-                        .expect("calling dump in the environment shouldn't fail");
-
-                    Self::Repl(Repl { mode, env, ..Default::default() })
-                }
-                (_, Some(path)) => Self::File { mode, path },
-                (true, None) => Self::Repl(Repl { mode, ..Default::default() }),
-                (false, None) => Self::Stdin { mode },
-            }
-        }
-    }
-    impl CLI {
-        pub fn run(&mut self) -> Result<(), Box<dyn Error>> {
-            use std::{fs, io};
-            match self {
-                CLI::Repl(repl) => repl.repl(),
-                CLI::File { mode, ref path } => {
-                    // read file
-                    Self::no_repl(*mode, Some(path), &fs::read_to_string(path)?)
-                }
-                CLI::Stdin { mode } => {
-                    Self::no_repl(*mode, None, &io::read_to_string(io::stdin())?)
-                }
-            }
-            Ok(())
-        }
-        fn no_repl(mode: Mode, path: Option<&Path>, code: &str) {
-            let program = Program::new(code);
-            match mode {
-                Mode::Tokenize => {
-                    for token in program.lex() {
-                        if let Some(path) = path {
-                            print!("{}:", path.display());
-                        }
-                        match token {
-                            Ok(token) => print_token(&token),
-                            Err(e) => println!("{e}"),
-                        }
-                    }
-                }
-                Mode::Beautify => Self::beautify(program),
-                Mode::Resolve => Self::resolve(program, Default::default()),
-                Mode::Interpret => Self::interpret(program, Environment::new()),
-            }
-        }
-        fn beautify(program: Program<Parsable>) {
-            match program.parse() {
-                Ok(program) => program.print(),
-                Err(e) => eprintln!("{e}"),
-            };
-        }
-        fn resolve(program: Program<Parsable>, mut resolver: Resolver) {
-            let mut program = match program.parse() {
-                Ok(program) => program,
-                Err(e) => {
-                    eprintln!("{e}");
-                    return;
-                }
-            };
-            if let Err(e) = program.resolve(&mut resolver) {
-                eprintln!("{e}");
-            }
-        }
-        fn interpret(program: Program<Parsable>, mut interpreter: Environment) {
-            let program = match program.parse() {
-                Ok(program) => program,
-                Err(e) => {
-                    eprintln!("{e}");
-                    return;
-                }
-            };
-            if let Err(e) = program.run(&mut interpreter) {
-                eprintln!("{e}");
-                return;
-            }
-            if let Err(e) = interpreter.call("main", &[]) {
-                eprintln!("{e}");
-            }
-        }
-    }
-
-    /// The CLI's operating mode
-    #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-    pub enum Mode {
-        Tokenize,
-        Beautify,
-        Resolve,
-        #[default]
-        Interpret,
-    }
-    impl Mode {
-        pub fn ansi_color(self) -> &'static str {
-            match self {
-                Mode::Tokenize => ANSI_BRIGHT_BLUE,
-                Mode::Beautify => ANSI_BRIGHT_MAGENTA,
-                Mode::Resolve => ANSI_GREEN,
-                Mode::Interpret => ANSI_CYAN,
-            }
-        }
-    }
-    impl FromStr for Mode {
-        type Err = Infallible;
-        fn from_str(s: &str) -> Result<Self, Infallible> {
-            Ok(match s {
-                "i" | "interpret" | "run" => Mode::Interpret,
-                "b" | "beautify" | "p" | "pretty" => Mode::Beautify,
-                "r" | "resolve" | "typecheck" | "type" => Mode::Resolve,
-                "t" | "tokenize" | "tokens" => Mode::Tokenize,
-                _ => Mode::Interpret,
-            })
-        }
-    }
-
-    /// Implements the interactive interpreter
-    #[derive(Clone, Debug)]
-    pub struct Repl {
-        prompt_again: &'static str, // " ?>"
-        prompt_begin: &'static str, // "cl>"
-        prompt_error: &'static str, // "! >"
-        env: Environment,
-        resolver: Resolver,
-        mode: Mode,
-    }
-
-    impl Default for Repl {
-        fn default() -> Self {
-            Self {
-                prompt_begin: "cl>",
-                prompt_again: " ?>",
-                prompt_error: "! >",
-                env: Default::default(),
-                resolver: Default::default(),
-                mode: Default::default(),
-            }
-        }
-    }
-
-    /// Prompt functions
-    impl Repl {
-        pub fn prompt_error(&self, err: &impl Error) {
-            let Self { prompt_error: prompt, .. } = self;
-            println!("{ANSI_CLEAR_LINES}{ANSI_RED}{prompt} {err}{ANSI_RESET}",)
-        }
-        /// Resets the cursor to the start of the line, clears the terminal,
-        /// and sets the output color
-        pub fn begin_output(&self) {
-            print!("{ANSI_CLEAR_LINES}{ANSI_OUTPUT}")
-        }
-        pub fn clear_line(&self) {}
-    }
-    /// The actual REPL
-    impl Repl {
-        /// Constructs a new [Repl] with the provided [Mode]
-        pub fn new(mode: Mode) -> Self {
-            Self { mode, ..Default::default() }
-        }
-        /// Runs the main REPL loop
-        pub fn repl(&mut self) {
-            use crate::repline::{error::Error, Repline};
-            let mut rl = Repline::new(self.mode.ansi_color(), self.prompt_begin, self.prompt_again);
-            fn clear_line() {
-                print!("\x1b[G\x1b[J");
-            }
-            loop {
-                let buf = match rl.read() {
-                    Ok(buf) => buf,
-                    // Ctrl-C: break if current line is empty
-                    Err(Error::CtrlC(buf)) => {
-                        if buf.is_empty() || buf.ends_with('\n') {
-                            return;
-                        }
-                        rl.accept();
-                        println!("Cancelled. (Press Ctrl+C again to quit.)");
-                        continue;
-                    }
-                    // Ctrl-D: reset input, and parse it for errors
-                    Err(Error::CtrlD(buf)) => {
-                        rl.deny();
-                        if let Err(e) = Program::new(&buf).parse() {
-                            clear_line();
-                            self.prompt_error(&e);
-                        }
-                        continue;
-                    }
-                    Err(e) => {
-                        self.prompt_error(&e);
-                        return;
-                    }
-                };
-
-                self.begin_output();
-                if self.command(&buf) {
-                    rl.deny();
-                    rl.set_color(self.mode.ansi_color());
-                    continue;
-                }
-                let code = Program::new(&buf);
-                if self.mode == Mode::Tokenize {
-                    self.tokenize(&code);
-                    rl.deny();
-                    continue;
-                }
-                match code.lex().into_iter().find(|l| l.is_err()) {
-                    None => {}
-                    Some(Ok(_)) => unreachable!(),
-                    Some(Err(error)) => {
-                        rl.deny();
-                        self.prompt_error(&error);
-                        continue;
-                    }
-                }
-                if let Ok(mut code) = code.parse() {
-                    rl.accept();
-                    self.dispatch(&mut code);
-                }
-            }
-        }
-
-        fn help(&self) {
-            println!(
-                "Commands:\n- $tokens\n    Tokenize Mode:\n    Outputs information derived by the Lexer\n- $pretty\n    Beautify Mode:\n    Pretty-prints the input\n- $type\n    Resolve Mode:\n    Attempts variable resolution and type-checking on the input\n- $run\n    Interpret Mode:\n    Interprets the input using Conlang\'s work-in-progress interpreter\n- $mode\n    Prints the current mode\n- $help\n    Prints this help message"
-            );
-        }
-        fn command(&mut self, line: &str) -> bool {
-            match line.trim() {
-                "$pretty" => self.mode = Mode::Beautify,
-                "$tokens" => self.mode = Mode::Tokenize,
-                "$type" => self.mode = Mode::Resolve,
-                "$run" => self.mode = Mode::Interpret,
-                "$mode" => println!("{:?} Mode", self.mode),
-                "$help" => self.help(),
-                _ => return false,
-            }
-            true
-        }
-        /// Dispatches calls to repl functions based on the program
-        fn dispatch(&mut self, code: &mut Program<Parsed>) {
-            match self.mode {
-                Mode::Tokenize => (),
-                Mode::Beautify => self.beautify(code),
-                Mode::Resolve => self.typecheck(code),
-                Mode::Interpret => self.interpret(code),
-            }
-        }
-        fn tokenize(&mut self, code: &Program<Parsable>) {
-            for token in code.lex() {
-                match token {
-                    Ok(token) => print_token(&token),
-                    Err(e) => println!("{e}"),
-                }
-            }
-        }
-        fn interpret(&mut self, code: &Program<Parsed>) {
-            if let Err(e) = code.run(&mut self.env) {
-                self.prompt_error(&e)
-            }
-        }
-        fn typecheck(&mut self, code: &mut Program<Parsed>) {
-            if let Err(e) = code.resolve(&mut self.resolver) {
-                self.prompt_error(&e)
-            }
-        }
-        fn beautify(&mut self, code: &Program<Parsed>) {
-            code.print()
-        }
-    }
-
-    fn print_token(t: &Token) {
-        println!(
-            "{:02}:{:02}: {:#19} │{}│",
-            t.line(),
-            t.col(),
-            t.ty(),
-            t.data(),
-        )
-    }
-}
-
-pub mod repline;

cl-repl/src/main.rs

@@ -1,6 +0,0 @@
-use cl_repl::{args::Args, cli::CLI};
-use std::error::Error;
-
-fn main() -> Result<(), Box<dyn Error>> {
-    CLI::from(Args::new().parse().unwrap_or_default()).run()
-}

cl-repl/src/repline.rs

@@ -1,636 +0,0 @@
-//! A small pseudo-multiline editing library
-// #![allow(unused)]
-
-pub mod error {
-    /// Result type for Repline
-    pub type ReplResult<T> = std::result::Result<T, Error>;
-    /// Borrowed error (does not implement [Error](std::error::Error)!)
-    #[derive(Debug)]
-    pub enum Error {
-        /// User broke with Ctrl+C
-        CtrlC(String),
-        /// User broke with Ctrl+D
-        CtrlD(String),
-        /// Invalid unicode codepoint
-        BadUnicode(u32),
-        /// Error came from [std::io]
-        IoFailure(std::io::Error),
-        /// End of input
-        EndOfInput,
-    }
-
-    impl std::error::Error for Error {}
-    impl std::fmt::Display for Error {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            match self {
-                Error::CtrlC(_) => write!(f, "Ctrl+C"),
-                Error::CtrlD(_) => write!(f, "Ctrl+D"),
-                Error::BadUnicode(u) => write!(f, "0x{u:x} is not a valid unicode codepoint"),
-                Error::IoFailure(s) => write!(f, "{s}"),
-                Error::EndOfInput => write!(f, "End of input"),
-            }
-        }
-    }
-    impl From<std::io::Error> for Error {
-        fn from(value: std::io::Error) -> Self {
-            Self::IoFailure(value)
-        }
-    }
-}
-
-pub mod ignore {
-    //! Does nothing, universally.
-    //!
-    //! Introduces the [Ignore] trait, and its singular function, [ignore](Ignore::ignore),
-    //! which does nothing.
-    impl<T> Ignore for T {}
-    /// Does nothing
-    ///
-    /// # Examples
-    /// ```rust
-    /// #![deny(unused_must_use)]
-    /// # use cl_frontend::repline::ignore::Ignore;
-    /// ().ignore();
-    /// Err::<(), &str>("Foo").ignore();
-    /// Some("Bar").ignore();
-    /// 42.ignore();
-    ///
-    /// #[must_use]
-    /// fn the_meaning() -> usize {
-    ///     42
-    /// }
-    /// the_meaning().ignore();
-    /// ```
-    pub trait Ignore {
-        /// Does nothing
-        fn ignore(&self) {}
-    }
-}
-
-pub mod chars {
-    //! Converts an <code>[Iterator]<Item = [u8]></code> into an
-    //! <code>[Iterator]<Item = [char]></code>
-
-    use super::error::*;
-
-    /// Converts an <code>[Iterator]<Item = [u8]></code> into an
-    /// <code>[Iterator]<Item = [char]></code>
-    #[derive(Clone, Debug)]
-    pub struct Chars<I: Iterator<Item = u8>>(pub I);
-    impl<I: Iterator<Item = u8>> Chars<I> {
-        pub fn new(bytes: I) -> Self {
-            Self(bytes)
-        }
-    }
-    impl<I: Iterator<Item = u8>> Iterator for Chars<I> {
-        type Item = ReplResult<char>;
-        fn next(&mut self) -> Option<Self::Item> {
-            let Self(bytes) = self;
-            let start = bytes.next()? as u32;
-            let (mut out, count) = match start {
-                start if start & 0x80 == 0x00 => (start, 0), // ASCII valid range
-                start if start & 0xe0 == 0xc0 => (start & 0x1f, 1), // 1 continuation byte
-                start if start & 0xf0 == 0xe0 => (start & 0x0f, 2), // 2 continuation bytes
-                start if start & 0xf8 == 0xf0 => (start & 0x07, 3), // 3 continuation bytes
-                _ => return None,
-            };
-            for _ in 0..count {
-                let cont = bytes.next()? as u32;
-                if cont & 0xc0 != 0x80 {
-                    return None;
-                }
-                out = out << 6 | (cont & 0x3f);
-            }
-            Some(char::from_u32(out).ok_or(Error::BadUnicode(out)))
-        }
-    }
-}
-
-pub mod flatten {
-    //! Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
-    //! into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
-
-    /// Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
-    /// into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
-    pub struct Flatten<T, I: Iterator<Item = T>>(pub I);
-    impl<T, E, I: Iterator<Item = Result<T, E>>> Iterator for Flatten<Result<T, E>, I> {
-        type Item = T;
-        fn next(&mut self) -> Option<Self::Item> {
-            self.0.next()?.ok()
-        }
-    }
-    impl<T, I: Iterator<Item = Option<T>>> Iterator for Flatten<Option<T>, I> {
-        type Item = T;
-        fn next(&mut self) -> Option<Self::Item> {
-            self.0.next()?
-        }
-    }
-}
-
-pub mod raw {
-    //! Sets the terminal to [`raw`] mode for the duration of the returned object's lifetime.
-
-    /// Sets the terminal to raw mode for the duration of the returned object's lifetime.
-    pub fn raw() -> impl Drop {
-        Raw::default()
-    }
-    struct Raw();
-    impl Default for Raw {
-        fn default() -> Self {
-            std::thread::yield_now();
-            crossterm::terminal::enable_raw_mode()
-                .expect("should be able to transition into raw mode");
-            Raw()
-        }
-    }
-    impl Drop for Raw {
-        fn drop(&mut self) {
-            crossterm::terminal::disable_raw_mode()
-                .expect("should be able to transition out of raw mode");
-            // std::thread::yield_now();
-        }
-    }
-}
-
-mod out {
-    #![allow(unused)]
-    use std::io::{Result, Write};
-
-    /// A [Writer](Write) that flushes after every wipe
-    #[derive(Clone, Debug)]
-    pub(super) struct EagerWriter<W: Write> {
-        out: W,
-    }
-    impl<W: Write> EagerWriter<W> {
-        pub fn new(writer: W) -> Self {
-            Self { out: writer }
-        }
-    }
-    impl<W: Write> Write for EagerWriter<W> {
-        fn write(&mut self, buf: &[u8]) -> Result<usize> {
-            let out = self.out.write(buf)?;
-            self.out.flush()?;
-            Ok(out)
-        }
-        fn flush(&mut self) -> Result<()> {
-            self.out.flush()
-        }
-    }
-}
-
-use self::{chars::Chars, editor::Editor, error::*, flatten::Flatten, ignore::Ignore, raw::raw};
-use std::{
-    collections::VecDeque,
-    io::{stdout, Bytes, Read, Result, Write},
-};
-
-pub struct Repline<'a, R: Read> {
-    input: Chars<Flatten<Result<u8>, Bytes<R>>>,
-
-    history: VecDeque<String>, // previous lines
-    hindex: usize,             // current index into the history buffer
-
-    ed: Editor<'a>, // the current line buffer
-}
-
-impl<'a, R: Read> Repline<'a, R> {
-    /// Constructs a [Repline] with the given [Reader](Read), color, begin, and again prompts.
-    pub fn with_input(input: R, color: &'a str, begin: &'a str, again: &'a str) -> Self {
-        Self {
-            input: Chars(Flatten(input.bytes())),
-            history: Default::default(),
-            hindex: 0,
-            ed: Editor::new(color, begin, again),
-        }
-    }
-    /// Set the terminal prompt color
-    pub fn set_color(&mut self, color: &'a str) {
-        self.ed.color = color
-    }
-    /// Reads in a line, and returns it for validation
-    pub fn read(&mut self) -> ReplResult<String> {
-        const INDENT: &str = "    ";
-        let mut stdout = stdout().lock();
-        let stdout = &mut stdout;
-        let _make_raw = raw();
-        // self.ed.begin_frame(stdout)?;
-        // self.ed.redraw_frame(stdout)?;
-        self.ed.print_head(stdout)?;
-        loop {
-            stdout.flush()?;
-            match self.input.next().ok_or(Error::EndOfInput)?? {
-                // Ctrl+C: End of Text. Immediately exits.
-                // Ctrl+D: End of Transmission. Ends the current line.
-                '\x03' => {
-                    drop(_make_raw);
-                    writeln!(stdout)?;
-                    return Err(Error::CtrlC(self.ed.to_string()));
-                }
-                '\x04' => {
-                    drop(_make_raw);
-                    writeln!(stdout)?;
-                    return Err(Error::CtrlD(self.ed.to_string()));
-                }
-                // Tab: extend line by 4 spaces
-                '\t' => {
-                    self.ed.extend(INDENT.chars(), stdout)?;
-                }
-                // ignore newlines, process line feeds. Not sure how cross-platform this is.
-                '\n' => {}
-                '\r' => {
-                    self.ed.push('\n', stdout)?;
-                    return Ok(self.ed.to_string());
-                }
-                // Escape sequence
-                '\x1b' => self.escape(stdout)?,
-                // backspace
-                '\x08' | '\x7f' => {
-                    let ed = &mut self.ed;
-                    if ed.ends_with(INDENT.chars()) {
-                        for _ in 0..INDENT.len() {
-                            ed.pop(stdout)?;
-                        }
-                    } else {
-                        ed.pop(stdout)?;
-                    }
-                }
-                c if c.is_ascii_control() => {
-                    if cfg!(debug_assertions) {
-                        eprint!("\\x{:02x}", c as u32);
-                    }
-                }
-                c => {
-                    self.ed.push(c, stdout)?;
-                }
-            }
-        }
-    }
-    /// Handle ANSI Escape
-    fn escape<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
-        match self.input.next().ok_or(Error::EndOfInput)?? {
-            '[' => self.csi(w)?,
-            'O' => todo!("Process alternate character mode"),
-            other => self.ed.extend(['\x1b', other], w)?,
-        }
-        Ok(())
-    }
-    /// Handle ANSI Control Sequence Introducer
-    fn csi<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
-        match self.input.next().ok_or(Error::EndOfInput)?? {
-            'A' => {
-                self.hindex = self.hindex.saturating_sub(1);
-                self.restore_history(w)?
-            }
-            'B' => {
-                self.hindex = self
-                    .hindex
-                    .saturating_add(1)
-                    .min(self.history.len().saturating_sub(1));
-                self.restore_history(w)?
-            }
-            'C' => self.ed.cursor_forward(1, w)?,
-            'D' => self.ed.cursor_back(1, w)?,
-            'H' => self.ed.home(w)?,
-            'F' => self.ed.end(w)?,
-            '3' => {
-                if let '~' = self.input.next().ok_or(Error::EndOfInput)?? {
-                    self.ed.delete(w).ignore()
-                }
-            }
-            other => {
-                if cfg!(debug_assertions) {
-                    eprint!("{}", other.escape_unicode());
-                }
-            }
-        }
-        Ok(())
-    }
-    /// Restores the currently selected history
-    pub fn restore_history<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
-        let Self { history, hindex, ed, .. } = self;
-        if !(0..history.len()).contains(hindex) {
-            return Ok(());
-        };
-        ed.undraw(w)?;
-        ed.clear();
-        ed.print_head(w)?;
-        ed.extend(
-            history
-                .get(*hindex)
-                .expect("history should contain index")
-                .chars(),
-            w,
-        )
-    }
-
-    /// Append line to history and clear it
-    pub fn accept(&mut self) {
-        self.history_append(self.ed.iter().collect());
-        self.ed.clear();
-        self.hindex = self.history.len();
-    }
-    /// Append line to history
-    pub fn history_append(&mut self, mut buf: String) {
-        while buf.ends_with(char::is_whitespace) {
-            buf.pop();
-        }
-        if !self.history.contains(&buf) {
-            self.history.push_back(buf)
-        }
-        while self.history.len() > 20 {
-            self.history.pop_front();
-        }
-    }
-    /// Clear the line
-    pub fn deny(&mut self) {
-        self.ed.clear()
-    }
-}
-
-impl<'a> Repline<'a, std::io::Stdin> {
-    pub fn new(color: &'a str, begin: &'a str, again: &'a str) -> Self {
-        Self::with_input(std::io::stdin(), color, begin, again)
-    }
-}
-
-pub mod editor {
-    use crossterm::{cursor::*, execute, queue, style::*, terminal::*};
-    use std::{collections::VecDeque, fmt::Display, io::Write};
-
-    use super::error::{Error, ReplResult};
-
-    fn is_newline(c: &char) -> bool {
-        *c == '\n'
-    }
-
-    fn write_chars<'a, W: Write>(
-        c: impl IntoIterator<Item = &'a char>,
-        w: &mut W,
-    ) -> std::io::Result<()> {
-        for c in c {
-            write!(w, "{c}")?;
-        }
-        Ok(())
-    }
-
-    #[derive(Debug)]
-    pub struct Editor<'a> {
-        head: VecDeque<char>,
-        tail: VecDeque<char>,
-
-        pub color: &'a str,
-        begin: &'a str,
-        again: &'a str,
-    }
-
-    impl<'a> Editor<'a> {
-        pub fn new(color: &'a str, begin: &'a str, again: &'a str) -> Self {
-            Self { head: Default::default(), tail: Default::default(), color, begin, again }
-        }
-        pub fn iter(&self) -> impl Iterator<Item = &char> {
-            self.head.iter()
-        }
-        pub fn undraw<W: Write>(&self, w: &mut W) -> ReplResult<()> {
-            let Self { head, .. } = self;
-            match head.iter().copied().filter(is_newline).count() {
-                0 => write!(w, "\x1b[0G"),
-                lines => write!(w, "\x1b[{}F", lines),
-            }?;
-            queue!(w, Clear(ClearType::FromCursorDown))?;
-            // write!(w, "\x1b[0J")?;
-            Ok(())
-        }
-        pub fn redraw<W: Write>(&self, w: &mut W) -> ReplResult<()> {
-            let Self { head, tail, color, begin, again } = self;
-            write!(w, "{color}{begin}\x1b[0m ")?;
-            // draw head
-            for c in head {
-                match c {
-                    '\n' => write!(w, "\r\n{color}{again}\x1b[0m "),
-                    _ => w.write_all({ *c as u32 }.to_le_bytes().as_slice()),
-                }?
-            }
-            // save cursor
-            execute!(w, SavePosition)?;
-            // draw tail
-            for c in tail {
-                match c {
-                    '\n' => write!(w, "\r\n{color}{again}\x1b[0m "),
-                    _ => write!(w, "{c}"),
-                }?
-            }
-            // restore cursor
-            execute!(w, RestorePosition)?;
-            Ok(())
-        }
-        pub fn prompt<W: Write>(&self, w: &mut W) -> ReplResult<()> {
-            let Self { head, color, begin, again, .. } = self;
-            queue!(
-                w,
-                MoveToColumn(0),
-                Print(color),
-                Print(if head.is_empty() { begin } else { again }),
-                ResetColor,
-                Print(' '),
-            )?;
-            Ok(())
-        }
-        pub fn print_head<W: Write>(&self, w: &mut W) -> ReplResult<()> {
-            self.prompt(w)?;
-            write_chars(
-                self.head.iter().skip(
-                    self.head
-                        .iter()
-                        .rposition(is_newline)
-                        .unwrap_or(self.head.len())
-                        + 1,
-                ),
-                w,
-            )?;
-            Ok(())
-        }
-        pub fn print_tail<W: Write>(&self, w: &mut W) -> ReplResult<()> {
-            let Self { tail, .. } = self;
-            queue!(w, SavePosition, Clear(ClearType::UntilNewLine))?;
-            write_chars(tail.iter().take_while(|&c| !is_newline(c)), w)?;
-            queue!(w, RestorePosition)?;
-            Ok(())
-        }
-        pub fn push<W: Write>(&mut self, c: char, w: &mut W) -> ReplResult<()> {
-            // Tail optimization: if the tail is empty,
-            //we don't have to undraw and redraw on newline
-            if self.tail.is_empty() {
-                self.head.push_back(c);
-                match c {
-                    '\n' => {
-                        write!(w, "\r\n")?;
-                        self.print_head(w)?;
-                    }
-                    c => {
-                        queue!(w, Print(c))?;
-                    }
-                };
-                return Ok(());
-            }
-
-            if '\n' == c {
-                self.undraw(w)?;
-            }
-            self.head.push_back(c);
-            match c {
-                '\n' => self.redraw(w)?,
-                _ => {
-                    write!(w, "{c}")?;
-                    self.print_tail(w)?;
-                }
-            }
-            Ok(())
-        }
-        pub fn pop<W: Write>(&mut self, w: &mut W) -> ReplResult<Option<char>> {
-            if let Some('\n') = self.head.back() {
-                self.undraw(w)?;
-            }
-            let c = self.head.pop_back();
-            // if the character was a newline, we need to go back a line
-            match c {
-                Some('\n') => self.redraw(w)?,
-                Some(_) => {
-                    // go back a char
-                    queue!(w, MoveLeft(1), Print(' '), MoveLeft(1))?;
-                    self.print_tail(w)?;
-                }
-                None => {}
-            }
-            Ok(c)
-        }
-
-        pub fn extend<T: IntoIterator<Item = char>, W: Write>(
-            &mut self,
-            iter: T,
-            w: &mut W,
-        ) -> ReplResult<()> {
-            for c in iter {
-                self.push(c, w)?;
-            }
-            Ok(())
-        }
-        pub fn restore(&mut self, s: &str) {
-            self.clear();
-            self.head.extend(s.chars())
-        }
-        pub fn clear(&mut self) {
-            self.head.clear();
-            self.tail.clear();
-        }
-        pub fn delete<W: Write>(&mut self, w: &mut W) -> ReplResult<char> {
-            match self.tail.front() {
-                Some('\n') => {
-                    self.undraw(w)?;
-                    let out = self.tail.pop_front();
-                    self.redraw(w)?;
-                    out
-                }
-                _ => {
-                    let out = self.tail.pop_front();
-                    self.print_tail(w)?;
-                    out
-                }
-            }
-            .ok_or(Error::EndOfInput)
-        }
-        pub fn len(&self) -> usize {
-            self.head.len() + self.tail.len()
-        }
-        pub fn is_empty(&self) -> bool {
-            self.head.is_empty() && self.tail.is_empty()
-        }
-        pub fn ends_with(&self, iter: impl DoubleEndedIterator<Item = char>) -> bool {
-            let mut iter = iter.rev();
-            let mut head = self.head.iter().rev();
-            loop {
-                match (iter.next(), head.next()) {
-                    (None, _) => break true,
-                    (Some(_), None) => break false,
-                    (Some(a), Some(b)) if a != *b => break false,
-                    (Some(_), Some(_)) => continue,
-                }
-            }
-        }
-        /// Moves the cursor back `steps` steps
-        pub fn cursor_back<W: Write>(&mut self, steps: usize, w: &mut W) -> ReplResult<()> {
-            for _ in 0..steps {
-                if let Some('\n') = self.head.back() {
-                    self.undraw(w)?;
-                }
-                let Some(c) = self.head.pop_back() else {
-                    return Ok(());
-                };
-                self.tail.push_front(c);
-                match c {
-                    '\n' => self.redraw(w)?,
-                    _ => queue!(w, MoveLeft(1))?,
-                }
-            }
-            Ok(())
-        }
-        /// Moves the cursor forward `steps` steps
-        pub fn cursor_forward<W: Write>(&mut self, steps: usize, w: &mut W) -> ReplResult<()> {
-            for _ in 0..steps {
-                if let Some('\n') = self.tail.front() {
-                    self.undraw(w)?
-                }
-                let Some(c) = self.tail.pop_front() else {
-                    return Ok(());
-                };
-                self.head.push_back(c);
-                match c {
-                    '\n' => self.redraw(w)?,
-                    _ => queue!(w, MoveRight(1))?,
-                }
-            }
-            Ok(())
-        }
-        /// Goes to the beginning of the current line
-        pub fn home<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
-            loop {
-                match self.head.back() {
-                    Some('\n') | None => break Ok(()),
-                    Some(_) => self.cursor_back(1, w)?,
-                }
-            }
-        }
-        /// Goes to the end of the current line
-        pub fn end<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
-            loop {
-                match self.tail.front() {
-                    Some('\n') | None => break Ok(()),
-                    Some(_) => self.cursor_forward(1, w)?,
-                }
-            }
-        }
-    }
-
-    impl<'a, 'e> IntoIterator for &'e Editor<'a> {
-        type Item = &'e char;
-        type IntoIter = std::iter::Chain<
-            std::collections::vec_deque::Iter<'e, char>,
-            std::collections::vec_deque::Iter<'e, char>,
-        >;
-        fn into_iter(self) -> Self::IntoIter {
-            self.head.iter().chain(self.tail.iter())
-        }
-    }
-    impl<'a> Display for Editor<'a> {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            use std::fmt::Write;
-            let Self { head, tail, .. } = self;
-            for c in head {
-                f.write_char(*c)?;
-            }
-            for c in tail {
-                f.write_char(*c)?;
-            }
-            Ok(())
-        }
-    }
-}

compiler/cl-ast/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "cl-repl"
+name = "cl-ast"
 repository.workspace = true
 version.workspace = true
 authors.workspace = true
@@ -7,8 +7,5 @@ edition.workspace = true
 license.workspace = true
 publish.workspace = true
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
-conlang = { path = "../libconlang" }
-crossterm = "0.27.0"
+cl-structures = { path = "../cl-structures" }

compiler/cl-ast/src/ast.rs

@@ -0,0 +1,650 @@
+//! # The Abstract Syntax Tree
+//! Contains definitions of Conlang AST Nodes.
+//!
+//! # Notable nodes
+//! - [Item] and [ItemKind]: Top-level constructs
+//! - [Stmt] and [StmtKind]: Statements
+//! - [Expr] and [ExprKind]: Expressions
+//!   - [Assign], [Modify], [Binary], and [Unary] expressions
+//!   - [ModifyKind], [BinaryKind], and [UnaryKind] operators
+//! - [Ty] and [TyKind]: Type qualifiers
+//! - [Pattern]: Pattern matching operators
+//! - [Path]: Path expressions
+use cl_structures::{intern::interned::Interned, span::*};
+
+/// An [Interned] static [str], used in place of an identifier
+pub type Sym = Interned<'static, str>;
+
+/// Whether a binding ([Static] or [Let]) or reference is mutable or not
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+pub enum Mutability {
+    #[default]
+    Not,
+    Mut,
+}
+
+/// Whether an [Item] is visible outside of the current [Module]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+pub enum Visibility {
+    #[default]
+    Private,
+    Public,
+}
+
+/// A list of [Item]s
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct File {
+    pub name: &'static str,
+    pub items: Vec<Item>,
+}
+
+/// A list of [Meta] decorators
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct Attrs {
+    pub meta: Vec<Meta>,
+}
+
+/// A metadata decorator
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Meta {
+    pub name: Sym,
+    pub kind: MetaKind,
+}
+
+/// Information attached to [Meta]data
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum MetaKind {
+    Plain,
+    Equals(Literal),
+    Func(Vec<Literal>),
+}
+
+// Items
+/// Anything that can appear at the top level of a [File]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Item {
+    pub span: Span,
+    pub attrs: Attrs,
+    pub vis: Visibility,
+    pub kind: ItemKind,
+}
+
+/// What kind of [Item] is this?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum ItemKind {
+    // TODO: Trait declaration ("trait") item?
+    /// A [module](Module)
+    Module(Module),
+    /// A [type alias](Alias)
+    Alias(Alias),
+    /// An [enumerated type](Enum), with a discriminant and optional data
+    Enum(Enum),
+    /// A [structure](Struct)
+    Struct(Struct),
+    /// A [constant](Const)
+    Const(Const),
+    /// A [static](Static) variable
+    Static(Static),
+    /// A [function definition](Function)
+    Function(Function),
+    /// An [implementation](Impl)
+    Impl(Impl),
+    /// An [import](Use)
+    Use(Use),
+}
+
+/// A list of type variables to introduce
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct Generics {
+    pub vars: Vec<Sym>,
+}
+
+/// An ordered collection of [Items](Item)
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Module {
+    pub name: Sym,
+    pub file: Option<File>,
+}
+
+/// An alias to another [Ty]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Alias {
+    pub name: Sym,
+    pub from: Option<Box<Ty>>,
+}
+
+/// A compile-time constant
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Const {
+    pub name: Sym,
+    pub ty: Box<Ty>,
+    pub init: Box<Expr>,
+}
+
+/// A `static` variable
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Static {
+    pub mutable: Mutability,
+    pub name: Sym,
+    pub ty: Box<Ty>,
+    pub init: Box<Expr>,
+}
+
+/// Code, and the interface to that code
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Function {
+    pub name: Sym,
+    pub gens: Generics,
+    pub sign: TyFn,
+    pub bind: Pattern,
+    pub body: Option<Expr>,
+}
+
+/// A user-defined product type
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Struct {
+    pub name: Sym,
+    pub gens: Generics,
+    pub kind: StructKind,
+}
+
+/// Either a [Struct]'s [StructMember]s or tuple [Ty]pes, if present.
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum StructKind {
+    Empty,
+    Tuple(Vec<Ty>),
+    Struct(Vec<StructMember>),
+}
+
+/// The [Visibility], [Sym], and [Ty]pe of a single [Struct] member
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct StructMember {
+    pub vis: Visibility,
+    pub name: Sym,
+    pub ty: Ty,
+}
+
+/// A user-defined sum type
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Enum {
+    pub name: Sym,
+    pub gens: Generics,
+    pub variants: Vec<Variant>,
+}
+
+/// A single [Enum] variant
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Variant {
+    pub name: Sym,
+    pub kind: StructKind,
+    pub body: Option<Box<Expr>>,
+}
+
+/// Sub-[items](Item) (associated functions, etc.) for a [Ty]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Impl {
+    pub gens: Generics,
+    pub target: ImplKind,
+    pub body: File,
+}
+
+// TODO: `impl` Trait for <Target> { }
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum ImplKind {
+    Type(Ty),
+    Trait { impl_trait: Path, for_type: Box<Ty> },
+}
+
+/// An import of nonlocal [Item]s
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Use {
+    pub absolute: bool,
+    pub tree: UseTree,
+}
+
+/// A tree of [Item] imports
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum UseTree {
+    Tree(Vec<UseTree>),
+    Path(PathPart, Box<UseTree>),
+    Alias(Sym, Sym),
+    Name(Sym),
+    Glob,
+}
+
+/// A type expression
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Ty {
+    pub span: Span,
+    pub kind: TyKind,
+    pub gens: Generics,
+}
+
+/// Information about a [Ty]pe expression
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum TyKind {
+    Never,
+    Infer,
+    Path(Path),
+    Array(TyArray),
+    Slice(TySlice),
+    Tuple(TyTuple),
+    Ref(TyRef),
+    Ptr(TyPtr),
+    Fn(TyFn),
+}
+
+/// An array of [`T`](Ty)
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyArray {
+    pub ty: Box<Ty>,
+    pub count: usize,
+}
+
+/// A [Ty]pe slice expression: `[T]`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TySlice {
+    pub ty: Box<Ty>,
+}
+
+/// A tuple of [Ty]pes
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyTuple {
+    pub types: Vec<Ty>,
+}
+
+/// A [Ty]pe-reference expression as (number of `&`, [Path])
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyRef {
+    pub mutable: Mutability,
+    pub count: u16,
+    pub to: Box<Ty>,
+}
+
+/// A [Ty]pe-reference expression as (number of `&`, [Path])
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyPtr {
+    pub to: Box<Ty>,
+}
+
+/// The args and return value for a function pointer [Ty]pe
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyFn {
+    pub args: Box<Ty>,
+    pub rety: Box<Ty>,
+}
+
+/// A path to an [Item] in the [Module] tree
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct Path {
+    pub absolute: bool,
+    pub parts: Vec<PathPart>,
+}
+
+/// A single component of a [Path]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum PathPart {
+    SuperKw,
+    SelfTy,
+    Ident(Sym),
+}
+
+/// An abstract statement, and associated metadata
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Stmt {
+    pub span: Span,
+    pub kind: StmtKind,
+    pub semi: Semi,
+}
+
+/// Whether the [Stmt] is a [Let], [Item], or [Expr] statement
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum StmtKind {
+    Empty,
+    Item(Box<Item>),
+    Expr(Box<Expr>),
+}
+
+/// Whether or not a [Stmt] is followed by a semicolon
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Semi {
+    Terminated,
+    Unterminated,
+}
+
+/// An expression, the beating heart of the language
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Expr {
+    pub span: Span,
+    pub kind: ExprKind,
+}
+
+/// Any of the different [Expr]essions
+#[derive(Clone, Default, Debug, PartialEq, Eq, Hash)]
+pub enum ExprKind {
+    /// An empty expression: `(` `)`
+    #[default]
+    Empty,
+    /// A [Closure] expression: `|` [`Expr`] `|` ( -> [`Ty`])? [`Expr`]
+    Closure(Closure),
+    /// A [Tuple] expression: `(` [`Expr`] (`,` [`Expr`])+ `)`
+    Tuple(Tuple),
+    /// A [Struct creation](Structor) expression: [Path] `{` ([Fielder] `,`)* [Fielder]? `}`
+    Structor(Structor),
+    /// An [Array] literal: `[` [`Expr`] (`,` [`Expr`])\* `]`
+    Array(Array),
+    /// An Array literal constructed with [repeat syntax](ArrayRep)
+    /// `[` [Expr] `;` [Literal] `]`
+    ArrayRep(ArrayRep),
+    /// An address-of expression: `&` `mut`? [`Expr`]
+    AddrOf(AddrOf),
+    /// A backtick-quoted expression
+    Quote(Quote),
+    /// A [Literal]: 0x42, 1e123, 2.4, "Hello"
+    Literal(Literal),
+    /// A [Grouping](Group) expression `(` [`Expr`] `)`
+    Group(Group),
+    /// A [Block] expression: `{` [`Stmt`]\* [`Expr`]? `}`
+    Block(Block),
+
+    /// An [Assign]ment expression: [`Expr`] (`=` [`Expr`])\+
+    Assign(Assign),
+    /// A [Modify]-assignment expression: [`Expr`] ([`ModifyKind`] [`Expr`])\+
+    Modify(Modify),
+    /// A [Binary] expression: [`Expr`] ([`BinaryKind`] [`Expr`])\+
+    Binary(Binary),
+    /// A [Unary] expression: [`UnaryKind`]\* [`Expr`]
+    Unary(Unary),
+    /// A [Member] access expression: [`Expr`] [`MemberKind`]\*
+    Member(Member),
+    /// An Array [Index] expression: a[10, 20, 30]
+    Index(Index),
+    /// A [Cast] expression: [`Expr`] `as` [`Ty`]
+    Cast(Cast),
+    /// A [path expression](Path): `::`? [PathPart] (`::` [PathPart])*
+    Path(Path),
+    /// A local bind instruction, `let` [`Sym`] `=` [`Expr`]
+    Let(Let),
+    /// A [Match] expression: `match` [Expr] `{` ([MatchArm] `,`)* [MatchArm]? `}`
+    Match(Match),
+    /// A [While] expression: `while` [`Expr`] [`Block`] [`Else`]?
+    While(While),
+    /// An [If] expression: `if` [`Expr`] [`Block`] [`Else`]?
+    If(If),
+    /// A [For] expression: `for` [`Pattern`] `in` [`Expr`] [`Block`] [`Else`]?
+    For(For),
+    /// A [Break] expression: `break` [`Expr`]?
+    Break(Break),
+    /// A [Return] expression `return` [`Expr`]?
+    Return(Return),
+    /// A continue expression: `continue`
+    Continue,
+}
+
+/// A Closure [expression](Expr): `|` [`Expr`] `|` ( -> [`Ty`])? [`Expr`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Closure {
+    pub arg: Box<Pattern>,
+    pub body: Box<Expr>,
+}
+
+/// A [Tuple] expression: `(` [`Expr`] (`,` [`Expr`])+ `)`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Tuple {
+    pub exprs: Vec<Expr>,
+}
+
+/// A [Struct creation](Structor) expression: [Path] `{` ([Fielder] `,`)* [Fielder]? `}`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Structor {
+    pub to: Path,
+    pub init: Vec<Fielder>,
+}
+
+/// A [Struct field initializer] expression: [Sym] (`=` [Expr])?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Fielder {
+    pub name: Sym,
+    pub init: Option<Box<Expr>>,
+}
+
+/// An [Array] literal: `[` [`Expr`] (`,` [`Expr`])\* `]`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Array {
+    pub values: Vec<Expr>,
+}
+
+/// An Array literal constructed with [repeat syntax](ArrayRep)
+/// `[` [Expr] `;` [Literal] `]`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct ArrayRep {
+    pub value: Box<Expr>,
+    pub repeat: Box<Expr>,
+}
+
+/// An address-of expression: `&` `mut`? [`Expr`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct AddrOf {
+    pub mutable: Mutability,
+    pub expr: Box<Expr>,
+}
+
+/// A cast expression: [`Expr`] `as` [`Ty`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Cast {
+    pub head: Box<Expr>,
+    pub ty: Ty,
+}
+
+/// A backtick-quoted subexpression-literal
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Quote {
+    pub quote: Box<Expr>,
+}
+
+/// A [Literal]: 0x42, 1e123, 2.4, "Hello"
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Literal {
+    Bool(bool),
+    Char(char),
+    Int(u128),
+    Float(u64),
+    String(String),
+}
+
+/// A [Grouping](Group) expression `(` [`Expr`] `)`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Group {
+    pub expr: Box<Expr>,
+}
+
+/// A [Block] expression: `{` [`Stmt`]\* [`Expr`]? `}`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Block {
+    pub stmts: Vec<Stmt>,
+}
+
+/// An [Assign]ment expression: [`Expr`] ([`ModifyKind`] [`Expr`])\+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Assign {
+    pub parts: Box<(Expr, Expr)>,
+}
+
+/// A [Modify]-assignment expression: [`Expr`] ([`ModifyKind`] [`Expr`])\+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Modify {
+    pub kind: ModifyKind,
+    pub parts: Box<(Expr, Expr)>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum ModifyKind {
+    And,
+    Or,
+    Xor,
+    Shl,
+    Shr,
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Rem,
+}
+
+/// A [Binary] expression: [`Expr`] ([`BinaryKind`] [`Expr`])\+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Binary {
+    pub kind: BinaryKind,
+    pub parts: Box<(Expr, Expr)>,
+}
+
+/// A [Binary] operator
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum BinaryKind {
+    Lt,
+    LtEq,
+    Equal,
+    NotEq,
+    GtEq,
+    Gt,
+    RangeExc,
+    RangeInc,
+    LogAnd,
+    LogOr,
+    LogXor,
+    BitAnd,
+    BitOr,
+    BitXor,
+    Shl,
+    Shr,
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Rem,
+    Call,
+}
+
+/// A [Unary] expression: [`UnaryKind`]\* [`Expr`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Unary {
+    pub kind: UnaryKind,
+    pub tail: Box<Expr>,
+}
+
+/// A [Unary] operator
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum UnaryKind {
+    Deref,
+    Neg,
+    Not,
+    RangeInc,
+    RangeExc,
+    /// A Loop expression: `loop` [`Block`]
+    Loop,
+    /// Unused
+    At,
+    /// Unused
+    Tilde,
+}
+
+/// A [Member] access expression: [`Expr`] [`MemberKind`]\*
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Member {
+    pub head: Box<Expr>,
+    pub kind: MemberKind,
+}
+
+/// The kind of [Member] access
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum MemberKind {
+    Call(Sym, Tuple),
+    Struct(Sym),
+    Tuple(Literal),
+}
+
+/// A repeated [Index] expression: a[10, 20, 30][40, 50, 60]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Index {
+    pub head: Box<Expr>,
+    pub indices: Vec<Expr>,
+}
+
+/// A local variable declaration [Stmt]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Let {
+    pub mutable: Mutability,
+    pub name: Pattern,
+    pub ty: Option<Box<Ty>>,
+    pub init: Option<Box<Expr>>,
+}
+
+/// A `match` expression: `match` `{` ([MatchArm] `,`)* [MatchArm]? `}`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Match {
+    pub scrutinee: Box<Expr>,
+    pub arms: Vec<MatchArm>,
+}
+
+/// A single arm of a [Match] expression: [`Pattern`] `=>` [`Expr`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct MatchArm(pub Pattern, pub Expr);
+
+/// A [Pattern] meta-expression (any [`ExprKind`] that fits pattern rules)
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Pattern {
+    Name(Sym),
+    Path(Path),
+    Literal(Literal),
+    Rest(Option<Box<Pattern>>),
+    Ref(Mutability, Box<Pattern>),
+    RangeExc(Box<Pattern>, Box<Pattern>),
+    RangeInc(Box<Pattern>, Box<Pattern>),
+    Tuple(Vec<Pattern>),
+    Array(Vec<Pattern>),
+    Struct(Path, Vec<(Sym, Option<Pattern>)>),
+    TupleStruct(Path, Vec<Pattern>),
+}
+
+/// A [While] expression: `while` [`Expr`] [`Block`] [`Else`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct While {
+    pub cond: Box<Expr>,
+    pub pass: Box<Block>,
+    pub fail: Else,
+}
+
+/// An [If] expression: `if` [`Expr`] [`Block`] [`Else`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct If {
+    pub cond: Box<Expr>,
+    pub pass: Box<Block>,
+    pub fail: Else,
+}
+
+/// A [For] expression: `for` Pattern `in` [`Expr`] [`Block`] [`Else`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct For {
+    pub bind: Pattern,
+    pub cond: Box<Expr>,
+    pub pass: Box<Block>,
+    pub fail: Else,
+}
+
+/// The (optional) `else` clause of a [While], [If], or [For] expression
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Else {
+    pub body: Option<Box<Expr>>,
+}
+
+/// A [Break] expression: `break` [`Expr`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Break {
+    pub body: Option<Box<Expr>>,
+}
+
+/// A [Return] expression `return` [`Expr`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Return {
+    pub body: Option<Box<Expr>>,
+}

compiler/cl-ast/src/ast_impl.rs

@@ -0,0 +1,8 @@
+//! Implementations of AST nodes and traits
+use super::*;
+
+mod convert;
+mod display;
+mod path;
+
+pub(crate) mod weight_of;

compiler/cl-ast/src/ast_impl/convert.rs

@@ -0,0 +1,162 @@
+//! Converts between major enums and enum variants
+use super::*;
+
+impl<T: AsRef<str>> From<T> for PathPart {
+    fn from(value: T) -> Self {
+        match value.as_ref() {
+            "super" => PathPart::SuperKw,
+            ident => PathPart::Ident(ident.into()),
+        }
+    }
+}
+
+macro impl_from ($(impl From for $T:ty {$($from:ty => $to:expr),*$(,)?})*) {$($(
+    impl From<$from> for $T {
+        fn from(value: $from) -> Self {
+            $to(value.into()) // Uses *tuple constructor*
+        }
+    }
+    impl From<Box<$from>> for $T {
+        fn from(value: Box<$from>) -> Self {
+            $to((*value).into())
+        }
+    }
+)*)*}
+
+impl_from! {
+    impl From for ItemKind {
+        Alias => ItemKind::Alias,
+        Const => ItemKind::Const,
+        Static => ItemKind::Static,
+        Module => ItemKind::Module,
+        Function => ItemKind::Function,
+        Struct => ItemKind::Struct,
+        Enum => ItemKind::Enum,
+        Impl => ItemKind::Impl,
+        Use => ItemKind::Use,
+    }
+    impl From for StructKind {
+        Vec<Ty> => StructKind::Tuple,
+        // TODO: Struct members in struct
+    }
+    impl From for TyKind {
+        Path => TyKind::Path,
+        TyTuple => TyKind::Tuple,
+        TyRef => TyKind::Ref,
+        TyPtr => TyKind::Ptr,
+        TyFn => TyKind::Fn,
+    }
+    impl From for StmtKind {
+        Item => StmtKind::Item,
+        Expr => StmtKind::Expr,
+    }
+    impl From for ExprKind {
+        Let => ExprKind::Let,
+        Closure => ExprKind::Closure,
+        Quote => ExprKind::Quote,
+        Match => ExprKind::Match,
+        Assign => ExprKind::Assign,
+        Modify => ExprKind::Modify,
+        Binary => ExprKind::Binary,
+        Unary => ExprKind::Unary,
+        Cast => ExprKind::Cast,
+        Member => ExprKind::Member,
+        Index => ExprKind::Index,
+        Path => ExprKind::Path,
+        Literal => ExprKind::Literal,
+        Array => ExprKind::Array,
+        ArrayRep => ExprKind::ArrayRep,
+        AddrOf => ExprKind::AddrOf,
+        Block => ExprKind::Block,
+        Group => ExprKind::Group,
+        Tuple => ExprKind::Tuple,
+        While => ExprKind::While,
+        If => ExprKind::If,
+        For => ExprKind::For,
+        Break => ExprKind::Break,
+        Return => ExprKind::Return,
+    }
+    impl From for Literal {
+        bool => Literal::Bool,
+        char => Literal::Char,
+        u128 => Literal::Int,
+        String => Literal::String,
+    }
+}
+
+impl From<Option<Expr>> for Else {
+    fn from(value: Option<Expr>) -> Self {
+        Self { body: value.map(Into::into) }
+    }
+}
+impl From<Expr> for Else {
+    fn from(value: Expr) -> Self {
+        Self { body: Some(value.into()) }
+    }
+}
+
+impl TryFrom<Expr> for Pattern {
+    type Error = Expr;
+
+    /// Performs the conversion. On failure, returns the *first* non-pattern subexpression.
+    fn try_from(value: Expr) -> Result<Self, Self::Error> {
+        Ok(match value.kind {
+            ExprKind::Literal(literal) => Pattern::Literal(literal),
+            ExprKind::Path(Path { absolute: false, ref parts }) => match parts.as_slice() {
+                [PathPart::Ident(name)] => Pattern::Name(*name),
+                _ => Err(value)?,
+            },
+            ExprKind::Empty => Pattern::Tuple(vec![]),
+            ExprKind::Group(Group { expr }) => Pattern::Tuple(vec![Pattern::try_from(*expr)?]),
+            ExprKind::Tuple(Tuple { exprs }) => Pattern::Tuple(
+                exprs
+                    .into_iter()
+                    .map(Pattern::try_from)
+                    .collect::<Result<_, _>>()?,
+            ),
+            ExprKind::AddrOf(AddrOf { mutable, expr }) => {
+                Pattern::Ref(mutable, Box::new(Pattern::try_from(*expr)?))
+            }
+            ExprKind::Array(Array { values }) => Pattern::Array(
+                values
+                    .into_iter()
+                    .map(Pattern::try_from)
+                    .collect::<Result<_, _>>()?,
+            ),
+            ExprKind::Binary(Binary { kind: BinaryKind::Call, parts }) => {
+                let (Expr { kind: ExprKind::Path(path), .. }, args) = *parts else {
+                    return Err(parts.0);
+                };
+                match args.kind {
+                    ExprKind::Empty | ExprKind::Tuple(_) => {}
+                    _ => return Err(args),
+                }
+                let Pattern::Tuple(args) = Pattern::try_from(args)? else {
+                    unreachable!("Arguments should be convertible to pattern!")
+                };
+                Pattern::TupleStruct(path, args)
+            }
+            ExprKind::Binary(Binary { kind: BinaryKind::RangeExc, parts }) => {
+                let (head, tail) = (Pattern::try_from(parts.0)?, Pattern::try_from(parts.1)?);
+                Pattern::RangeExc(head.into(), tail.into())
+            }
+            ExprKind::Binary(Binary { kind: BinaryKind::RangeInc, parts }) => {
+                let (head, tail) = (Pattern::try_from(parts.0)?, Pattern::try_from(parts.1)?);
+                Pattern::RangeInc(head.into(), tail.into())
+            }
+            ExprKind::Unary(Unary { kind: UnaryKind::RangeExc, tail }) => {
+                Pattern::Rest(Some(Pattern::try_from(*tail)?.into()))
+            }
+            ExprKind::Structor(Structor { to, init }) => {
+                let fields = init
+                    .into_iter()
+                    .map(|Fielder { name, init }| {
+                        Ok((name, init.map(|i| Pattern::try_from(*i)).transpose()?))
+                    })
+                    .collect::<Result<_, Self::Error>>()?;
+                Pattern::Struct(to, fields)
+            }
+            _ => Err(value)?,
+        })
+    }
+}

compiler/cl-ast/src/ast_impl/display.rs

@@ -0,0 +1,773 @@
+//! Implements [Display] for [AST](super::super) Types
+
+use super::*;
+use format::{delimiters::*, *};
+use std::{
+    borrow::Borrow,
+    fmt::{Display, Write},
+};
+
+fn separate<I: Display, W: Write>(
+    iterable: impl IntoIterator<Item = I>,
+    sep: &'static str,
+) -> impl FnOnce(W) -> std::fmt::Result {
+    move |mut f| {
+        for (idx, item) in iterable.into_iter().enumerate() {
+            if idx > 0 {
+                f.write_str(sep)?;
+            }
+            write!(f, "{item}")?;
+        }
+        Ok(())
+    }
+}
+
+impl Display for Mutability {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Mutability::Not => Ok(()),
+            Mutability::Mut => "mut ".fmt(f),
+        }
+    }
+}
+
+impl Display for Visibility {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Visibility::Private => Ok(()),
+            Visibility::Public => "pub ".fmt(f),
+        }
+    }
+}
+
+impl Display for Literal {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Literal::Bool(v) => v.fmt(f),
+            Literal::Char(v) => write!(f, "'{}'", v.escape_debug()),
+            Literal::Int(v) => v.fmt(f),
+            Literal::Float(v) => write!(f, "{:?}", f64::from_bits(*v)),
+            Literal::String(v) => write!(f, "\"{}\"", v.escape_debug()),
+        }
+    }
+}
+
+impl Display for File {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        separate(&self.items, "\n\n")(f)
+    }
+}
+
+impl Display for Attrs {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { meta } = self;
+        if meta.is_empty() {
+            return Ok(());
+        }
+        "#".fmt(f)?;
+        separate(meta, ", ")(&mut f.delimit(INLINE_SQUARE))?;
+        "\n".fmt(f)
+    }
+}
+
+impl Display for Meta {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, kind } = self;
+        write!(f, "{name}{kind}")
+    }
+}
+
+impl Display for MetaKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            MetaKind::Plain => Ok(()),
+            MetaKind::Equals(v) => write!(f, " = {v}"),
+            MetaKind::Func(args) => separate(args, ", ")(f.delimit(INLINE_PARENS)),
+        }
+    }
+}
+
+impl Display for Item {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { span: _, attrs, vis, kind } = self;
+        attrs.fmt(f)?;
+        vis.fmt(f)?;
+        kind.fmt(f)
+    }
+}
+
+impl Display for ItemKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ItemKind::Alias(v) => v.fmt(f),
+            ItemKind::Const(v) => v.fmt(f),
+            ItemKind::Static(v) => v.fmt(f),
+            ItemKind::Module(v) => v.fmt(f),
+            ItemKind::Function(v) => v.fmt(f),
+            ItemKind::Struct(v) => v.fmt(f),
+            ItemKind::Enum(v) => v.fmt(f),
+            ItemKind::Impl(v) => v.fmt(f),
+            ItemKind::Use(v) => v.fmt(f),
+        }
+    }
+}
+
+impl Display for Generics {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Generics { vars } = self;
+        if !vars.is_empty() {
+            separate(vars, ", ")(f.delimit_with("<", ">"))?
+        }
+        Ok(())
+    }
+}
+
+impl Display for Alias {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, from } = self;
+        match from {
+            Some(from) => write!(f, "type {name} = {from};"),
+            None => write!(f, "type {name};"),
+        }
+    }
+}
+
+impl Display for Const {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, ty, init } = self;
+        write!(f, "const {name}: {ty} = {init}")
+    }
+}
+
+impl Display for Static {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { mutable, name, ty, init } = self;
+        write!(f, "static {mutable}{name}: {ty} = {init}")
+    }
+}
+
+impl Display for Module {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, file } = self;
+        write!(f, "mod {name}")?;
+        match file {
+            Some(items) => {
+                ' '.fmt(f)?;
+                write!(f.delimit(BRACES), "{items}")
+            }
+            None => Ok(()),
+        }
+    }
+}
+
+impl Display for Function {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, gens, sign: sign @ TyFn { args, rety }, bind, body } = self;
+        let types = match args.kind {
+            TyKind::Tuple(TyTuple { ref types }) => types.as_slice(),
+            _ => {
+                write!(f, "Invalid function signature: {sign}")?;
+                Default::default()
+            }
+        };
+        let bind = match bind {
+            Pattern::Tuple(patterns) => patterns.as_slice(),
+            _ => {
+                write!(f, "Invalid argument binder: {bind}")?;
+                Default::default()
+            }
+        };
+
+        debug_assert_eq!(bind.len(), types.len());
+        write!(f, "fn {name}{gens} ")?;
+        {
+            let mut f = f.delimit(INLINE_PARENS);
+
+            for (idx, (arg, ty)) in bind.iter().zip(types.iter()).enumerate() {
+                if idx != 0 {
+                    f.write_str(", ")?;
+                }
+                write!(f, "{arg}: {ty}")?;
+            }
+        }
+        if let TyKind::Tuple(TyTuple { types }) = &rety.kind
+            && !types.as_slice().is_empty()
+        {
+            write!(f, " -> {rety}")?
+        }
+
+        match body {
+            Some(body) => write!(f, " {body}"),
+            None => ';'.fmt(f),
+        }
+    }
+}
+
+impl Display for Struct {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, gens, kind } = self;
+        write!(f, "struct {name}{gens}{kind}")
+    }
+}
+
+impl Display for StructKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            StructKind::Empty => ';'.fmt(f),
+            StructKind::Tuple(v) => separate(v, ", ")(f.delimit(INLINE_PARENS)),
+            StructKind::Struct(v) => separate(v, ",\n")(f.delimit(SPACED_BRACES)),
+        }
+    }
+}
+
+impl Display for StructMember {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { vis, name, ty } = self;
+        write!(f, "{vis}{name}: {ty}")
+    }
+}
+
+impl Display for Enum {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, gens, variants } = self;
+        write!(f, "enum {name}{gens}")?;
+        separate(variants, ",\n")(f.delimit(SPACED_BRACES))
+    }
+}
+
+impl Display for Variant {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, kind, body } = self;
+        write!(f, "{name}{kind}")?;
+        match body {
+            Some(body) => write!(f, " {body}"),
+            None => Ok(()),
+        }
+    }
+}
+
+impl Display for Impl {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { gens, target, body } = self;
+        write!(f, "impl{gens} {target} ")?;
+        write!(f.delimit(BRACES), "{body}")
+    }
+}
+
+impl Display for ImplKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ImplKind::Type(t) => t.fmt(f),
+            ImplKind::Trait { impl_trait, for_type } => {
+                write!(f, "{impl_trait} for {for_type}")
+            }
+        }
+    }
+}
+
+impl Display for Use {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { absolute, tree } = self;
+        f.write_str(if *absolute { "use ::" } else { "use " })?;
+        write!(f, "{tree};")
+    }
+}
+
+impl Display for UseTree {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            UseTree::Tree(tree) => separate(tree, ", ")(f.delimit(INLINE_BRACES)),
+            UseTree::Path(path, rest) => write!(f, "{path}::{rest}"),
+            UseTree::Alias(path, name) => write!(f, "{path} as {name}"),
+            UseTree::Name(name) => write!(f, "{name}"),
+            UseTree::Glob => write!(f, "*"),
+        }
+    }
+}
+
+impl Display for Ty {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { span: _, kind, gens } = self;
+        write!(f, "{kind}{gens}")
+    }
+}
+
+impl Display for TyKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TyKind::Never => "!".fmt(f),
+            TyKind::Infer => "_".fmt(f),
+            TyKind::Path(v) => v.fmt(f),
+            TyKind::Array(v) => v.fmt(f),
+            TyKind::Slice(v) => v.fmt(f),
+            TyKind::Tuple(v) => v.fmt(f),
+            TyKind::Ref(v) => v.fmt(f),
+            TyKind::Ptr(v) => v.fmt(f),
+            TyKind::Fn(v) => v.fmt(f),
+        }
+    }
+}
+
+impl Display for TyArray {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { ty, count } = self;
+        write!(f, "[{ty}; {count}]")
+    }
+}
+
+impl Display for TySlice {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { ty } = self;
+        write!(f, "[{ty}]")
+    }
+}
+
+impl Display for TyTuple {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        separate(&self.types, ", ")(f.delimit(INLINE_PARENS))
+    }
+}
+
+impl Display for TyRef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let &Self { count, mutable, ref to } = self;
+        for _ in 0..count {
+            f.write_char('&')?;
+        }
+        write!(f, "{mutable}{to}")
+    }
+}
+
+impl Display for TyPtr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { to } = self;
+        write!(f, "*{to}")
+    }
+}
+
+impl Display for TyFn {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { args, rety } = self;
+        write!(f, "fn {args}")?;
+        if let TyKind::Tuple(TyTuple { types }) = &rety.kind
+            && !types.as_slice().is_empty()
+        {
+            write!(f, " -> {rety}")?
+        }
+        Ok(())
+    }
+}
+
+impl Display for Path {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { absolute, parts } = self;
+        if *absolute {
+            "::".fmt(f)?;
+        }
+        separate(parts, "::")(f)
+    }
+}
+
+impl Display for PathPart {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            PathPart::SuperKw => "super".fmt(f),
+            PathPart::SelfTy => "Self".fmt(f),
+            PathPart::Ident(id) => id.fmt(f),
+        }
+    }
+}
+
+impl Display for Stmt {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Stmt { span: _, kind, semi } = self;
+        write!(f, "{kind}{semi}")
+    }
+}
+
+impl Display for StmtKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            StmtKind::Empty => Ok(()),
+            StmtKind::Item(v) => v.fmt(f),
+            StmtKind::Expr(v) => v.fmt(f),
+        }
+    }
+}
+
+impl Display for Semi {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Semi::Terminated => ';'.fmt(f),
+            Semi::Unterminated => Ok(()),
+        }
+    }
+}
+
+impl Display for Expr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.kind.fmt(f)
+    }
+}
+
+impl Display for ExprKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ExprKind::Empty => "()".fmt(f),
+            ExprKind::Closure(v) => v.fmt(f),
+            ExprKind::Quote(v) => v.fmt(f),
+            ExprKind::Let(v) => v.fmt(f),
+            ExprKind::Match(v) => v.fmt(f),
+            ExprKind::Assign(v) => v.fmt(f),
+            ExprKind::Modify(v) => v.fmt(f),
+            ExprKind::Binary(v) => v.fmt(f),
+            ExprKind::Unary(v) => v.fmt(f),
+            ExprKind::Cast(v) => v.fmt(f),
+            ExprKind::Member(v) => v.fmt(f),
+            ExprKind::Index(v) => v.fmt(f),
+            ExprKind::Structor(v) => v.fmt(f),
+            ExprKind::Path(v) => v.fmt(f),
+            ExprKind::Literal(v) => v.fmt(f),
+            ExprKind::Array(v) => v.fmt(f),
+            ExprKind::ArrayRep(v) => v.fmt(f),
+            ExprKind::AddrOf(v) => v.fmt(f),
+            ExprKind::Block(v) => v.fmt(f),
+            ExprKind::Group(v) => v.fmt(f),
+            ExprKind::Tuple(v) => v.fmt(f),
+            ExprKind::While(v) => v.fmt(f),
+            ExprKind::If(v) => v.fmt(f),
+            ExprKind::For(v) => v.fmt(f),
+            ExprKind::Break(v) => v.fmt(f),
+            ExprKind::Return(v) => v.fmt(f),
+            ExprKind::Continue => "continue".fmt(f),
+        }
+    }
+}
+
+impl Display for Closure {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { arg, body } = self;
+        match arg.as_ref() {
+            Pattern::Tuple(args) => separate(args, ", ")(f.delimit_with("|", "|")),
+            _ => arg.fmt(f),
+        }?;
+        write!(f, " {body}")
+    }
+}
+
+impl Display for Quote {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { quote } = self;
+        write!(f, "`{quote}`")
+    }
+}
+
+impl Display for Let {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { mutable, name, ty, init } = self;
+        write!(f, "let {mutable}{name}")?;
+        if let Some(value) = ty {
+            write!(f, ": {value}")?;
+        }
+        if let Some(value) = init {
+            write!(f, " = {value}")?;
+        }
+        Ok(())
+    }
+}
+
+impl Display for Pattern {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Pattern::Name(sym) => sym.fmt(f),
+            Pattern::Path(path) => path.fmt(f),
+            Pattern::Literal(literal) => literal.fmt(f),
+            Pattern::Rest(Some(name)) => write!(f, "..{name}"),
+            Pattern::Rest(None) => "..".fmt(f),
+            Pattern::Ref(mutability, pattern) => write!(f, "&{mutability}{pattern}"),
+            Pattern::RangeExc(head, tail) => write!(f, "{head}..{tail}"),
+            Pattern::RangeInc(head, tail) => write!(f, "{head}..={tail}"),
+            Pattern::Tuple(patterns) => separate(patterns, ", ")(f.delimit(INLINE_PARENS)),
+            Pattern::Array(patterns) => separate(patterns, ", ")(f.delimit(INLINE_SQUARE)),
+            Pattern::Struct(path, items) => {
+                write!(f, "{path} ")?;
+                let f = &mut f.delimit(INLINE_BRACES);
+                for (idx, (name, item)) in items.iter().enumerate() {
+                    if idx != 0 {
+                        f.write_str(", ")?;
+                    }
+                    write!(f, "{name}")?;
+                    if let Some(pattern) = item {
+                        write!(f, ": {pattern}")?
+                    }
+                }
+                Ok(())
+            }
+            Pattern::TupleStruct(path, items) => {
+                write!(f, "{path}")?;
+                separate(items, ", ")(f.delimit(INLINE_PARENS))
+            }
+        }
+    }
+}
+
+impl Display for Match {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { scrutinee, arms } = self;
+        write!(f, "match {scrutinee} ")?;
+        separate(arms, ",\n")(f.delimit(BRACES))
+    }
+}
+
+impl Display for MatchArm {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self(pat, expr) = self;
+        write!(f, "{pat} => {expr}")
+    }
+}
+
+impl Display for Assign {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { parts } = self;
+        write!(f, "{} = {}", parts.0, parts.1)
+    }
+}
+
+impl Display for Modify {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { kind, parts } = self;
+        write!(f, "{} {kind} {}", parts.0, parts.1)
+    }
+}
+
+impl Display for ModifyKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ModifyKind::Mul => "*=",
+            ModifyKind::Div => "/=",
+            ModifyKind::Rem => "%=",
+            ModifyKind::Add => "+=",
+            ModifyKind::Sub => "-=",
+            ModifyKind::And => "&=",
+            ModifyKind::Or => "|=",
+            ModifyKind::Xor => "^=",
+            ModifyKind::Shl => "<<=",
+            ModifyKind::Shr => ">>=",
+        }
+        .fmt(f)
+    }
+}
+
+impl Display for Binary {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { kind, parts } = self;
+        let (head, tail) = parts.borrow();
+        match kind {
+            BinaryKind::Call => write!(f, "{head}{tail}"),
+            _ => write!(f, "{head} {kind} {tail}"),
+        }
+    }
+}
+
+impl Display for BinaryKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            BinaryKind::Lt => "<",
+            BinaryKind::LtEq => "<=",
+            BinaryKind::Equal => "==",
+            BinaryKind::NotEq => "!=",
+            BinaryKind::GtEq => ">=",
+            BinaryKind::Gt => ">",
+            BinaryKind::RangeExc => "..",
+            BinaryKind::RangeInc => "..=",
+            BinaryKind::LogAnd => "&&",
+            BinaryKind::LogOr => "||",
+            BinaryKind::LogXor => "^^",
+            BinaryKind::BitAnd => "&",
+            BinaryKind::BitOr => "|",
+            BinaryKind::BitXor => "^",
+            BinaryKind::Shl => "<<",
+            BinaryKind::Shr => ">>",
+            BinaryKind::Add => "+",
+            BinaryKind::Sub => "-",
+            BinaryKind::Mul => "*",
+            BinaryKind::Div => "/",
+            BinaryKind::Rem => "%",
+            BinaryKind::Call => "()",
+        }
+        .fmt(f)
+    }
+}
+
+impl Display for Unary {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { kind, tail } = self;
+        write!(f, "{kind}{tail}")
+    }
+}
+
+impl Display for UnaryKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            UnaryKind::Loop => "loop ",
+            UnaryKind::Deref => "*",
+            UnaryKind::Neg => "-",
+            UnaryKind::Not => "!",
+            UnaryKind::RangeExc => "..",
+            UnaryKind::RangeInc => "..=",
+            UnaryKind::At => "@",
+            UnaryKind::Tilde => "~",
+        }
+        .fmt(f)
+    }
+}
+
+impl Display for Cast {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { head, ty } = self;
+        write!(f, "{head} as {ty}")
+    }
+}
+
+impl Display for Member {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { head, kind } = self;
+        write!(f, "{head}.{kind}")
+    }
+}
+
+impl Display for MemberKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            MemberKind::Call(name, args) => write!(f, "{name}{args}"),
+            MemberKind::Struct(name) => write!(f, "{name}"),
+            MemberKind::Tuple(name) => write!(f, "{name}"),
+        }
+    }
+}
+
+impl Display for Index {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { head, indices } = self;
+        write!(f, "{head}")?;
+        separate(indices, ", ")(f.delimit(INLINE_SQUARE))
+    }
+}
+
+impl Display for Structor {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { to, init } = self;
+        write!(f, "{to} ")?;
+        separate(init, ", ")(f.delimit(INLINE_BRACES))
+    }
+}
+
+impl Display for Fielder {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { name, init } = self;
+        write!(f, "{name}")?;
+        if let Some(init) = init {
+            write!(f, ": {init}")?;
+        }
+        Ok(())
+    }
+}
+
+impl Display for Array {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        separate(&self.values, ", ")(f.delimit(INLINE_SQUARE))
+    }
+}
+
+impl Display for ArrayRep {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { value, repeat } = self;
+        write!(f, "[{value}; {repeat}]")
+    }
+}
+
+impl Display for AddrOf {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { mutable, expr } = self;
+        write!(f, "&{mutable}{expr}")
+    }
+}
+
+impl Display for Block {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { stmts } = self;
+
+        match stmts.as_slice() {
+            [] => "{}".fmt(f),
+            stmts => separate(stmts, "\n")(f.delimit(BRACES)),
+        }
+    }
+}
+
+impl Display for Group {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "({})", self.expr)
+    }
+}
+
+impl Display for Tuple {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { exprs } = self;
+
+        match exprs.as_slice() {
+            [] => write!(f, "()"),
+            [expr] => write!(f, "({expr},)"),
+            exprs => separate(exprs, ", ")(f.delimit(INLINE_PARENS)),
+        }
+    }
+}
+
+impl Display for While {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { cond, pass, fail } = self;
+        write!(f, "while {cond} {pass}{fail}")
+    }
+}
+
+impl Display for If {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { cond, pass, fail } = self;
+        write!(f, "if {cond} {pass}{fail}")
+    }
+}
+
+impl Display for For {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { bind, cond, pass, fail } = self;
+        write!(f, "for {bind} in {cond} {pass}{fail}")
+    }
+}
+
+impl Display for Else {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &self.body {
+            Some(body) => write!(f, " else {body}"),
+            _ => Ok(()),
+        }
+    }
+}
+
+impl Display for Break {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "break")?;
+        match &self.body {
+            Some(body) => write!(f, " {body}"),
+            _ => Ok(()),
+        }
+    }
+}
+
+impl Display for Return {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "return")?;
+        match &self.body {
+            Some(body) => write!(f, " {body}"),
+            _ => Ok(()),
+        }
+    }
+}

compiler/cl-ast/src/ast_impl/path.rs

@@ -0,0 +1,60 @@
+//! Utils for [Path]
+use crate::{PathPart, Sym, ast::Path};
+
+impl Path {
+    /// Appends a [PathPart] to this [Path]
+    pub fn push(&mut self, part: PathPart) {
+        self.parts.push(part);
+    }
+    /// Removes a [PathPart] from this [Path]
+    pub fn pop(&mut self) -> Option<PathPart> {
+        self.parts.pop()
+    }
+    /// Concatenates `self::other`. If `other` is an absolute [Path],
+    /// this replaces `self` with `other`
+    pub fn concat(mut self, other: &Self) -> Self {
+        if other.absolute {
+            other.clone()
+        } else {
+            self.parts.extend(other.parts.iter().cloned());
+            self
+        }
+    }
+
+    /// Gets the defining [Sym] of this path
+    pub fn as_sym(&self) -> Option<Sym> {
+        match self.parts.as_slice() {
+            [.., PathPart::Ident(name)] => Some(*name),
+            _ => None,
+        }
+    }
+
+    /// Checks whether this path ends in the given [Sym]
+    pub fn ends_with(&self, name: &str) -> bool {
+        match self.parts.as_slice() {
+            [.., PathPart::Ident(last)] => name == &**last,
+            _ => false,
+        }
+    }
+
+    /// Checks whether this path refers to the sinkhole identifier, `_`
+    pub fn is_sinkhole(&self) -> bool {
+        if let [PathPart::Ident(id)] = self.parts.as_slice()
+            && let "_" = id.to_ref()
+        {
+            return true;
+        }
+        false
+    }
+}
+impl PathPart {
+    pub fn from_sym(ident: Sym) -> Self {
+        Self::Ident(ident)
+    }
+}
+
+impl From<Sym> for Path {
+    fn from(value: Sym) -> Self {
+        Self { parts: vec![PathPart::Ident(value)], absolute: false }
+    }
+}

compiler/cl-ast/src/ast_impl/weight_of.rs

@@ -0,0 +1,617 @@
+//! Approximates the size of an AST
+
+use std::mem::size_of_val;
+
+use crate::ast::*;
+use cl_structures::{intern::interned::Interned, span::Span};
+
+/// Approximates the size of an AST without including indirection (pointers) or padding
+pub trait WeightOf {
+    /// Approximates the size of a syntax tree without including pointer/indirection or padding.
+    fn weight_of(&self) -> usize;
+}
+
+impl WeightOf for File {
+    fn weight_of(&self) -> usize {
+        let Self { name, items } = self;
+        name.weight_of() + items.weight_of()
+    }
+}
+
+impl WeightOf for Attrs {
+    fn weight_of(&self) -> usize {
+        let Self { meta } = self;
+        meta.weight_of()
+    }
+}
+
+impl WeightOf for Meta {
+    fn weight_of(&self) -> usize {
+        let Self { name, kind } = self;
+        name.weight_of() + kind.weight_of()
+    }
+}
+
+impl WeightOf for MetaKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            MetaKind::Plain => size_of_val(self),
+            MetaKind::Equals(v) => v.weight_of(),
+            MetaKind::Func(v) => v.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Item {
+    fn weight_of(&self) -> usize {
+        let Self { span, attrs, vis, kind } = self;
+        span.weight_of() + attrs.weight_of() + vis.weight_of() + kind.weight_of()
+    }
+}
+
+impl WeightOf for ItemKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            ItemKind::Module(v) => v.weight_of(),
+            ItemKind::Alias(v) => v.weight_of(),
+            ItemKind::Enum(v) => v.weight_of(),
+            ItemKind::Struct(v) => v.weight_of(),
+            ItemKind::Const(v) => v.weight_of(),
+            ItemKind::Static(v) => v.weight_of(),
+            ItemKind::Function(v) => v.weight_of(),
+            ItemKind::Impl(v) => v.weight_of(),
+            ItemKind::Use(v) => v.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Generics {
+    fn weight_of(&self) -> usize {
+        let Self { vars } = self;
+        vars.iter().map(|v| v.weight_of()).sum()
+    }
+}
+
+impl WeightOf for Module {
+    fn weight_of(&self) -> usize {
+        let Self { name, file } = self;
+        name.weight_of() + file.weight_of()
+    }
+}
+
+impl WeightOf for Alias {
+    fn weight_of(&self) -> usize {
+        let Self { name, from } = self;
+        name.weight_of() + from.weight_of()
+    }
+}
+
+impl WeightOf for Const {
+    fn weight_of(&self) -> usize {
+        let Self { name, ty, init } = self;
+        name.weight_of() + ty.weight_of() + init.weight_of()
+    }
+}
+
+impl WeightOf for Static {
+    fn weight_of(&self) -> usize {
+        let Self { mutable, name, ty, init } = self;
+        mutable.weight_of() + name.weight_of() + ty.weight_of() + init.weight_of()
+    }
+}
+
+impl WeightOf for Function {
+    fn weight_of(&self) -> usize {
+        let Self { name, gens, sign, bind, body } = self;
+        name.weight_of() + gens.weight_of() + sign.weight_of() + bind.weight_of() + body.weight_of()
+    }
+}
+
+impl WeightOf for Struct {
+    fn weight_of(&self) -> usize {
+        let Self { name, gens, kind } = self;
+        name.weight_of() + gens.weight_of() + kind.weight_of()
+    }
+}
+
+impl WeightOf for StructKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            StructKind::Empty => size_of_val(self),
+            StructKind::Tuple(items) => items.weight_of(),
+            StructKind::Struct(sm) => sm.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for StructMember {
+    fn weight_of(&self) -> usize {
+        let Self { vis, name, ty } = self;
+        vis.weight_of() + name.weight_of() + ty.weight_of()
+    }
+}
+
+impl WeightOf for Enum {
+    fn weight_of(&self) -> usize {
+        let Self { name, gens, variants } = self;
+        name.weight_of() + gens.weight_of() + variants.weight_of()
+    }
+}
+
+impl WeightOf for Variant {
+    fn weight_of(&self) -> usize {
+        let Self { name, kind, body } = self;
+        name.weight_of() + kind.weight_of() + body.weight_of()
+    }
+}
+
+impl WeightOf for Impl {
+    fn weight_of(&self) -> usize {
+        let Self { gens, target, body } = self;
+        gens.weight_of() + target.weight_of() + body.weight_of()
+    }
+}
+
+impl WeightOf for ImplKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            ImplKind::Type(ty) => ty.weight_of(),
+            ImplKind::Trait { impl_trait, for_type } => {
+                impl_trait.weight_of() + for_type.weight_of()
+            }
+        }
+    }
+}
+
+impl WeightOf for Use {
+    fn weight_of(&self) -> usize {
+        let Self { absolute, tree } = self;
+        absolute.weight_of() + tree.weight_of()
+    }
+}
+
+impl WeightOf for UseTree {
+    fn weight_of(&self) -> usize {
+        match self {
+            UseTree::Tree(tr) => tr.weight_of(),
+            UseTree::Path(pa, tr) => pa.weight_of() + tr.weight_of(),
+            UseTree::Alias(src, dst) => src.weight_of() + dst.weight_of(),
+            UseTree::Name(src) => src.weight_of(),
+            UseTree::Glob => size_of_val(self),
+        }
+    }
+}
+
+impl WeightOf for Ty {
+    fn weight_of(&self) -> usize {
+        let Self { span, kind, gens } = self;
+        span.weight_of() + kind.weight_of() + gens.weight_of()
+    }
+}
+
+impl WeightOf for TyKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            TyKind::Never | TyKind::Infer => size_of_val(self),
+            TyKind::Path(v) => v.weight_of(),
+            TyKind::Array(v) => v.weight_of(),
+            TyKind::Slice(v) => v.weight_of(),
+            TyKind::Tuple(v) => v.weight_of(),
+            TyKind::Ref(v) => v.weight_of(),
+            TyKind::Ptr(v) => v.weight_of(),
+            TyKind::Fn(v) => v.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for TyArray {
+    fn weight_of(&self) -> usize {
+        let Self { ty, count } = self;
+        ty.weight_of() + count.weight_of()
+    }
+}
+
+impl WeightOf for TySlice {
+    fn weight_of(&self) -> usize {
+        let Self { ty } = self;
+        ty.weight_of()
+    }
+}
+
+impl WeightOf for TyTuple {
+    fn weight_of(&self) -> usize {
+        let Self { types } = self;
+        types.weight_of()
+    }
+}
+
+impl WeightOf for TyRef {
+    fn weight_of(&self) -> usize {
+        let Self { mutable, count, to } = self;
+        mutable.weight_of() + count.weight_of() + to.weight_of()
+    }
+}
+
+impl WeightOf for TyPtr {
+    fn weight_of(&self) -> usize {
+        let Self { to } = self;
+        to.weight_of()
+    }
+}
+
+impl WeightOf for TyFn {
+    fn weight_of(&self) -> usize {
+        let Self { args, rety } = self;
+        args.weight_of() + rety.weight_of()
+    }
+}
+
+impl WeightOf for Path {
+    fn weight_of(&self) -> usize {
+        let Self { absolute, parts } = self;
+        absolute.weight_of() + parts.weight_of()
+    }
+}
+
+impl WeightOf for PathPart {
+    fn weight_of(&self) -> usize {
+        match self {
+            PathPart::SuperKw => size_of_val(self),
+            PathPart::SelfTy => size_of_val(self),
+            PathPart::Ident(interned) => interned.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Stmt {
+    fn weight_of(&self) -> usize {
+        let Self { span, kind, semi } = self;
+        span.weight_of() + kind.weight_of() + semi.weight_of()
+    }
+}
+
+impl WeightOf for StmtKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            StmtKind::Empty => size_of_val(self),
+            StmtKind::Item(item) => item.weight_of(),
+            StmtKind::Expr(expr) => expr.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Expr {
+    fn weight_of(&self) -> usize {
+        let Self { span, kind } = self;
+        span.weight_of() + kind.weight_of()
+    }
+}
+
+impl WeightOf for ExprKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            ExprKind::Empty => size_of_val(self),
+            ExprKind::Closure(v) => v.weight_of(),
+            ExprKind::Quote(v) => v.weight_of(),
+            ExprKind::Let(v) => v.weight_of(),
+            ExprKind::Match(v) => v.weight_of(),
+            ExprKind::Assign(v) => v.weight_of(),
+            ExprKind::Modify(v) => v.weight_of(),
+            ExprKind::Binary(v) => v.weight_of(),
+            ExprKind::Unary(v) => v.weight_of(),
+            ExprKind::Cast(v) => v.weight_of(),
+            ExprKind::Member(v) => v.weight_of(),
+            ExprKind::Index(v) => v.weight_of(),
+            ExprKind::Structor(v) => v.weight_of(),
+            ExprKind::Path(v) => v.weight_of(),
+            ExprKind::Literal(v) => v.weight_of(),
+            ExprKind::Array(v) => v.weight_of(),
+            ExprKind::ArrayRep(v) => v.weight_of(),
+            ExprKind::AddrOf(v) => v.weight_of(),
+            ExprKind::Block(v) => v.weight_of(),
+            ExprKind::Group(v) => v.weight_of(),
+            ExprKind::Tuple(v) => v.weight_of(),
+            ExprKind::While(v) => v.weight_of(),
+            ExprKind::If(v) => v.weight_of(),
+            ExprKind::For(v) => v.weight_of(),
+            ExprKind::Break(v) => v.weight_of(),
+            ExprKind::Return(v) => v.weight_of(),
+            ExprKind::Continue => size_of_val(self),
+        }
+    }
+}
+
+impl WeightOf for Closure {
+    fn weight_of(&self) -> usize {
+        let Self { arg, body } = self;
+        arg.weight_of() + body.weight_of()
+    }
+}
+
+impl WeightOf for Quote {
+    fn weight_of(&self) -> usize {
+        let Self { quote } = self;
+        quote.weight_of()
+    }
+}
+
+impl WeightOf for Let {
+    fn weight_of(&self) -> usize {
+        let Self { mutable, name, ty, init } = self;
+        mutable.weight_of() + name.weight_of() + ty.weight_of() + init.weight_of()
+    }
+}
+
+impl WeightOf for Pattern {
+    fn weight_of(&self) -> usize {
+        match self {
+            Pattern::Name(s) => size_of_val(s),
+            Pattern::Path(p) => p.weight_of(),
+            Pattern::Literal(literal) => literal.weight_of(),
+            Pattern::Rest(Some(pattern)) => pattern.weight_of(),
+            Pattern::Rest(None) => 0,
+            Pattern::Ref(mutability, pattern) => mutability.weight_of() + pattern.weight_of(),
+            Pattern::RangeExc(head, tail) => head.weight_of() + tail.weight_of(),
+            Pattern::RangeInc(head, tail) => head.weight_of() + tail.weight_of(),
+            Pattern::Tuple(patterns) | Pattern::Array(patterns) => patterns.weight_of(),
+            Pattern::Struct(path, items) => {
+                let sitems: usize = items
+                    .iter()
+                    .map(|(name, opt)| name.weight_of() + opt.weight_of())
+                    .sum();
+                path.weight_of() + sitems
+            }
+            Pattern::TupleStruct(path, patterns) => path.weight_of() + patterns.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Match {
+    fn weight_of(&self) -> usize {
+        let Self { scrutinee, arms } = self;
+        scrutinee.weight_of() + arms.weight_of()
+    }
+}
+
+impl WeightOf for MatchArm {
+    fn weight_of(&self) -> usize {
+        let Self(pattern, expr) = self;
+        pattern.weight_of() + expr.weight_of()
+    }
+}
+
+impl WeightOf for Assign {
+    fn weight_of(&self) -> usize {
+        let Self { parts } = self;
+
+        parts.0.weight_of() + parts.1.weight_of()
+    }
+}
+
+impl WeightOf for Modify {
+    #[rustfmt::skip]
+    fn weight_of(&self) -> usize {
+        let Self { kind, parts } = self;
+        kind.weight_of()
+            + parts.0.weight_of()
+            + parts.1.weight_of()
+    }
+}
+
+impl WeightOf for Binary {
+    fn weight_of(&self) -> usize {
+        let Self { kind, parts } = self;
+
+        kind.weight_of() + parts.0.weight_of() + parts.1.weight_of()
+    }
+}
+
+impl WeightOf for Unary {
+    #[rustfmt::skip]
+    fn weight_of(&self) -> usize {
+        let Self { kind, tail } = self;
+         kind.weight_of() + tail.weight_of()
+    }
+}
+
+impl WeightOf for Cast {
+    fn weight_of(&self) -> usize {
+        let Self { head, ty } = self;
+        head.weight_of() + ty.weight_of()
+    }
+}
+
+impl WeightOf for Member {
+    fn weight_of(&self) -> usize {
+        let Self { head, kind } = self;
+
+        head.weight_of() + kind.weight_of() // accounting
+    }
+}
+
+impl WeightOf for MemberKind {
+    fn weight_of(&self) -> usize {
+        match self {
+            MemberKind::Call(_, tuple) => tuple.weight_of(),
+            MemberKind::Struct(_) => 0,
+            MemberKind::Tuple(literal) => literal.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Index {
+    fn weight_of(&self) -> usize {
+        let Self { head, indices } = self;
+        head.weight_of() + indices.weight_of()
+    }
+}
+
+impl WeightOf for Literal {
+    fn weight_of(&self) -> usize {
+        match self {
+            Literal::Bool(v) => v.weight_of(),
+            Literal::Char(v) => v.weight_of(),
+            Literal::Int(v) => v.weight_of(),
+            Literal::Float(v) => v.weight_of(),
+            Literal::String(v) => v.weight_of(),
+        }
+    }
+}
+
+impl WeightOf for Structor {
+    fn weight_of(&self) -> usize {
+        let Self { to, init } = self;
+        to.weight_of() + init.weight_of()
+    }
+}
+
+impl WeightOf for Fielder {
+    fn weight_of(&self) -> usize {
+        let Self { name, init } = self;
+        name.weight_of() + init.weight_of()
+    }
+}
+
+impl WeightOf for Array {
+    fn weight_of(&self) -> usize {
+        let Self { values } = self;
+        values.weight_of()
+    }
+}
+
+impl WeightOf for ArrayRep {
+    fn weight_of(&self) -> usize {
+        let Self { value, repeat } = self;
+        value.weight_of() + repeat.weight_of()
+    }
+}
+
+impl WeightOf for AddrOf {
+    fn weight_of(&self) -> usize {
+        let Self { mutable, expr } = self;
+        mutable.weight_of() + expr.weight_of()
+    }
+}
+
+impl WeightOf for Block {
+    fn weight_of(&self) -> usize {
+        let Self { stmts } = self;
+        stmts.weight_of()
+    }
+}
+
+impl WeightOf for Group {
+    fn weight_of(&self) -> usize {
+        let Self { expr } = self;
+        expr.weight_of()
+    }
+}
+
+impl WeightOf for Tuple {
+    fn weight_of(&self) -> usize {
+        let Self { exprs } = self;
+        exprs.weight_of()
+    }
+}
+
+impl WeightOf for While {
+    fn weight_of(&self) -> usize {
+        let Self { cond, pass, fail } = self;
+        cond.weight_of() + pass.weight_of() + fail.weight_of()
+    }
+}
+
+impl WeightOf for If {
+    fn weight_of(&self) -> usize {
+        let Self { cond, pass, fail } = self;
+        cond.weight_of() + pass.weight_of() + fail.weight_of()
+    }
+}
+
+impl WeightOf for For {
+    fn weight_of(&self) -> usize {
+        let Self { bind, cond, pass, fail } = self;
+        bind.weight_of() + cond.weight_of() + pass.weight_of() + fail.weight_of()
+    }
+}
+
+impl WeightOf for Else {
+    fn weight_of(&self) -> usize {
+        let Self { body } = self;
+        body.weight_of()
+    }
+}
+
+impl WeightOf for Break {
+    fn weight_of(&self) -> usize {
+        let Self { body } = self;
+        body.weight_of()
+    }
+}
+
+impl WeightOf for Return {
+    fn weight_of(&self) -> usize {
+        let Self { body } = self;
+        body.weight_of()
+    }
+}
+
+// ------------ SizeOf Blanket Implementations
+
+impl<T: WeightOf> WeightOf for Option<T> {
+    fn weight_of(&self) -> usize {
+        match self {
+            Some(t) => t.weight_of().max(size_of_val(t)),
+            None => size_of_val(self),
+        }
+    }
+}
+
+impl<T: WeightOf> WeightOf for [T] {
+    fn weight_of(&self) -> usize {
+        self.iter().map(WeightOf::weight_of).sum()
+    }
+}
+
+impl<T: WeightOf> WeightOf for Vec<T> {
+    fn weight_of(&self) -> usize {
+        size_of::<Self>() + self.iter().map(WeightOf::weight_of).sum::<usize>()
+    }
+}
+
+impl<T: WeightOf> WeightOf for Box<T> {
+    fn weight_of(&self) -> usize {
+        (**self).weight_of() + size_of::<Self>()
+    }
+}
+
+impl WeightOf for str {
+    fn weight_of(&self) -> usize {
+        self.len()
+    }
+}
+
+impl_size_of! {
+    // primitives
+    u8, u16, u32, u64, u128, usize,
+    i8, i16, i32, i64, i128, isize,
+    f32, f64, bool, char,
+    // cl-structures
+    Span,
+    // cl-ast
+    Visibility, Mutability, Semi, ModifyKind, BinaryKind, UnaryKind
+}
+
+impl<T> WeightOf for Interned<'_, T> {
+    fn weight_of(&self) -> usize {
+        size_of_val(self) // interned values are opaque to SizeOF
+    }
+}
+
+macro impl_size_of($($T:ty),*$(,)?) {
+    $(impl WeightOf for $T {
+        fn weight_of(&self) -> usize {
+            ::std::mem::size_of_val(self)
+        }
+    })*
+}

compiler/cl-ast/src/ast_visitor.rs

@@ -0,0 +1,12 @@
+//! Contains an [immutable visitor](Visit) and an [owned folder](Fold) trait,
+//! with default implementations across the entire AST
+
+pub mod fold;
+
+pub mod visit;
+pub mod walk;
+
+pub use fold::Fold;
+
+pub use visit::Visit;
+pub use walk::Walk;

compiler/cl-ast/src/ast_visitor/fold.rs

@@ -0,0 +1,595 @@
+//! A folder (implementer of the [Fold] trait) maps ASTs to ASTs
+
+use crate::ast::*;
+use cl_structures::span::Span;
+
+/// Deconstructs the entire AST, and reconstructs it from scratch.
+///
+/// Each method acts as a customization point.
+///
+/// There are a set of default implementations for enums
+/// under the name [`or_fold_`*](or_fold_expr_kind),
+/// provided for ease of use.
+///
+/// For all other nodes, traversal is *explicit*.
+pub trait Fold {
+    fn fold_span(&mut self, span: Span) -> Span {
+        span
+    }
+    fn fold_mutability(&mut self, mutability: Mutability) -> Mutability {
+        mutability
+    }
+    fn fold_visibility(&mut self, visibility: Visibility) -> Visibility {
+        visibility
+    }
+    fn fold_sym(&mut self, ident: Sym) -> Sym {
+        ident
+    }
+    fn fold_literal(&mut self, lit: Literal) -> Literal {
+        or_fold_literal(self, lit)
+    }
+    fn fold_bool(&mut self, b: bool) -> bool {
+        b
+    }
+    fn fold_char(&mut self, c: char) -> char {
+        c
+    }
+    fn fold_int(&mut self, i: u128) -> u128 {
+        i
+    }
+    fn fold_smuggled_float(&mut self, f: u64) -> u64 {
+        f
+    }
+    fn fold_string(&mut self, s: String) -> String {
+        s
+    }
+    fn fold_file(&mut self, f: File) -> File {
+        let File { name, items } = f;
+        File { name, items: items.into_iter().map(|i| self.fold_item(i)).collect() }
+    }
+    fn fold_attrs(&mut self, a: Attrs) -> Attrs {
+        let Attrs { meta } = a;
+        Attrs { meta: meta.into_iter().map(|m| self.fold_meta(m)).collect() }
+    }
+    fn fold_meta(&mut self, m: Meta) -> Meta {
+        let Meta { name, kind } = m;
+        Meta { name: self.fold_sym(name), kind: self.fold_meta_kind(kind) }
+    }
+    fn fold_meta_kind(&mut self, kind: MetaKind) -> MetaKind {
+        or_fold_meta_kind(self, kind)
+    }
+    fn fold_item(&mut self, i: Item) -> Item {
+        let Item { span, attrs, vis, kind } = i;
+        Item {
+            span: self.fold_span(span),
+            attrs: self.fold_attrs(attrs),
+            vis: self.fold_visibility(vis),
+            kind: self.fold_item_kind(kind),
+        }
+    }
+    fn fold_item_kind(&mut self, kind: ItemKind) -> ItemKind {
+        or_fold_item_kind(self, kind)
+    }
+    fn fold_generics(&mut self, gens: Generics) -> Generics {
+        let Generics { vars } = gens;
+        Generics { vars: vars.into_iter().map(|sym| self.fold_sym(sym)).collect() }
+    }
+    fn fold_alias(&mut self, a: Alias) -> Alias {
+        let Alias { name, from } = a;
+        Alias { name: self.fold_sym(name), from: from.map(|from| Box::new(self.fold_ty(*from))) }
+    }
+    fn fold_const(&mut self, c: Const) -> Const {
+        let Const { name, ty, init } = c;
+        Const {
+            name: self.fold_sym(name),
+            ty: Box::new(self.fold_ty(*ty)),
+            init: Box::new(self.fold_expr(*init)),
+        }
+    }
+    fn fold_static(&mut self, s: Static) -> Static {
+        let Static { mutable, name, ty, init } = s;
+        Static {
+            mutable: self.fold_mutability(mutable),
+            name: self.fold_sym(name),
+            ty: Box::new(self.fold_ty(*ty)),
+            init: Box::new(self.fold_expr(*init)),
+        }
+    }
+    fn fold_module(&mut self, m: Module) -> Module {
+        let Module { name, file } = m;
+        Module { name: self.fold_sym(name), file: file.map(|v| self.fold_file(v)) }
+    }
+    fn fold_function(&mut self, f: Function) -> Function {
+        let Function { name, gens, sign, bind, body } = f;
+        Function {
+            name: self.fold_sym(name),
+            gens: self.fold_generics(gens),
+            sign: self.fold_ty_fn(sign),
+            bind: self.fold_pattern(bind),
+            body: body.map(|b| self.fold_expr(b)),
+        }
+    }
+    fn fold_struct(&mut self, s: Struct) -> Struct {
+        let Struct { name, gens, kind } = s;
+        Struct {
+            name: self.fold_sym(name),
+            gens: self.fold_generics(gens),
+            kind: self.fold_struct_kind(kind),
+        }
+    }
+    fn fold_struct_kind(&mut self, kind: StructKind) -> StructKind {
+        match kind {
+            StructKind::Empty => StructKind::Empty,
+            StructKind::Tuple(tys) => {
+                StructKind::Tuple(tys.into_iter().map(|t| self.fold_ty(t)).collect())
+            }
+            StructKind::Struct(mem) => StructKind::Struct(
+                mem.into_iter()
+                    .map(|m| self.fold_struct_member(m))
+                    .collect(),
+            ),
+        }
+    }
+    fn fold_struct_member(&mut self, m: StructMember) -> StructMember {
+        let StructMember { vis, name, ty } = m;
+        StructMember {
+            vis: self.fold_visibility(vis),
+            name: self.fold_sym(name),
+            ty: self.fold_ty(ty),
+        }
+    }
+    fn fold_enum(&mut self, e: Enum) -> Enum {
+        let Enum { name, gens, variants: kind } = e;
+        Enum {
+            name: self.fold_sym(name),
+            gens: self.fold_generics(gens),
+            variants: kind.into_iter().map(|v| self.fold_variant(v)).collect(),
+        }
+    }
+    fn fold_variant(&mut self, v: Variant) -> Variant {
+        let Variant { name, kind, body } = v;
+
+        Variant {
+            name: self.fold_sym(name),
+            kind: self.fold_struct_kind(kind),
+            body: body.map(|e| Box::new(self.fold_expr(*e))),
+        }
+    }
+    fn fold_impl(&mut self, i: Impl) -> Impl {
+        let Impl { gens, target, body } = i;
+        Impl {
+            gens: self.fold_generics(gens),
+            target: self.fold_impl_kind(target),
+            body: self.fold_file(body),
+        }
+    }
+    fn fold_impl_kind(&mut self, kind: ImplKind) -> ImplKind {
+        or_fold_impl_kind(self, kind)
+    }
+    fn fold_use(&mut self, u: Use) -> Use {
+        let Use { absolute, tree } = u;
+        Use { absolute, tree: self.fold_use_tree(tree) }
+    }
+    fn fold_use_tree(&mut self, tree: UseTree) -> UseTree {
+        or_fold_use_tree(self, tree)
+    }
+    fn fold_ty(&mut self, t: Ty) -> Ty {
+        let Ty { span, kind, gens } = t;
+        Ty {
+            span: self.fold_span(span),
+            kind: self.fold_ty_kind(kind),
+            gens: self.fold_generics(gens),
+        }
+    }
+    fn fold_ty_kind(&mut self, kind: TyKind) -> TyKind {
+        or_fold_ty_kind(self, kind)
+    }
+    fn fold_ty_array(&mut self, a: TyArray) -> TyArray {
+        let TyArray { ty, count } = a;
+        TyArray { ty: Box::new(self.fold_ty(*ty)), count }
+    }
+    fn fold_ty_slice(&mut self, s: TySlice) -> TySlice {
+        let TySlice { ty } = s;
+        TySlice { ty: Box::new(self.fold_ty(*ty)) }
+    }
+    fn fold_ty_tuple(&mut self, t: TyTuple) -> TyTuple {
+        let TyTuple { types } = t;
+        TyTuple { types: types.into_iter().map(|kind| self.fold_ty(kind)).collect() }
+    }
+    fn fold_ty_ref(&mut self, t: TyRef) -> TyRef {
+        let TyRef { mutable, count, to } = t;
+        TyRef { mutable: self.fold_mutability(mutable), count, to: Box::new(self.fold_ty(*to)) }
+    }
+    fn fold_ty_ptr(&mut self, t: TyPtr) -> TyPtr {
+        let TyPtr { to } = t;
+        TyPtr { to: Box::new(self.fold_ty(*to)) }
+    }
+    fn fold_ty_fn(&mut self, t: TyFn) -> TyFn {
+        let TyFn { args, rety } = t;
+        TyFn { args: Box::new(self.fold_ty(*args)), rety: Box::new(self.fold_ty(*rety)) }
+    }
+    fn fold_path(&mut self, p: Path) -> Path {
+        let Path { absolute, parts } = p;
+        Path { absolute, parts: parts.into_iter().map(|p| self.fold_path_part(p)).collect() }
+    }
+    fn fold_path_part(&mut self, p: PathPart) -> PathPart {
+        match p {
+            PathPart::SuperKw => PathPart::SuperKw,
+            PathPart::SelfTy => PathPart::SelfTy,
+            PathPart::Ident(i) => PathPart::Ident(self.fold_sym(i)),
+        }
+    }
+    fn fold_stmt(&mut self, s: Stmt) -> Stmt {
+        let Stmt { span, kind, semi } = s;
+        Stmt {
+            span: self.fold_span(span),
+            kind: self.fold_stmt_kind(kind),
+            semi: self.fold_semi(semi),
+        }
+    }
+    fn fold_stmt_kind(&mut self, kind: StmtKind) -> StmtKind {
+        or_fold_stmt_kind(self, kind)
+    }
+    fn fold_semi(&mut self, s: Semi) -> Semi {
+        s
+    }
+    fn fold_expr(&mut self, e: Expr) -> Expr {
+        let Expr { span, kind } = e;
+        Expr { span: self.fold_span(span), kind: self.fold_expr_kind(kind) }
+    }
+    fn fold_expr_kind(&mut self, kind: ExprKind) -> ExprKind {
+        or_fold_expr_kind(self, kind)
+    }
+    fn fold_closure(&mut self, value: Closure) -> Closure {
+        let Closure { arg, body } = value;
+        Closure { arg: Box::new(self.fold_pattern(*arg)), body: Box::new(self.fold_expr(*body)) }
+    }
+    fn fold_let(&mut self, l: Let) -> Let {
+        let Let { mutable, name, ty, init } = l;
+        Let {
+            mutable: self.fold_mutability(mutable),
+            name: self.fold_pattern(name),
+            ty: ty.map(|t| Box::new(self.fold_ty(*t))),
+            init: init.map(|e| Box::new(self.fold_expr(*e))),
+        }
+    }
+
+    fn fold_pattern(&mut self, p: Pattern) -> Pattern {
+        match p {
+            Pattern::Name(sym) => Pattern::Name(self.fold_sym(sym)),
+            Pattern::Path(path) => Pattern::Path(self.fold_path(path)),
+            Pattern::Literal(literal) => Pattern::Literal(self.fold_literal(literal)),
+            Pattern::Rest(Some(name)) => Pattern::Rest(Some(self.fold_pattern(*name).into())),
+            Pattern::Rest(None) => Pattern::Rest(None),
+            Pattern::Ref(mutability, pattern) => Pattern::Ref(
+                self.fold_mutability(mutability),
+                Box::new(self.fold_pattern(*pattern)),
+            ),
+            Pattern::RangeExc(head, tail) => Pattern::RangeInc(
+                Box::new(self.fold_pattern(*head)),
+                Box::new(self.fold_pattern(*tail)),
+            ),
+            Pattern::RangeInc(head, tail) => Pattern::RangeInc(
+                Box::new(self.fold_pattern(*head)),
+                Box::new(self.fold_pattern(*tail)),
+            ),
+            Pattern::Tuple(patterns) => {
+                Pattern::Tuple(patterns.into_iter().map(|p| self.fold_pattern(p)).collect())
+            }
+            Pattern::Array(patterns) => {
+                Pattern::Array(patterns.into_iter().map(|p| self.fold_pattern(p)).collect())
+            }
+            Pattern::Struct(path, items) => Pattern::Struct(
+                self.fold_path(path),
+                items
+                    .into_iter()
+                    .map(|(name, bind)| (name, bind.map(|p| self.fold_pattern(p))))
+                    .collect(),
+            ),
+            Pattern::TupleStruct(path, items) => Pattern::TupleStruct(
+                self.fold_path(path),
+                items
+                    .into_iter()
+                    .map(|bind| self.fold_pattern(bind))
+                    .collect(),
+            ),
+        }
+    }
+
+    fn fold_match(&mut self, m: Match) -> Match {
+        let Match { scrutinee, arms } = m;
+        Match {
+            scrutinee: self.fold_expr(*scrutinee).into(),
+            arms: arms
+                .into_iter()
+                .map(|arm| self.fold_match_arm(arm))
+                .collect(),
+        }
+    }
+
+    fn fold_match_arm(&mut self, a: MatchArm) -> MatchArm {
+        let MatchArm(pat, expr) = a;
+        MatchArm(self.fold_pattern(pat), self.fold_expr(expr))
+    }
+
+    fn fold_assign(&mut self, a: Assign) -> Assign {
+        let Assign { parts } = a;
+        let (head, tail) = *parts;
+        Assign { parts: Box::new((self.fold_expr(head), self.fold_expr(tail))) }
+    }
+    fn fold_modify(&mut self, m: Modify) -> Modify {
+        let Modify { kind, parts } = m;
+        let (head, tail) = *parts;
+        Modify {
+            kind: self.fold_modify_kind(kind),
+            parts: Box::new((self.fold_expr(head), self.fold_expr(tail))),
+        }
+    }
+    fn fold_modify_kind(&mut self, kind: ModifyKind) -> ModifyKind {
+        kind
+    }
+    fn fold_binary(&mut self, b: Binary) -> Binary {
+        let Binary { kind, parts } = b;
+        let (head, tail) = *parts;
+        Binary {
+            kind: self.fold_binary_kind(kind),
+            parts: Box::new((self.fold_expr(head), self.fold_expr(tail))),
+        }
+    }
+    fn fold_binary_kind(&mut self, kind: BinaryKind) -> BinaryKind {
+        kind
+    }
+    fn fold_unary(&mut self, u: Unary) -> Unary {
+        let Unary { kind, tail } = u;
+        Unary { kind: self.fold_unary_kind(kind), tail: Box::new(self.fold_expr(*tail)) }
+    }
+    fn fold_unary_kind(&mut self, kind: UnaryKind) -> UnaryKind {
+        kind
+    }
+    fn fold_cast(&mut self, cast: Cast) -> Cast {
+        let Cast { head, ty } = cast;
+        Cast { head: Box::new(self.fold_expr(*head)), ty: self.fold_ty(ty) }
+    }
+    fn fold_member(&mut self, m: Member) -> Member {
+        let Member { head, kind } = m;
+        Member { head: Box::new(self.fold_expr(*head)), kind: self.fold_member_kind(kind) }
+    }
+    fn fold_member_kind(&mut self, kind: MemberKind) -> MemberKind {
+        or_fold_member_kind(self, kind)
+    }
+    fn fold_index(&mut self, i: Index) -> Index {
+        let Index { head, indices } = i;
+        Index {
+            head: Box::new(self.fold_expr(*head)),
+            indices: indices.into_iter().map(|e| self.fold_expr(e)).collect(),
+        }
+    }
+
+    fn fold_structor(&mut self, s: Structor) -> Structor {
+        let Structor { to, init } = s;
+        Structor {
+            to: self.fold_path(to),
+            init: init.into_iter().map(|f| self.fold_fielder(f)).collect(),
+        }
+    }
+
+    fn fold_fielder(&mut self, f: Fielder) -> Fielder {
+        let Fielder { name, init } = f;
+        Fielder { name: self.fold_sym(name), init: init.map(|e| Box::new(self.fold_expr(*e))) }
+    }
+    fn fold_array(&mut self, a: Array) -> Array {
+        let Array { values } = a;
+        Array { values: values.into_iter().map(|e| self.fold_expr(e)).collect() }
+    }
+    fn fold_array_rep(&mut self, a: ArrayRep) -> ArrayRep {
+        let ArrayRep { value, repeat } = a;
+        ArrayRep { value: Box::new(self.fold_expr(*value)), repeat }
+    }
+    fn fold_addrof(&mut self, a: AddrOf) -> AddrOf {
+        let AddrOf { mutable, expr } = a;
+        AddrOf { mutable: self.fold_mutability(mutable), expr: Box::new(self.fold_expr(*expr)) }
+    }
+    fn fold_block(&mut self, b: Block) -> Block {
+        let Block { stmts } = b;
+        Block { stmts: stmts.into_iter().map(|s| self.fold_stmt(s)).collect() }
+    }
+    fn fold_group(&mut self, g: Group) -> Group {
+        let Group { expr } = g;
+        Group { expr: Box::new(self.fold_expr(*expr)) }
+    }
+    fn fold_tuple(&mut self, t: Tuple) -> Tuple {
+        let Tuple { exprs } = t;
+        Tuple { exprs: exprs.into_iter().map(|e| self.fold_expr(e)).collect() }
+    }
+    fn fold_while(&mut self, w: While) -> While {
+        let While { cond, pass, fail } = w;
+        While {
+            cond: Box::new(self.fold_expr(*cond)),
+            pass: Box::new(self.fold_block(*pass)),
+            fail: self.fold_else(fail),
+        }
+    }
+    fn fold_if(&mut self, i: If) -> If {
+        let If { cond, pass, fail } = i;
+        If {
+            cond: Box::new(self.fold_expr(*cond)),
+            pass: Box::new(self.fold_block(*pass)),
+            fail: self.fold_else(fail),
+        }
+    }
+    fn fold_for(&mut self, f: For) -> For {
+        let For { bind, cond, pass, fail } = f;
+        For {
+            bind: self.fold_pattern(bind),
+            cond: Box::new(self.fold_expr(*cond)),
+            pass: Box::new(self.fold_block(*pass)),
+            fail: self.fold_else(fail),
+        }
+    }
+    fn fold_else(&mut self, e: Else) -> Else {
+        let Else { body } = e;
+        Else { body: body.map(|e| Box::new(self.fold_expr(*e))) }
+    }
+    fn fold_break(&mut self, b: Break) -> Break {
+        let Break { body } = b;
+        Break { body: body.map(|e| Box::new(self.fold_expr(*e))) }
+    }
+    fn fold_return(&mut self, r: Return) -> Return {
+        let Return { body } = r;
+        Return { body: body.map(|e| Box::new(self.fold_expr(*e))) }
+    }
+}
+
+#[inline]
+/// Folds a [Literal] in the default way
+pub fn or_fold_literal<F: Fold + ?Sized>(folder: &mut F, lit: Literal) -> Literal {
+    match lit {
+        Literal::Bool(b) => Literal::Bool(folder.fold_bool(b)),
+        Literal::Char(c) => Literal::Char(folder.fold_char(c)),
+        Literal::Int(i) => Literal::Int(folder.fold_int(i)),
+        Literal::Float(f) => Literal::Float(folder.fold_smuggled_float(f)),
+        Literal::String(s) => Literal::String(folder.fold_string(s)),
+    }
+}
+
+#[inline]
+/// Folds a [MetaKind] in the default way
+pub fn or_fold_meta_kind<F: Fold + ?Sized>(folder: &mut F, kind: MetaKind) -> MetaKind {
+    match kind {
+        MetaKind::Plain => MetaKind::Plain,
+        MetaKind::Equals(l) => MetaKind::Equals(folder.fold_literal(l)),
+        MetaKind::Func(lits) => {
+            MetaKind::Func(lits.into_iter().map(|l| folder.fold_literal(l)).collect())
+        }
+    }
+}
+
+#[inline]
+/// Folds an [ItemKind] in the default way
+pub fn or_fold_item_kind<F: Fold + ?Sized>(folder: &mut F, kind: ItemKind) -> ItemKind {
+    match kind {
+        ItemKind::Module(m) => ItemKind::Module(folder.fold_module(m)),
+        ItemKind::Alias(a) => ItemKind::Alias(folder.fold_alias(a)),
+        ItemKind::Enum(e) => ItemKind::Enum(folder.fold_enum(e)),
+        ItemKind::Struct(s) => ItemKind::Struct(folder.fold_struct(s)),
+        ItemKind::Const(c) => ItemKind::Const(folder.fold_const(c)),
+        ItemKind::Static(s) => ItemKind::Static(folder.fold_static(s)),
+        ItemKind::Function(f) => ItemKind::Function(folder.fold_function(f)),
+        ItemKind::Impl(i) => ItemKind::Impl(folder.fold_impl(i)),
+        ItemKind::Use(u) => ItemKind::Use(folder.fold_use(u)),
+    }
+}
+
+#[inline]
+/// Folds a [StructKind] in the default way
+pub fn or_fold_struct_kind<F: Fold + ?Sized>(folder: &mut F, kind: StructKind) -> StructKind {
+    match kind {
+        StructKind::Empty => StructKind::Empty,
+        StructKind::Tuple(tys) => {
+            StructKind::Tuple(tys.into_iter().map(|t| folder.fold_ty(t)).collect())
+        }
+        StructKind::Struct(mem) => StructKind::Struct(
+            mem.into_iter()
+                .map(|m| folder.fold_struct_member(m))
+                .collect(),
+        ),
+    }
+}
+
+#[inline]
+/// Folds an [ImplKind] in the default way
+pub fn or_fold_impl_kind<F: Fold + ?Sized>(folder: &mut F, kind: ImplKind) -> ImplKind {
+    match kind {
+        ImplKind::Type(t) => ImplKind::Type(folder.fold_ty(t)),
+        ImplKind::Trait { impl_trait, for_type } => ImplKind::Trait {
+            impl_trait: folder.fold_path(impl_trait),
+            for_type: Box::new(folder.fold_ty(*for_type)),
+        },
+    }
+}
+
+#[inline]
+pub fn or_fold_use_tree<F: Fold + ?Sized>(folder: &mut F, tree: UseTree) -> UseTree {
+    match tree {
+        UseTree::Tree(tree) => UseTree::Tree(
+            tree.into_iter()
+                .map(|tree| folder.fold_use_tree(tree))
+                .collect(),
+        ),
+        UseTree::Path(path, rest) => UseTree::Path(
+            folder.fold_path_part(path),
+            Box::new(folder.fold_use_tree(*rest)),
+        ),
+        UseTree::Alias(path, name) => UseTree::Alias(folder.fold_sym(path), folder.fold_sym(name)),
+        UseTree::Name(name) => UseTree::Name(folder.fold_sym(name)),
+        UseTree::Glob => UseTree::Glob,
+    }
+}
+
+#[inline]
+/// Folds a [TyKind] in the default way
+pub fn or_fold_ty_kind<F: Fold + ?Sized>(folder: &mut F, kind: TyKind) -> TyKind {
+    match kind {
+        TyKind::Never => TyKind::Never,
+        TyKind::Infer => TyKind::Infer,
+        TyKind::Path(p) => TyKind::Path(folder.fold_path(p)),
+        TyKind::Array(a) => TyKind::Array(folder.fold_ty_array(a)),
+        TyKind::Slice(s) => TyKind::Slice(folder.fold_ty_slice(s)),
+        TyKind::Tuple(t) => TyKind::Tuple(folder.fold_ty_tuple(t)),
+        TyKind::Ref(t) => TyKind::Ref(folder.fold_ty_ref(t)),
+        TyKind::Ptr(t) => TyKind::Ptr(folder.fold_ty_ptr(t)),
+        TyKind::Fn(t) => TyKind::Fn(folder.fold_ty_fn(t)),
+    }
+}
+
+#[inline]
+/// Folds a [StmtKind] in the default way
+pub fn or_fold_stmt_kind<F: Fold + ?Sized>(folder: &mut F, kind: StmtKind) -> StmtKind {
+    match kind {
+        StmtKind::Empty => StmtKind::Empty,
+        StmtKind::Item(i) => StmtKind::Item(Box::new(folder.fold_item(*i))),
+        StmtKind::Expr(e) => StmtKind::Expr(Box::new(folder.fold_expr(*e))),
+    }
+}
+#[inline]
+/// Folds an [ExprKind] in the default way
+pub fn or_fold_expr_kind<F: Fold + ?Sized>(folder: &mut F, kind: ExprKind) -> ExprKind {
+    match kind {
+        ExprKind::Empty => ExprKind::Empty,
+        ExprKind::Closure(c) => ExprKind::Closure(folder.fold_closure(c)),
+        ExprKind::Quote(q) => ExprKind::Quote(q), // quoted expressions are left unmodified
+        ExprKind::Let(l) => ExprKind::Let(folder.fold_let(l)),
+        ExprKind::Match(m) => ExprKind::Match(folder.fold_match(m)),
+        ExprKind::Assign(a) => ExprKind::Assign(folder.fold_assign(a)),
+        ExprKind::Modify(m) => ExprKind::Modify(folder.fold_modify(m)),
+        ExprKind::Binary(b) => ExprKind::Binary(folder.fold_binary(b)),
+        ExprKind::Unary(u) => ExprKind::Unary(folder.fold_unary(u)),
+        ExprKind::Cast(c) => ExprKind::Cast(folder.fold_cast(c)),
+        ExprKind::Member(m) => ExprKind::Member(folder.fold_member(m)),
+        ExprKind::Index(i) => ExprKind::Index(folder.fold_index(i)),
+        ExprKind::Structor(s) => ExprKind::Structor(folder.fold_structor(s)),
+        ExprKind::Path(p) => ExprKind::Path(folder.fold_path(p)),
+        ExprKind::Literal(l) => ExprKind::Literal(folder.fold_literal(l)),
+        ExprKind::Array(a) => ExprKind::Array(folder.fold_array(a)),
+        ExprKind::ArrayRep(a) => ExprKind::ArrayRep(folder.fold_array_rep(a)),
+        ExprKind::AddrOf(a) => ExprKind::AddrOf(folder.fold_addrof(a)),
+        ExprKind::Block(b) => ExprKind::Block(folder.fold_block(b)),
+        ExprKind::Group(g) => ExprKind::Group(folder.fold_group(g)),
+        ExprKind::Tuple(t) => ExprKind::Tuple(folder.fold_tuple(t)),
+        ExprKind::While(w) => ExprKind::While(folder.fold_while(w)),
+        ExprKind::If(i) => ExprKind::If(folder.fold_if(i)),
+        ExprKind::For(f) => ExprKind::For(folder.fold_for(f)),
+        ExprKind::Break(b) => ExprKind::Break(folder.fold_break(b)),
+        ExprKind::Return(r) => ExprKind::Return(folder.fold_return(r)),
+        ExprKind::Continue => ExprKind::Continue,
+    }
+}
+pub fn or_fold_member_kind<F: Fold + ?Sized>(folder: &mut F, kind: MemberKind) -> MemberKind {
+    match kind {
+        MemberKind::Call(name, args) => {
+            MemberKind::Call(folder.fold_sym(name), folder.fold_tuple(args))
+        }
+        MemberKind::Struct(name) => MemberKind::Struct(folder.fold_sym(name)),
+        MemberKind::Tuple(name) => MemberKind::Tuple(folder.fold_literal(name)),
+    }
+}

compiler/cl-ast/src/ast_visitor/visit.rs

@@ -0,0 +1,260 @@
+//! A [visitor](Visit) (implementer of the [Visit] trait) walks the immutable AST, mutating itself.
+
+use crate::ast::*;
+use cl_structures::span::Span;
+
+use super::walk::Walk;
+
+/// Immutably walks the entire AST
+///
+/// Each method acts as a customization point.
+pub trait Visit<'a>: Sized {
+    /// Visits a [Walker](Walk)
+    #[inline]
+    fn visit<W: Walk>(&mut self, walker: &'a W) -> &mut Self {
+        walker.visit_in(self);
+        self
+    }
+    /// Visits the children of a [Walker](Walk)
+    fn visit_children<W: Walk>(&mut self, walker: &'a W) {
+        walker.children(self)
+    }
+
+    fn visit_span(&mut self, value: &'a Span) {
+        value.children(self)
+    }
+    fn visit_mutability(&mut self, value: &'a Mutability) {
+        value.children(self)
+    }
+    fn visit_visibility(&mut self, value: &'a Visibility) {
+        value.children(self)
+    }
+    fn visit_sym(&mut self, value: &'a Sym) {
+        value.children(self)
+    }
+    fn visit_literal(&mut self, value: &'a Literal) {
+        value.children(self)
+    }
+    fn visit_bool(&mut self, value: &'a bool) {
+        value.children(self)
+    }
+    fn visit_char(&mut self, value: &'a char) {
+        value.children(self)
+    }
+    fn visit_int(&mut self, value: &'a u128) {
+        value.children(self)
+    }
+    fn visit_smuggled_float(&mut self, value: &'a u64) {
+        value.children(self)
+    }
+    fn visit_string(&mut self, value: &'a str) {
+        value.children(self)
+    }
+    fn visit_file(&mut self, value: &'a File) {
+        value.children(self)
+    }
+    fn visit_attrs(&mut self, value: &'a Attrs) {
+        value.children(self)
+    }
+    fn visit_meta(&mut self, value: &'a Meta) {
+        value.children(self)
+    }
+    fn visit_meta_kind(&mut self, value: &'a MetaKind) {
+        value.children(self)
+    }
+    fn visit_item(&mut self, value: &'a Item) {
+        value.children(self)
+    }
+    fn visit_item_kind(&mut self, value: &'a ItemKind) {
+        value.children(self)
+    }
+    fn visit_generics(&mut self, value: &'a Generics) {
+        value.children(self)
+    }
+    fn visit_alias(&mut self, value: &'a Alias) {
+        value.children(self)
+    }
+    fn visit_const(&mut self, value: &'a Const) {
+        value.children(self)
+    }
+    fn visit_static(&mut self, value: &'a Static) {
+        value.children(self)
+    }
+    fn visit_module(&mut self, value: &'a Module) {
+        value.children(self)
+    }
+    fn visit_function(&mut self, value: &'a Function) {
+        value.children(self)
+    }
+    fn visit_struct(&mut self, value: &'a Struct) {
+        value.children(self)
+    }
+    fn visit_struct_kind(&mut self, value: &'a StructKind) {
+        value.children(self)
+    }
+    fn visit_struct_member(&mut self, value: &'a StructMember) {
+        value.children(self)
+    }
+    fn visit_enum(&mut self, value: &'a Enum) {
+        value.children(self)
+    }
+    fn visit_variant(&mut self, value: &'a Variant) {
+        value.children(self)
+    }
+    fn visit_impl(&mut self, value: &'a Impl) {
+        value.children(self)
+    }
+    fn visit_impl_kind(&mut self, value: &'a ImplKind) {
+        value.children(self)
+    }
+    fn visit_use(&mut self, value: &'a Use) {
+        value.children(self)
+    }
+    fn visit_use_tree(&mut self, value: &'a UseTree) {
+        value.children(self)
+    }
+    fn visit_ty(&mut self, value: &'a Ty) {
+        value.children(self)
+    }
+    fn visit_ty_kind(&mut self, value: &'a TyKind) {
+        value.children(self)
+    }
+    fn visit_ty_array(&mut self, value: &'a TyArray) {
+        value.children(self)
+    }
+    fn visit_ty_slice(&mut self, value: &'a TySlice) {
+        value.children(self)
+    }
+    fn visit_ty_tuple(&mut self, value: &'a TyTuple) {
+        value.children(self)
+    }
+    fn visit_ty_ref(&mut self, value: &'a TyRef) {
+        value.children(self)
+    }
+    fn visit_ty_ptr(&mut self, value: &'a TyPtr) {
+        value.children(self)
+    }
+    fn visit_ty_fn(&mut self, value: &'a TyFn) {
+        value.children(self)
+    }
+    fn visit_path(&mut self, value: &'a Path) {
+        value.children(self)
+    }
+    fn visit_path_part(&mut self, value: &'a PathPart) {
+        value.children(self)
+    }
+    fn visit_stmt(&mut self, value: &'a Stmt) {
+        value.children(self)
+    }
+    fn visit_stmt_kind(&mut self, value: &'a StmtKind) {
+        value.children(self)
+    }
+    fn visit_semi(&mut self, value: &'a Semi) {
+        value.children(self)
+    }
+    fn visit_expr(&mut self, value: &'a Expr) {
+        value.children(self)
+    }
+    fn visit_expr_kind(&mut self, value: &'a ExprKind) {
+        value.children(self)
+    }
+    fn visit_closure(&mut self, value: &'a Closure) {
+        value.children(self)
+    }
+    fn visit_quote(&mut self, value: &'a Quote) {
+        value.children(self)
+    }
+    fn visit_let(&mut self, value: &'a Let) {
+        value.children(self)
+    }
+
+    fn visit_pattern(&mut self, value: &'a Pattern) {
+        value.children(self)
+    }
+
+    fn visit_match(&mut self, value: &'a Match) {
+        value.children(self)
+    }
+
+    fn visit_match_arm(&mut self, value: &'a MatchArm) {
+        value.children(self)
+    }
+
+    fn visit_assign(&mut self, value: &'a Assign) {
+        value.children(self)
+    }
+    fn visit_modify(&mut self, value: &'a Modify) {
+        value.children(self)
+    }
+    fn visit_modify_kind(&mut self, value: &'a ModifyKind) {
+        value.children(self)
+    }
+    fn visit_binary(&mut self, value: &'a Binary) {
+        value.children(self)
+    }
+    fn visit_binary_kind(&mut self, value: &'a BinaryKind) {
+        value.children(self)
+    }
+    fn visit_unary(&mut self, value: &'a Unary) {
+        value.children(self)
+    }
+    fn visit_unary_kind(&mut self, value: &'a UnaryKind) {
+        value.children(self)
+    }
+
+    fn visit_cast(&mut self, value: &'a Cast) {
+        value.children(self)
+    }
+    fn visit_member(&mut self, value: &'a Member) {
+        value.children(self)
+    }
+    fn visit_member_kind(&mut self, value: &'a MemberKind) {
+        value.children(self)
+    }
+    fn visit_index(&mut self, value: &'a Index) {
+        value.children(self)
+    }
+    fn visit_structor(&mut self, value: &'a Structor) {
+        value.children(self)
+    }
+    fn visit_fielder(&mut self, value: &'a Fielder) {
+        value.children(self)
+    }
+    fn visit_array(&mut self, value: &'a Array) {
+        value.children(self)
+    }
+    fn visit_array_rep(&mut self, value: &'a ArrayRep) {
+        value.children(self)
+    }
+    fn visit_addrof(&mut self, value: &'a AddrOf) {
+        value.children(self)
+    }
+    fn visit_block(&mut self, value: &'a Block) {
+        value.children(self)
+    }
+    fn visit_group(&mut self, value: &'a Group) {
+        value.children(self)
+    }
+    fn visit_tuple(&mut self, value: &'a Tuple) {
+        value.children(self)
+    }
+    fn visit_while(&mut self, value: &'a While) {
+        value.children(self)
+    }
+    fn visit_if(&mut self, value: &'a If) {
+        value.children(self)
+    }
+    fn visit_for(&mut self, value: &'a For) {
+        value.children(self)
+    }
+    fn visit_else(&mut self, value: &'a Else) {
+        value.children(self)
+    }
+    fn visit_break(&mut self, value: &'a Break) {
+        value.children(self)
+    }
+    fn visit_return(&mut self, value: &'a Return) {
+        value.children(self)
+    }
+    fn visit_continue(&mut self) {}
+}

compiler/cl-ast/src/ast_visitor/walk.rs

@@ -0,0 +1,963 @@
+//! Accepts an AST Visitor. Walks the AST, calling the visitor on each step.
+
+use super::visit::Visit;
+use crate::ast::*;
+use cl_structures::span::Span;
+
+/// Helps a [Visitor](Visit) walk through `Self`.
+pub trait Walk {
+    /// Calls the respective `visit_*` function in V
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V);
+
+    #[allow(unused)]
+    /// Walks the children of self, visiting them in V
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {}
+}
+
+impl Walk for Span {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_span(self);
+    }
+}
+impl Walk for Sym {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_sym(self);
+    }
+}
+impl Walk for Mutability {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_mutability(self);
+    }
+}
+impl Walk for Visibility {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_visibility(self);
+    }
+}
+impl Walk for bool {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_bool(self);
+    }
+}
+impl Walk for char {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_char(self);
+    }
+}
+impl Walk for u128 {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_int(self);
+    }
+}
+impl Walk for u64 {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_smuggled_float(self);
+    }
+}
+impl Walk for str {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_string(self);
+    }
+}
+impl Walk for Literal {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_literal(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            Literal::Bool(value) => value.children(v),
+            Literal::Char(value) => value.children(v),
+            Literal::Int(value) => value.children(v),
+            Literal::Float(value) => value.children(v),
+            Literal::String(value) => value.children(v),
+        };
+    }
+}
+impl Walk for File {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_file(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let File { name: _, items } = self;
+        items.iter().for_each(|i| v.visit_item(i));
+    }
+}
+impl Walk for Attrs {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_attrs(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Attrs { meta } = self;
+        meta.children(v);
+    }
+}
+impl Walk for Meta {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_meta(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Meta { name, kind } = self;
+        name.visit_in(v);
+        kind.visit_in(v);
+    }
+}
+impl Walk for MetaKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_meta_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            MetaKind::Plain => {}
+            MetaKind::Equals(lit) => lit.visit_in(v),
+            MetaKind::Func(lits) => lits.visit_in(v),
+        }
+    }
+}
+impl Walk for Item {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_item(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Item { span, attrs, vis, kind } = self;
+        span.visit_in(v);
+        attrs.visit_in(v);
+        vis.visit_in(v);
+        kind.visit_in(v);
+    }
+}
+impl Walk for ItemKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_item_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            ItemKind::Module(value) => value.visit_in(v),
+            ItemKind::Alias(value) => value.visit_in(v),
+            ItemKind::Enum(value) => value.visit_in(v),
+            ItemKind::Struct(value) => value.visit_in(v),
+            ItemKind::Const(value) => value.visit_in(v),
+            ItemKind::Static(value) => value.visit_in(v),
+            ItemKind::Function(value) => value.visit_in(v),
+            ItemKind::Impl(value) => value.visit_in(v),
+            ItemKind::Use(value) => value.visit_in(v),
+        }
+    }
+}
+impl Walk for Generics {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_generics(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Self { vars } = self;
+        vars.visit_in(v);
+    }
+}
+impl Walk for Module {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_module(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Module { name, file } = self;
+        name.visit_in(v);
+        file.visit_in(v);
+    }
+}
+impl Walk for Alias {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_alias(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Alias { name, from } = self;
+        name.visit_in(v);
+        from.visit_in(v);
+    }
+}
+impl Walk for Const {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_const(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Const { name, ty, init } = self;
+        name.visit_in(v);
+        ty.visit_in(v);
+        init.visit_in(v);
+    }
+}
+impl Walk for Static {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_static(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Static { mutable, name, ty, init } = self;
+        mutable.visit_in(v);
+        name.visit_in(v);
+        ty.visit_in(v);
+        init.visit_in(v);
+    }
+}
+impl Walk for Function {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_function(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Function { name, gens, sign, bind, body } = self;
+        name.visit_in(v);
+        gens.visit_in(v);
+        sign.visit_in(v);
+        bind.visit_in(v);
+        body.visit_in(v);
+    }
+}
+impl Walk for Struct {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_struct(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Struct { name, gens, kind } = self;
+        name.visit_in(v);
+        gens.visit_in(v);
+        kind.visit_in(v);
+    }
+}
+impl Walk for StructKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_struct_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            StructKind::Empty => {}
+            StructKind::Tuple(tys) => tys.visit_in(v),
+            StructKind::Struct(ms) => ms.visit_in(v),
+        }
+    }
+}
+impl Walk for StructMember {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_struct_member(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let StructMember { vis, name, ty } = self;
+        vis.visit_in(v);
+        name.visit_in(v);
+        ty.visit_in(v);
+    }
+}
+impl Walk for Enum {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_enum(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Enum { name, gens, variants } = self;
+        name.visit_in(v);
+        gens.visit_in(v);
+        variants.visit_in(v);
+    }
+}
+impl Walk for Variant {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_variant(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Variant { name, kind, body } = self;
+        name.visit_in(v);
+        kind.visit_in(v);
+        body.visit_in(v);
+    }
+}
+impl Walk for Impl {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_impl(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Impl { gens, target, body } = self;
+        gens.visit_in(v);
+        target.visit_in(v);
+        body.visit_in(v);
+    }
+}
+impl Walk for ImplKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_impl_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            ImplKind::Type(t) => t.visit_in(v),
+            ImplKind::Trait { impl_trait, for_type } => {
+                impl_trait.visit_in(v);
+                for_type.visit_in(v);
+            }
+        }
+    }
+}
+impl Walk for Use {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_use(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Use { absolute: _, tree } = self;
+        tree.visit_in(v);
+    }
+}
+impl Walk for UseTree {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_use_tree(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            UseTree::Tree(tree) => tree.iter().for_each(|t| t.visit_in(v)),
+            UseTree::Path(part, tree) => {
+                part.visit_in(v);
+                tree.visit_in(v);
+            }
+            UseTree::Alias(from, to) => {
+                from.visit_in(v);
+                to.visit_in(v);
+            }
+            UseTree::Name(name) => name.visit_in(v),
+            UseTree::Glob => {}
+        }
+    }
+}
+impl Walk for Ty {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Ty { span, kind, gens } = self;
+        span.visit_in(v);
+        kind.visit_in(v);
+        gens.visit_in(v);
+    }
+}
+impl Walk for TyKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            TyKind::Never => {}
+            TyKind::Infer => {}
+            TyKind::Path(value) => value.visit_in(v),
+            TyKind::Array(value) => value.visit_in(v),
+            TyKind::Slice(value) => value.visit_in(v),
+            TyKind::Tuple(value) => value.visit_in(v),
+            TyKind::Ref(value) => value.visit_in(v),
+            TyKind::Ptr(value) => value.visit_in(v),
+            TyKind::Fn(value) => value.visit_in(v),
+        }
+    }
+}
+impl Walk for TyArray {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_array(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TyArray { ty, count: _ } = self;
+        ty.visit_in(v);
+        // count.walk(v); // not available
+    }
+}
+impl Walk for TySlice {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_slice(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TySlice { ty } = self;
+        ty.visit_in(v);
+    }
+}
+impl Walk for TyTuple {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_tuple(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TyTuple { types } = self;
+        types.visit_in(v);
+    }
+}
+impl Walk for TyRef {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_ref(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TyRef { mutable, count: _, to } = self;
+        mutable.children(v);
+        to.children(v);
+    }
+}
+impl Walk for TyPtr {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_ptr(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TyPtr { to } = self;
+        to.children(v);
+    }
+}
+impl Walk for TyFn {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_ty_fn(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let TyFn { args, rety } = self;
+        args.visit_in(v);
+        rety.visit_in(v);
+    }
+}
+impl Walk for Path {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_path(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Path { absolute: _, parts } = self;
+        parts.visit_in(v);
+    }
+}
+impl Walk for PathPart {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_path_part(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            PathPart::SuperKw => {}
+            PathPart::SelfTy => {}
+            PathPart::Ident(sym) => sym.visit_in(v),
+        }
+    }
+}
+impl Walk for Stmt {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_stmt(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Stmt { span, kind, semi } = self;
+        span.visit_in(v);
+        kind.visit_in(v);
+        semi.visit_in(v);
+    }
+}
+impl Walk for StmtKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_stmt_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            StmtKind::Empty => {}
+            StmtKind::Item(value) => value.visit_in(v),
+            StmtKind::Expr(value) => value.visit_in(v),
+        }
+    }
+}
+impl Walk for Semi {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_semi(self);
+    }
+}
+impl Walk for Expr {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_expr(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Expr { span, kind } = self;
+        span.visit_in(v);
+        kind.visit_in(v);
+    }
+}
+impl Walk for ExprKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_expr_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            ExprKind::Empty => {}
+            ExprKind::Closure(value) => value.visit_in(v),
+            ExprKind::Tuple(value) => value.visit_in(v),
+            ExprKind::Structor(value) => value.visit_in(v),
+            ExprKind::Array(value) => value.visit_in(v),
+            ExprKind::ArrayRep(value) => value.visit_in(v),
+            ExprKind::AddrOf(value) => value.visit_in(v),
+            ExprKind::Quote(value) => value.visit_in(v),
+            ExprKind::Literal(value) => value.visit_in(v),
+            ExprKind::Group(value) => value.visit_in(v),
+            ExprKind::Block(value) => value.visit_in(v),
+            ExprKind::Assign(value) => value.visit_in(v),
+            ExprKind::Modify(value) => value.visit_in(v),
+            ExprKind::Binary(value) => value.visit_in(v),
+            ExprKind::Unary(value) => value.visit_in(v),
+            ExprKind::Member(value) => value.visit_in(v),
+            ExprKind::Index(value) => value.visit_in(v),
+            ExprKind::Cast(value) => value.visit_in(v),
+            ExprKind::Path(value) => value.visit_in(v),
+            ExprKind::Let(value) => value.visit_in(v),
+            ExprKind::Match(value) => value.visit_in(v),
+            ExprKind::While(value) => value.visit_in(v),
+            ExprKind::If(value) => value.visit_in(v),
+            ExprKind::For(value) => value.visit_in(v),
+            ExprKind::Break(value) => value.visit_in(v),
+            ExprKind::Return(value) => value.visit_in(v),
+            ExprKind::Continue => v.visit_continue(),
+        }
+    }
+}
+
+impl Walk for Closure {
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_closure(self);
+    }
+
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Self { arg, body } = self;
+        v.visit_pattern(arg);
+        v.visit_expr(body);
+    }
+}
+
+impl Walk for Tuple {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_tuple(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Tuple { exprs } = self;
+        exprs.visit_in(v);
+    }
+}
+impl Walk for Structor {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_structor(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Structor { to, init } = self;
+        to.visit_in(v);
+        init.visit_in(v);
+    }
+}
+impl Walk for Fielder {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_fielder(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Fielder { name, init } = self;
+        name.visit_in(v);
+        init.visit_in(v);
+    }
+}
+impl Walk for Array {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_array(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Array { values } = self;
+        values.visit_in(v);
+    }
+}
+impl Walk for ArrayRep {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_array_rep(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let ArrayRep { value, repeat: _ } = self;
+        value.visit_in(v);
+        // repeat.visit_in(v) // TODO
+    }
+}
+impl Walk for AddrOf {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_addrof(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let AddrOf { mutable, expr } = self;
+        mutable.visit_in(v);
+        expr.visit_in(v);
+    }
+}
+impl Walk for Cast {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_cast(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Cast { head, ty } = self;
+        head.visit_in(v);
+        ty.visit_in(v);
+    }
+}
+impl Walk for Quote {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_quote(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Quote { quote } = self;
+        quote.visit_in(v);
+    }
+}
+impl Walk for Group {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_group(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Group { expr } = self;
+        expr.visit_in(v);
+    }
+}
+impl Walk for Block {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_block(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Block { stmts } = self;
+        stmts.visit_in(v);
+    }
+}
+impl Walk for Assign {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_assign(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Assign { parts } = self;
+        parts.visit_in(v);
+    }
+}
+impl Walk for Modify {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_modify(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Modify { kind, parts } = self;
+        kind.visit_in(v);
+        parts.visit_in(v);
+    }
+}
+impl Walk for ModifyKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_modify_kind(self);
+    }
+}
+impl Walk for Binary {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_binary(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Binary { kind, parts } = self;
+        kind.visit_in(v);
+        parts.visit_in(v);
+    }
+}
+impl Walk for BinaryKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_binary_kind(self);
+    }
+}
+impl Walk for Unary {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_unary(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Unary { kind, tail } = self;
+        kind.visit_in(v);
+        tail.visit_in(v);
+    }
+}
+impl Walk for UnaryKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_unary_kind(self);
+    }
+}
+impl Walk for Member {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_member(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Member { head, kind } = self;
+        head.visit_in(v);
+        kind.visit_in(v);
+    }
+}
+impl Walk for MemberKind {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_member_kind(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            MemberKind::Call(sym, tuple) => {
+                sym.visit_in(v);
+                tuple.visit_in(v);
+            }
+            MemberKind::Struct(sym) => sym.visit_in(v),
+            MemberKind::Tuple(literal) => literal.visit_in(v),
+        }
+    }
+}
+impl Walk for Index {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_index(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Index { head, indices } = self;
+        head.visit_in(v);
+        indices.visit_in(v);
+    }
+}
+impl Walk for Let {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_let(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Let { mutable, name, ty, init } = self;
+        mutable.visit_in(v);
+        name.visit_in(v);
+        ty.visit_in(v);
+        init.visit_in(v);
+    }
+}
+impl Walk for Match {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_match(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Match { scrutinee, arms } = self;
+        scrutinee.visit_in(v);
+        arms.visit_in(v);
+    }
+}
+impl Walk for MatchArm {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_match_arm(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let MatchArm(pat, expr) = self;
+        pat.visit_in(v);
+        expr.visit_in(v);
+    }
+}
+impl Walk for Pattern {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_pattern(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        match self {
+            Pattern::Name(sym) => sym.visit_in(v),
+            Pattern::Path(path) => path.visit_in(v),
+            Pattern::Literal(literal) => literal.visit_in(v),
+            Pattern::Rest(pattern) => pattern.visit_in(v),
+            Pattern::Ref(mutability, pattern) => {
+                mutability.visit_in(v);
+                pattern.visit_in(v);
+            }
+            Pattern::RangeExc(from, to) => {
+                from.visit_in(v);
+                to.visit_in(v);
+            }
+            Pattern::RangeInc(from, to) => {
+                from.visit_in(v);
+                to.visit_in(v);
+            }
+            Pattern::Tuple(patterns) => patterns.visit_in(v),
+            Pattern::Array(patterns) => patterns.visit_in(v),
+            Pattern::Struct(path, items) => {
+                path.visit_in(v);
+                items.visit_in(v);
+            }
+            Pattern::TupleStruct(path, patterns) => {
+                path.visit_in(v);
+                patterns.visit_in(v);
+            }
+        }
+    }
+}
+impl Walk for While {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_while(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let While { cond, pass, fail } = self;
+        cond.visit_in(v);
+        pass.visit_in(v);
+        fail.visit_in(v);
+    }
+}
+impl Walk for If {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_if(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let If { cond, pass, fail } = self;
+        cond.visit_in(v);
+        pass.visit_in(v);
+        fail.visit_in(v);
+    }
+}
+impl Walk for For {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_for(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let For { bind, cond, pass, fail } = self;
+        cond.visit_in(v);
+        fail.visit_in(v);
+        bind.visit_in(v);
+        pass.visit_in(v);
+    }
+}
+impl Walk for Else {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_else(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Else { body } = self;
+        body.visit_in(v);
+    }
+}
+impl Walk for Break {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_break(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Break { body } = self;
+        body.visit_in(v);
+    }
+}
+impl Walk for Return {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        v.visit_return(self);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let Return { body } = self;
+        body.visit_in(v);
+    }
+}
+
+// --- BLANKET IMPLEMENTATIONS
+
+impl<T: Walk> Walk for [T] {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.iter().for_each(|value| value.visit_in(v));
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.iter().for_each(|value| value.children(v));
+    }
+}
+
+impl<T: Walk> Walk for Vec<T> {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.as_slice().visit_in(v);
+    }
+
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.as_slice().children(v);
+    }
+}
+
+impl<A: Walk, B: Walk> Walk for (A, B) {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let (a, b) = self;
+        a.visit_in(v);
+        b.visit_in(v);
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        let (a, b) = self;
+        a.children(v);
+        b.children(v);
+    }
+}
+
+impl<T: Walk> Walk for Option<T> {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        if let Some(value) = self.as_ref() {
+            value.visit_in(v)
+        }
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        if let Some(value) = self {
+            value.children(v)
+        }
+    }
+}
+
+impl<T: Walk> Walk for Box<T> {
+    #[inline]
+    fn visit_in<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.as_ref().visit_in(v)
+    }
+    fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
+        self.as_ref().children(v)
+    }
+}

compiler/cl-ast/src/desugar.rs

@@ -0,0 +1,11 @@
+//! Desugaring passes for Conlang
+
+pub mod constant_folder;
+pub mod path_absoluter;
+pub mod squash_groups;
+pub mod while_else;
+
+pub use constant_folder::ConstantFolder;
+pub use path_absoluter::NormalizePaths;
+pub use squash_groups::SquashGroups;
+pub use while_else::WhileElseDesugar;

compiler/cl-ast/src/desugar/constant_folder.rs

@@ -0,0 +1,90 @@
+use crate::{
+    ast::{ExprKind as Ek, *},
+    ast_visitor::{Fold, fold::or_fold_expr_kind},
+};
+
+pub struct ConstantFolder;
+
+macro bin_rule(
+    match ($kind: ident, $head: expr, $tail: expr) {
+        $(($op:ident, $impl:expr, $($ty:ident -> $rety:ident),*)),*$(,)?
+    }
+) {
+    #[allow(clippy::all)]
+    match ($kind, $head, $tail) {
+    $($((   BinaryKind::$op,
+            Expr { kind: ExprKind::Literal(Literal::$ty(a)), .. },
+            Expr { kind: ExprKind::Literal(Literal::$ty(b)), .. },
+        ) => {
+            ExprKind::Literal(Literal::$rety($impl(a, b)))
+        },)*)*
+        (kind, head, tail) => ExprKind::Binary(Binary {
+            kind,
+            parts: Box::new((head, tail)),
+        }),
+    }
+}
+
+macro un_rule(
+    match ($kind: ident, $tail: expr) {
+        $(($op:ident, $impl:expr, $($ty:ident),*)),*$(,)?
+    }
+) {
+    match ($kind, $tail) {
+    $($((UnaryKind::$op, Expr { kind: ExprKind::Literal(Literal::$ty(v)), .. }) => {
+            ExprKind::Literal(Literal::$ty($impl(v)))
+        },)*)*
+        (kind, tail) => ExprKind::Unary(Unary { kind, tail: Box::new(tail) }),
+    }
+}
+
+impl Fold for ConstantFolder {
+    fn fold_expr_kind(&mut self, kind: Ek) -> Ek {
+        match kind {
+            Ek::Group(Group { expr }) => self.fold_expr_kind(expr.kind),
+            Ek::Binary(Binary { kind, parts }) => {
+                let (head, tail) = *parts;
+                bin_rule! (match (kind, self.fold_expr(head), self.fold_expr(tail)) {
+                    (Lt,     |a, b| a < b,  Bool -> Bool, Int -> Bool),
+                    (LtEq,   |a, b| a <= b, Bool -> Bool, Int -> Bool),
+                    (Equal,  |a, b| a == b, Bool -> Bool, Int -> Bool),
+                    (NotEq,  |a, b| a != b, Bool -> Bool, Int -> Bool),
+                    (GtEq,   |a, b| a >= b, Bool -> Bool, Int -> Bool),
+                    (Gt,     |a, b| a > b,  Bool -> Bool, Int -> Bool),
+                    (BitAnd, |a, b| a & b,  Bool -> Bool, Int -> Int),
+                    (BitOr,  |a, b| a | b,  Bool -> Bool, Int -> Int),
+                    (BitXor, |a, b| a ^ b,  Bool -> Bool, Int -> Int),
+                    (Shl,    |a, b| a << b, Int -> Int),
+                    (Shr,    |a, b| a >> b, Int -> Int),
+                    (Add,    |a, b| a + b,  Int -> Int),
+                    (Sub,    |a, b| a - b,  Int -> Int),
+                    (Mul,    |a, b| a * b,  Int -> Int),
+                    (Div,    |a, b| a / b,  Int -> Int),
+                    (Rem,    |a, b| a % b,  Int -> Int),
+                    // Cursed bit-smuggled float shenanigans
+                    (Lt,     |a, b| f64::from_bits(a) < f64::from_bits(b),  Float -> Bool),
+                    (LtEq,   |a, b| f64::from_bits(a) >= f64::from_bits(b), Float -> Bool),
+                    (Equal,  |a, b| f64::from_bits(a) == f64::from_bits(b), Float -> Bool),
+                    (NotEq,  |a, b| f64::from_bits(a) != f64::from_bits(b), Float -> Bool),
+                    (GtEq,   |a, b| f64::from_bits(a) <= f64::from_bits(b), Float -> Bool),
+                    (Gt,     |a, b| f64::from_bits(a) > f64::from_bits(b),  Float -> Bool),
+                    (Add,    |a, b| (f64::from_bits(a) + f64::from_bits(b)).to_bits(),  Float -> Float),
+                    (Sub,    |a, b| (f64::from_bits(a) - f64::from_bits(b)).to_bits(),  Float -> Float),
+                    (Mul,    |a, b| (f64::from_bits(a) * f64::from_bits(b)).to_bits(),  Float -> Float),
+                    (Div,    |a, b| (f64::from_bits(a) / f64::from_bits(b)).to_bits(),  Float -> Float),
+                    (Rem,    |a, b| (f64::from_bits(a) % f64::from_bits(b)).to_bits(),  Float -> Float),
+                })
+            }
+            Ek::Unary(Unary { kind, tail }) => {
+                un_rule! (match (kind, self.fold_expr(*tail)) {
+                    (Not, std::ops::Not::not, Int, Bool),
+                    (Neg, std::ops::Not::not, Bool),
+                    (Neg, |i| -(i as i128) as u128, Int),
+                    (Neg, |f| (-f64::from_bits(f)).to_bits(), Float),
+                    (At, std::ops::Not::not, Float), /* Lmao */
+                })
+            }
+            _ => or_fold_expr_kind(self, kind),
+        }
+    }
+}

compiler/cl-ast/src/desugar/path_absoluter.rs

@@ -0,0 +1,55 @@
+use crate::{ast::*, ast_visitor::Fold};
+
+/// Converts relative paths into absolute paths
+pub struct NormalizePaths {
+    path: Path,
+}
+
+impl NormalizePaths {
+    pub fn new() -> Self {
+        Self { path: Path { absolute: true, parts: vec![] } }
+    }
+    /// Normalizes paths as if they came from within the provided paths
+    pub fn in_path(path: Path) -> Self {
+        Self { path }
+    }
+}
+
+impl Default for NormalizePaths {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Fold for NormalizePaths {
+    fn fold_module(&mut self, m: Module) -> Module {
+        let Module { name, file } = m;
+        self.path.push(PathPart::Ident(name));
+
+        let name = self.fold_sym(name);
+        let file = file.map(|f| self.fold_file(f));
+
+        self.path.pop();
+        Module { name, file }
+    }
+
+    fn fold_path(&mut self, p: Path) -> Path {
+        if p.absolute {
+            p
+        } else {
+            self.path.clone().concat(&p)
+        }
+    }
+
+    fn fold_use(&mut self, u: Use) -> Use {
+        let Use { absolute, mut tree } = u;
+
+        if !absolute {
+            for segment in self.path.parts.iter().rev() {
+                tree = UseTree::Path(*segment, Box::new(tree))
+            }
+        }
+
+        Use { absolute: true, tree: self.fold_use_tree(tree) }
+    }
+}

compiler/cl-ast/src/desugar/squash_groups.rs

@@ -0,0 +1,14 @@
+//! Squashes group expressions
+use crate::{ast::*, ast_visitor::fold::*};
+
+/// Squashes group expressions
+pub struct SquashGroups;
+
+impl Fold for SquashGroups {
+    fn fold_expr_kind(&mut self, kind: ExprKind) -> ExprKind {
+        match kind {
+            ExprKind::Group(Group { expr }) => self.fold_expr(*expr).kind,
+            _ => or_fold_expr_kind(self, kind),
+        }
+    }
+}

compiler/cl-ast/src/desugar/while_else.rs

@@ -0,0 +1,37 @@
+//! Desugars `while {...} else` expressions
+//! into `loop if {...} else break` expressions
+
+use crate::{ast::*, ast_visitor::fold::Fold};
+use cl_structures::span::Span;
+
+/// Desugars while-else expressions
+/// into loop-if-else-break expressions
+pub struct WhileElseDesugar;
+
+impl Fold for WhileElseDesugar {
+    fn fold_expr(&mut self, e: Expr) -> Expr {
+        let Expr { span, kind } = e;
+        let kind = desugar_while(span, kind);
+        Expr { span: self.fold_span(span), kind: self.fold_expr_kind(kind) }
+    }
+}
+
+/// Desugars while(-else) expressions into loop-if-else-break expressions
+fn desugar_while(span: Span, kind: ExprKind) -> ExprKind {
+    match kind {
+        // work backwards: fail -> break -> if -> loop
+        ExprKind::While(While { cond, pass, fail: Else { body } }) => {
+            // Preserve the else-expression's span, if present, or use the parent's span
+            let fail_span = body.as_ref().map(|body| body.span).unwrap_or(span);
+            let break_expr = Expr { span: fail_span, kind: ExprKind::Break(Break { body }) };
+
+            let loop_body = If { cond, pass, fail: Else { body: Some(Box::new(break_expr)) } };
+            let loop_body = ExprKind::If(loop_body);
+            ExprKind::Unary(Unary {
+                kind: UnaryKind::Loop,
+                tail: Box::new(Expr { span, kind: loop_body }),
+            })
+        }
+        _ => kind,
+    }
+}

compiler/cl-ast/src/format.rs

@@ -0,0 +1,82 @@
+use delimiters::Delimiters;
+use std::fmt::Write;
+
+impl<W: Write + ?Sized> FmtAdapter for W {}
+pub trait FmtAdapter: Write {
+    fn indent(&mut self) -> Indent<'_, Self> {
+        Indent { f: self }
+    }
+
+    fn delimit(&mut self, delim: Delimiters) -> Delimit<'_, Self> {
+        Delimit::new(self, delim)
+    }
+
+    fn delimit_with(&mut self, open: &'static str, close: &'static str) -> Delimit<'_, Self> {
+        Delimit::new(self, Delimiters { open, close })
+    }
+}
+
+/// Pads text with leading indentation after every newline
+pub struct Indent<'f, F: Write + ?Sized> {
+    f: &'f mut F,
+}
+
+impl<F: Write + ?Sized> Write for Indent<'_, F> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        for s in s.split_inclusive('\n') {
+            self.f.write_str(s)?;
+            if s.ends_with('\n') {
+                self.f.write_str("    ")?;
+            }
+        }
+        Ok(())
+    }
+}
+
+/// Prints [Delimiters] around anything formatted with this. Implies [Indent]
+pub struct Delimit<'f, F: Write + ?Sized> {
+    f: Indent<'f, F>,
+    delim: Delimiters,
+}
+impl<'f, F: Write + ?Sized> Delimit<'f, F> {
+    pub fn new(f: &'f mut F, delim: Delimiters) -> Self {
+        let mut f = f.indent();
+        let _ = f.write_str(delim.open);
+        Self { f, delim }
+    }
+}
+impl<F: Write + ?Sized> Drop for Delimit<'_, F> {
+    fn drop(&mut self) {
+        let Self { f: Indent { f, .. }, delim } = self;
+        let _ = f.write_str(delim.close);
+    }
+}
+
+impl<F: Write + ?Sized> Write for Delimit<'_, F> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        self.f.write_str(s)
+    }
+}
+
+pub mod delimiters {
+    #![allow(dead_code)]
+    #[derive(Clone, Copy, Debug)]
+    pub struct Delimiters {
+        pub open: &'static str,
+        pub close: &'static str,
+    }
+    /// Delimits with braces decorated with spaces  `" {\n"`, ..., `"\n}"`
+    pub const SPACED_BRACES: Delimiters = Delimiters { open: " {\n", close: "\n}" };
+    /// Delimits with braces on separate lines `{\n`, ..., `\n}`
+    pub const BRACES: Delimiters = Delimiters { open: "{\n", close: "\n}" };
+    /// Delimits with parentheses on separate lines `{\n`, ..., `\n}`
+    pub const PARENS: Delimiters = Delimiters { open: "(\n", close: "\n)" };
+    /// Delimits with square brackets on separate lines `{\n`, ..., `\n}`
+    pub const SQUARE: Delimiters = Delimiters { open: "[\n", close: "\n]" };
+    /// Delimits with braces on the same line `{ `, ..., ` }`
+    pub const INLINE_BRACES: Delimiters = Delimiters { open: "{ ", close: " }" };
+    /// Delimits with parentheses on the same line `( `, ..., ` )`
+    pub const INLINE_PARENS: Delimiters = Delimiters { open: "(", close: ")" };
+    /// Delimits with square brackets on the same line `[ `, ..., ` ]`
+    pub const INLINE_SQUARE: Delimiters = Delimiters { open: "[", close: "]" };
+}

compiler/cl-ast/src/lib.rs

@@ -0,0 +1,23 @@
+//! # The Abstract Syntax Tree
+//! Contains definitions of Conlang AST Nodes.
+//!
+//! # Notable nodes
+//! - [Item] and [ItemKind]: Top-level constructs
+//! - [Stmt] and [StmtKind]: Statements
+//! - [Expr] and [ExprKind]: Expressions
+//!   - [Assign], [Binary], and [Unary] expressions
+//!   - [ModifyKind], [BinaryKind], and [UnaryKind] operators
+//! - [Ty] and [TyKind]: Type qualifiers
+//! - [Pattern]: Pattern matching operators
+//! - [Path]: Path expressions
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+
+pub use ast::*;
+pub use ast_impl::weight_of::WeightOf;
+
+pub mod ast;
+pub mod ast_impl;
+pub mod ast_visitor;
+pub mod desugar;
+pub mod format;

compiler/cl-embed/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "cl-embed"
+version = "0.1.0"
+repository.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-interpret = { path = "../cl-interpret" }
+cl-ast = { path = "../cl-ast" }
+cl-structures = { path = "../cl-structures" }
+cl-lexer = { path = "../cl-lexer" }
+cl-parser = { path = "../cl-parser" }
+
+[dev-dependencies]
+repline = { version = "*", registry = "soft-fish" }

compiler/cl-embed/examples/calculator.rs

@@ -0,0 +1,27 @@
+//! Demonstrates the cl_embed library
+
+use cl_embed::*;
+use repline::{Response, prebaked};
+
+fn main() -> Result<(), repline::Error> {
+    let mut env = Environment::new();
+
+    if let Err(e) = conlang_include!("calculator/expression.cl")(&mut env) {
+        panic!("{e}")
+    }
+
+    prebaked::read_and("", "calc >", "   ? >", |line| {
+        env.bind("line", line);
+
+        let res = conlang! {
+
+            let (expr, rest) = parse(line.chars(), Power::None);
+            execute(expr)
+
+        }(&mut env)?;
+
+        println!("{res}");
+
+        Ok(Response::Accept)
+    })
+}

compiler/cl-embed/examples/calculator/expression.cl

@@ -0,0 +1 @@
+../../../../sample-code/calculator.cl

compiler/cl-embed/src/lib.rs

@@ -0,0 +1,182 @@
+//! Embed Conlang code into your Rust project!
+//!
+//! # This crate is experimental, and has no guarantees of stability.
+#![feature(decl_macro)]
+#![cfg_attr(test, feature(assert_matches))]
+#![allow(unused_imports)]
+
+pub use cl_interpret::{convalue::ConValue as Value, env::Environment};
+
+use cl_ast::{Block, File, Module, ast_visitor::Fold};
+use cl_interpret::{convalue::ConValue, interpret::Interpret};
+use cl_lexer::Lexer;
+use cl_parser::{Parser, error::Error as ParseError, inliner::ModuleInliner};
+use std::{path::Path, sync::OnceLock};
+
+/// Constructs a function which evaluates a Conlang Block
+///
+/// # Examples
+///
+/// Bind and use a variable
+/// ```rust
+/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+/// use cl_embed::{conlang, Environment, Value};
+///
+/// let mut env = Environment::new();
+///
+/// // Bind a variable named `message` to "Hello, world!"
+/// env.bind("message", "Hello, World!");
+///
+/// let print_hello = conlang!{
+///     println(message);
+/// };
+///
+/// // Run the function
+/// let ret = print_hello(&mut env)?;
+///
+/// // `println` returns Empty
+/// assert!(matches!(ret, Value::Empty));
+///
+/// # Ok(())
+/// # }
+/// ```
+pub macro conlang(
+    $($t:tt)*
+) {{
+    // Parse once
+    static FN: OnceLock<Result<Block, ParseError>> = OnceLock::new();
+
+    |env: &mut Environment| -> Result<ConValue, EvalError> {
+        FN.get_or_init(|| {
+            // TODO: embed the full module tree at compile time
+            let path =
+                AsRef::<Path>::as_ref(&concat!(env!("CARGO_MANIFEST_DIR"), "/../../", file!()))
+                    .with_extension("");
+            let mut mi = ModuleInliner::new(path);
+            let code = mi.fold_block(
+                Parser::new(
+                    concat!(file!(), ":", line!(), ":", column!()),
+                    Lexer::new(stringify!({ $($t)* })),
+                )
+                .parse::<Block>()?,
+            );
+            if let Some((ie, pe)) = mi.into_errs() {
+                for (file, err) in ie {
+                    eprintln!("{}: {err}", file.display());
+                }
+                for (file, err) in pe {
+                    eprintln!("{}: {err}", file.display());
+                }
+            }
+            Ok(code)
+        })
+        .as_ref()
+        .map_err(Clone::clone)?
+        .interpret(env)
+        .map_err(Into::into)
+    }
+}}
+
+pub macro conlang_include{
+    ($path:literal, $name:ident) => {
+        |env: &mut Environment| -> Result<ConValue, EvalError> {
+            // TODO: embed the full module tree at compile time
+            let path = AsRef::<Path>::as_ref(&concat!(env!("CARGO_MANIFEST_DIR"), "/../../", file!()))
+                .with_file_name(concat!($path));
+            let mut mi = ModuleInliner::new(path);
+            let code = mi.fold_module(Module {
+                name: stringify!($name).into(),
+                file: Some(
+                    Parser::new(
+                        concat!(file!(), ":", line!(), ":", column!()),
+                        Lexer::new(include_str!($path)),
+                    )
+                    .parse()?,
+                ),
+            });
+            if let Some((ie, pe)) = mi.into_errs() {
+                for (file, err) in ie {
+                    eprintln!("{}: {err}", file.display());
+                }
+                for (file, err) in pe {
+                    eprintln!("{}: {err}", file.display());
+                }
+            }
+            code.interpret(env).map_err(Into::into)
+        }
+    },
+    ($path:literal) => {
+        |env: &mut Environment| -> Result<ConValue, EvalError> {
+            // TODO: embed the full module tree at compile time
+            let path = AsRef::<Path>::as_ref(&concat!(env!("CARGO_MANIFEST_DIR"), "/../../", file!()))
+                .with_file_name(concat!($path));
+            let mut mi = ModuleInliner::new(path);
+            let code = mi.fold_file(
+                Parser::new(
+                    concat!(file!(), ":", line!(), ":", column!()),
+                    Lexer::new(include_str!($path)),
+                )
+                .parse()?,
+            );
+            if let Some((ie, pe)) = mi.into_errs() {
+                for (file, err) in ie {
+                    eprintln!("{}: {err}", file.display());
+                }
+                for (file, err) in pe {
+                    eprintln!("{}: {err}", file.display());
+                }
+            }
+            code.interpret(env).map_err(Into::into)
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum EvalError {
+    Parse(cl_parser::error::Error),
+    Interpret(cl_interpret::error::Error),
+}
+
+impl From<cl_parser::error::Error> for EvalError {
+    fn from(value: cl_parser::error::Error) -> Self {
+        Self::Parse(value)
+    }
+}
+impl From<cl_interpret::error::Error> for EvalError {
+    fn from(value: cl_interpret::error::Error) -> Self {
+        Self::Interpret(value)
+    }
+}
+impl std::error::Error for EvalError {}
+impl std::fmt::Display for EvalError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            EvalError::Parse(error) => error.fmt(f),
+            EvalError::Interpret(error) => error.fmt(f),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::assert_matches::assert_matches;
+
+    use super::*;
+
+    #[test]
+    fn it_works() -> Result<(), EvalError> {
+        let mut env = Environment::new();
+
+        let result = conlang! {
+            fn add(left, right) -> isize {
+                left + right
+            }
+
+            add(2, 2)
+        }(&mut env);
+
+        assert_matches!(result, Ok(Value::Int(4)));
+
+        Ok(())
+    }
+}

compiler/cl-interpret/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "cl-interpret"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-ast = { path = "../cl-ast" }
+cl-structures = { path = "../cl-structures" }
+
+
+[dev-dependencies]
+cl-lexer = { path = "../cl-lexer" }
+cl-parser = { path = "../cl-parser" }

compiler/cl-interpret/examples/conlang-run.rs

@@ -0,0 +1,59 @@
+//! A bare-minimum harness to evaluate a Conlang program
+
+use std::{error::Error, path::PathBuf};
+
+use cl_ast::Expr;
+use cl_interpret::{convalue::ConValue, env::Environment};
+use cl_lexer::Lexer;
+use cl_parser::{Parser, inliner::ModuleInliner};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let mut args = std::env::args();
+
+    let prog = args.next().unwrap();
+    let Some(path) = args.next().map(PathBuf::from) else {
+        println!("Usage: {prog} `file.cl` [ args... ]");
+        return Ok(());
+    };
+
+    let parent = path.parent().unwrap_or("".as_ref());
+
+    let code = std::fs::read_to_string(&path)?;
+    let code = Parser::new(path.display().to_string(), Lexer::new(&code)).parse()?;
+    let code = match ModuleInliner::new(parent).inline(code) {
+        Ok(code) => code,
+        Err((code, ioerrs, perrs)) => {
+            for (p, err) in ioerrs {
+                eprintln!("{}:{err}", p.display());
+            }
+            for (p, err) in perrs {
+                eprintln!("{}:{err}", p.display());
+            }
+            code
+        }
+    };
+
+    let mut env = Environment::new();
+    env.eval(&code)?;
+
+    let main = "main".into();
+    if env.get(main).is_ok() {
+        let args = args
+            .flat_map(|arg| {
+                Parser::new(&arg, Lexer::new(&arg))
+                    .parse::<Expr>()
+                    .map(|arg| env.eval(&arg))
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+
+        match env.call(main, &args) {
+            Ok(ConValue::Empty) => {}
+            Ok(retval) => println!("{retval}"),
+            Err(e) => {
+                panic!("{e}");
+            }
+        }
+    }
+
+    Ok(())
+}

compiler/cl-interpret/examples/fib.rs

@@ -0,0 +1,12 @@
+// Calculate Fibonacci numbers
+
+fn main() {
+    for num in 0..=30 {
+        println!("fib({num}) = {}", fib(num))
+    }
+}
+
+/// Implements the classic recursive definition of fib()
+fn fib(a: i64) -> i64 {
+    if a > 1 { fib(a - 1) + fib(a - 2) } else { a }
+}

compiler/cl-interpret/src/builtin.rs

@@ -0,0 +1,410 @@
+#![allow(non_upper_case_globals)]
+
+use crate::{
+    convalue::ConValue,
+    env::Environment,
+    error::{Error, IResult},
+};
+use std::io::{Write, stdout};
+
+/// A function built into the interpreter.
+#[derive(Clone, Copy)]
+pub struct Builtin {
+    /// An identifier to be used during registration
+    pub name: &'static str,
+    /// The signature, displayed when the builtin is printed
+    pub desc: &'static str,
+    /// The function to be run when called
+    pub func: &'static dyn Fn(&mut Environment, &[ConValue]) -> IResult<ConValue>,
+}
+
+impl Builtin {
+    /// Constructs a new Builtin
+    pub const fn new(
+        name: &'static str,
+        desc: &'static str,
+        func: &'static impl Fn(&mut Environment, &[ConValue]) -> IResult<ConValue>,
+    ) -> Builtin {
+        Builtin { name, desc, func }
+    }
+
+    pub const fn description(&self) -> &'static str {
+        self.desc
+    }
+}
+
+impl std::fmt::Debug for Builtin {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Builtin")
+            .field("description", &self.desc)
+            .finish_non_exhaustive()
+    }
+}
+
+impl std::fmt::Display for Builtin {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.desc)
+    }
+}
+
+impl super::Callable for Builtin {
+    fn call(&self, interpreter: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+        (self.func)(interpreter, args)
+    }
+
+    fn name(&self) -> cl_ast::Sym {
+        self.name.into()
+    }
+}
+
+/// Turns a function definition into a [Builtin].
+///
+/// ```rust
+/// # use cl_interpret::{builtin::builtin, convalue::ConValue};
+/// let my_builtin = builtin! {
+///     /// Use the `@env` suffix to bind the environment!
+///     /// (needed for recursive calls)
+///     fn my_builtin(ConValue::Bool(b), rest @ ..) @env {
+///         // This is all Rust code!
+///         eprintln!("my_builtin({b}, ..)");
+///         match rest {
+///             [] => Ok(ConValue::Empty),
+///             _ => my_builtin(env, rest), // Can be called as a normal function!
+///         }
+///     }
+/// };
+/// ```
+pub macro builtin(
+    $(#[$($meta:tt)*])*
+    fn $name:ident ($($arg:pat),*$(,)?) $(@$env:tt)? $body:block
+) {{
+    $(#[$($meta)*])*
+    fn $name(_env: &mut Environment, _args: &[ConValue]) -> IResult<ConValue> {
+        // Set up the builtin! environment
+        $(#[allow(unused)]let $env = _env;)?
+        // Allow for single argument `fn foo(args @ ..)` pattern
+        #[allow(clippy::redundant_at_rest_pattern, irrefutable_let_patterns)]
+        let [$($arg),*] = _args else {
+            Err($crate::error::Error::TypeError())?
+        };
+        $body.map(Into::into)
+    }
+    Builtin {
+        name: stringify!($name),
+        desc: stringify![builtin fn $name($($arg),*)],
+        func: &$name,
+    }
+}}
+
+/// Constructs an array of [Builtin]s from pseudo-function definitions
+pub macro builtins($(
+    $(#[$($meta:tt)*])*
+    fn $name:ident ($($args:tt)*) $(@$env:tt)? $body:block
+)*) {
+    [$(builtin!($(#[$($meta)*])* fn $name ($($args)*) $(@$env)? $body)),*]
+}
+
+/// Creates an [Error::BuiltinError] using interpolation of runtime expressions.
+/// See [std::format].
+pub macro error_format ($($t:tt)*) {
+    $crate::error::Error::BuiltinError(format!($($t)*))
+}
+
+pub const Builtins: &[Builtin] = &builtins![
+    /// Unstable variadic format function
+    fn fmt(args @ ..) {
+        use std::fmt::Write;
+        let mut out = String::new();
+        if let Err(e) = args.iter().try_for_each(|arg| write!(out, "{arg}")) {
+            eprintln!("{e}");
+        }
+        Ok(out)
+    }
+
+    /// Prints the arguments in-order, with no separators
+    fn print(args @ ..) {
+        let mut out = stdout().lock();
+        args.iter().try_for_each(|arg| write!(out, "{arg}") ).ok();
+        Ok(())
+    }
+
+    /// Prints the arguments in-order, followed by a newline
+    fn println(args @ ..) {
+        let mut out = stdout().lock();
+        args.iter().try_for_each(|arg| write!(out, "{arg}") ).ok();
+        writeln!(out).ok();
+        Ok(())
+    }
+
+    /// Debug-prints the argument, returning a copy
+    fn dbg(arg) {
+        println!("{arg:?}");
+        Ok(arg.clone())
+    }
+
+    /// Debug-prints the argument
+    fn dbgp(args @ ..) {
+        let mut out = stdout().lock();
+        args.iter().try_for_each(|arg| writeln!(out, "{arg:#?}") ).ok();
+        Ok(())
+    }
+
+    fn panic(args @ ..) @env {
+        use std::fmt::Write;
+        let mut out = String::new();
+        if let Err(e) = args.iter().try_for_each(|arg| write!(out, "{arg}")) {
+            println!("{e}");
+        }
+        let mut stdout = stdout().lock();
+        write!(stdout, "Explicit panic: `").ok();
+        args.iter().try_for_each(|arg| write!(stdout, "{arg}") ).ok();
+        writeln!(stdout, "`").ok();
+        Err(Error::Panic(out))?;
+        Ok(())
+    }
+
+    /// Dumps the environment
+    fn dump() @env {
+        println!("{env}");
+        Ok(())
+    }
+
+    /// Gets all global variables in the environment
+    fn globals() @env {
+        let globals = env.globals();
+        Ok(ConValue::Slice(globals.base, globals.binds.len()))
+    }
+
+    fn builtins() @env {
+        let len = env.globals().binds.len();
+        for builtin in 0..len {
+            if let Some(value @ ConValue::Builtin(_)) = env.get_id(builtin) {
+                println!("{builtin}: {value}")
+            }
+        }
+        Ok(())
+    }
+
+    fn alloca(ConValue::Int(len)) @env {
+        Ok(env.alloca(ConValue::Empty, *len as usize))
+    }
+
+    /// Returns the length of the input list as a [ConValue::Int]
+    fn len(list) @env {
+        Ok(match list {
+            ConValue::Empty => 0,
+            ConValue::Str(s) => s.chars().count() as _,
+            ConValue::String(s) => s.chars().count() as _,
+            ConValue::Ref(r) => {
+                return len(env, &[env.get_id(*r).ok_or(Error::StackOverflow(*r))?.clone()])
+            }
+            ConValue::Slice(_, len) => *len as _,
+            ConValue::Array(arr) => arr.len() as _,
+            ConValue::Tuple(t) => t.len() as _,
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    fn push(ConValue::Ref(index), item) @env{
+        let Some(ConValue::Array(v)) = env.get_id_mut(*index) else {
+            Err(Error::TypeError())?
+        };
+
+        let mut items = std::mem::take(v).into_vec();
+        items.push(item.clone());
+        *v = items.into_boxed_slice();
+
+        Ok(ConValue::Empty)
+    }
+
+    fn chars(string) @env {
+        Ok(match string {
+            ConValue::Str(s) => ConValue::Array(s.chars().map(Into::into).collect()),
+            ConValue::String(s) => ConValue::Array(s.chars().map(Into::into).collect()),
+            ConValue::Ref(r) => {
+                return chars(env, &[env.get_id(*r).ok_or(Error::StackOverflow(*r))?.clone()])
+            }
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    fn dump_symbols() {
+        println!("{}", cl_structures::intern::string_interner::StringInterner::global());
+        Ok(ConValue::Empty)
+    }
+
+    fn slice_of(ConValue::Ref(arr), ConValue::Int(start)) {
+        Ok(ConValue::Slice(*arr, *start as usize))
+    }
+
+    /// Returns a shark
+    fn shark() {
+        Ok('\u{1f988}')
+    }
+];
+
+pub const Math: &[Builtin] = &builtins![
+    /// Multiplication `a * b`
+    fn mul(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a * b),
+            _ => Err(Error::TypeError())?
+        })
+    }
+
+    /// Division `a / b`
+    fn div(lhs, rhs) {
+        Ok(match (lhs, rhs){
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a / b),
+            _ => Err(Error::TypeError())?
+        })
+    }
+
+    /// Remainder `a % b`
+    fn rem(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a % b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Addition `a + b`
+    fn add(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a + b),
+            (ConValue::Str(a), ConValue::Str(b)) => (a.to_string() + b).into(),
+            (ConValue::Str(a), ConValue::String(b)) => (a.to_string() + b).into(),
+            (ConValue::String(a), ConValue::Str(b)) => (a.to_string() + b).into(),
+            (ConValue::String(a), ConValue::String(b)) => (a.to_string() + b).into(),
+            (ConValue::Str(s), ConValue::Char(c)) => { let mut s = s.to_string(); s.push(*c); s.into() }
+            (ConValue::String(s), ConValue::Char(c)) => { let mut s = s.to_string(); s.push(*c); s.into() }
+            (ConValue::Char(a), ConValue::Char(b)) => {
+                ConValue::String([a, b].into_iter().collect::<String>())
+            }
+            _ => Err(Error::TypeError())?
+        })
+    }
+
+    /// Subtraction `a - b`
+    fn sub(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a - b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Shift Left `a << b`
+    fn shl(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a << b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Shift Right `a >> b`
+    fn shr(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a >> b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Bitwise And `a & b`
+    fn and(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a & b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a & b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Bitwise Or `a | b`
+    fn or(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a | b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a | b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Bitwise Exclusive Or `a ^ b`
+    fn xor(lhs, rhs) {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a ^ b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a ^ b),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    #[allow(non_snake_case)]
+    fn RangeExc(start, end) @env {
+        Ok(ConValue::TupleStruct("RangeExc".into(), Box::new(Box::new([start.clone(), end.clone()]))))
+    }
+
+    #[allow(non_snake_case)]
+    fn RangeInc(start, end) @env {
+        Ok(ConValue::TupleStruct("RangeInc".into(), Box::new(Box::new([start.clone(), end.clone()]))))
+    }
+
+    #[allow(non_snake_case)]
+    fn RangeTo(end) @env {
+        Ok(ConValue::TupleStruct("RangeTo".into(), Box::new(Box::new([end.clone()]))))
+    }
+
+    #[allow(non_snake_case)]
+    fn RangeToInc(end) @env {
+        Ok(ConValue::TupleStruct("RangeToInc".into(), Box::new(Box::new([end.clone()]))))
+    }
+
+    /// Negates the ConValue
+    fn neg(tail) {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(v.wrapping_neg()),
+            ConValue::Float(v) => ConValue::Float(-v),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Inverts the ConValue
+    fn not(tail) {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(!v),
+            ConValue::Bool(v) => ConValue::Bool(!v),
+            _ => Err(Error::TypeError())?,
+        })
+    }
+
+    /// Compares two values
+    fn cmp(head, tail) {
+        Ok(ConValue::Int(match (head, tail) {
+            (ConValue::Int(a), ConValue::Int(b)) => a.cmp(b) as _,
+            (ConValue::Bool(a), ConValue::Bool(b)) => a.cmp(b) as _,
+            (ConValue::Char(a), ConValue::Char(b)) => a.cmp(b) as _,
+            (ConValue::Str(a), ConValue::Str(b)) => a.cmp(b) as _,
+            (ConValue::Str(a), ConValue::String(b)) => a.to_ref().cmp(b.as_str()) as _,
+            (ConValue::String(a), ConValue::Str(b)) => a.as_str().cmp(b.to_ref()) as _,
+            (ConValue::String(a), ConValue::String(b)) => a.cmp(b) as _,
+            _ => Err(error_format!("Incomparable values: {head}, {tail}"))?
+        }))
+    }
+
+    /// Does the opposite of `&`
+    fn deref(tail) @env {
+        Ok(match tail {
+            ConValue::Ref(v) => env.get_id(*v).cloned().ok_or(Error::StackOverflow(*v))?,
+            _ => tail.clone(),
+        })
+    }
+];

compiler/cl-interpret/src/closure.rs

@@ -0,0 +1,68 @@
+use crate::{
+    Callable,
+    convalue::ConValue,
+    env::Environment,
+    error::{Error, ErrorKind, IResult},
+    function::collect_upvars::CollectUpvars,
+    interpret::Interpret,
+    pattern,
+};
+use cl_ast::{Sym, ast_visitor::Visit};
+use std::{collections::HashMap, fmt::Display};
+
+/// Represents an ad-hoc anonymous function
+/// which captures surrounding state by COPY
+#[derive(Clone, Debug)]
+pub struct Closure {
+    decl: cl_ast::Closure,
+    lift: HashMap<Sym, ConValue>,
+}
+
+impl Closure {
+    const NAME: &'static str = "{closure}";
+}
+
+impl Closure {
+    pub fn new(env: &mut Environment, decl: &cl_ast::Closure) -> Self {
+        let lift = CollectUpvars::new(env).visit(decl).finish_copied();
+        Self { decl: decl.clone(), lift }
+    }
+}
+
+impl Display for Closure {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { decl, lift: _ } = self;
+        write!(f, "{decl}")
+    }
+}
+
+impl Callable for Closure {
+    fn call(&self, env: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+        let Self { decl, lift } = self;
+        let mut env = env.frame(Self::NAME);
+
+        // place lifts in scope
+        for (name, value) in lift.clone() {
+            env.insert(name, value);
+        }
+
+        let mut env = env.frame("args");
+
+        for (name, value) in pattern::substitution(&env, &decl.arg, ConValue::Tuple(args.into()))? {
+            env.insert(name, value);
+        }
+
+        let res = decl.body.interpret(&mut env);
+        drop(env);
+
+        match res {
+            Err(Error { kind: ErrorKind::Return(value), .. }) => Ok(value),
+            Err(Error { kind: ErrorKind::Break(value), .. }) => Err(Error::BadBreak(value)),
+            other => other,
+        }
+    }
+
+    fn name(&self) -> cl_ast::Sym {
+        Self::NAME.into()
+    }
+}

compiler/cl-interpret/src/convalue.rs

@@ -0,0 +1,449 @@
+//! Values in the dynamically typed AST interpreter.
+//!
+//! The most permanent fix is a temporary one.
+use cl_ast::{Expr, Sym, format::FmtAdapter};
+
+use crate::{closure::Closure, constructor::Constructor};
+
+use super::{
+    Callable, Environment,
+    builtin::Builtin,
+    error::{Error, IResult},
+    function::Function,
+};
+use std::{collections::HashMap, ops::*, rc::Rc};
+
+/*
+A Value can be:
+- A Primitive (Empty, isize, etc.)
+- A Record (Array, Tuple, Struct)
+- A Variant (discriminant, Value) pair
+
+array [
+    10,     // 0
+    20,     // 1
+]
+
+tuple (
+    10,     // 0
+    20,     // 1
+)
+
+struct {
+    x: 10,  // x => 0
+    y: 20,  // y => 1
+}
+*/
+
+type Integer = isize;
+
+/// A Conlang value stores data in the interpreter
+#[derive(Clone, Debug, Default)]
+pub enum ConValue {
+    /// The empty/unit `()` type
+    #[default]
+    Empty,
+    /// An integer
+    Int(Integer),
+    /// A floating point number
+    Float(f64),
+    /// A boolean
+    Bool(bool),
+    /// A unicode character
+    Char(char),
+    /// A string literal
+    Str(Sym),
+    /// A dynamic string
+    String(String),
+    /// A reference
+    Ref(usize),
+    /// A reference to an array
+    Slice(usize, usize),
+    /// An Array
+    Array(Box<[ConValue]>),
+    /// A tuple
+    Tuple(Box<[ConValue]>),
+    // TODO: Instead of storing the identifier, store the index of the struct module
+    /// A value of a product type
+    Struct(Sym, Box<HashMap<Sym, ConValue>>),
+    /// A value of a product type with anonymous members
+    TupleStruct(Sym, Box<Box<[ConValue]>>),
+    /// An entire namespace
+    Module(Box<HashMap<Sym, ConValue>>),
+    /// A quoted expression
+    Quote(Rc<Expr>),
+    /// A callable thing
+    Function(Rc<Function>),
+    /// A tuple constructor
+    TupleConstructor(Constructor),
+    /// A closure, capturing by reference
+    Closure(Rc<Closure>),
+    /// A built-in function
+    Builtin(&'static Builtin),
+}
+
+impl ConValue {
+    /// Gets whether the current value is true or false
+    pub fn truthy(&self) -> IResult<bool> {
+        match self {
+            ConValue::Bool(v) => Ok(*v),
+            _ => Err(Error::TypeError())?,
+        }
+    }
+
+    pub fn typename(&self) -> &'static str {
+        match self {
+            ConValue::Empty => "Empty",
+            ConValue::Int(_) => "i64",
+            ConValue::Float(_) => "f64",
+            ConValue::Bool(_) => "bool",
+            ConValue::Char(_) => "char",
+            ConValue::Str(_) => "str",
+            ConValue::String(_) => "String",
+            ConValue::Ref(_) => "Ref",
+            ConValue::Slice(_, _) => "Slice",
+            ConValue::Array(_) => "Array",
+            ConValue::Tuple(_) => "Tuple",
+            ConValue::Struct(_, _) => "Struct",
+            ConValue::TupleStruct(_, _) => "TupleStruct",
+            ConValue::Module(_) => "",
+            ConValue::Quote(_) => "Quote",
+            ConValue::Function(_) => "Fn",
+            ConValue::TupleConstructor(_) => "Fn",
+            ConValue::Closure(_) => "Fn",
+            ConValue::Builtin(_) => "Fn",
+        }
+    }
+
+    #[allow(non_snake_case)]
+    pub fn TupleStruct(id: Sym, values: Box<[ConValue]>) -> Self {
+        Self::TupleStruct(id, Box::new(values))
+    }
+    #[allow(non_snake_case)]
+    pub fn Struct(id: Sym, values: HashMap<Sym, ConValue>) -> Self {
+        Self::Struct(id, Box::new(values))
+    }
+
+    pub fn index(&self, index: &Self, _env: &Environment) -> IResult<ConValue> {
+        let &Self::Int(index) = index else {
+            Err(Error::TypeError())?
+        };
+        match self {
+            ConValue::Str(string) => string
+                .chars()
+                .nth(index as _)
+                .map(ConValue::Char)
+                .ok_or(Error::OobIndex(index as usize, string.chars().count())),
+            ConValue::String(string) => string
+                .chars()
+                .nth(index as _)
+                .map(ConValue::Char)
+                .ok_or(Error::OobIndex(index as usize, string.chars().count())),
+            ConValue::Array(arr) => arr
+                .get(index as usize)
+                .cloned()
+                .ok_or(Error::OobIndex(index as usize, arr.len())),
+            &ConValue::Slice(id, len) => {
+                let index = if index < 0 {
+                    len.wrapping_add_signed(index)
+                } else {
+                    index as usize
+                };
+                if index < len {
+                    Ok(ConValue::Ref(id + index))
+                } else {
+                    Err(Error::OobIndex(index, len))
+                }
+            }
+            _ => Err(Error::TypeError()),
+        }
+    }
+    cmp! {
+        lt: false, <;
+        lt_eq: true, <=;
+        eq: true, ==;
+        neq: false, !=;
+        gt_eq: true, >=;
+        gt: false, >;
+    }
+    assign! {
+        add_assign: +;
+        bitand_assign: &;
+        bitor_assign: |;
+        bitxor_assign: ^;
+        div_assign: /;
+        mul_assign: *;
+        rem_assign: %;
+        shl_assign: <<;
+        shr_assign: >>;
+        sub_assign: -;
+    }
+}
+
+impl Callable for ConValue {
+    fn name(&self) -> Sym {
+        match self {
+            ConValue::Function(func) => func.name(),
+            ConValue::Closure(func) => func.name(),
+            ConValue::Builtin(func) => func.name(),
+            _ => "".into(),
+        }
+    }
+    fn call(&self, env: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+        match self {
+            Self::Function(func) => func.call(env, args),
+            Self::TupleConstructor(func) => func.call(env, args),
+            Self::Closure(func) => func.call(env, args),
+            Self::Builtin(func) => func.call(env, args),
+            Self::Module(m) => {
+                if let Some(func) = m.get(&"call".into()) {
+                    func.call(env, args)
+                } else {
+                    Err(Error::NotCallable(self.clone()))
+                }
+            }
+            &Self::Ref(ptr) => {
+                // Move onto stack, and call
+                let func = env.get_id(ptr).ok_or(Error::StackOverflow(ptr))?.clone();
+                func.call(env, args)
+            }
+            _ => Err(Error::NotCallable(self.clone())),
+        }
+    }
+}
+/// Templates comparison functions for [ConValue]
+macro cmp ($($fn:ident: $empty:literal, $op:tt);*$(;)?) {$(
+    /// TODO: Remove when functions are implemented:
+    ///       Desugar into function calls
+    pub fn $fn(&self, other: &Self) -> IResult<Self> {
+        match (self, other) {
+            (Self::Empty, Self::Empty) => Ok(Self::Bool($empty)),
+            (Self::Int(a), Self::Int(b)) => Ok(Self::Bool(a $op b)),
+            (Self::Float(a), Self::Float(b)) => Ok(Self::Bool(a $op b)),
+            (Self::Bool(a), Self::Bool(b)) => Ok(Self::Bool(a $op b)),
+            (Self::Char(a), Self::Char(b)) => Ok(Self::Bool(a $op b)),
+            (Self::Str(a), Self::Str(b)) => Ok(Self::Bool(&**a $op &**b)),
+            (Self::Str(a), Self::String(b)) => Ok(Self::Bool(&**a $op &**b)),
+            (Self::String(a), Self::Str(b)) => Ok(Self::Bool(&**a $op &**b)),
+            (Self::String(a), Self::String(b)) => Ok(Self::Bool(&**a $op &**b)),
+            _ => Err(Error::TypeError())
+        }
+    }
+)*}
+macro assign($( $fn: ident: $op: tt );*$(;)?) {$(
+    pub fn $fn(&mut self, other: Self) -> IResult<()> {
+        *self = (std::mem::take(self) $op other)?;
+        Ok(())
+    }
+)*}
+/// Implements [From] for an enum with 1-tuple variants
+macro from ($($T:ty => $v:expr),*$(,)?) {
+    $(impl From<$T> for ConValue {
+        fn from(value: $T) -> Self { $v(value.into()) }
+    })*
+}
+impl From<&Sym> for ConValue {
+    fn from(value: &Sym) -> Self {
+        ConValue::Str(*value)
+    }
+}
+from! {
+    Integer => ConValue::Int,
+    f64 => ConValue::Float,
+    bool => ConValue::Bool,
+    char => ConValue::Char,
+    Sym => ConValue::Str,
+    &str => ConValue::Str,
+    Expr => ConValue::Quote,
+    String => ConValue::String,
+    Rc<str> => ConValue::Str,
+    Function => ConValue::Function,
+    Vec<ConValue> => ConValue::Tuple,
+    &'static Builtin => ConValue::Builtin,
+}
+impl From<()> for ConValue {
+    fn from(_: ()) -> Self {
+        Self::Empty
+    }
+}
+impl From<&[ConValue]> for ConValue {
+    fn from(value: &[ConValue]) -> Self {
+        match value {
+            [] => Self::Empty,
+            [value] => value.clone(),
+            _ => Self::Tuple(value.into()),
+        }
+    }
+}
+
+/// Implements binary [std::ops] traits for [ConValue]
+///
+/// TODO: Desugar operators into function calls
+macro ops($($trait:ty: $fn:ident = [$($match:tt)*])*) {
+    $(impl $trait for ConValue {
+        type Output = IResult<Self>;
+        /// TODO: Desugar operators into function calls
+        fn $fn(self, rhs: Self) -> Self::Output {Ok(match (self, rhs) {$($match)*})}
+    })*
+}
+ops! {
+    Add: add = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_add(b)),
+        (ConValue::Float(a), ConValue::Float(b)) => ConValue::Float(a + b),
+        (ConValue::Str(a), ConValue::Str(b)) => (a.to_string() + &*b).into(),
+        (ConValue::Str(a), ConValue::String(b)) => (a.to_string() + &*b).into(),
+        (ConValue::String(a), ConValue::Str(b)) => (a.to_string() + &*b).into(),
+        (ConValue::String(a), ConValue::String(b)) => (a.to_string() + &*b).into(),
+        (ConValue::Str(s), ConValue::Char(c)) => { let mut s = s.to_string(); s.push(c); s.into() }
+        (ConValue::String(s), ConValue::Char(c)) => { let mut s = s.to_string(); s.push(c); s.into() }
+        (ConValue::Char(a), ConValue::Char(b)) => {
+            ConValue::String([a, b].into_iter().collect::<String>())
+        }
+        _ => Err(Error::TypeError())?
+        ]
+    BitAnd: bitand = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a & b),
+        (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a & b),
+        _ => Err(Error::TypeError())?
+    ]
+    BitOr: bitor = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a | b),
+        (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a | b),
+        _ => Err(Error::TypeError())?
+    ]
+    BitXor: bitxor = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a ^ b),
+        (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a ^ b),
+        _ => Err(Error::TypeError())?
+    ]
+    Div: div = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.checked_div(b).unwrap_or_else(|| {
+            eprintln!("Warning: Divide by zero in {a} / {b}"); a
+        })),
+        (ConValue::Float(a), ConValue::Float(b)) => ConValue::Float(a / b),
+        _ => Err(Error::TypeError())?
+    ]
+    Mul: mul = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_mul(b)),
+        (ConValue::Float(a), ConValue::Float(b)) => ConValue::Float(a * b),
+        _ => Err(Error::TypeError())?
+    ]
+    Rem: rem = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.checked_rem(b).unwrap_or_else(|| {
+            println!("Warning: Divide by zero in {a} % {b}"); a
+        })),
+        (ConValue::Float(a), ConValue::Float(b)) => ConValue::Float(a % b),
+        _ => Err(Error::TypeError())?
+    ]
+    Shl: shl = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_shl(b as _)),
+        _ => Err(Error::TypeError())?
+    ]
+    Shr: shr = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_shr(b as _)),
+        _ => Err(Error::TypeError())?
+    ]
+    Sub: sub = [
+        (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+        (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_sub(b)),
+        (ConValue::Float(a), ConValue::Float(b)) => ConValue::Float(a - b),
+        _ => Err(Error::TypeError())?
+    ]
+}
+impl std::fmt::Display for ConValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ConValue::Empty => "Empty".fmt(f),
+            ConValue::Int(v) => v.fmt(f),
+            ConValue::Float(v) => v.fmt(f),
+            ConValue::Bool(v) => v.fmt(f),
+            ConValue::Char(v) => v.fmt(f),
+            ConValue::Str(v) => v.fmt(f),
+            ConValue::String(v) => v.fmt(f),
+            ConValue::Ref(v) => write!(f, "&<{}>", v),
+            ConValue::Slice(id, len) => write!(f, "&<{id}>[{len}..]"),
+            ConValue::Array(array) => {
+                '['.fmt(f)?;
+                for (idx, element) in array.iter().enumerate() {
+                    if idx > 0 {
+                        ", ".fmt(f)?
+                    }
+                    element.fmt(f)?
+                }
+                ']'.fmt(f)
+            }
+            ConValue::Tuple(tuple) => {
+                '('.fmt(f)?;
+                for (idx, element) in tuple.iter().enumerate() {
+                    if idx > 0 {
+                        ", ".fmt(f)?
+                    }
+                    element.fmt(f)?
+                }
+                ')'.fmt(f)
+            }
+            ConValue::TupleStruct(id, tuple) => {
+                write!(f, "{id}")?;
+                '('.fmt(f)?;
+                for (idx, element) in tuple.iter().enumerate() {
+                    if idx > 0 {
+                        ", ".fmt(f)?
+                    }
+                    element.fmt(f)?
+                }
+                ')'.fmt(f)
+            }
+            ConValue::Struct(id, map) => {
+                use std::fmt::Write;
+                write!(f, "{id} ")?;
+                let mut f = f.delimit_with("{", "\n}");
+                for (k, v) in map.iter() {
+                    write!(f, "\n{k}: {v},")?;
+                }
+                Ok(())
+            }
+            ConValue::Module(module) => {
+                use std::fmt::Write;
+                let mut f = f.delimit_with("{", "\n}");
+                for (k, v) in module.iter() {
+                    write!(f, "\n{k}: {v},")?;
+                }
+                Ok(())
+            }
+            ConValue::Quote(q) => {
+                write!(f, "`{q}`")
+            }
+            ConValue::Function(func) => {
+                write!(f, "{}", func.decl())
+            }
+            ConValue::TupleConstructor(Constructor { name: index, arity }) => {
+                write!(f, "{index}(..{arity})")
+            }
+            ConValue::Closure(func) => {
+                write!(f, "{}", func.as_ref())
+            }
+            ConValue::Builtin(func) => {
+                write!(f, "{}", func)
+            }
+        }
+    }
+}
+
+pub macro cvstruct (
+    $Name:ident {
+        $($member:ident : $expr:expr),*
+    }
+) {{
+    let mut members = HashMap::new();
+    $(members.insert(stringify!($member).into(), ($expr).into());)*
+    ConValue::Struct(Box::new((stringify!($Name).into(), members)))
+}}

compiler/cl-interpret/src/env.rs

@@ -0,0 +1,310 @@
+//! Lexical and non-lexical scoping for variables
+
+use crate::{builtin::Builtin, constructor::Constructor, modules::ModuleTree};
+
+use super::{
+    Callable, Interpret,
+    builtin::{Builtins, Math},
+    convalue::ConValue,
+    error::{Error, IResult},
+    function::Function,
+};
+use cl_ast::{Function as FnDecl, Sym};
+use std::{
+    collections::HashMap,
+    fmt::Display,
+    ops::{Deref, DerefMut},
+    rc::Rc,
+};
+
+pub type StackFrame = HashMap<Sym, ConValue>;
+
+pub type StackBinds = HashMap<Sym, usize>;
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct EnvFrame {
+    pub name: Option<&'static str>,
+    /// The length of the array when this stack frame was constructed
+    pub base: usize,
+    /// The bindings of name to stack position
+    pub binds: StackBinds,
+}
+
+/// Implements a nested lexical scope
+#[derive(Clone, Debug)]
+pub struct Environment {
+    values: Vec<ConValue>,
+    frames: Vec<EnvFrame>,
+    modules: ModuleTree,
+}
+
+impl Display for Environment {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for EnvFrame { name, base: _, binds } in self.frames.iter().rev() {
+            writeln!(
+                f,
+                "--- {}[{}] ---",
+                if let Some(name) = name { name } else { "" },
+                binds.len(),
+            )?;
+            let mut binds: Vec<_> = binds.iter().collect();
+            binds.sort_by(|(_, a), (_, b)| a.cmp(b));
+            for (name, idx) in binds {
+                write!(f, "{idx:4} {name}: ")?;
+                match self.values.get(*idx) {
+                    Some(value) => writeln!(f, "\t{value}"),
+                    None => writeln!(f, "ERROR: {name}'s address blows the stack!"),
+                }?
+            }
+        }
+        Ok(())
+    }
+}
+
+impl Default for Environment {
+    fn default() -> Self {
+        let mut this = Self::no_builtins();
+        this.add_builtins(Builtins).add_builtins(Math);
+        this
+    }
+}
+
+impl Environment {
+    pub fn new() -> Self {
+        Self::default()
+    }
+    /// Creates an [Environment] with no [builtins](super::builtin)
+    pub fn no_builtins() -> Self {
+        Self {
+            values: Vec::new(),
+            frames: vec![EnvFrame::default()],
+            modules: ModuleTree::default(),
+        }
+    }
+
+    /// Reflexively evaluates a node
+    pub fn eval(&mut self, node: &impl Interpret) -> IResult<ConValue> {
+        node.interpret(self)
+    }
+
+    /// Calls a function inside the Environment's scope,
+    /// and returns the result
+    pub fn call(&mut self, name: Sym, args: &[ConValue]) -> IResult<ConValue> {
+        let function = self.get(name)?;
+        function.call(self, args)
+    }
+
+    pub fn modules_mut(&mut self) -> &mut ModuleTree {
+        &mut self.modules
+    }
+
+    pub fn modules(&self) -> &ModuleTree {
+        &self.modules
+    }
+
+    /// Binds a value to the given name in the current scope.
+    pub fn bind(&mut self, name: impl Into<Sym>, value: impl Into<ConValue>) {
+        self.insert(name.into(), value.into());
+    }
+
+    pub fn bind_raw(&mut self, name: Sym, id: usize) -> Option<()> {
+        let EnvFrame { name: _, base: _, binds } = self.frames.last_mut()?;
+        binds.insert(name, id);
+        Some(())
+    }
+
+    /// Gets all registered globals, bound or unbound.
+    pub(crate) fn globals(&self) -> &EnvFrame {
+        self.frames.first().unwrap()
+    }
+
+    /// Adds builtins
+    ///
+    /// # Panics
+    ///
+    /// Will panic if stack contains more than the globals frame!
+    pub fn add_builtins(&mut self, builtins: &'static [Builtin]) -> &mut Self {
+        if self.frames.len() != 1 {
+            panic!("Cannot add builtins to full stack: {self}")
+        }
+
+        for builtin in builtins {
+            self.insert(builtin.name(), builtin.into());
+        }
+
+        self
+    }
+
+    pub fn push_frame(&mut self, name: &'static str, frame: StackFrame) {
+        self.frames.push(EnvFrame {
+            name: Some(name),
+            base: self.values.len(),
+            binds: HashMap::new(),
+        });
+        for (k, v) in frame {
+            self.insert(k, v);
+        }
+    }
+
+    pub fn pop_frame(&mut self) -> Option<(StackFrame, &'static str)> {
+        let mut out = HashMap::new();
+        let EnvFrame { name, base, binds } = self.frames.pop()?;
+        for (k, v) in binds {
+            out.insert(k, self.values.get_mut(v).map(std::mem::take)?);
+        }
+        self.values.truncate(base);
+        Some((out, name.unwrap_or("")))
+    }
+
+    /// Enters a nested scope, returning a [`Frame`] stack-guard.
+    ///
+    /// [`Frame`] implements Deref/DerefMut for [`Environment`].
+    pub fn frame(&mut self, name: &'static str) -> Frame<'_> {
+        Frame::new(self, name)
+    }
+
+    /// Enters a nested scope, assigning the contents of `frame`,
+    /// and returning a [`Frame`] stack-guard.
+    ///
+    /// [`Frame`] implements Deref/DerefMut for [`Environment`].
+    pub fn with_frame<'e>(&'e mut self, name: &'static str, frame: StackFrame) -> Frame<'e> {
+        let mut scope = self.frame(name);
+        for (k, v) in frame {
+            scope.insert(k, v);
+        }
+        scope
+    }
+
+    /// Resolves a variable mutably.
+    ///
+    /// Returns a mutable reference to the variable's record, if it exists.
+    pub fn get_mut(&mut self, name: Sym) -> IResult<&mut ConValue> {
+        let at = self.id_of(name)?;
+        self.get_id_mut(at).ok_or(Error::NotDefined(name))
+    }
+
+    /// Resolves a variable immutably.
+    ///
+    /// Returns a reference to the variable's contents, if it is defined and initialized.
+    pub fn get(&self, name: Sym) -> IResult<ConValue> {
+        let id = self.id_of(name)?;
+        let res = self.values.get(id);
+        Ok(res.ok_or(Error::NotDefined(name))?.clone())
+    }
+
+    /// Resolves the index associated with a [Sym]
+    pub fn id_of(&self, name: Sym) -> IResult<usize> {
+        for EnvFrame { binds, .. } in self.frames.iter().rev() {
+            if let Some(id) = binds.get(&name).copied() {
+                return Ok(id);
+            }
+        }
+        Err(Error::NotDefined(name))
+    }
+
+    pub fn get_id(&self, id: usize) -> Option<&ConValue> {
+        self.values.get(id)
+    }
+
+    pub fn get_id_mut(&mut self, id: usize) -> Option<&mut ConValue> {
+        self.values.get_mut(id)
+    }
+
+    pub fn get_slice(&self, start: usize, len: usize) -> Option<&[ConValue]> {
+        self.values.get(start..start + len)
+    }
+
+    pub fn get_slice_mut(&mut self, start: usize, len: usize) -> Option<&mut [ConValue]> {
+        self.values.get_mut(start..start + len)
+    }
+
+    /// Inserts a new [ConValue] into this [Environment]
+    pub fn insert(&mut self, k: Sym, v: ConValue) {
+        if self.bind_raw(k, self.values.len()).is_some() {
+            self.values.push(v);
+        }
+    }
+
+    /// A convenience function for registering a [FnDecl] as a [Function]
+    pub fn insert_fn(&mut self, decl: &FnDecl) {
+        let FnDecl { name, .. } = decl;
+        let (name, function) = (*name, Rc::new(Function::new(decl)));
+        self.insert(name, ConValue::Function(function.clone()));
+        // Tell the function to lift its upvars now, after it's been declared
+        function.lift_upvars(self);
+    }
+
+    pub fn insert_tup_constructor(&mut self, name: Sym, arity: usize) {
+        let cs = Constructor { arity: arity as _, name };
+        self.insert(name, ConValue::TupleConstructor(cs));
+    }
+
+    /// Gets the current stack top position
+    pub fn pos(&self) -> usize {
+        self.values.len()
+    }
+
+    /// Allocates a local variable
+    pub fn stack_alloc(&mut self, value: ConValue) -> IResult<usize> {
+        let adr = self.values.len();
+        self.values.push(value);
+        Ok(adr)
+    }
+
+    /// Allocates some space on the stack
+    pub fn alloca(&mut self, value: ConValue, len: usize) -> ConValue {
+        let idx = self.values.len();
+        self.values.extend(std::iter::repeat_n(value, len));
+        ConValue::Slice(idx, len)
+    }
+}
+
+/// Represents a stack frame
+#[derive(Debug)]
+pub struct Frame<'scope> {
+    scope: &'scope mut Environment,
+}
+impl<'scope> Frame<'scope> {
+    fn new(scope: &'scope mut Environment, name: &'static str) -> Self {
+        scope.frames.push(EnvFrame {
+            name: Some(name),
+            base: scope.values.len(),
+            binds: HashMap::new(),
+        });
+
+        Self { scope }
+    }
+
+    pub fn pop_values(mut self) -> Option<StackFrame> {
+        let mut out = HashMap::new();
+        let binds = std::mem::take(&mut self.frames.last_mut()?.binds);
+        for (k, v) in binds {
+            out.insert(k, self.values.get_mut(v).map(std::mem::take)?);
+        }
+        Some(out)
+    }
+
+    pub fn into_binds(mut self) -> Option<StackBinds> {
+        let EnvFrame { name: _, base: _, binds } = self.frames.pop()?;
+        std::mem::forget(self);
+        Some(binds)
+    }
+}
+impl Deref for Frame<'_> {
+    type Target = Environment;
+    fn deref(&self) -> &Self::Target {
+        self.scope
+    }
+}
+impl DerefMut for Frame<'_> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.scope
+    }
+}
+impl Drop for Frame<'_> {
+    fn drop(&mut self) {
+        if let Some(frame) = self.frames.pop() {
+            self.values.truncate(frame.base);
+        }
+    }
+}

compiler/cl-interpret/src/error.rs

@@ -0,0 +1,218 @@
+//! The [Error] type represents any error thrown by the [Environment](super::Environment)
+
+use cl_ast::{Pattern, Sym};
+use cl_structures::span::Span;
+
+use super::convalue::ConValue;
+
+pub type IResult<T> = Result<T, Error>;
+
+#[derive(Clone, Debug)]
+pub struct Error {
+    pub kind: ErrorKind,
+    pub(super) span: Option<Span>,
+}
+
+impl Error {
+    #![allow(non_snake_case)]
+
+    /// Adds a [struct Span] to this [Error], if there isn't already a more specific one.
+    pub fn with_span(self, span: Span) -> Self {
+        Self { span: self.span.or(Some(span)), ..self }
+    }
+
+    pub fn kind(&self) -> &ErrorKind {
+        &self.kind
+    }
+
+    /// Propagate a Return value
+    pub fn Return(value: ConValue) -> Self {
+        Self { kind: ErrorKind::Return(value), span: None }
+    }
+    /// Propagate a Break value
+    pub fn Break(value: ConValue) -> Self {
+        Self { kind: ErrorKind::Break(value), span: None }
+    }
+    /// Break propagated across function bounds
+    pub fn BadBreak(value: ConValue) -> Self {
+        Self { kind: ErrorKind::BadBreak(value), span: None }
+    }
+    /// Continue to the next iteration of a loop
+    pub fn Continue() -> Self {
+        Self { kind: ErrorKind::Continue, span: None }
+    }
+    /// Underflowed the stack
+    pub fn StackUnderflow() -> Self {
+        Self { kind: ErrorKind::StackUnderflow, span: None }
+    }
+    /// Overflowed the stack
+    pub fn StackOverflow(place: usize) -> Self {
+        Self { kind: ErrorKind::StackOverflow(place), span: None }
+    }
+    /// Exited the last scope
+    pub fn ScopeExit() -> Self {
+        Self { kind: ErrorKind::ScopeExit, span: None }
+    }
+    /// Type incompatibility
+    // TODO: store the type information in this error
+    pub fn TypeError() -> Self {
+        Self { kind: ErrorKind::TypeError, span: None }
+    }
+    /// In clause of For loop didn't yield a Range
+    pub fn NotIterable() -> Self {
+        Self { kind: ErrorKind::NotIterable, span: None }
+    }
+    /// A value could not be indexed
+    pub fn NotIndexable() -> Self {
+        Self { kind: ErrorKind::NotIndexable, span: None }
+    }
+    /// An array index went out of bounds
+    pub fn OobIndex(index: usize, length: usize) -> Self {
+        Self { kind: ErrorKind::OobIndex(index, length), span: None }
+    }
+    /// An expression is not assignable
+    pub fn NotAssignable() -> Self {
+        Self { kind: ErrorKind::NotAssignable, span: None }
+    }
+    /// A name was not defined in scope before being used
+    pub fn NotDefined(name: Sym) -> Self {
+        Self { kind: ErrorKind::NotDefined(name), span: None }
+    }
+    /// A name was defined but not initialized
+    pub fn NotInitialized(name: Sym) -> Self {
+        Self { kind: ErrorKind::NotInitialized(name), span: None }
+    }
+    /// A value was called, but is not callable
+    pub fn NotCallable(value: ConValue) -> Self {
+        Self { kind: ErrorKind::NotCallable(value), span: None }
+    }
+    /// A function was called with the wrong number of arguments
+    pub fn ArgNumber(want: usize, got: usize) -> Self {
+        Self { kind: ErrorKind::ArgNumber { want, got }, span: None }
+    }
+    /// A pattern failed to match
+    pub fn PatFailed(pat: Box<Pattern>) -> Self {
+        Self { kind: ErrorKind::PatFailed(pat), span: None }
+    }
+    /// Fell through a non-exhaustive match
+    pub fn MatchNonexhaustive() -> Self {
+        Self { kind: ErrorKind::MatchNonexhaustive, span: None }
+    }
+    /// Explicit panic
+    pub fn Panic(msg: String) -> Self {
+        Self { kind: ErrorKind::Panic(msg, 0), span: None }
+    }
+    /// Error produced by a Builtin
+    pub fn BuiltinError(msg: String) -> Self {
+        Self { kind: ErrorKind::BuiltinError(msg), span: None }
+    }
+}
+
+impl std::error::Error for Error {}
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { kind, span } = self;
+        if let Some(Span { head, tail }) = span {
+            write!(f, "{head}..{tail}: ")?;
+        }
+        write!(f, "{kind}")
+    }
+}
+
+/// Represents any error thrown by the [Environment](super::Environment)
+#[derive(Clone, Debug)]
+pub enum ErrorKind {
+    /// Propagate a Return value
+    Return(ConValue),
+    /// Propagate a Break value
+    Break(ConValue),
+    /// Break propagated across function bounds
+    BadBreak(ConValue),
+    /// Continue to the next iteration of a loop
+    Continue,
+    /// Underflowed the stack
+    StackUnderflow,
+    /// Overflowed the stack
+    StackOverflow(usize),
+    /// Exited the last scope
+    ScopeExit,
+    /// Type incompatibility
+    // TODO: store the type information in this error
+    TypeError,
+    /// In clause of For loop didn't yield a Range
+    NotIterable,
+    /// A value could not be indexed
+    NotIndexable,
+    /// An array index went out of bounds
+    OobIndex(usize, usize),
+    /// An expression is not assignable
+    NotAssignable,
+    /// A name was not defined in scope before being used
+    NotDefined(Sym),
+    /// A name was defined but not initialized
+    NotInitialized(Sym),
+    /// A value was called, but is not callable
+    NotCallable(ConValue),
+    /// A function was called with the wrong number of arguments
+    ArgNumber { want: usize, got: usize },
+    /// A pattern failed to match
+    PatFailed(Box<Pattern>),
+    /// Fell through a non-exhaustive match
+    MatchNonexhaustive,
+    /// Explicit panic
+    Panic(String, usize),
+    /// Error produced by a Builtin
+    BuiltinError(String),
+}
+
+impl std::error::Error for ErrorKind {}
+impl std::fmt::Display for ErrorKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ErrorKind::Return(value) => write!(f, "return {value}"),
+            ErrorKind::Break(value) => write!(f, "break {value}"),
+            ErrorKind::BadBreak(value) => write!(f, "rogue break: {value}"),
+            ErrorKind::Continue => "continue".fmt(f),
+            ErrorKind::StackUnderflow => "Stack underflow".fmt(f),
+            ErrorKind::StackOverflow(id) => {
+                write!(f, "Attempt to access <{id}> resulted in stack overflow.")
+            }
+            ErrorKind::ScopeExit => "Exited the last scope. This is a logic bug.".fmt(f),
+            ErrorKind::TypeError => "Incompatible types".fmt(f),
+            ErrorKind::NotIterable => "`in` clause of `for` loop did not yield an iterable".fmt(f),
+            ErrorKind::NotIndexable => {
+                write!(f, "expression cannot be indexed")
+            }
+            ErrorKind::OobIndex(idx, len) => {
+                write!(f, "Index out of bounds: index was {idx}. but len is {len}")
+            }
+            ErrorKind::NotAssignable => {
+                write!(f, "expression is not assignable")
+            }
+            ErrorKind::NotDefined(value) => {
+                write!(f, "{value} not bound. Did you mean `let {value};`?")
+            }
+            ErrorKind::NotInitialized(value) => {
+                write!(f, "{value} bound, but not initialized")
+            }
+            ErrorKind::NotCallable(value) => {
+                write!(f, "{value} is not callable.")
+            }
+            ErrorKind::ArgNumber { want, got } => {
+                write!(
+                    f,
+                    "Expected {want} argument{}, got {got}",
+                    if *want == 1 { "" } else { "s" }
+                )
+            }
+            ErrorKind::PatFailed(pattern) => {
+                write!(f, "Failed to match pattern {pattern}")
+            }
+            ErrorKind::MatchNonexhaustive => {
+                write!(f, "Fell through a non-exhaustive match expression!")
+            }
+            ErrorKind::Panic(s, _depth) => write!(f, "Explicit panic: {s}"),
+            ErrorKind::BuiltinError(s) => write!(f, "{s}"),
+        }
+    }
+}

compiler/cl-interpret/src/function.rs

@@ -0,0 +1,83 @@
+//! Represents a block of code which lives inside the Interpreter
+
+use collect_upvars::collect_upvars;
+
+use crate::error::ErrorKind;
+
+use super::{Callable, ConValue, Environment, Error, IResult, Interpret, pattern};
+use cl_ast::{Function as FnDecl, Sym};
+use std::{
+    cell::{Ref, RefCell},
+    collections::HashMap,
+    rc::Rc,
+};
+
+pub mod collect_upvars;
+
+type Upvars = HashMap<Sym, ConValue>;
+
+/// Represents a block of code which persists inside the Interpreter
+#[derive(Clone, Debug)]
+pub struct Function {
+    /// Stores the contents of the function declaration
+    decl: Rc<FnDecl>,
+    /// Stores data from the enclosing scopes
+    upvars: RefCell<Upvars>,
+}
+
+impl Function {
+    pub fn new(decl: &FnDecl) -> Self {
+        // let upvars = collect_upvars(decl, env);
+        Self { decl: decl.clone().into(), upvars: Default::default() }
+    }
+    pub fn decl(&self) -> &FnDecl {
+        &self.decl
+    }
+    pub fn upvars(&self) -> Ref<'_, Upvars> {
+        self.upvars.borrow()
+    }
+    pub fn lift_upvars(&self, env: &Environment) {
+        let upvars = collect_upvars(&self.decl, env);
+        if let Ok(mut self_upvars) = self.upvars.try_borrow_mut() {
+            *self_upvars = upvars;
+        }
+    }
+}
+
+impl Callable for Function {
+    fn name(&self) -> Sym {
+        let FnDecl { name, .. } = *self.decl;
+        name
+    }
+    fn call(&self, env: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+        let FnDecl { name, gens: _, bind, body, sign: _ } = &*self.decl;
+
+        // Check arg mapping
+        let Some(body) = body else {
+            return Err(Error::NotDefined(*name));
+        };
+
+        let upvars = self.upvars.take();
+        let mut env = env.with_frame("upvars", upvars);
+
+        // TODO: completely refactor data storage
+        let mut frame = env.frame("fn args");
+        for (name, value) in pattern::substitution(&frame, bind, ConValue::Tuple(args.into()))? {
+            frame.insert(name, value);
+        }
+        let res = body.interpret(&mut frame);
+        drop(frame);
+        if let Some(upvars) = env.pop_values() {
+            self.upvars.replace(upvars);
+        }
+        match res {
+            Err(Error { kind: ErrorKind::Return(value), .. }) => Ok(value),
+            Err(Error { kind: ErrorKind::Break(value), .. }) => Err(Error::BadBreak(value)),
+            Err(Error { kind: ErrorKind::Panic(msg, depth), span: Some(span) }) => {
+                println!("{depth:>4}: {name}{bind} at {}", span.head);
+                Err(Error { kind: ErrorKind::Panic(msg, depth + 1), span: None })
+            }
+            other => other,
+        }
+    }
+}

compiler/cl-interpret/src/function/collect_upvars.rs

@@ -0,0 +1,112 @@
+//! Collects the "Upvars" of a function at the point of its creation, allowing variable capture
+use crate::env::Environment;
+use cl_ast::{
+    Function, Let, Path, PathPart, Pattern, Sym,
+    ast_visitor::{visit::*, walk::Walk},
+};
+use std::collections::{HashMap, HashSet};
+
+pub fn collect_upvars(f: &Function, env: &Environment) -> super::Upvars {
+    CollectUpvars::new(env).visit(f).finish_copied()
+}
+
+#[derive(Clone, Debug)]
+pub struct CollectUpvars<'env> {
+    env: &'env Environment,
+    upvars: HashMap<Sym, usize>,
+    blacklist: HashSet<Sym>,
+}
+
+impl<'env> CollectUpvars<'env> {
+    pub fn new(env: &'env Environment) -> Self {
+        Self { upvars: HashMap::new(), blacklist: HashSet::new(), env }
+    }
+
+    pub fn finish(&mut self) -> HashMap<Sym, usize> {
+        std::mem::take(&mut self.upvars)
+    }
+
+    pub fn finish_copied(&mut self) -> super::Upvars {
+        let Self { env, upvars, blacklist: _ } = self;
+        std::mem::take(upvars)
+            .into_iter()
+            .filter_map(|(k, v)| env.get_id(v).cloned().map(|v| (k, v)))
+            .collect()
+    }
+
+    pub fn add_upvar(&mut self, name: &Sym) {
+        let Self { env, upvars, blacklist } = self;
+        if blacklist.contains(name) || upvars.contains_key(name) {
+            return;
+        }
+        if let Ok(place) = env.id_of(*name) {
+            upvars.insert(*name, place);
+        }
+    }
+
+    pub fn bind_name(&mut self, name: &Sym) {
+        self.blacklist.insert(*name);
+    }
+
+    pub fn scope(&mut self, f: impl Fn(&mut CollectUpvars<'env>)) {
+        let blacklist = self.blacklist.clone();
+
+        // visit the scope
+        f(self);
+
+        // restore the blacklist
+        self.blacklist = blacklist;
+    }
+}
+
+impl<'a> Visit<'a> for CollectUpvars<'_> {
+    fn visit_block(&mut self, b: &'a cl_ast::Block) {
+        self.scope(|cu| b.children(cu));
+    }
+
+    fn visit_let(&mut self, l: &'a cl_ast::Let) {
+        let Let { mutable, name, ty, init } = l;
+        self.visit_mutability(mutable);
+
+        ty.visit_in(self);
+        // visit the initializer, which may use the bound name
+        init.visit_in(self);
+        // a bound name can never be an upvar
+        self.visit_pattern(name);
+    }
+
+    fn visit_path(&mut self, p: &'a cl_ast::Path) {
+        // TODO: path resolution in environments
+        let Path { absolute: false, parts } = p else {
+            return;
+        };
+        let [PathPart::Ident(name)] = parts.as_slice() else {
+            return;
+        };
+        self.add_upvar(name);
+    }
+
+    fn visit_fielder(&mut self, f: &'a cl_ast::Fielder) {
+        let cl_ast::Fielder { name, init } = f;
+        if let Some(init) = init {
+            self.visit_expr(init);
+        } else {
+            self.add_upvar(name); // fielder without init grabs from env
+        }
+    }
+
+    fn visit_pattern(&mut self, value: &'a cl_ast::Pattern) {
+        match value {
+            Pattern::Name(name) => {
+                self.bind_name(name);
+            }
+            Pattern::RangeExc(_, _) | Pattern::RangeInc(_, _) => {}
+            _ => value.children(self),
+        }
+    }
+
+    fn visit_match_arm(&mut self, value: &'a cl_ast::MatchArm) {
+        // MatchArms bind variables with a very small local scope
+        self.scope(|cu| value.children(cu));
+    }
+}

compiler/cl-interpret/src/lib.rs

@@ -0,0 +1,671 @@
+//! Walks a Conlang AST, interpreting it as a program.
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+
+use cl_ast::Sym;
+use convalue::ConValue;
+use env::Environment;
+use error::{Error, ErrorKind, IResult};
+use interpret::Interpret;
+
+/// Callable types can be called from within a Conlang program
+pub trait Callable {
+    /// Calls this [Callable] in the provided [Environment], with [ConValue] args  \
+    /// The Callable is responsible for checking the argument count and validating types
+    fn call(&self, interpreter: &mut Environment, args: &[ConValue]) -> IResult<ConValue>;
+    /// Returns the common name of this identifier.
+    fn name(&self) -> Sym;
+}
+
+pub mod convalue;
+
+pub mod interpret;
+
+pub mod function;
+
+pub mod constructor {
+    use cl_ast::Sym;
+
+    use crate::{
+        Callable,
+        convalue::ConValue,
+        env::Environment,
+        error::{Error, IResult},
+    };
+
+    #[derive(Clone, Copy, Debug)]
+    pub struct Constructor {
+        pub name: Sym,
+        pub arity: u32,
+    }
+
+    impl Callable for Constructor {
+        fn call(&self, _env: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+            let &Self { name, arity } = self;
+            if arity as usize == args.len() {
+                Ok(ConValue::TupleStruct(name, Box::new(args.into())))
+            } else {
+                Err(Error::ArgNumber(arity as usize, args.len()))
+            }
+        }
+
+        fn name(&self) -> cl_ast::Sym {
+            "tuple-constructor".into()
+        }
+    }
+}
+
+pub mod closure;
+
+pub mod builtin;
+
+pub mod pattern;
+
+pub mod env;
+
+pub mod modules {
+    use crate::env::StackBinds;
+    use cl_ast::{PathPart, Sym};
+    use std::collections::HashMap;
+
+    /// Immutable object-oriented interface to a [ModuleTree]
+    #[derive(Clone, Copy, Debug)]
+    pub struct ModuleNode<'tree> {
+        tree: &'tree ModuleTree,
+        index: usize,
+    }
+
+    /// Mutable object-oriented interface to a [ModuleTree]
+    #[derive(Debug)]
+    pub struct ModuleNodeMut<'tree> {
+        tree: &'tree mut ModuleTree,
+        index: usize,
+    }
+
+    macro_rules! module_node_impl {
+        () => {
+            /// Gets the index from this node
+            pub fn index(self) -> usize {
+                self.index
+            }
+            /// Gets this node's parent
+            pub fn parent(self) -> Option<Self> {
+                let parent = self.tree.parent(self.index)?;
+                Some(Self { index: parent, ..self })
+            }
+            /// Gets the node's "encompassing Type"
+            pub fn selfty(self) -> Option<Self> {
+                let selfty = self.tree.selfty(self.index)?;
+                Some(Self { index: selfty, ..self })
+            }
+            /// Gets the child of this node with the given name
+            pub fn child(self, name: &Sym) -> Option<Self> {
+                let child = self.tree.child(self.index, name)?;
+                Some(Self { index: child, ..self })
+            }
+            /// Gets a stack value in this node with the given name
+            pub fn item(self, name: &Sym) -> Option<usize> {
+                self.tree.items(self.index)?.get(name).copied()
+            }
+            /// Returns true when this node represents type information
+            pub fn is_ty(self) -> Option<bool> {
+                self.tree.is_ty.get(self.index).copied()
+            }
+            /// Returns a reference to this node's children, if present
+            pub fn children(&self) -> Option<&HashMap<Sym, usize>> {
+                self.tree.children(self.index)
+            }
+            /// Returns a reference to this node's items, if present
+            pub fn items(&self) -> Option<&StackBinds> {
+                self.tree.items(self.index)
+            }
+            /// Traverses a path starting at this node
+            ///
+            /// Returns a new node, and the unconsumed path portion.
+            pub fn find(self, path: &[PathPart]) -> (Self, &[PathPart]) {
+                let (index, path) = self.tree.find(self.index, path);
+                (Self { index, ..self }, path)
+            }
+            /// Traverses a path starting at this node
+            ///
+            /// Returns an item address if the path terminated in an item.
+            pub fn find_item(&self, path: &[PathPart]) -> Option<usize> {
+                self.tree.find_item(self.index, path)
+            }
+        };
+    }
+
+    impl ModuleNode<'_> {
+        module_node_impl! {}
+    }
+
+    impl ModuleNodeMut<'_> {
+        module_node_impl! {}
+        /// Creates a new child in this node
+        pub fn add_child(self, name: Sym, is_ty: bool) -> Self {
+            let node = self.tree.add_child(self.index, name, is_ty);
+            self.tree.get_mut(node)
+        }
+        /// Creates an arbitrary edge in the module graph
+        pub fn add_import(&mut self, name: Sym, child: usize) {
+            self.tree.add_import(self.index, name, child)
+        }
+        pub fn add_imports(&mut self, binds: HashMap<Sym, usize>) {
+            self.tree.add_imports(self.index, binds)
+        }
+        /// Binds a new item in this node
+        pub fn add_item(&mut self, name: Sym, stack_index: usize) {
+            self.tree.add_item(self.index, name, stack_index)
+        }
+        /// Binds an entire stack frame in this node
+        pub fn add_items(&mut self, binds: StackBinds) {
+            self.tree.add_items(self.index, binds)
+        }
+        /// Constructs a borrowing [ModuleNode]
+        pub fn as_ref(&self) -> ModuleNode<'_> {
+            let Self { tree, index } = self;
+            ModuleNode { tree, index: *index }
+        }
+    }
+
+    #[derive(Clone, Debug)]
+    pub struct ModuleTree {
+        parents: Vec<usize>,
+        children: Vec<HashMap<Sym, usize>>,
+        items: Vec<StackBinds>,
+        is_ty: Vec<bool>,
+    }
+
+    impl ModuleTree {
+        /// Constructs a new ModuleTree with a single root module
+        pub fn new() -> Self {
+            Self {
+                parents: vec![0],
+                children: vec![HashMap::new()],
+                items: vec![HashMap::new()],
+                is_ty: vec![false],
+            }
+        }
+
+        /// Gets a borrowed handle to the node at `index`
+        pub fn get(&self, index: usize) -> ModuleNode<'_> {
+            ModuleNode { tree: self, index }
+        }
+
+        /// Gets a mutable handle to the node at `index`
+        pub fn get_mut(&mut self, index: usize) -> ModuleNodeMut<'_> {
+            ModuleNodeMut { tree: self, index }
+        }
+
+        /// Creates a new child in this node
+        pub fn add_child(&mut self, parent: usize, name: Sym, is_ty: bool) -> usize {
+            let index = self.parents.len();
+            self.children[parent].insert(name, index);
+            self.parents.push(parent);
+            self.children.push(HashMap::new());
+            self.is_ty.push(is_ty);
+            index
+        }
+
+        /// Binds a new item in this node
+        pub fn add_item(&mut self, node: usize, name: Sym, stack_index: usize) {
+            self.items[node].insert(name, stack_index);
+        }
+
+        /// Creates an arbitrary child edge
+        pub fn add_import(&mut self, parent: usize, name: Sym, child: usize) {
+            self.children[parent].insert(name, child);
+        }
+
+        /// Binds an entire stack frame in this node
+        pub fn add_items(&mut self, node: usize, binds: StackBinds) {
+            self.items[node].extend(binds);
+        }
+
+        /// Binds an arbitrary set of child edges
+        pub fn add_imports(&mut self, node: usize, binds: HashMap<Sym, usize>) {
+            self.children[node].extend(binds);
+        }
+
+        /// Gets this node's parent
+        pub fn parent(&self, node: usize) -> Option<usize> {
+            if node == 0 {
+                return None;
+            }
+            self.parents.get(node).copied()
+        }
+
+        /// Gets the node's "encompassing Type"
+        pub fn selfty(&self, node: usize) -> Option<usize> {
+            if self.is_ty[node] {
+                return Some(node);
+            }
+            self.selfty(self.parent(node)?)
+        }
+
+        /// Gets the child of this node with the given name
+        pub fn child(&self, node: usize, id: &Sym) -> Option<usize> {
+            self.children[node].get(id).copied()
+        }
+
+        /// Gets a stack value in this node with the given name
+        pub fn item(&self, node: usize, name: &Sym) -> Option<usize> {
+            self.items.get(node).and_then(|map| map.get(name).copied())
+        }
+
+        /// Returns a reference to this node's children, if present
+        pub fn children(&self, node: usize) -> Option<&HashMap<Sym, usize>> {
+            self.children.get(node)
+        }
+
+        /// Returns a reference to this node's items, if present
+        pub fn items(&self, node: usize) -> Option<&StackBinds> {
+            self.items.get(node)
+        }
+
+        /// Traverses a path starting at this node
+        ///
+        /// Returns a new node, and the unconsumed path portion.
+        pub fn find<'p>(&self, node: usize, path: &'p [PathPart]) -> (usize, &'p [PathPart]) {
+            match path {
+                [PathPart::SuperKw, tail @ ..] => match self.parent(node) {
+                    Some(node) => self.find(node, tail),
+                    None => (node, path),
+                },
+                [PathPart::Ident(name), tail @ ..] => match self.child(node, name) {
+                    Some(node) => self.find(node, tail),
+                    None => (node, path),
+                },
+                [PathPart::SelfTy, tail @ ..] => match self.selfty(node) {
+                    Some(node) => self.find(node, tail),
+                    None => (node, path),
+                },
+                [] => (node, path),
+            }
+        }
+
+        /// Traverses a path starting at this node
+        ///
+        /// Returns an item address if the path terminated in an item.
+        pub fn find_item(&self, node: usize, path: &[PathPart]) -> Option<usize> {
+            let (node, [PathPart::Ident(name)]) = self.find(node, path) else {
+                return None;
+            };
+            self.item(node, name)
+        }
+    }
+
+    impl Default for ModuleTree {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+}
+
+pub mod collector {
+    use std::ops::{Deref, DerefMut};
+
+    use crate::{
+        convalue::ConValue,
+        env::Environment,
+        modules::{ModuleNode, ModuleNodeMut},
+    };
+    use cl_ast::{
+        ast_visitor::{Visit, Walk},
+        *,
+    };
+
+    pub struct Collector<'env> {
+        module: usize,
+        env: &'env mut Environment,
+    }
+
+    impl Collector<'_> {
+        pub fn as_node(&self) -> ModuleNode<'_> {
+            self.env.modules().get(self.module)
+        }
+
+        pub fn as_node_mut(&mut self) -> ModuleNodeMut<'_> {
+            self.env.modules_mut().get_mut(self.module)
+        }
+
+        pub fn scope(&mut self, name: Sym, is_ty: bool, f: impl Fn(&mut Collector<'_>)) {
+            let module = match self.as_node_mut().child(&name) {
+                Some(m) => m,
+                None => self.as_node_mut().add_child(name, is_ty),
+            }
+            .index();
+
+            let mut frame = self.env.frame(name.to_ref());
+            f(&mut Collector { env: &mut frame, module });
+            let binds = frame.into_binds().unwrap_or_default();
+
+            self.modules_mut().add_items(module, binds);
+        }
+
+        pub fn in_foreign_scope<F, T>(&mut self, path: &[PathPart], f: F) -> Option<T>
+        where F: Fn(&mut Collector<'_>) -> T {
+            let (module, []) = self.env.modules_mut().find(self.module, path) else {
+                return None;
+            };
+
+            let mut frame = self.env.frame("impl");
+            let out = f(&mut Collector { env: &mut frame, module });
+            let binds = frame.into_binds().unwrap_or_default();
+
+            self.env.modules_mut().add_items(module, binds);
+            Some(out)
+        }
+    }
+
+    impl<'env> Deref for Collector<'env> {
+        type Target = Environment;
+        fn deref(&self) -> &Self::Target {
+            self.env
+        }
+    }
+
+    impl DerefMut for Collector<'_> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.env
+        }
+    }
+
+    impl<'a, 'env> Visit<'a> for Collector<'env> {
+        fn visit_file(&mut self, value: &'a File) {
+            let mut sorter = ItemSorter::default();
+            sorter.visit(value);
+            sorter.visit_all(self);
+        }
+        fn visit_block(&mut self, value: &'a Block) {
+            let mut sorter = ItemSorter::default();
+            sorter.visit(value);
+            sorter.visit_all(self);
+        }
+        fn visit_module(&mut self, value: &'a cl_ast::Module) {
+            self.scope(value.name, false, |scope| value.children(scope));
+        }
+        fn visit_alias(&mut self, value: &'a cl_ast::Alias) {
+            let Alias { name, from } = value;
+            match from.as_ref().map(Box::as_ref) {
+                Some(Ty { kind: TyKind::Path(path), .. }) => {
+                    let mut node = if path.absolute {
+                        self.modules_mut().get_mut(0)
+                    } else {
+                        self.as_node_mut()
+                    };
+                    if let Some(item) = node.find_item(&path.parts) {
+                        node.add_item(*name, item);
+                    }
+                }
+                Some(other) => todo!("Type expressions in the collector: {other}"),
+                None => self.scope(*name, true, |_| {}),
+            }
+        }
+        fn visit_enum(&mut self, value: &'a cl_ast::Enum) {
+            let Enum { name, gens: _, variants } = value;
+
+            self.scope(*name, true, |frame| {
+                for (idx, Variant { name, kind, body }) in variants.iter().enumerate() {
+                    frame.visit(body);
+                    frame.scope(*name, false, |frame| {
+                        frame.bind("__discriminant", idx as isize);
+                        match kind {
+                            StructKind::Empty => {
+                                frame.insert_tup_constructor("call".into(), 0);
+                                frame.bind("__nmemb", ConValue::Int(0));
+                            }
+                            StructKind::Tuple(args) => {
+                                // Constructs the AST from scratch. TODO: This, better.
+                                frame.insert_tup_constructor("call".into(), args.len());
+                                frame.bind("__nmemb", ConValue::Int(args.len() as _));
+                            }
+                            StructKind::Struct(members) => {
+                                // TODO: more precise type checking of structs
+                                for (idx, memb) in members.iter().enumerate() {
+                                    let StructMember { vis: _, name, ty: _ } = memb;
+                                    frame.bind(*name, idx as isize);
+                                }
+                                frame.bind("__nmemb", ConValue::Int(members.len() as _));
+                            }
+                        }
+                    });
+                }
+            });
+        }
+        fn visit_struct(&mut self, value: &'a cl_ast::Struct) {
+            let Struct { name, gens: _, kind } = value;
+
+            self.scope(*name, true, |frame| {
+                match kind {
+                    StructKind::Empty => {
+                        frame.insert_tup_constructor("call".into(), 0);
+                        frame.bind("__nmemb", ConValue::Int(0));
+                    }
+                    StructKind::Tuple(args) => {
+                        // Constructs the AST from scratch. TODO: This, better.
+                        frame.insert_tup_constructor("call".into(), args.len());
+                        frame.bind("__nmemb", ConValue::Int(args.len() as _));
+                    }
+                    StructKind::Struct(members) => {
+                        // TODO: more precise type checking of structs
+                        for (idx, memb) in members.iter().enumerate() {
+                            let StructMember { vis: _, name, ty: _ } = memb;
+                            frame.bind(*name, idx as isize);
+                        }
+                        frame.bind("__nmemb", ConValue::Int(members.len() as _));
+                    }
+                }
+            });
+        }
+        fn visit_const(&mut self, value: &'a cl_ast::Const) {
+            let Const { name, ty: _, init } = value;
+            self.visit(init);
+            self.bind(*name, ());
+        }
+        fn visit_static(&mut self, value: &'a cl_ast::Static) {
+            let Static { mutable: _, name, ty: _, init } = value;
+            self.visit(init);
+            self.bind(*name, ());
+        }
+        fn visit_function(&mut self, value: &'a cl_ast::Function) {
+            let Function { name, gens: _, sign: _, bind: _, body } = value;
+            self.scope(*name, false, |scope| {
+                scope.visit(body);
+                let f = crate::function::Function::new(value);
+                scope.bind("call", f);
+            });
+        }
+        fn visit_impl(&mut self, value: &'a cl_ast::Impl) {
+            let Impl { gens: _, target: ImplKind::Type(Ty { kind: TyKind::Path(name), .. }), body } =
+                value
+            else {
+                eprintln!("TODO: impl X for Ty");
+                return;
+            };
+            self.in_foreign_scope(&name.parts, |scope| {
+                body.visit_in(scope);
+            });
+        }
+        fn visit_use(&mut self, value: &'a cl_ast::Use) {
+            fn traverse(dest: &mut Collector<'_>, node: usize, tree: &UseTree) {
+                match tree {
+                    UseTree::Tree(ts) => ts.iter().for_each(|tree| traverse(dest, node, tree)),
+                    UseTree::Path(PathPart::Ident(name), tree) => {
+                        if let (node, []) = dest.modules().find(node, &[PathPart::Ident(*name)]) {
+                            traverse(dest, node, tree)
+                        }
+                    }
+                    UseTree::Path(PathPart::SuperKw, tree) => {
+                        if let Some(node) = dest.modules().parent(node) {
+                            traverse(dest, node, tree)
+                        }
+                    }
+                    UseTree::Path(PathPart::SelfTy, tree) => {
+                        if let Some(node) = dest.modules().selfty(node) {
+                            traverse(dest, node, tree)
+                        }
+                    }
+                    UseTree::Alias(name, as_name) => {
+                        if let Some(child) = dest.modules().child(node, name) {
+                            dest.as_node_mut().add_import(*as_name, child);
+                        }
+                        if let Some(item) = dest.modules().item(node, name) {
+                            dest.as_node_mut().add_item(*as_name, item);
+                        }
+                    }
+                    UseTree::Name(name) => {
+                        if let Some(child) = dest.modules().child(node, name) {
+                            dest.as_node_mut().add_import(*name, child);
+                        }
+                        if let Some(item) = dest.modules().item(node, name) {
+                            dest.as_node_mut().add_item(*name, item);
+                        }
+                    }
+                    UseTree::Glob => {
+                        let &mut Collector { module, ref mut env } = dest;
+                        if let Some(children) = env.modules().children(node) {
+                            for (name, index) in children.clone() {
+                                env.modules_mut().add_import(module, name, index);
+                            }
+                        }
+                        if let Some(items) = env.modules().items(node).cloned() {
+                            env.modules_mut().add_items(node, items);
+                        }
+                    }
+                }
+            }
+
+            let Use { absolute, tree } = value;
+            let node = if *absolute { 0 } else { self.module };
+            traverse(self, node, tree);
+        }
+    }
+
+    // fn make_tuple_constructor(name: Sym, args: &[Ty]) -> ConValue {
+    //     let span = match (
+    //         args.first().map(|a| a.span.head),
+    //         args.last().map(|a| a.span.tail),
+    //     ) {
+    //         (Some(head), Some(tail)) => Span(head, tail),
+    //         _ => Span::dummy(),
+    //     };
+
+    //     let constructor = Function {
+    //         name,
+    //         gens: Default::default(),
+    //         sign: TyFn {
+    //             args: Ty { kind: TyKind::Tuple(TyTuple { types: args.to_vec() }), span }.into(),
+    //             rety: Some(Ty { span: Span::dummy(), kind: TyKind::Path(Path::from(name))
+    // }.into()),         },
+    //         bind: Pattern::Tuple(
+    //             args.iter()
+    //                 .enumerate()
+    //                 .map(|(idx, _)| Pattern::Name(idx.to_string().into()))
+    //                 .collect(),
+    //         ),
+    //         body: None,
+    //     };
+    //     // ConValue::TupleConstructor(crate::constructor::Constructor {ind})
+    //     todo!("Tuple constructor {constructor}")
+    // }
+
+    /// Sorts items
+    #[derive(Debug, Default)]
+    struct ItemSorter<'ast> {
+        modules: Vec<&'ast Module>,
+        structs: Vec<&'ast Struct>,
+        enums: Vec<&'ast Enum>,
+        aliases: Vec<&'ast Alias>,
+        consts: Vec<&'ast Const>,
+        statics: Vec<&'ast Static>,
+        functions: Vec<&'ast Function>,
+        impls: Vec<&'ast Impl>,
+        imports: Vec<&'ast Use>,
+    }
+
+    impl<'a> ItemSorter<'a> {
+        fn visit_all<V: Visit<'a>>(&self, v: &mut V) {
+            let Self {
+                modules,
+                aliases,
+                enums,
+                structs,
+                consts,
+                statics,
+                functions,
+                impls,
+                imports,
+            } = self;
+
+            // 0
+            for item in modules {
+                item.visit_in(v);
+            }
+            // 1
+            for item in structs {
+                item.visit_in(v);
+            }
+            for item in enums {
+                item.visit_in(v);
+            }
+            for item in aliases {
+                item.visit_in(v);
+            }
+            // 2
+            // 5
+            for item in consts {
+                item.visit_in(v);
+            }
+            for item in statics {
+                item.visit_in(v);
+            }
+            for item in functions {
+                item.visit_in(v);
+            }
+            // 4
+            for item in impls {
+                item.visit_in(v);
+            }
+            // 3
+            for item in imports {
+                item.visit_in(v);
+            }
+        }
+    }
+
+    impl<'a> Visit<'a> for ItemSorter<'a> {
+        fn visit_module(&mut self, value: &'a cl_ast::Module) {
+            self.modules.push(value);
+        }
+        fn visit_alias(&mut self, value: &'a cl_ast::Alias) {
+            self.aliases.push(value);
+        }
+        fn visit_enum(&mut self, value: &'a cl_ast::Enum) {
+            self.enums.push(value);
+        }
+        fn visit_struct(&mut self, value: &'a cl_ast::Struct) {
+            self.structs.push(value);
+        }
+        fn visit_const(&mut self, value: &'a cl_ast::Const) {
+            self.consts.push(value);
+        }
+        fn visit_static(&mut self, value: &'a cl_ast::Static) {
+            self.statics.push(value);
+        }
+        fn visit_function(&mut self, value: &'a cl_ast::Function) {
+            self.functions.push(value);
+        }
+        fn visit_impl(&mut self, value: &'a cl_ast::Impl) {
+            self.impls.push(value);
+        }
+        fn visit_use(&mut self, value: &'a cl_ast::Use) {
+            self.imports.push(value);
+        }
+    }
+}
+
+pub mod error;
+
+#[cfg(test)]
+mod tests;

compiler/cl-interpret/src/pattern.rs

@@ -0,0 +1,347 @@
+//! Unification algorithm for cl-ast [Pattern]s and [ConValue]s
+//!
+//! [`variables()`] returns a flat list of symbols that are bound by a given pattern
+//! [`substitution()`] unifies a ConValue with a pattern, and produces a list of bound names
+
+use crate::{
+    convalue::ConValue,
+    env::Environment,
+    error::{Error, IResult},
+};
+use cl_ast::{Literal, Pattern, Sym};
+use std::collections::{HashMap, VecDeque};
+
+/// Gets the path variables in the given Pattern
+pub fn variables(pat: &Pattern) -> Vec<&Sym> {
+    fn patvars<'p>(set: &mut Vec<&'p Sym>, pat: &'p Pattern) {
+        match pat {
+            Pattern::Name(name) if name.to_ref() == "_" => {}
+            Pattern::Name(name) => set.push(name),
+            Pattern::Path(_) => {}
+            Pattern::Literal(_) => {}
+            Pattern::Rest(Some(pattern)) => patvars(set, pattern),
+            Pattern::Rest(None) => {}
+            Pattern::Ref(_, pattern) => patvars(set, pattern),
+            Pattern::RangeExc(_, _) => {}
+            Pattern::RangeInc(_, _) => {}
+            Pattern::Tuple(patterns) | Pattern::Array(patterns) => {
+                patterns.iter().for_each(|pat| patvars(set, pat))
+            }
+            Pattern::Struct(_path, items) => {
+                items.iter().for_each(|(name, pat)| match pat {
+                    Some(pat) => patvars(set, pat),
+                    None => set.push(name),
+                });
+            }
+            Pattern::TupleStruct(_path, items) => {
+                items.iter().for_each(|pat| patvars(set, pat));
+            }
+        }
+    }
+    let mut set = Vec::new();
+    patvars(&mut set, pat);
+    set
+}
+
+fn rest_binding<'pat>(
+    env: &Environment,
+    sub: &mut HashMap<Sym, ConValue>,
+    mut patterns: &'pat [Pattern],
+    mut values: VecDeque<ConValue>,
+) -> IResult<Option<(&'pat Pattern, VecDeque<ConValue>)>> {
+    // Bind the head of the list
+    while let [pattern, tail @ ..] = patterns {
+        if matches!(pattern, Pattern::Rest(_)) {
+            break;
+        }
+        let value = values
+            .pop_front()
+            .ok_or_else(|| Error::PatFailed(Box::new(pattern.clone())))?;
+        append_sub(env, sub, pattern, value)?;
+        patterns = tail;
+    }
+    // Bind the tail of the list
+    while let [head @ .., pattern] = patterns {
+        if matches!(pattern, Pattern::Rest(_)) {
+            break;
+        }
+        let value = values
+            .pop_back()
+            .ok_or_else(|| Error::PatFailed(Box::new(pattern.clone())))?;
+        append_sub(env, sub, pattern, value)?;
+        patterns = head;
+    }
+    // Bind the ..rest of the list
+    match patterns {
+        [] | [Pattern::Rest(None)] => Ok(None),
+        [Pattern::Rest(Some(pattern))] => Ok(Some((pattern.as_ref(), values))),
+        _ => Err(Error::PatFailed(Box::new(Pattern::Array(patterns.into())))),
+    }
+}
+
+fn rest_binding_ref<'pat>(
+    env: &Environment,
+    sub: &mut HashMap<Sym, ConValue>,
+    mut patterns: &'pat [Pattern],
+    mut head: usize,
+    mut tail: usize,
+) -> IResult<Option<(&'pat Pattern, usize, usize)>> {
+    // Bind the head of the list
+    while let [pattern, pat_tail @ ..] = patterns {
+        if matches!(pattern, Pattern::Rest(_)) {
+            break;
+        }
+        if head >= tail {
+            return Err(Error::PatFailed(Box::new(pattern.clone())));
+        }
+
+        append_sub(env, sub, pattern, ConValue::Ref(head))?;
+        head += 1;
+        patterns = pat_tail;
+    }
+    // Bind the tail of the list
+    while let [pat_head @ .., pattern] = patterns {
+        if matches!(pattern, Pattern::Rest(_)) {
+            break;
+        }
+        if head >= tail {
+            return Err(Error::PatFailed(Box::new(pattern.clone())));
+        };
+        append_sub(env, sub, pattern, ConValue::Ref(tail))?;
+        tail -= 1;
+        patterns = pat_head;
+    }
+    // Bind the ..rest of the list
+    match (patterns, tail - head) {
+        ([], 0) | ([Pattern::Rest(None)], _) => Ok(None),
+        ([Pattern::Rest(Some(pattern))], _) => Ok(Some((pattern.as_ref(), head, tail))),
+        _ => Err(Error::PatFailed(Box::new(Pattern::Array(patterns.into())))),
+    }
+}
+
+/// Appends a substitution to the provided table
+pub fn append_sub(
+    env: &Environment,
+    sub: &mut HashMap<Sym, ConValue>,
+    pat: &Pattern,
+    value: ConValue,
+) -> IResult<()> {
+    match (pat, value) {
+        (Pattern::Literal(Literal::Bool(a)), ConValue::Bool(b)) => {
+            (*a == b).then_some(()).ok_or(Error::NotAssignable())
+        }
+        (Pattern::Literal(Literal::Char(a)), ConValue::Char(b)) => {
+            (*a == b).then_some(()).ok_or(Error::NotAssignable())
+        }
+        (Pattern::Literal(Literal::Float(a)), ConValue::Float(b)) => (f64::from_bits(*a) == b)
+            .then_some(())
+            .ok_or(Error::NotAssignable()),
+        (Pattern::Literal(Literal::Int(a)), ConValue::Int(b)) => {
+            (b == *a as _).then_some(()).ok_or(Error::NotAssignable())
+        }
+        (Pattern::Literal(Literal::String(a)), ConValue::Str(b)) => {
+            (*a == *b).then_some(()).ok_or(Error::NotAssignable())
+        }
+        (Pattern::Literal(Literal::String(a)), ConValue::String(b)) => {
+            (*a == *b).then_some(()).ok_or(Error::NotAssignable())
+        }
+        (Pattern::Literal(_), _) => Err(Error::NotAssignable()),
+
+        (Pattern::Rest(Some(pat)), value) => match (pat.as_ref(), value) {
+            (Pattern::Literal(Literal::Int(a)), ConValue::Int(b)) => {
+                (b < *a as _).then_some(()).ok_or(Error::NotAssignable())
+            }
+            (Pattern::Literal(Literal::Char(a)), ConValue::Char(b)) => {
+                (b < *a as _).then_some(()).ok_or(Error::NotAssignable())
+            }
+            (Pattern::Literal(Literal::Bool(a)), ConValue::Bool(b)) => {
+                (!b & *a).then_some(()).ok_or(Error::NotAssignable())
+            }
+            (Pattern::Literal(Literal::Float(a)), ConValue::Float(b)) => {
+                (b < *a as _).then_some(()).ok_or(Error::NotAssignable())
+            }
+            (Pattern::Literal(Literal::String(a)), ConValue::Str(b)) => {
+                (&*b < a).then_some(()).ok_or(Error::NotAssignable())
+            }
+            (Pattern::Literal(Literal::String(a)), ConValue::String(b)) => {
+                (&*b < a).then_some(()).ok_or(Error::NotAssignable())
+            }
+            _ => Err(Error::NotAssignable()),
+        },
+
+        (Pattern::Name(name), _) if "_".eq(&**name) => Ok(()),
+        (Pattern::Name(name), value) => {
+            sub.insert(*name, value);
+            Ok(())
+        }
+
+        (Pattern::Ref(_, pat), ConValue::Ref(r)) => match env.get_id(r) {
+            Some(value) => append_sub(env, sub, pat, value.clone()),
+            None => Err(Error::PatFailed(pat.clone())),
+        },
+
+        (Pattern::Ref(_, pat), ConValue::Slice(head, len)) => {
+            let mut values = Vec::with_capacity(len);
+            for idx in head..(head + len) {
+                values.push(env.get_id(idx).cloned().ok_or(Error::StackOverflow(idx))?);
+            }
+            append_sub(env, sub, pat, ConValue::Array(values.into_boxed_slice()))
+        }
+
+        (Pattern::RangeExc(head, tail), value) => match (head.as_ref(), tail.as_ref(), value) {
+            (
+                Pattern::Literal(Literal::Int(a)),
+                Pattern::Literal(Literal::Int(c)),
+                ConValue::Int(b),
+            ) => (*a as isize <= b as _ && b < *c as isize)
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::Char(a)),
+                Pattern::Literal(Literal::Char(c)),
+                ConValue::Char(b),
+            ) => (*a <= b && b < *c)
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::Float(a)),
+                Pattern::Literal(Literal::Float(c)),
+                ConValue::Float(b),
+            ) => (f64::from_bits(*a) <= b && b < f64::from_bits(*c))
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::String(a)),
+                Pattern::Literal(Literal::String(c)),
+                ConValue::Str(b),
+            ) => (a.as_str() <= b.to_ref() && b.to_ref() < c.as_str())
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::String(a)),
+                Pattern::Literal(Literal::String(c)),
+                ConValue::String(b),
+            ) => (a.as_str() <= b.as_str() && b.as_str() < c.as_str())
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            _ => Err(Error::NotAssignable()),
+        },
+
+        (Pattern::RangeInc(head, tail), value) => match (head.as_ref(), tail.as_ref(), value) {
+            (
+                Pattern::Literal(Literal::Int(a)),
+                Pattern::Literal(Literal::Int(c)),
+                ConValue::Int(b),
+            ) => (*a as isize <= b && b <= *c as isize)
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::Char(a)),
+                Pattern::Literal(Literal::Char(c)),
+                ConValue::Char(b),
+            ) => (*a <= b && b <= *c)
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::Float(a)),
+                Pattern::Literal(Literal::Float(c)),
+                ConValue::Float(b),
+            ) => (f64::from_bits(*a) <= b && b <= f64::from_bits(*c))
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::String(a)),
+                Pattern::Literal(Literal::String(c)),
+                ConValue::Str(b),
+            ) => (a.as_str() <= b.to_ref() && b.to_ref() <= c.as_str())
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            (
+                Pattern::Literal(Literal::String(a)),
+                Pattern::Literal(Literal::String(c)),
+                ConValue::String(b),
+            ) => (a.as_str() <= b.as_str() && b.as_str() <= c.as_str())
+                .then_some(())
+                .ok_or(Error::NotAssignable()),
+            _ => Err(Error::NotAssignable()),
+        },
+
+        (Pattern::Array(patterns), ConValue::Array(values)) => {
+            match rest_binding(env, sub, patterns, values.into_vec().into())? {
+                Some((pattern, values)) => {
+                    append_sub(env, sub, pattern, ConValue::Array(Vec::from(values).into()))
+                }
+                _ => Ok(()),
+            }
+        }
+
+        (Pattern::Array(patterns), ConValue::Slice(head, len)) => {
+            match rest_binding_ref(env, sub, patterns, head, head + len)? {
+                Some((pat, head, tail)) => {
+                    append_sub(env, sub, pat, ConValue::Slice(head, tail - head))
+                }
+                None => Ok(()),
+            }
+        }
+
+        (Pattern::Tuple(patterns), ConValue::Empty) if patterns.is_empty() => Ok(()),
+        (Pattern::Tuple(patterns), ConValue::Tuple(values)) => {
+            match rest_binding(env, sub, patterns, values.into_vec().into())? {
+                Some((pattern, values)) => {
+                    append_sub(env, sub, pattern, ConValue::Tuple(Vec::from(values).into()))
+                }
+                _ => Ok(()),
+            }
+        }
+
+        (Pattern::TupleStruct(path, patterns), ConValue::TupleStruct(id, values)) => {
+            let tid = path
+                .as_sym()
+                .ok_or_else(|| Error::PatFailed(pat.clone().into()))?;
+            if id != tid {
+                return Err(Error::PatFailed(pat.clone().into()));
+            }
+            match rest_binding(env, sub, patterns, values.into_vec().into())? {
+                Some((pattern, values)) => {
+                    append_sub(env, sub, pattern, ConValue::Tuple(Vec::from(values).into()))
+                }
+                _ => Ok(()),
+            }
+        }
+
+        (Pattern::Struct(path, patterns), ConValue::Struct(id, mut values)) => {
+            let tid = path
+                .as_sym()
+                .ok_or_else(|| Error::PatFailed(pat.clone().into()))?;
+            if id != tid {
+                return Err(Error::PatFailed(pat.clone().into()));
+            }
+            for (name, pat) in patterns {
+                let value = values.remove(name).ok_or(Error::TypeError())?;
+                match pat {
+                    Some(pat) => append_sub(env, sub, pat, value)?,
+                    None => {
+                        sub.insert(*name, value);
+                    }
+                }
+            }
+            Ok(())
+        }
+
+        _ => {
+            // eprintln!("Could not match pattern `{pat}` with value `{value}`!");
+            Err(Error::NotAssignable())
+        }
+    }
+}
+
+/// Constructs a substitution from a pattern and a value
+pub fn substitution(
+    env: &Environment,
+    pat: &Pattern,
+    value: ConValue,
+) -> IResult<HashMap<Sym, ConValue>> {
+    let mut sub = HashMap::new();
+    append_sub(env, &mut sub, pat, value)?;
+    Ok(sub)
+}

compiler/cl-interpret/src/tests.rs

@@ -1,10 +1,8 @@
 #![allow(unused_imports)]
-use crate::{
-    ast::*,
-    interpreter::{env::Environment, temp_type_impl::ConValue, Interpret},
-    lexer::Lexer,
-    parser::Parser,
-};
+use crate::{Interpret, convalue::ConValue, env::Environment};
+use cl_ast::*;
+use cl_lexer::Lexer;
+use cl_parser::Parser;
 pub use macros::*;
 
 mod macros {
@@ -49,7 +47,8 @@ mod macros {
     //! env_eq!(env.x, 10); // like assert_eq! for Environments
     //! ```
     #![allow(unused_macros)]
-    use crate::interpreter::IResult;
+    use crate::IResult;
+    use cl_parser::parser::Parse;
 
     use super::*;
 
@@ -65,14 +64,14 @@ mod macros {
     ///
     /// Returns a `Result<`[`File`]`, ParseError>`
     pub macro file($($t:tt)*) {
-        Parser::new(Lexer::new(stringify!( $($t)* ))).file()
+        File::parse(&mut Parser::new(Lexer::new(stringify!( $($t)* ))))
     }
 
     /// Stringifies, lexes, and parses everything you give to it
     ///
     /// Returns a `Result<`[`Block`]`, ParseError>`
     pub macro block($($t:tt)*) {
-        Parser::new(Lexer::new(stringify!({ $($t)* }))).block()
+        Block::parse(&mut Parser::new("test", Lexer::new(stringify!({ $($t)* }))))
     }
 
     /// Evaluates a block of code in the given environment
@@ -129,7 +128,7 @@ mod macros {
     }
 
     pub macro env_ne($env:ident.$var:ident, $expr:expr) {{
-        let evaluated = $env.get(stringify!($var))
+        let evaluated = $env.get(stringify!($var).into())
             .expect(stringify!($var should be defined and initialized));
         if !conv_cmp!(neq, evaluated, $expr) {
             panic!("assertion {} ({evaluated}) != {} failed.", stringify!($var), stringify!($expr))
@@ -137,7 +136,7 @@ mod macros {
     }}
 
     pub macro env_eq($env:ident.$var:ident, $expr:expr) {{
-        let evaluated = $env.get(stringify!($var))
+        let evaluated = $env.get(stringify!($var).into())
             .expect(stringify!($var should be defined and initialized));
         if !conv_cmp!(eq, evaluated, $expr) {
             panic!("assertion {} ({evaluated}) == {} failed.", stringify!($var), stringify!($expr))
@@ -179,6 +178,45 @@ mod let_declarations {
         env_eq!(env.x, 10);
         env_eq!(env.y, 10);
     }
+
+    #[test]
+    fn let_destructuring_tuple() {
+        let mut env = Environment::new();
+        assert_eval!(env,
+            let (x, y) = (10, 20);
+        );
+
+        env_eq!(env.x, 10);
+        env_eq!(env.y, 20);
+    }
+
+    #[test]
+    fn let_destructuring_array() {
+        let mut env = Environment::new();
+        assert_eval!(env,
+            let [x, y] = [10, 20];
+        );
+
+        env_eq!(env.x, 10);
+        env_eq!(env.y, 20);
+    }
+
+    #[test]
+    fn let_destructuring_nested() {
+        let mut env = Environment::new();
+        assert_eval!(env,
+            let (x, [one, two, three], (a, b, c))
+              = ('x', [1, 2, 3], ('a', 'b', 'c'));
+        );
+
+        env_eq!(env.x, 'x');
+        env_eq!(env.one, 1);
+        env_eq!(env.two, 2);
+        env_eq!(env.three, 3);
+        env_eq!(env.a, 'a');
+        env_eq!(env.b, 'b');
+        env_eq!(env.c, 'c');
+    }
 }
 
 mod fn_declarations {
@@ -189,10 +227,10 @@ mod fn_declarations {
         assert_eval!(env, fn empty_fn() {});
         // TODO: true equality for functions
         assert_eq!(
-            "fn empty_fn",
+            "fn empty_fn () {}",
             format!(
                 "{}",
-                env.get("empty_fn")
+                env.get("empty_fn".into())
                     .expect(stringify!(empty_fn should be defined and initialized))
             )
         )
@@ -212,7 +250,7 @@ mod fn_declarations {
 }
 
 mod operators {
-    use crate::ast::Tuple;
+    use cl_ast::Tuple;
 
     use super::*;
     #[test]
@@ -365,7 +403,7 @@ mod operators {
         env_eq!(env.is_10_ne_20, true); //  !=
         env_eq!(env.is_10_ge_20, false); // >=
         env_eq!(env.is_10_gt_20, false); // >
-                                         // Equal to
+        // Equal to
         env_eq!(env.is_10_lt_10, false);
         env_eq!(env.is_10_le_10, true);
         env_eq!(env.is_10_eq_10, true);
@@ -438,16 +476,17 @@ mod operators {
         env_eq!(env.y, 10);
         env_eq!(env.z, 10);
     }
-    #[test]
-    #[should_panic]
-    fn assignment_accounts_for_type() {
-        let mut env = Default::default();
-        assert_eval!(env,
-            let x = "a string";
-            let y = 0xdeadbeef;
-            y = x; // should crash: type error
-        );
-    }
+    // Test is disabled, since new assignment system intentionally does not care.
+    // #[test]
+    // #[should_panic]
+    // fn assignment_accounts_for_type() {
+    //     let mut env = Default::default();
+    //     assert_eval!(env,
+    //         let x = "a string";
+    //         let y = 0xdeadbeef;
+    //         y = x; // should crash: type error
+    //     );
+    // }
     #[test]
     fn precedence() {
         let mut env = Default::default();
@@ -470,6 +509,75 @@ mod operators {
     }
 }
 
+mod control_flow {
+    use super::*;
+
+    #[test]
+    fn if_evaluates_pass_block_on_true() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let evaluated = if true { "pass" } else { "fail" }
+        );
+        env_eq!(env.evaluated, "pass");
+    }
+
+    #[test]
+    fn if_evaluates_fail_block_on_false() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let evaluated = if false { "pass" } else { "fail" }
+        );
+        env_eq!(env.evaluated, "fail");
+    }
+
+    #[test]
+    fn while_evaluates_fail_block_on_false() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let cond = true;
+            let evaluated = while cond { cond = false } else { true }
+        );
+        env_eq!(env.evaluated, true);
+    }
+
+    #[test]
+    fn while_does_not_evaluate_fail_block_on_break() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let evaluated = while true { break true } else { false }
+        );
+        env_eq!(env.evaluated, true);
+    }
+
+    #[test]
+    fn match_evaluates_in_order() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let x = '\u{1f988}';
+            let passed = match x {
+                '\u{1f988}' => true,
+                _ => false,
+            };
+        );
+        env_eq!(env.passed, true);
+    }
+
+    #[test]
+    fn match_sinkoles_underscore_patterns() {
+        let mut env = Default::default();
+        assert_eval!(env,
+            let x = '\u{1f988}';
+            let passed = match x {
+                _ => true,
+                '\u{1f988}' => false,
+            };
+        );
+        env_eq!(env.passed, true);
+    }
+
+    //TODO: test other control flow constructs like loops, while-else, etc.
+}
+
 #[allow(dead_code)]
 fn test_template() {
     let mut env = Default::default();

compiler/cl-lexer/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "cl-lexer"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-token = { path = "../cl-token" }
+cl-structures = { path = "../cl-structures" }
+unicode-ident = "1.0.12"

compiler/cl-lexer/src/lib.rs

@@ -0,0 +1,522 @@
+//! Converts a text file into tokens
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+use cl_structures::span::Loc;
+use cl_token::{TokenKind as Kind, *};
+use std::{
+    iter::Peekable,
+    str::{CharIndices, FromStr},
+};
+use unicode_ident::*;
+
+#[cfg(test)]
+mod tests;
+
+pub mod lexer_iter {
+    //! Iterator over a [`Lexer`], returning [`LResult<Token>`]s
+    use super::{
+        Lexer, Token,
+        error::{LResult, Reason},
+    };
+
+    /// Iterator over a [`Lexer`], returning [`LResult<Token>`]s
+    pub struct LexerIter<'t> {
+        lexer: Lexer<'t>,
+    }
+    impl Iterator for LexerIter<'_> {
+        type Item = LResult<Token>;
+        fn next(&mut self) -> Option<Self::Item> {
+            match self.lexer.scan() {
+                Ok(v) => Some(Ok(v)),
+                Err(e) => {
+                    if e.reason == Reason::EndOfFile {
+                        None
+                    } else {
+                        Some(Err(e))
+                    }
+                }
+            }
+        }
+    }
+    impl<'t> IntoIterator for Lexer<'t> {
+        type Item = LResult<Token>;
+        type IntoIter = LexerIter<'t>;
+        fn into_iter(self) -> Self::IntoIter {
+            LexerIter { lexer: self }
+        }
+    }
+}
+
+/// The Lexer iterates over the characters in a body of text, searching for [Tokens](Token).
+///
+/// # Examples
+/// ```rust
+/// # use cl_lexer::Lexer;
+/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+/// // Read in your code from somewhere
+/// let some_code = "
+/// fn main () {
+///     // TODO: code goes here!
+/// }
+/// ";
+/// // Create a lexer over your code
+/// let mut lexer = Lexer::new(some_code);
+/// // Scan for a single token
+/// let first_token = lexer.scan()?;
+/// println!("{first_token:?}");
+/// // Loop over all the rest of the tokens
+/// for token in lexer {
+/// #   let token: Result<_,()> = Ok(token?);
+///     match token {
+///         Ok(token) => println!("{token:?}"),
+///         Err(e) => eprintln!("{e:?}"),
+///     }
+/// }
+/// # Ok(()) }
+/// ```
+#[derive(Clone, Debug)]
+pub struct Lexer<'t> {
+    /// The source text
+    text: &'t str,
+    /// A peekable iterator over the source text
+    iter: Peekable<CharIndices<'t>>,
+    /// The end of the current token
+    head: usize,
+    /// The (line, col) end of the current token
+    head_loc: (u32, u32),
+    /// The start of the current token
+    tail: usize,
+    /// The (line, col) start of the current token
+    tail_loc: (u32, u32),
+}
+
+impl<'t> Lexer<'t> {
+    /// Creates a new [Lexer] over a [str]
+    pub fn new(text: &'t str) -> Self {
+        Self {
+            text,
+            iter: text.char_indices().peekable(),
+            head: 0,
+            head_loc: (1, 1),
+            tail: 0,
+            tail_loc: (1, 1),
+        }
+    }
+
+    /// Returns the current line
+    pub fn line(&self) -> u32 {
+        self.tail_loc.0
+    }
+
+    /// Returns the current column
+    pub fn col(&self) -> u32 {
+        self.tail_loc.1
+    }
+
+    /// Returns the current token's lexeme
+    fn lexeme(&mut self) -> &'t str {
+        &self.text[self.tail..self.head]
+    }
+
+    /// Peeks the next character without advancing the lexer
+    fn peek(&mut self) -> Option<char> {
+        self.iter.peek().map(|(_, c)| *c)
+    }
+
+    /// Advances the 'tail' (current position)
+    fn advance_tail(&mut self) {
+        let (idx, c) = self.iter.peek().copied().unwrap_or((self.text.len(), '\0'));
+        let (line, col) = &mut self.head_loc;
+        let diff = idx - self.head;
+
+        self.head = idx;
+        match c {
+            '\n' => {
+                *line += 1;
+                *col = 1;
+            }
+            _ => *col += diff as u32,
+        }
+    }
+
+    /// Takes the last-peeked character, or the next character if none peeked.
+    pub fn take(&mut self) -> Option<char> {
+        let (_, c) = self.iter.next()?;
+        self.advance_tail();
+        Some(c)
+    }
+
+    /// Takes the next char if it matches the `expected` char
+    pub fn next_if(&mut self, expected: char) -> Option<char> {
+        let (_, c) = self.iter.next_if(|&(_, c)| c == expected)?;
+        self.advance_tail();
+        Some(c)
+    }
+
+    /// Consumes the last-peeked character, advancing the tail
+    pub fn consume(&mut self) -> &mut Self {
+        self.iter.next();
+        self.advance_tail();
+        self
+    }
+
+    /// Produces an [Error] at the start of the current token
+    fn error(&self, reason: Reason) -> Error {
+        Error { reason, line: self.line(), col: self.col() }
+    }
+
+    /// Produces a token with the current [lexeme](Lexer::lexeme) as its data
+    fn produce(&mut self, kind: Kind) -> LResult<Token> {
+        let lexeme = self.lexeme().to_owned();
+        self.produce_with(kind, lexeme)
+    }
+
+    /// Produces a token with the provided `data`
+    fn produce_with(&mut self, kind: Kind, data: impl Into<TokenData>) -> LResult<Token> {
+        let loc = self.tail_loc;
+        self.tail_loc = self.head_loc;
+        self.tail = self.head;
+        Ok(Token::new(kind, data, loc.0, loc.1))
+    }
+
+    /// Produces a token with no `data`
+    fn produce_op(&mut self, kind: Kind) -> LResult<Token> {
+        self.produce_with(kind, ())
+    }
+
+    /// Consumes 0 or more whitespace
+    fn skip_whitespace(&mut self) -> &mut Self {
+        while self.peek().is_some_and(char::is_whitespace) {
+            let _ = self.consume();
+        }
+        self
+    }
+
+    /// Starts a new token
+    fn start_token(&mut self) -> &mut Self {
+        self.tail_loc = self.head_loc;
+        self.tail = self.head;
+        self
+    }
+
+    /// Scans through the text, searching for the next [Token]
+    pub fn scan(&mut self) -> LResult<Token> {
+        use TokenKind::*;
+        // !"#%&'()*+,-./:;<=>?@[\\]^`{|}~
+        let tok = match self
+            .skip_whitespace()
+            .start_token()
+            .peek()
+            .ok_or_else(|| self.error(Reason::EndOfFile))?
+        {
+            '!' => Bang,
+            '"' => return self.string(),
+            '#' => Hash,
+            '%' => Rem,
+            '&' => Amp,
+            '\'' => return self.character(),
+            '(' => LParen,
+            ')' => RParen,
+            '*' => Star,
+            '+' => Plus,
+            ',' => Comma,
+            '-' => Minus,
+            '.' => Dot,
+            '/' => Slash,
+            '0' => TokenKind::Literal,
+            '1'..='9' => return self.digits::<10>(),
+            ':' => Colon,
+            ';' => Semi,
+            '<' => Lt,
+            '=' => Eq,
+            '>' => Gt,
+            '?' => Question,
+            '@' => At,
+            '[' => LBrack,
+            '\\' => Backslash,
+            ']' => RBrack,
+            '^' => Xor,
+            '`' => Grave,
+            '{' => LCurly,
+            '|' => Bar,
+            '}' => RCurly,
+            '~' => Tilde,
+            '_' => return self.identifier(),
+            c if is_xid_start(c) => return self.identifier(),
+            e => {
+                let err = Err(self.error(Reason::UnexpectedChar(e)));
+                let _ = self.consume();
+                err?
+            }
+        };
+
+        // Handle digraphs
+        let tok = match (tok, self.consume().peek()) {
+            (Literal, Some('b')) => return self.consume().digits::<2>(),
+            (Literal, Some('d')) => return self.consume().digits::<10>(),
+            (Literal, Some('o')) => return self.consume().digits::<8>(),
+            (Literal, Some('x')) => return self.consume().digits::<16>(),
+            (Literal, Some('~')) => return self.consume().digits::<36>(),
+            (Literal, _) => return self.digits::<10>(),
+            (Amp, Some('&')) => AmpAmp,
+            (Amp, Some('=')) => AmpEq,
+            (Bang, Some('!')) => BangBang,
+            (Bang, Some('=')) => BangEq,
+            (Bar, Some('|')) => BarBar,
+            (Bar, Some('=')) => BarEq,
+            (Colon, Some(':')) => ColonColon,
+            (Dot, Some('.')) => DotDot,
+            (Eq, Some('=')) => EqEq,
+            (Eq, Some('>')) => FatArrow,
+            (Gt, Some('=')) => GtEq,
+            (Gt, Some('>')) => GtGt,
+            (Hash, Some('!')) => HashBang,
+            (Lt, Some('=')) => LtEq,
+            (Lt, Some('<')) => LtLt,
+            (Minus, Some('=')) => MinusEq,
+            (Minus, Some('>')) => Arrow,
+            (Plus, Some('=')) => PlusEq,
+            (Rem, Some('=')) => RemEq,
+            (Slash, Some('*')) => return self.block_comment()?.produce(Kind::Comment),
+            (Slash, Some('/')) => return self.line_comment(),
+            (Slash, Some('=')) => SlashEq,
+            (Star, Some('=')) => StarEq,
+            (Xor, Some('=')) => XorEq,
+            (Xor, Some('^')) => XorXor,
+            _ => return self.produce_op(tok),
+        };
+
+        // Handle trigraphs
+        let tok = match (tok, self.consume().peek()) {
+            (HashBang, Some('/')) => return self.line_comment(),
+            (DotDot, Some('=')) => DotDotEq,
+            (GtGt, Some('=')) => GtGtEq,
+            (LtLt, Some('=')) => LtLtEq,
+            _ => return self.produce_op(tok),
+        };
+
+        self.consume().produce_op(tok)
+    }
+}
+
+/// Comments
+impl Lexer<'_> {
+    /// Consumes until the next newline '\n', producing a [Comment](Kind::Comment)
+    fn line_comment(&mut self) -> LResult<Token> {
+        while self.consume().peek().is_some_and(|c| c != '\n') {}
+        self.produce(Kind::Comment)
+    }
+
+    /// Consumes nested block-comments. Does not produce by itself.
+    fn block_comment(&mut self) -> LResult<&mut Self> {
+        self.consume();
+        while let Some(c) = self.take() {
+            match (c, self.peek()) {
+                ('/', Some('*')) => self.block_comment()?,
+                ('*', Some('/')) => return Ok(self.consume()),
+                _ => continue,
+            };
+        }
+        Err(self.error(Reason::UnmatchedDelimiters('/')))
+    }
+}
+
+/// Identifiers
+impl Lexer<'_> {
+    /// Produces an [Identifier](Kind::Identifier) or keyword
+    fn identifier(&mut self) -> LResult<Token> {
+        while self.consume().peek().is_some_and(is_xid_continue) {}
+        if let Ok(keyword) = Kind::from_str(self.lexeme()) {
+            self.produce_with(keyword, ())
+        } else {
+            self.produce(Kind::Identifier)
+        }
+    }
+}
+
+/// Integers
+impl Lexer<'_> {
+    /// Produces a [Literal](Kind::Literal) with an integer or float value.
+    fn digits<const B: u32>(&mut self) -> LResult<Token> {
+        let mut value = 0;
+        while let Some(true) = self.peek().as_ref().map(char::is_ascii_alphanumeric) {
+            value = value * B as u128 + self.digit::<B>()? as u128;
+        }
+        // TODO: find a better way to handle floats in the tokenizer
+        match self.peek() {
+            Some('.') => {
+                // FIXME: hack: 0.. is not [0.0, '.']
+                if let Some('.') = self.clone().consume().take() {
+                    return self.produce_with(Kind::Literal, value);
+                }
+                let mut float = format!("{value}.");
+                self.consume();
+                while let Some(true) = self.peek().as_ref().map(char::is_ascii_digit) {
+                    float.push(self.iter.next().map(|(_, c)| c).unwrap_or_default());
+                }
+                let float = f64::from_str(&float).expect("must be parsable as float");
+                self.produce_with(Kind::Literal, float)
+            }
+            _ => self.produce_with(Kind::Literal, value),
+        }
+    }
+
+    /// Consumes a single digit of base [B](Lexer::digit)
+    fn digit<const B: u32>(&mut self) -> LResult<u32> {
+        let digit = self.take().ok_or_else(|| self.error(Reason::EndOfFile))?;
+        digit
+            .to_digit(B)
+            .ok_or_else(|| self.error(Reason::InvalidDigit(digit)))
+    }
+}
+
+/// Strings and characters
+impl Lexer<'_> {
+    /// Produces a [Literal](Kind::Literal) with a pre-escaped [String]
+    pub fn string(&mut self) -> Result<Token, Error> {
+        let mut lexeme = String::new();
+        let mut depth = 0;
+        self.consume();
+        loop {
+            lexeme.push(match self.take() {
+                None => Err(self.error(Reason::UnmatchedDelimiters('"')))?,
+                Some('\\') => self.unescape()?,
+                Some('"') if depth == 0 => break,
+                Some(c @ '{') => {
+                    depth += 1;
+                    c
+                }
+                Some(c @ '}') => {
+                    depth -= 1;
+                    c
+                }
+                Some(c) => c,
+            })
+        }
+        lexeme.shrink_to_fit();
+        self.produce_with(Kind::Literal, lexeme)
+    }
+
+    /// Produces a [Literal](Kind::Literal) with a pre-escaped [char]
+    fn character(&mut self) -> Result<Token, Error> {
+        let c = match self.consume().take() {
+            Some('\\') => self.unescape()?,
+            Some(c) => c,
+            None => '\0',
+        };
+        if self.take().is_some_and(|c| c == '\'') {
+            self.produce_with(Kind::Literal, c)
+        } else {
+            Err(self.error(Reason::UnmatchedDelimiters('\'')))
+        }
+    }
+
+    /// Unescapes a single character
+    #[rustfmt::skip]
+    fn unescape(&mut self) -> LResult<char> {
+        Ok(match self.take().ok_or_else(|| self.error(Reason::EndOfFile))? {
+            ' ' => '\u{a0}',
+            '0' => '\0',
+            'a' => '\x07',
+            'b' => '\x08',
+            'e' => '\x1b',
+            'f' => '\x0c',
+            'n' => '\n',
+            'r' => '\r',
+            't' => '\t',
+            'u' => self.unicode_escape()?,
+            'x' => self.hex_escape()?,
+            chr => chr,
+        })
+    }
+    /// Unescapes a single 2-digit hex escape
+    fn hex_escape(&mut self) -> LResult<char> {
+        let out = (self.digit::<16>()? << 4) + self.digit::<16>()?;
+        char::from_u32(out).ok_or_else(|| self.error(Reason::BadUnicode(out)))
+    }
+
+    /// Unescapes a single \u{} unicode escape
+    pub fn unicode_escape(&mut self) -> Result<char, Error> {
+        self.next_if('{')
+            .ok_or_else(|| self.error(Reason::InvalidEscape('u')))?;
+        let mut out = 0;
+        while let Some(c) = self.take() {
+            if c == '}' {
+                return char::from_u32(out).ok_or_else(|| self.error(Reason::BadUnicode(out)));
+            }
+            out = out * 16
+                + c.to_digit(16)
+                    .ok_or_else(|| self.error(Reason::InvalidDigit(c)))?;
+        }
+        Err(self.error(Reason::UnmatchedDelimiters('}')))
+    }
+}
+
+impl<'t> From<&Lexer<'t>> for Loc {
+    fn from(value: &Lexer<'t>) -> Self {
+        Loc(value.line(), value.col())
+    }
+}
+
+use error::{Error, LResult, Reason};
+pub mod error {
+    //! [Error] type for the [Lexer](super::Lexer)
+    use std::fmt::Display;
+
+    /// Result type with [Err] = [Error]
+    pub type LResult<T> = Result<T, Error>;
+    #[derive(Clone, Debug, PartialEq, Eq)]
+    pub struct Error {
+        pub reason: Reason,
+        pub line: u32,
+        pub col: u32,
+    }
+    /// The reason for the [Error]
+    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+    pub enum Reason {
+        /// Found an opening delimiter of type [char], but not the expected closing delimiter
+        UnmatchedDelimiters(char),
+        /// Found a character that doesn't belong to any [TokenKind](cl_token::TokenKind)
+        UnexpectedChar(char),
+        /// Found a character that's not valid in an escape sequence while looking for an escape
+        /// sequence
+        UnknownEscape(char),
+        /// Escape sequence contains invalid hexadecimal digit or unmatched braces
+        InvalidEscape(char),
+        /// Character is not a valid digit in the requested base
+        InvalidDigit(char),
+        /// Unicode escape does not map to a valid unicode code-point
+        BadUnicode(u32),
+        /// Reached end of input
+        EndOfFile,
+    }
+    impl Error {
+        /// Returns the [Reason] for this error
+        pub fn reason(&self) -> &Reason {
+            &self.reason
+        }
+        /// Returns the (line, col) where the error happened
+        pub fn location(&self) -> (u32, u32) {
+            (self.line, self.col)
+        }
+    }
+    impl std::error::Error for Error {}
+    impl Display for Error {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "{}:{}: {}", self.line, self.col, self.reason)
+        }
+    }
+    impl Display for Reason {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            match self {
+                Reason::UnmatchedDelimiters(c) => write! {f, "Unmatched `{c:?}` in input"},
+                Reason::UnexpectedChar(c) => write!(f, "Character `{c:?}` not expected"),
+                Reason::UnknownEscape(c) => write!(f, "`\\{c}` is not a known escape sequence"),
+                Reason::InvalidEscape(c) => write!(f, "Escape sequence `\\{c}`... is malformed"),
+                Reason::InvalidDigit(c) => write!(f, "`{c:?}` is not a valid digit"),
+                Reason::BadUnicode(c) => write!(f, "`\\u{{{c:x}}}` is not valid unicode"),
+                Reason::EndOfFile => write!(f, "Reached end of input"),
+            }
+        }
+    }
+}

compiler/cl-lexer/src/tests.rs

@@ -0,0 +1,171 @@
+use crate::Lexer;
+use cl_token::*;
+
+macro test_lexer_output_type  ($($f:ident {$($test:expr => $expect:expr),*$(,)?})*) {$(
+    #[test]
+    fn $f() {$(
+        assert_eq!(
+            Lexer::new($test)
+                .into_iter()
+                .map(|t| t.unwrap().ty())
+                .collect::<Vec<_>>(),
+            dbg!($expect)
+        );
+    )*}
+)*}
+
+macro test_lexer_data_type  ($($f:ident {$($test:expr => $expect:expr),*$(,)?})*) {$(
+    #[test]
+    fn $f() {$(
+        assert_eq!(
+            Lexer::new($test)
+                .into_iter()
+                .map(|t| t.unwrap().into_data())
+                .collect::<Vec<_>>(),
+            dbg!($expect)
+        );
+    )*}
+)*}
+
+/// Convert an `[ expr, ... ]` into a `[ *, ... ]`
+macro td ($($id:expr),*) {
+    [$($id.into()),*]
+}
+
+mod ident {
+    use super::*;
+    macro ident ($($id:literal),*) {
+        [$(TokenData::String($id.into())),*]
+    }
+    test_lexer_data_type! {
+        underscore { "_ _" => ident!["_", "_"] }
+        unicode { "_ε ε_" => ident!["_ε", "ε_"] }
+        many_underscore { "____________________________________" =>
+        ident!["____________________________________"] }
+    }
+}
+mod keyword {
+    use super::*;
+    macro kw($($k:ident),*) {
+        [ $(TokenKind::$k,)* ]
+    }
+    test_lexer_output_type! {
+        kw_break { "break break" => kw![Break, Break] }
+        kw_continue { "continue continue" => kw![Continue, Continue] }
+        kw_else { "else else" => kw![Else, Else] }
+        kw_false { "false false" => kw![False, False] }
+        kw_for { "for for" => kw![For, For] }
+        kw_fn { "fn fn" => kw![Fn, Fn] }
+        kw_if { "if if" => kw![If, If] }
+        kw_in { "in in" => kw![In, In] }
+        kw_let { "let let" => kw![Let, Let] }
+        kw_return { "return return" => kw![Return, Return] }
+        kw_true { "true true" => kw![True, True] }
+        kw_while { "while while" => kw![While, While] }
+        keywords { "break continue else false for fn if in let return true while" =>
+            kw![Break, Continue, Else, False, For, Fn, If, In, Let, Return, True, While] }
+    }
+}
+mod integer {
+    use super::*;
+    test_lexer_data_type! {
+        hex {
+            "0x0 0x1 0x15 0x2100 0x8000" =>
+            td![0x0, 0x1, 0x15, 0x2100, 0x8000]
+        }
+        dec {
+            "0d0 0d1 0d21 0d8448 0d32768" =>
+            td![0, 0x1, 0x15, 0x2100, 0x8000]
+        }
+        oct {
+            "0o0 0o1 0o25 0o20400 0o100000" =>
+            td![0x0, 0x1, 0x15, 0x2100, 0x8000]
+        }
+        bin {
+            "0b0 0b1 0b10101 0b10000100000000 0b1000000000000000" =>
+            td![0x0, 0x1, 0x15, 0x2100, 0x8000]
+        }
+        baseless {
+            "0 1 21 8448 32768" =>
+            td![0x0, 0x1, 0x15, 0x2100, 0x8000]
+        }
+    }
+}
+mod string {
+    use super::*;
+    test_lexer_data_type! {
+        empty_string {
+            "\"\"" =>
+            td![String::from("")]
+        }
+        unicode_string {
+            "\"I 💙 🦈!\"" =>
+            td![String::from("I 💙 🦈!")]
+        }
+        escape_string {
+            " \"This is a shark: \\u{1f988}\" " =>
+            td![String::from("This is a shark: 🦈")]
+        }
+    }
+}
+mod punct {
+    macro op($op:ident) {
+        TokenKind::$op
+    }
+
+    use super::*;
+    test_lexer_output_type! {
+        l_curly   { "{ {"   => [ op!(LCurly), op!(LCurly) ] }
+        r_curly   { "} }"   => [ op!(RCurly), op!(RCurly) ] }
+        l_brack   { "[ ["   => [ op!(LBrack), op!(LBrack) ] }
+        r_brack   { "] ]"   => [ op!(RBrack), op!(RBrack) ] }
+        l_paren   { "( ("   => [ op!(LParen), op!(LParen) ] }
+        r_paren   { ") )"   => [ op!(RParen), op!(RParen) ] }
+        amp       { "& &"   => [ op!(Amp), op!(Amp) ] }
+        amp_amp   { "&& &&" => [ op!(AmpAmp), op!(AmpAmp) ] }
+        amp_eq    { "&= &=" => [ op!(AmpEq), op!(AmpEq) ] }
+        arrow     { "-> ->" => [ op!(Arrow), op!(Arrow)] }
+        at        { "@ @"   => [ op!(At), op!(At)] }
+        backslash { "\\ \\" => [ op!(Backslash), op!(Backslash)] }
+        bang      { "! !"   => [ op!(Bang), op!(Bang)] }
+        bangbang  { "!! !!" => [ op!(BangBang), op!(BangBang)] }
+        bangeq    { "!= !=" => [ op!(BangEq), op!(BangEq)] }
+        bar       { "| |"   => [ op!(Bar), op!(Bar)] }
+        barbar    { "|| ||" => [ op!(BarBar), op!(BarBar)] }
+        bareq     { "|= |=" => [ op!(BarEq), op!(BarEq)] }
+        colon     { ": :"   => [ op!(Colon), op!(Colon)] }
+        comma     { ", ,"   => [ op!(Comma), op!(Comma)] }
+        dot       { ". ."   => [ op!(Dot), op!(Dot)] }
+        dotdot    { ".. .." => [ op!(DotDot), op!(DotDot)] }
+        dotdoteq  { "..= ..=" => [ op!(DotDotEq), op!(DotDotEq)] }
+        eq        { "= ="   => [ op!(Eq), op!(Eq)] }
+        eqeq      { "== ==" => [ op!(EqEq), op!(EqEq)] }
+        fatarrow  { "=> =>" => [ op!(FatArrow), op!(FatArrow)] }
+        grave     { "` `"   => [ op!(Grave), op!(Grave)] }
+        gt        { "> >"   => [ op!(Gt), op!(Gt)] }
+        gteq      { ">= >=" => [ op!(GtEq), op!(GtEq)] }
+        gtgt      { ">> >>" => [ op!(GtGt), op!(GtGt)] }
+        gtgteq    { ">>= >>=" => [ op!(GtGtEq), op!(GtGtEq)] }
+        hash      { "# #"   => [ op!(Hash), op!(Hash)] }
+        lt        { "< <"   => [ op!(Lt), op!(Lt)] }
+        lteq      { "<= <=" => [ op!(LtEq), op!(LtEq)] }
+        ltlt      { "<< <<" => [ op!(LtLt), op!(LtLt)] }
+        ltlteq    { "<<= <<=" => [ op!(LtLtEq), op!(LtLtEq)] }
+        minus     { "- -"   => [ op!(Minus), op!(Minus)] }
+        minuseq   { "-= -=" => [ op!(MinusEq), op!(MinusEq)] }
+        plus      { "+ +"   => [ op!(Plus), op!(Plus)] }
+        pluseq    { "+= +=" => [ op!(PlusEq), op!(PlusEq)] }
+        question  { "? ?"   => [ op!(Question), op!(Question)] }
+        rem       { "% %"   => [ op!(Rem), op!(Rem)] }
+        remeq     { "%= %=" => [ op!(RemEq), op!(RemEq)] }
+        semi      { "; ;"   => [ op!(Semi), op!(Semi)] }
+        slash     { "/ /"   => [ op!(Slash), op!(Slash)] }
+        slasheq   { "/= /=" => [ op!(SlashEq), op!(SlashEq)] }
+        star      { "* *"   => [ op!(Star), op!(Star)] }
+        stareq    { "*= *=" => [ op!(StarEq), op!(StarEq)] }
+        tilde     { "~ ~"   => [ op!(Tilde), op!(Tilde)] }
+        xor       { "^ ^"   => [ op!(Xor), op!(Xor)] }
+        xoreq     { "^= ^=" => [ op!(XorEq), op!(XorEq)] }
+        xorxor    { "^^ ^^" => [ op!(XorXor), op!(XorXor)] }
+    }
+}

compiler/cl-parser/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "cl-parser"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-ast = { path = "../cl-ast" }
+cl-lexer = { path = "../cl-lexer" }
+cl-token = { path = "../cl-token" }
+cl-structures = { path = "../cl-structures" }

compiler/cl-parser/src/error.rs

@@ -0,0 +1,252 @@
+use super::*;
+
+use cl_ast::{Expr, Sym};
+use cl_lexer::error::{Error as LexError, Reason};
+use std::fmt::Display;
+pub type PResult<T> = Result<T, Error>;
+
+/// Contains information about [Parser] errors
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Error {
+    pub in_file: Sym,
+    pub reason: ErrorKind,
+    pub while_parsing: Parsing,
+    pub loc: Loc,
+}
+impl std::error::Error for Error {}
+
+/// Represents the reason for parse failure
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ErrorKind {
+    Lexical(LexError),
+    EndOfInput,
+    UnmatchedParentheses,
+    UnmatchedCurlyBraces,
+    UnmatchedSquareBrackets,
+    Unexpected(TokenKind),
+    ExpectedToken {
+        want: TokenKind,
+        got: TokenKind,
+    },
+    ExpectedParsing {
+        want: Parsing,
+    },
+    InvalidPattern(Box<Expr>),
+    /// Indicates unfinished code
+    Todo(&'static str),
+}
+impl From<LexError> for ErrorKind {
+    fn from(value: LexError) -> Self {
+        match value.reason() {
+            Reason::EndOfFile => Self::EndOfInput,
+            _ => Self::Lexical(value),
+        }
+    }
+}
+
+/// Compactly represents the stage of parsing an [Error] originated in
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Parsing {
+    Mutability,
+    Visibility,
+    Identifier,
+    Literal,
+
+    File,
+
+    Attrs,
+    Meta,
+    MetaKind,
+
+    Item,
+    ItemKind,
+    Generics,
+    Alias,
+    Const,
+    Static,
+    Module,
+    ModuleKind,
+    Function,
+    Param,
+    Struct,
+    StructKind,
+    StructMember,
+    Enum,
+    EnumKind,
+    Variant,
+    VariantKind,
+    Impl,
+    ImplKind,
+    Use,
+    UseTree,
+
+    Ty,
+    TyKind,
+    TySlice,
+    TyArray,
+    TyTuple,
+    TyRef,
+    TyFn,
+
+    Path,
+    PathPart,
+
+    Stmt,
+    StmtKind,
+    Let,
+
+    Expr,
+    ExprKind,
+    Closure,
+    Assign,
+    AssignKind,
+    Binary,
+    BinaryKind,
+    Unary,
+    UnaryKind,
+    Cast,
+    Index,
+    Structor,
+    Fielder,
+    Call,
+    Member,
+    Array,
+    ArrayRep,
+    AddrOf,
+    Block,
+    Group,
+    Tuple,
+    Loop,
+    While,
+    If,
+    For,
+    Else,
+    Break,
+    Return,
+    Continue,
+
+    Pattern,
+    Match,
+    MatchArm,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { in_file, reason, while_parsing, loc } = self;
+        match reason {
+            // TODO entries are debug-printed
+            ErrorKind::Todo(_) => write!(f, "{in_file}:{loc} {reason} {while_parsing:?}"),
+            // lexical errors print their own higher-resolution loc info
+            ErrorKind::Lexical(e) => write!(f, "{e} (while parsing {while_parsing})"),
+            _ => {
+                if !in_file.is_empty() {
+                    write!(f, "{in_file}:")?
+                }
+                write!(f, "{loc}: {reason} while parsing {while_parsing}")
+            }
+        }
+    }
+}
+impl Display for ErrorKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ErrorKind::Lexical(e) => e.fmt(f),
+            ErrorKind::EndOfInput => write!(f, "End of input"),
+            ErrorKind::UnmatchedParentheses => write!(f, "Unmatched parentheses"),
+            ErrorKind::UnmatchedCurlyBraces => write!(f, "Unmatched curly braces"),
+            ErrorKind::UnmatchedSquareBrackets => write!(f, "Unmatched square brackets"),
+            ErrorKind::Unexpected(t) => write!(f, "Encountered unexpected token `{t}`"),
+            ErrorKind::ExpectedToken { want: e, got: g } => write!(f, "Expected `{e}`, got `{g}`"),
+            ErrorKind::ExpectedParsing { want } => write!(f, "Expected {want}"),
+            ErrorKind::InvalidPattern(got) => write!(f, "Got invalid `{got}`"),
+            ErrorKind::Todo(unfinished) => write!(f, "TODO: {unfinished}"),
+        }
+    }
+}
+impl Display for Parsing {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Parsing::Visibility => "a visibility qualifier",
+            Parsing::Mutability => "a mutability qualifier",
+            Parsing::Identifier => "an identifier",
+            Parsing::Literal => "a literal",
+
+            Parsing::File => "a file",
+
+            Parsing::Attrs => "an attribute-set",
+            Parsing::Meta => "an attribute",
+            Parsing::MetaKind => "an attribute's arguments",
+            Parsing::Item => "an item",
+            Parsing::ItemKind => "an item",
+            Parsing::Generics => "a list of type arguments",
+            Parsing::Alias => "a type alias",
+            Parsing::Const => "a const item",
+            Parsing::Static => "a static variable",
+            Parsing::Module => "a module",
+            Parsing::ModuleKind => "a module",
+            Parsing::Function => "a function",
+            Parsing::Param => "a function parameter",
+            Parsing::Struct => "a struct",
+            Parsing::StructKind => "a struct",
+            Parsing::StructMember => "a struct member",
+            Parsing::Enum => "an enum",
+            Parsing::EnumKind => "an enum",
+            Parsing::Variant => "an enum variant",
+            Parsing::VariantKind => "an enum variant",
+            Parsing::Impl => "an impl block",
+            Parsing::ImplKind => "the target of an impl block",
+            Parsing::Use => "a use item",
+            Parsing::UseTree => "a use-tree",
+
+            Parsing::Ty => "a type",
+            Parsing::TyKind => "a type",
+            Parsing::TySlice => "a slice type",
+            Parsing::TyArray => "an array type",
+            Parsing::TyTuple => "a tuple of types",
+            Parsing::TyRef => "a reference type",
+            Parsing::TyFn => "a function pointer type",
+
+            Parsing::Path => "a path",
+            Parsing::PathPart => "a path component",
+
+            Parsing::Stmt => "a statement",
+            Parsing::StmtKind => "a statement",
+            Parsing::Let => "a local variable declaration",
+
+            Parsing::Expr => "an expression",
+            Parsing::ExprKind => "an expression",
+            Parsing::Closure => "an anonymous function",
+            Parsing::Assign => "an assignment",
+            Parsing::AssignKind => "an assignment operator",
+            Parsing::Binary => "a binary expression",
+            Parsing::BinaryKind => "a binary operator",
+            Parsing::Unary => "a unary expression",
+            Parsing::UnaryKind => "a unary operator",
+            Parsing::Cast => "an `as`-casting expression",
+            Parsing::Index => "an indexing expression",
+            Parsing::Structor => "a struct constructor expression",
+            Parsing::Fielder => "a struct field expression",
+            Parsing::Call => "a call expression",
+            Parsing::Member => "a member access expression",
+            Parsing::Array => "an array",
+            Parsing::ArrayRep => "an array of form [k;N]",
+            Parsing::AddrOf => "a borrow op",
+            Parsing::Block => "a block",
+            Parsing::Group => "a grouped expression",
+            Parsing::Tuple => "a tuple",
+            Parsing::Loop => "an unconditional loop expression",
+            Parsing::While => "a while expression",
+            Parsing::If => "an if expression",
+            Parsing::For => "a for expression",
+            Parsing::Else => "an else block",
+            Parsing::Break => "a break expression",
+            Parsing::Return => "a return expression",
+            Parsing::Continue => "a continue expression",
+
+            Parsing::Pattern => "a pattern",
+            Parsing::Match => "a match expression",
+            Parsing::MatchArm => "a match arm",
+        }
+        .fmt(f)
+    }
+}

compiler/cl-parser/src/inliner.rs

@@ -0,0 +1,118 @@
+//! The [ModuleInliner] reads files described in the module structure of the
+
+use crate::Parser;
+use cl_ast::{ast_visitor::Fold, *};
+use cl_lexer::Lexer;
+use std::path::{Path, PathBuf};
+
+pub type IoErrs = Vec<(PathBuf, std::io::Error)>;
+pub type ParseErrs = Vec<(PathBuf, crate::error::Error)>;
+
+pub struct ModuleInliner {
+    path: PathBuf,
+    io_errs: IoErrs,
+    parse_errs: ParseErrs,
+}
+
+impl ModuleInliner {
+    /// Creates a new [ModuleInliner]
+    pub fn new(root: impl AsRef<Path>) -> Self {
+        Self {
+            path: root.as_ref().to_path_buf(),
+            io_errs: Default::default(),
+            parse_errs: Default::default(),
+        }
+    }
+
+    /// Returns true when the [ModuleInliner] has errors to report
+    pub fn has_errors(&self) -> bool {
+        !(self.io_errs.is_empty() && self.parse_errs.is_empty())
+    }
+
+    /// Returns the [IO Errors](IoErrs) and [parse Errors](ParseErrs)
+    pub fn into_errs(self) -> Option<(IoErrs, ParseErrs)> {
+        self.has_errors().then_some((self.io_errs, self.parse_errs))
+    }
+
+    /// Traverses a [File], attempting to inline all submodules.
+    ///
+    /// This is a simple wrapper around [ModuleInliner::fold_file()] and
+    /// [ModuleInliner::into_errs()]
+    pub fn inline(mut self, file: File) -> Result<File, (File, IoErrs, ParseErrs)> {
+        let file = self.fold_file(file);
+
+        match self.into_errs() {
+            Some((io, parse)) => Err((file, io, parse)),
+            None => Ok(file),
+        }
+    }
+
+    /// Records an [I/O error](std::io::Error) for later
+    fn handle_io_error(&mut self, error: std::io::Error) -> Option<File> {
+        self.io_errs.push((self.path.clone(), error));
+        None
+    }
+
+    /// Records a [parse error](crate::error::Error) for later
+    fn handle_parse_error(&mut self, error: crate::error::Error) -> Option<File> {
+        self.parse_errs.push((self.path.clone(), error));
+        None
+    }
+}
+
+impl Fold for ModuleInliner {
+    /// Traverses down the module tree, entering ever nested directories
+    fn fold_module(&mut self, m: Module) -> Module {
+        let Module { name, file } = m;
+        self.path.push(&*name); // cd ./name
+
+        let file = self.fold_module_kind(file);
+
+        self.path.pop(); // cd ..
+        Module { name, file }
+    }
+}
+
+impl ModuleInliner {
+    /// Attempts to read and parse a file for every module in the tree
+    fn fold_module_kind(&mut self, m: Option<File>) -> Option<File> {
+        use std::borrow::Cow;
+        if let Some(f) = m {
+            return Some(self.fold_file(f));
+        }
+
+        // cd path/mod.cl
+        self.path.set_extension("cl");
+        let mut used_path: Cow<Path> = Cow::Borrowed(&self.path);
+
+        let file = match std::fs::read_to_string(&self.path) {
+            Err(error) => {
+                let Some(basename) = self.path.file_name() else {
+                    return self.handle_io_error(error);
+                };
+                used_path = Cow::Owned(
+                    self.path
+                        .parent()
+                        .and_then(Path::parent)
+                        .map(|path| path.join(basename))
+                        .unwrap_or_default(),
+                );
+
+                match std::fs::read_to_string(&used_path) {
+                    Err(error) => return self.handle_io_error(error),
+                    Ok(file) => file,
+                }
+            }
+            Ok(file) => file,
+        };
+
+        match Parser::new(used_path.display().to_string(), Lexer::new(&file)).parse() {
+            Err(e) => self.handle_parse_error(e),
+            Ok(file) => {
+                self.path.set_extension("");
+                // The newly loaded module may need further inlining
+                Some(self.fold_file(file))
+            }
+        }
+    }
+}

compiler/cl-parser/src/lib.rs

@@ -0,0 +1,18 @@
+//! Parses [tokens](cl_token::token) into an [AST](cl_ast)
+//!
+//! For the full grammar, see [grammar.ebnf][1]
+//!
+//! [1]: https://git.soft.fish/j/Conlang/src/branch/main/grammar.ebnf
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+
+pub use parser::Parser;
+
+use cl_structures::span::*;
+use cl_token::*;
+
+pub mod error;
+
+pub mod parser;
+
+pub mod inliner;

compiler/cl-parser/src/parser/prec.rs

@@ -0,0 +1,425 @@
+//! Parses an [ExprKind] using a modified pratt parser
+//!
+//! See also: [Expr::parse], [ExprKind::parse]
+//!
+//! Implementer's note: [ExprKind::parse] is the public API for parsing [ExprKind]s.
+//! Do not call it from within this function.
+
+use super::{Parse, *};
+
+/// Parses an [ExprKind]
+pub fn expr(p: &mut Parser, power: u8) -> PResult<Expr> {
+    let parsing = Parsing::ExprKind;
+    let start = p.loc();
+    // Prefix expressions
+    let mut head = Expr {
+        kind: match p.peek_kind(Parsing::Unary)? {
+            literal_like!() => Literal::parse(p)?.into(),
+            path_like!() => exprkind_pathlike(p)?,
+            TokenKind::Amp | TokenKind::AmpAmp => AddrOf::parse(p)?.into(),
+            TokenKind::Bar | TokenKind::BarBar => Closure::parse(p)?.into(),
+            TokenKind::Grave => Quote::parse(p)?.into(),
+            TokenKind::LCurly => Block::parse(p)?.into(),
+            TokenKind::LBrack => exprkind_arraylike(p)?,
+            TokenKind::LParen => exprkind_tuplelike(p)?,
+            TokenKind::Let => Let::parse(p)?.into(),
+            TokenKind::Match => Match::parse(p)?.into(),
+            TokenKind::While => ExprKind::While(While::parse(p)?),
+            TokenKind::If => ExprKind::If(If::parse(p)?),
+            TokenKind::For => ExprKind::For(For::parse(p)?),
+            TokenKind::Break => ExprKind::Break(Break::parse(p)?),
+            TokenKind::Return => ExprKind::Return(Return::parse(p)?),
+            TokenKind::Continue => {
+                p.consume_peeked();
+                ExprKind::Continue
+            }
+
+            op => {
+                let (kind, prec) =
+                    from_prefix(op).ok_or_else(|| p.error(Unexpected(op), parsing))?;
+                let ((), after) = prec.prefix().expect("should have a precedence");
+                p.consume_peeked();
+                Unary { kind, tail: expr(p, after)?.into() }.into()
+            }
+        },
+        span: Span(start, p.loc()),
+    };
+
+    fn from_postfix(op: TokenKind) -> Option<Precedence> {
+        Some(match op {
+            TokenKind::LBrack => Precedence::Index,
+            TokenKind::LParen => Precedence::Call,
+            TokenKind::LCurly => Precedence::Structor,
+            TokenKind::Dot => Precedence::Member,
+            TokenKind::As => Precedence::Cast,
+            _ => None?,
+        })
+    }
+
+    while let Ok(op) = p.peek_kind(parsing) {
+        // Postfix expressions
+        if let Some((before, ())) = from_postfix(op).and_then(Precedence::postfix) {
+            if before < power {
+                break;
+            }
+
+            head = Expr {
+                kind: match op {
+                    TokenKind::LBrack => {
+                        p.consume_peeked();
+                        let indices =
+                            sep(Expr::parse, TokenKind::Comma, TokenKind::RBrack, parsing)(p)?;
+                        p.match_type(TokenKind::RBrack, parsing)?;
+                        ExprKind::Index(Index { head: head.into(), indices })
+                    }
+                    TokenKind::LParen => {
+                        p.consume_peeked();
+                        let exprs =
+                            sep(Expr::parse, TokenKind::Comma, TokenKind::RParen, parsing)(p)?;
+                        p.match_type(TokenKind::RParen, parsing)?;
+                        Binary {
+                            kind: BinaryKind::Call,
+                            parts: (
+                                head,
+                                Expr { kind: Tuple { exprs }.into(), span: Span(start, p.loc()) },
+                            )
+                                .into(),
+                        }
+                        .into()
+                    }
+                    TokenKind::LCurly => match head.kind {
+                        ExprKind::Path(path) => ExprKind::Structor(structor_body(p, path)?),
+                        _ => break,
+                    },
+                    TokenKind::Dot => {
+                        p.consume_peeked();
+                        let kind = MemberKind::parse(p)?;
+                        Member { head: Box::new(head), kind }.into()
+                    }
+                    TokenKind::As => {
+                        p.consume_peeked();
+                        let ty = Ty::parse(p)?;
+                        Cast { head: head.into(), ty }.into()
+                    }
+                    _ => Err(p.error(Unexpected(op), parsing))?,
+                },
+                span: Span(start, p.loc()),
+            };
+            continue;
+        }
+        // infix expressions
+        if let Some((kind, prec)) = from_infix(op) {
+            let (before, after) = prec.infix().expect("should have a precedence");
+            if before < power {
+                break;
+            }
+            p.consume_peeked();
+
+            let tail = expr(p, after)?;
+            head = Expr {
+                kind: Binary { kind, parts: (head, tail).into() }.into(),
+                span: Span(start, p.loc()),
+            };
+            continue;
+        }
+
+        if let Some((kind, prec)) = from_modify(op) {
+            let (before, after) = prec.infix().expect("should have a precedence");
+            if before < power {
+                break;
+            }
+            p.consume_peeked();
+
+            let tail = expr(p, after)?;
+            head = Expr {
+                kind: Modify { kind, parts: (head, tail).into() }.into(),
+                span: Span(start, p.loc()),
+            };
+            continue;
+        }
+
+        if let TokenKind::Eq = op {
+            let (before, after) = Precedence::Assign
+                .infix()
+                .expect("should have a precedence");
+            if before < power {
+                break;
+            }
+            p.consume_peeked();
+
+            let tail = expr(p, after)?;
+            head = Expr {
+                kind: Assign { parts: (head, tail).into() }.into(),
+                span: Span(start, p.loc()),
+            };
+
+            continue;
+        }
+
+        if let TokenKind::As = op {
+            let before = Precedence::Cast.level();
+            if before < power {
+                break;
+            }
+            p.consume_peeked();
+
+            let ty = Ty::parse(p)?;
+            head = Expr { kind: Cast { head: head.into(), ty }.into(), span: Span(start, p.loc()) };
+
+            continue;
+        }
+
+        break;
+    }
+
+    Ok(head)
+}
+
+/// [Array] = '[' ([Expr] ',')* [Expr]? ']'
+///
+/// Array and ArrayRef are ambiguous until the second token,
+/// so they can't be independent subexpressions
+fn exprkind_arraylike(p: &mut Parser) -> PResult<ExprKind> {
+    const P: Parsing = Parsing::Array;
+    const START: TokenKind = TokenKind::LBrack;
+    const END: TokenKind = TokenKind::RBrack;
+
+    p.match_type(START, P)?;
+    let out = match p.peek_kind(P)? {
+        END => Array { values: vec![] }.into(),
+        _ => exprkind_array_rep(p)?,
+    };
+    p.match_type(END, P)?;
+    Ok(out)
+}
+
+/// [ArrayRep] = `[` [Expr] `;` [Expr] `]`
+fn exprkind_array_rep(p: &mut Parser) -> PResult<ExprKind> {
+    const P: Parsing = Parsing::Array;
+    const END: TokenKind = TokenKind::RBrack;
+
+    let first = Expr::parse(p)?;
+    Ok(match p.peek_kind(P)? {
+        TokenKind::Semi => ArrayRep {
+            value: first.into(),
+            repeat: {
+                p.consume_peeked();
+                p.parse()?
+            },
+        }
+        .into(),
+        TokenKind::RBrack => Array { values: vec![first] }.into(),
+        TokenKind::Comma => Array {
+            values: {
+                p.consume_peeked();
+                let mut out = vec![first];
+                out.extend(sep(Expr::parse, TokenKind::Comma, END, P)(p)?);
+                out
+            },
+        }
+        .into(),
+        ty => Err(p.error(Unexpected(ty), P))?,
+    })
+}
+
+/// [Group] = `(`([Empty](ExprKind::Empty)|[Expr]|[Tuple])`)`
+///
+/// [ExprKind::Empty] and [Group] are special cases of [Tuple]
+fn exprkind_tuplelike(p: &mut Parser) -> PResult<ExprKind> {
+    p.match_type(TokenKind::LParen, Parsing::Group)?;
+    let out = match p.peek_kind(Parsing::Group)? {
+        TokenKind::RParen => Ok(ExprKind::Empty),
+        _ => exprkind_group(p),
+    };
+    p.match_type(TokenKind::RParen, Parsing::Group)?;
+    out
+}
+
+/// [Group] = `(`([Empty](ExprKind::Empty)|[Expr]|[Tuple])`)`
+fn exprkind_group(p: &mut Parser) -> PResult<ExprKind> {
+    let first = Expr::parse(p)?;
+    match p.peek_kind(Parsing::Group)? {
+        TokenKind::Comma => {
+            let mut exprs = vec![first];
+            p.consume_peeked();
+            while TokenKind::RParen != p.peek_kind(Parsing::Tuple)? {
+                exprs.push(Expr::parse(p)?);
+                match p.peek_kind(Parsing::Tuple)? {
+                    TokenKind::Comma => p.consume_peeked(),
+                    _ => break,
+                };
+            }
+            Ok(Tuple { exprs }.into())
+        }
+        _ => Ok(Group { expr: first.into() }.into()),
+    }
+}
+
+/// Parses an expression beginning with a [Path] (i.e. [Path] or [Structor])
+fn exprkind_pathlike(p: &mut Parser) -> PResult<ExprKind> {
+    Path::parse(p).map(Into::into)
+}
+
+/// [Structor]Body = `{` ([Fielder] `,`)* [Fielder]? `}`
+fn structor_body(p: &mut Parser, to: Path) -> PResult<Structor> {
+    let init = delim(
+        sep(
+            Fielder::parse,
+            TokenKind::Comma,
+            CURLIES.1,
+            Parsing::Structor,
+        ),
+        CURLIES,
+        Parsing::Structor,
+    )(p)?;
+
+    Ok(Structor { to, init })
+}
+
+/// Precedence provides a total ordering among operators
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Precedence {
+    Assign,
+    Structor,  // A structor is never a valid conditional
+    Condition, // Anything that syntactically needs a block following it
+    Logic,
+    Compare,
+    Range,
+    Bitwise,
+    Shift,
+    Factor,
+    Term,
+    Unary,
+    Index,
+    Cast,
+    Member, // left-associative
+    Call,
+    Deref,
+}
+
+impl Precedence {
+    #[inline]
+    pub const fn level(self) -> u8 {
+        (self as u8) << 1
+    }
+
+    pub fn prefix(self) -> Option<((), u8)> {
+        match self {
+            Self::Assign => Some(((), self.level())),
+            Self::Unary => Some(((), self.level())),
+            Self::Deref => Some(((), self.level())),
+            _ => None,
+        }
+    }
+
+    pub fn infix(self) -> Option<(u8, u8)> {
+        let level = self.level();
+        match self {
+            Self::Unary => None,
+            Self::Assign => Some((level + 1, level)),
+            _ => Some((level, level + 1)),
+        }
+    }
+
+    pub fn postfix(self) -> Option<(u8, ())> {
+        match self {
+            Self::Structor | Self::Index | Self::Call | Self::Member | Self::Cast => {
+                Some((self.level(), ()))
+            }
+            _ => None,
+        }
+    }
+}
+
+impl From<ModifyKind> for Precedence {
+    fn from(_value: ModifyKind) -> Self {
+        Precedence::Assign
+    }
+}
+
+impl From<BinaryKind> for Precedence {
+    fn from(value: BinaryKind) -> Self {
+        use BinaryKind as Op;
+        match value {
+            Op::Call => Precedence::Call,
+            Op::Mul | Op::Div | Op::Rem => Precedence::Term,
+            Op::Add | Op::Sub => Precedence::Factor,
+            Op::Shl | Op::Shr => Precedence::Shift,
+            Op::BitAnd | Op::BitOr | Op::BitXor => Precedence::Bitwise,
+            Op::LogAnd | Op::LogOr | Op::LogXor => Precedence::Logic,
+            Op::RangeExc | Op::RangeInc => Precedence::Range,
+            Op::Lt | Op::LtEq | Op::Equal | Op::NotEq | Op::GtEq | Op::Gt => Precedence::Compare,
+        }
+    }
+}
+
+impl From<UnaryKind> for Precedence {
+    fn from(value: UnaryKind) -> Self {
+        use UnaryKind as Op;
+        match value {
+            Op::Loop => Precedence::Assign,
+            Op::Deref => Precedence::Deref,
+            _ => Precedence::Unary,
+        }
+    }
+}
+
+/// Creates helper functions for turning TokenKinds into AST operators
+macro operator($($name:ident ($takes:ident => $returns:ident) {$($t:ident => $p:ident),*$(,)?};)*) {$(
+    pub fn $name (value: $takes) -> Option<($returns, Precedence)> {
+        match value {
+            $($takes::$t => Some(($returns::$p, Precedence::from($returns::$p))),)*
+            _ => None?,
+        }
+    })*
+}
+
+operator! {
+    from_prefix (TokenKind => UnaryKind) {
+        Loop => Loop,
+        Star => Deref,
+        Minus => Neg,
+        Bang => Not,
+        DotDot => RangeExc,
+        DotDotEq => RangeInc,
+        At => At,
+        Tilde => Tilde,
+    };
+
+    from_modify(TokenKind => ModifyKind) {
+        AmpEq => And,
+        BarEq => Or,
+        XorEq => Xor,
+        LtLtEq => Shl,
+        GtGtEq => Shr,
+        PlusEq => Add,
+        MinusEq => Sub,
+        StarEq => Mul,
+        SlashEq => Div,
+        RemEq => Rem,
+    };
+
+    from_infix (TokenKind => BinaryKind) {
+        Lt => Lt,
+        LtEq => LtEq,
+        EqEq => Equal,
+        BangEq => NotEq,
+        GtEq => GtEq,
+        Gt => Gt,
+        DotDot => RangeExc,
+        DotDotEq => RangeInc,
+        AmpAmp => LogAnd,
+        BarBar => LogOr,
+        XorXor => LogXor,
+        Amp => BitAnd,
+        Bar => BitOr,
+        Xor => BitXor,
+        LtLt => Shl,
+        GtGt => Shr,
+        Plus => Add,
+        Minus => Sub,
+        Star => Mul,
+        Slash => Div,
+        Rem => Rem,
+    };
+}

compiler/cl-repl/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "cl-repl"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+cl-ast = { path = "../cl-ast" }
+cl-lexer = { path = "../cl-lexer" }
+cl-token = { path = "../cl-token" }
+cl-parser = { path = "../cl-parser" }
+cl-typeck = { path = "../cl-typeck" }
+cl-interpret = { path = "../cl-interpret" }
+cl-structures = { path = "../cl-structures" }
+cl-arena = { version = "0", registry = "soft-fish" }
+repline = { version = "*", registry = "soft-fish" }
+argwerk = "0.20.4"

compiler/cl-repl/examples/identify_tokens.rs

@@ -1,9 +1,10 @@
 //! This example grabs input from stdin, lexes it, and prints which lexer rules matched
 #![allow(unused_imports)]
-use conlang::lexer::Lexer;
+use cl_lexer::Lexer;
+use cl_token::Token;
 use std::{
     error::Error,
-    io::{stdin, IsTerminal, Read},
+    io::{IsTerminal, Read, stdin},
     path::{Path, PathBuf},
 };
 
@@ -57,7 +58,7 @@ fn lex_tokens(file: &str, path: Option<&Path>) -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
-fn print_token(t: conlang::token::Token) {
+fn print_token(t: Token) {
     println!(
         "{:02}:{:02}: {:#19} │{}│",
         t.line(),

compiler/cl-repl/examples/to_c.rs

@@ -0,0 +1,951 @@
+//! Pretty prints a conlang AST in yaml
+
+use cl_ast::{File, Stmt};
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use repline::{Repline, error::Error as RlError};
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    if let Some(path) = std::env::args().nth(1) {
+        let f = std::fs::read_to_string(&path).expect("Path must be valid.");
+        let mut parser = Parser::new(path, Lexer::new(&f));
+        let code: File = match parser.parse() {
+            Ok(f) => f,
+            Err(e) => {
+                eprintln!("{e}");
+                return Ok(());
+            }
+        };
+        CLangifier::new().p(&code);
+        println!();
+        return Ok(());
+    }
+    let mut rl = Repline::new("\x1b[33m", "cl>", "? >");
+    loop {
+        let mut line = match rl.read() {
+            Err(RlError::CtrlC(_)) => break,
+            Err(RlError::CtrlD(line)) => {
+                rl.deny();
+                line
+            }
+            Ok(line) => line,
+            Err(e) => Err(e)?,
+        };
+        if !line.ends_with(';') {
+            line.push(';');
+        }
+
+        let mut parser = Parser::new("stdin", Lexer::new(&line));
+        let code = match parser.parse::<Stmt>() {
+            Ok(code) => {
+                rl.accept();
+                code
+            }
+            Err(e) => {
+                print!("\x1b[40G\x1bJ\x1b[91m{e}\x1b[0m");
+                continue;
+            }
+        };
+        print!("\x1b[G\x1b[J");
+        CLangifier::new().p(&code);
+        println!();
+    }
+    Ok(())
+}
+
+pub use clangifier::CLangifier;
+pub mod clangifier {
+    use crate::clangify::CLangify;
+    use std::{
+        fmt::Display,
+        io::Write,
+        ops::{Add, Deref, DerefMut},
+    };
+    #[derive(Debug, Default)]
+    pub struct CLangifier {
+        depth: usize,
+    }
+
+    impl CLangifier {
+        pub fn new() -> Self {
+            Self::default()
+        }
+
+        pub fn indent(&mut self) -> Section<'_> {
+            Section::new(self)
+        }
+
+        /// Prints a [Yamlify] value
+        #[inline]
+        pub fn p<T: CLangify + ?Sized>(&mut self, yaml: &T) -> &mut Self {
+            yaml.print(self);
+            self
+        }
+
+        fn increase(&mut self) {
+            self.depth += 1;
+        }
+
+        fn decrease(&mut self) {
+            self.depth -= 1;
+        }
+
+        fn print_indentation(&self, writer: &mut impl Write) {
+            for _ in 0..self.depth {
+                let _ = write!(writer, "    ");
+            }
+        }
+
+        pub fn endl(&mut self) -> &mut Self {
+            self.p("\n")
+                .print_indentation(&mut std::io::stdout().lock());
+            self
+        }
+
+        /// Prints a section header and increases indentation
+        pub fn nest(&mut self, name: impl Display) -> Section<'_> {
+            print!("{name}");
+            self.indent()
+        }
+    }
+
+    impl<C: CLangify + ?Sized> Add<&C> for &mut CLangifier {
+        type Output = Self;
+
+        fn add(self, rhs: &C) -> Self::Output {
+            self.p(rhs)
+        }
+    }
+
+    /// Tracks the start and end of an indented block (a "section")
+    pub struct Section<'y> {
+        yamler: &'y mut CLangifier,
+    }
+
+    impl<'y> Section<'y> {
+        pub fn new(yamler: &'y mut CLangifier) -> Self {
+            yamler.increase();
+            Self { yamler }
+        }
+    }
+
+    impl Deref for Section<'_> {
+        type Target = CLangifier;
+        fn deref(&self) -> &Self::Target {
+            self.yamler
+        }
+    }
+    impl DerefMut for Section<'_> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.yamler
+        }
+    }
+
+    impl Drop for Section<'_> {
+        fn drop(&mut self) {
+            let Self { yamler } = self;
+            yamler.decrease();
+        }
+    }
+}
+
+pub mod clangify {
+    use core::panic;
+    use std::iter;
+
+    use super::clangifier::CLangifier;
+    use cl_ast::*;
+
+    pub trait CLangify {
+        fn print(&self, y: &mut CLangifier);
+    }
+
+    impl CLangify for File {
+        fn print(&self, mut y: &mut CLangifier) {
+            let File { name, items } = self;
+            // TODO: turn name into include guard
+            y = (y + "// Generated from " + name).endl();
+            for (idx, item) in items.iter().enumerate() {
+                if idx > 0 {
+                    y.endl().endl();
+                }
+                y.p(item);
+            }
+            y.endl();
+        }
+    }
+    impl CLangify for Visibility {
+        fn print(&self, _y: &mut CLangifier) {}
+    }
+    impl CLangify for Mutability {
+        fn print(&self, y: &mut CLangifier) {
+            if let Mutability::Not = self {
+                y.p("const ");
+            }
+        }
+    }
+
+    impl CLangify for Attrs {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { meta } = self;
+            y.nest("Attrs").p(meta);
+            todo!("Attributes");
+        }
+    }
+    impl CLangify for Meta {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, kind } = self;
+            y.nest("Meta").p(name).p(kind);
+            todo!("Attributes");
+        }
+    }
+    impl CLangify for MetaKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                MetaKind::Plain => y,
+                MetaKind::Equals(value) => y.p(value),
+                MetaKind::Func(args) => y.p(args),
+            };
+            todo!("Attributes");
+        }
+    }
+
+    impl CLangify for Item {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { span: _, attrs: _, vis, kind } = self;
+            y.p(vis).p(kind);
+        }
+    }
+    impl CLangify for ItemKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                ItemKind::Alias(f) => y.p(f),
+                ItemKind::Const(f) => y.p(f),
+                ItemKind::Static(f) => y.p(f),
+                ItemKind::Module(f) => y.p(f),
+                ItemKind::Function(f) => y.p(f),
+                ItemKind::Struct(f) => y.p(f),
+                ItemKind::Enum(f) => y.p(f),
+                ItemKind::Impl(f) => y.p(f),
+                ItemKind::Use(f) => y.p(f),
+            };
+        }
+    }
+    impl CLangify for Generics {
+        fn print(&self, _y: &mut CLangifier) {
+            let Self { vars } = self;
+            if !vars.is_empty() {
+                panic!("C doesn't have generics, dumbass.")
+            }
+        }
+    }
+    impl CLangify for Alias {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, from } = self;
+            y.p("typedef ").p(from).p(" ");
+            y.p(name).p("; ");
+        }
+    }
+    impl CLangify for Const {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, ty, init } = self;
+            y.p("const ").p(ty).p(" ");
+            y.p(name).p(" = ").p(init);
+        }
+    }
+    impl CLangify for Static {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { mutable, name, ty, init } = self;
+            y.p(mutable).p(ty).p(" ");
+            y.p(name).p(" = ").p(init);
+        }
+    }
+    impl CLangify for Module {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, file } = self;
+            y.nest("// mod ").p(name).p(" {").endl();
+            y.p(file);
+            y.endl().p("// } mod ").p(name);
+        }
+    }
+    impl CLangify for Function {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, gens: _, sign, bind, body } = self;
+            let TyFn { args, rety } = sign;
+            let types = match &args.kind {
+                TyKind::Tuple(TyTuple { types }) => types.as_slice(),
+                _ => panic!("Unsupported function args: {args}"),
+            };
+            let bind = match bind {
+                Pattern::Tuple(tup) => tup.as_slice(),
+                _ => panic!("Unsupported function binders: {args}"),
+            };
+            y.p(rety).p(" ").p(name).p(" (");
+            for (idx, (bind, ty)) in bind.iter().zip(types).enumerate() {
+                if idx > 0 {
+                    y.p(", ");
+                }
+                // y.print("/* TODO: desugar pat match args */");
+                y.p(ty).p(" ").p(bind);
+            }
+            y.p(") ").p(body);
+        }
+    }
+    impl CLangify for Struct {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, gens: _, kind } = self;
+            y.p("struct ").p(name).nest(" {").p(kind);
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for StructKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                StructKind::Empty => y.endl().p("char _zero_sized_t;"),
+                StructKind::Tuple(k) => {
+                    for (idx, ty) in k.iter().enumerate() {
+                        y.endl().p(ty).p(" _").p(&idx).p(";");
+                    }
+                    y
+                }
+                StructKind::Struct(k) => y.p(k),
+            };
+        }
+    }
+    impl CLangify for StructMember {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { vis, name, ty } = self;
+            y.p(vis).p(ty).p(" ").p(name).p(";");
+        }
+    }
+    impl CLangify for Enum {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, gens: _, variants } = self;
+            y.nest("enum ").p(name).p(" {").endl();
+            for (idx, variant) in variants.iter().enumerate() {
+                if idx > 0 {
+                    y.p(",").endl();
+                }
+                y.p(variant);
+            }
+            y.endl().p("\n}");
+        }
+    }
+    impl CLangify for Variant {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, kind, body } = self;
+            y.p(name).p(kind).p(body);
+        }
+    }
+    impl CLangify for Impl {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { gens, target, body } = self;
+            y.nest("/* TODO: impl ").p(gens).p(target).p(" { */ ");
+            y.p(body);
+            y.p("/* } // impl ").p(target).p(" */ ");
+        }
+    }
+    impl CLangify for ImplKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                ImplKind::Type(t) => y.p(t),
+                ImplKind::Trait { impl_trait, for_type } => {
+                    todo!("impl {impl_trait} for {for_type}")
+                }
+            };
+        }
+    }
+    impl CLangify for Use {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { absolute: _, tree } = self;
+            y.p(tree);
+        }
+    }
+    impl CLangify for UseTree {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                UseTree::Tree(trees) => y.p(trees),
+                UseTree::Path(path, tree) => y.p("/* ").p(path).p(" */").p(tree),
+                UseTree::Alias(from, to) => y.p("#import <").p(from).p(">.h// ").p(to).p(" "),
+                UseTree::Name(name) => y.p("#import <").p(name).p(".h> "),
+                UseTree::Glob => y.p("/* TODO: use globbing */"),
+            };
+        }
+    }
+    impl CLangify for Block {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { stmts } = self;
+            {
+                let mut y = y.nest("{");
+                y.endl();
+                if let [
+                    stmts @ ..,
+                    Stmt { span: _, kind: StmtKind::Expr(expr), semi: Semi::Unterminated },
+                ] = stmts.as_slice()
+                {
+                    y.p(stmts).p("return ").p(expr).p(";");
+                } else {
+                    y.p(stmts);
+                }
+            }
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for Stmt {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { span: _, kind, semi: _ } = self;
+            y.p(kind).p(";").endl();
+        }
+    }
+    impl CLangify for Semi {
+        fn print(&self, y: &mut CLangifier) {
+            y.p(";");
+        }
+    }
+    impl CLangify for StmtKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                StmtKind::Empty => y,
+                StmtKind::Item(s) => y.p(s),
+                StmtKind::Expr(s) => y.p(s),
+            };
+        }
+    }
+    impl CLangify for Expr {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { span: _, kind } = self;
+            y.p(kind);
+        }
+    }
+    impl CLangify for ExprKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                ExprKind::Closure(k) => todo!("Downgrade {k}"),
+                ExprKind::Quote(k) => k.print(y),
+                ExprKind::Let(k) => k.print(y),
+                ExprKind::Match(k) => k.print(y),
+                ExprKind::Assign(k) => k.print(y),
+                ExprKind::Modify(k) => k.print(y),
+                ExprKind::Binary(k) => k.print(y),
+                ExprKind::Unary(k) => k.print(y),
+                ExprKind::Cast(k) => k.print(y),
+                ExprKind::Member(k) => k.print(y),
+                ExprKind::Index(k) => k.print(y),
+                ExprKind::Structor(k) => k.print(y),
+                ExprKind::Path(k) => k.print(y),
+                ExprKind::Literal(k) => k.print(y),
+                ExprKind::Array(k) => k.print(y),
+                ExprKind::ArrayRep(k) => k.print(y),
+                ExprKind::AddrOf(k) => k.print(y),
+                ExprKind::Block(k) => k.print(y),
+                ExprKind::Empty => {}
+                ExprKind::Group(k) => k.print(y),
+                ExprKind::Tuple(k) => k.print(y),
+                ExprKind::While(k) => k.print(y),
+                ExprKind::If(k) => k.print(y),
+                ExprKind::For(k) => k.print(y),
+                ExprKind::Break(k) => k.print(y),
+                ExprKind::Return(k) => k.print(y),
+                ExprKind::Continue => {
+                    y.nest("continue");
+                }
+            }
+        }
+    }
+    impl CLangify for Quote {
+        fn print(&self, y: &mut CLangifier) {
+            y.nest("\"");
+            print!("{self}");
+            y.p("\"");
+        }
+    }
+    impl CLangify for Let {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { mutable, name, ty, init } = self;
+            let ty = ty.as_deref().map(|ty| &ty.kind).unwrap_or(&TyKind::Infer);
+            match ty {
+                TyKind::Array(TyArray { ty, count }) => {
+                    y.p(ty).p(" ").p(mutable).p(name).p("[").p(count).p("]");
+                }
+                TyKind::Fn(TyFn { args, rety }) => {
+                    y.nest("(").p(rety).p(" *").p(mutable).p(name).p(")(");
+                    match &args.kind {
+                        TyKind::Tuple(TyTuple { types }) => {
+                            for (idx, ty) in types.iter().enumerate() {
+                                if idx > 0 {
+                                    y.p(", ");
+                                }
+                                y.p(ty);
+                            }
+                        }
+                        _ => {
+                            y.p(args);
+                        }
+                    }
+                    y.p(")");
+                }
+                _ => {
+                    y.indent().p(ty).p(" ").p(mutable).p(name);
+                }
+            }
+            if let Some(init) = init {
+                y.p(" = ").p(init);
+            }
+        }
+    }
+
+    impl CLangify for Pattern {
+        fn print(&self, y: &mut CLangifier) {
+            // TODO: Pattern match desugaring!!!
+            match self {
+                Pattern::Name(name) => y.p(name),
+                Pattern::Path(path) => y.p(path),
+                Pattern::Literal(literal) => y.p(literal),
+                Pattern::Rest(name) => y.p("..").p(name),
+                Pattern::Ref(mutability, pattern) => y.p("&").p(mutability).p(pattern),
+                Pattern::RangeExc(head, tail) => y.p("RangeExc").p(head).p(tail),
+                Pattern::RangeInc(head, tail) => y.p("RangeExc").p(head).p(tail),
+                Pattern::Tuple(patterns) => y.nest("Tuple").p(patterns),
+                Pattern::Array(patterns) => y.nest("Array").p(patterns),
+                Pattern::Struct(path, items) => {
+                    {
+                        let mut y = y.nest("Struct");
+                        y.p(path);
+                        for (name, item) in items {
+                            y.p(name).p(item);
+                        }
+                    }
+                    y
+                }
+                Pattern::TupleStruct(path, items) => {
+                    {
+                        let mut y = y.nest("TupleStruct");
+                        y.p(path).p(items);
+                    }
+                    y
+                }
+            };
+        }
+    }
+    impl CLangify for Match {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { scrutinee, arms } = self;
+            y.p("/* match ").p(scrutinee);
+            y.nest(" { ").p(arms);
+            y.p(" } */");
+        }
+    }
+
+    impl CLangify for MatchArm {
+        fn print(&self, y: &mut CLangifier) {
+            let Self(pat, expr) = self;
+            y.p(pat).p(" => ").p(expr).p(", ");
+        }
+    }
+    impl CLangify for Assign {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { parts } = self;
+            y.p(&parts.0).p(" = ").p(&parts.1);
+        }
+    }
+    impl CLangify for Modify {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { kind, parts } = self;
+            y.p(&parts.0).p(kind).p(&parts.1);
+        }
+    }
+    impl CLangify for ModifyKind {
+        fn print(&self, _y: &mut CLangifier) {
+            print!(" {self} ");
+        }
+    }
+    impl CLangify for Binary {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { kind, parts } = self;
+            match kind {
+                BinaryKind::Call => y.p(&parts.0).p(&parts.1),
+                _ => y.p("(").p(&parts.0).p(kind).p(&parts.1).p(")"),
+            };
+        }
+    }
+    impl CLangify for BinaryKind {
+        fn print(&self, _y: &mut CLangifier) {
+            print!(" {self} ");
+        }
+    }
+    impl CLangify for Unary {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { kind, tail } = self;
+            match kind {
+                UnaryKind::Deref => y.p("*").p(tail),
+                UnaryKind::Neg => y.p("-").p(tail),
+                UnaryKind::Not => y.p("!").p(tail),
+                UnaryKind::RangeInc => todo!("Unary RangeInc in C"),
+                UnaryKind::RangeExc => todo!("Unary RangeExc in C"),
+                UnaryKind::Loop => y.nest("while (1) { ").p(tail).p(" }"),
+                UnaryKind::At => todo!(),
+                UnaryKind::Tilde => todo!(),
+            };
+        }
+    }
+    impl CLangify for Cast {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { head, ty } = self;
+            y.nest("(").p(ty).p(")");
+            y.p(head);
+        }
+    }
+    impl CLangify for Member {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { head, kind } = self;
+            match kind {
+                MemberKind::Call(name, Tuple { exprs }) => {
+                    y.p(name);
+                    y.p("(");
+                    for (idx, expr) in iter::once(head.as_ref()).chain(exprs).enumerate() {
+                        if idx > 0 {
+                            y.p(", ");
+                        }
+                        y.p(expr);
+                    }
+                    y.p(")")
+                }
+                MemberKind::Struct(name) => y.p(head).p(".").p(name),
+                MemberKind::Tuple(idx) => y.p(head).p("._").p(idx),
+            };
+        }
+    }
+    impl CLangify for Tuple {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { exprs } = self;
+            let mut y = y.nest("( ");
+            for (idx, expr) in exprs.iter().enumerate() {
+                if idx > 0 {
+                    y.p(", ");
+                }
+                y.p(expr);
+            }
+            y.p(" )");
+        }
+    }
+    impl CLangify for Index {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { head, indices } = self;
+            y.p(head);
+            for index in indices {
+                y.p("[").p(index).p("]");
+            }
+        }
+    }
+    impl CLangify for Structor {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { to, init } = self;
+            y.nest("(").p(to).p(")");
+            {
+                let mut y = y.nest("{ ");
+                for (idx, field) in init.iter().enumerate() {
+                    if idx > 0 {
+                        y.p(", ");
+                    }
+                    y.p(field);
+                }
+                y.p(init);
+            }
+            y.p("}");
+        }
+    }
+    impl CLangify for Fielder {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { name, init } = self;
+            y.p(".").p(name).p(" = ").p(init);
+        }
+    }
+    impl CLangify for Array {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { values } = self;
+            {
+                let mut y = y.nest("{");
+                y.endl();
+                for (idx, value) in values.iter().enumerate() {
+                    if idx > 0 {
+                        y.p(", ");
+                    }
+                    y.p(value);
+                }
+            }
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for ArrayRep {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { value, repeat } = self;
+            let ExprKind::Literal(Literal::Int(repeat)) = &repeat.kind else {
+                eprintln!("Constant needs folding: {repeat}");
+                return;
+            };
+            {
+                let mut y = y.nest("{");
+                for _ in 0..*repeat {
+                    y.endl().p(value).p(",");
+                }
+            }
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for AddrOf {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { mutable: _, expr } = self;
+            y.p("&").p(expr);
+        }
+    }
+    impl CLangify for Group {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { expr } = self;
+            y.p("(").p(expr).p(")");
+        }
+    }
+    impl CLangify for While {
+        fn print(&self, y: &mut CLangifier) {
+            // TODO: to properly propagate intermediate values, a new temp variable needs to be
+            // declared on every line lmao. This will require type info.
+            let Self { cond, pass, fail } = self;
+            let Else { body: fail } = fail;
+            y.nest("while(1) {")
+                .endl()
+                .p("if (")
+                .p(cond)
+                .p(") ")
+                .p(pass);
+            {
+                let mut y = y.nest(" else {");
+                y.endl();
+                if let Some(fail) = fail {
+                    y.p(fail).p(";").endl();
+                }
+                y.p("break;");
+            }
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for Else {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { body } = self;
+            if let Some(body) = body {
+                y.p(" else ").p(body);
+            }
+        }
+    }
+    impl CLangify for If {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { cond, pass, fail } = self;
+            y.p("if (").p(cond).p(")");
+            y.p(pass).p(fail);
+        }
+    }
+    impl CLangify for For {
+        #[rustfmt::skip]
+        fn print(&self, y: &mut CLangifier) {
+            let Self { bind, cond, pass, fail: _ } = self;
+            let (mode, (head, tail)) = match &cond.kind {
+                ExprKind::Binary(Binary { kind: BinaryKind::RangeExc, parts }) => (false, &**parts),
+                ExprKind::Binary(Binary { kind: BinaryKind::RangeInc, parts }) => (true, &**parts),
+                _ => todo!("Clangify for loops"),
+            };
+            // for (int bind = head; bind mode? < : <= tail; bind++);
+            y.p("for ( int ").p(bind).p(" = ").p(head).p("; ");
+            y.p(bind).p(if mode {"<="} else {"<"}).p(tail).p("; ");
+            y.p("++").p(bind).p(" ) ").p(pass);
+
+        }
+    }
+    impl CLangify for Break {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { body } = self;
+            y.nest("break ").p(body);
+        }
+    }
+    impl CLangify for Return {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { body } = self;
+            y.nest("return ").p(body);
+        }
+    }
+    impl CLangify for Literal {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                Literal::Float(l) => y.p(l),
+                Literal::Bool(l) => y.p(l),
+                Literal::Int(l) => y.p(l),
+                Literal::Char(l) => y.p("'").p(l).p("'"),
+                Literal::String(l) => y.p(&'"').p(l).p(&'"'),
+            };
+        }
+    }
+    impl CLangify for Sym {
+        fn print(&self, y: &mut CLangifier) {
+            y.p(self.to_ref());
+        }
+    }
+    impl CLangify for Ty {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { span: _, kind, gens: _ } = self;
+            y.p(kind);
+        }
+    }
+    impl CLangify for TyKind {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                TyKind::Never => y.p("Never"),
+                TyKind::Infer => y.p("auto"),
+                TyKind::Path(t) => y.p(t),
+                TyKind::Tuple(t) => y.p(t),
+                TyKind::Ref(t) => y.p(t),
+                TyKind::Ptr(t) => y.p(t),
+                TyKind::Fn(t) => y.p(t),
+                TyKind::Slice(t) => y.p(t),
+                TyKind::Array(t) => y.p(t),
+            };
+        }
+    }
+    impl CLangify for Path {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { absolute: _, parts } = self;
+            for (idx, part) in parts.iter().enumerate() {
+                if idx > 0 {
+                    y.p("_");
+                }
+                y.p(part);
+            }
+        }
+    }
+    impl CLangify for PathPart {
+        fn print(&self, y: &mut CLangifier) {
+            match self {
+                PathPart::SuperKw => y.p("super"),
+                PathPart::SelfTy => y.p("Self"),
+                PathPart::Ident(i) => y.p(i),
+            };
+        }
+    }
+    impl CLangify for TyArray {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { ty, count } = self;
+            y.p(ty).p("[").p(count).p("]");
+        }
+    }
+    impl CLangify for TySlice {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { ty } = self;
+            y.p(ty).p("* ");
+        }
+    }
+    impl CLangify for TyTuple {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { types } = self;
+            {
+                let mut y = y.nest("struct {");
+                y.endl();
+                for (idx, ty) in types.iter().enumerate() {
+                    if idx > 0 {
+                        y.p(",").endl();
+                    }
+                    y.p(ty);
+                }
+            }
+            y.endl().p("}");
+        }
+    }
+    impl CLangify for TyRef {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { count, mutable, to } = self;
+            y.p(mutable).p(to);
+            for _ in 0..*count {
+                y.p("*");
+            }
+        }
+    }
+    impl CLangify for TyPtr {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { to } = self;
+            y.p(to).p("*");
+        }
+    }
+    impl CLangify for TyFn {
+        fn print(&self, y: &mut CLangifier) {
+            let Self { args, rety } = self;
+            // TODO: function pointer syntax
+            y.nest("(").p(rety).p(" *)(");
+            match &args.kind {
+                TyKind::Tuple(TyTuple { types }) => {
+                    for (idx, ty) in types.iter().enumerate() {
+                        if idx > 0 {
+                            y.p(", ");
+                        }
+                        y.p(ty);
+                    }
+                    y
+                }
+                _ => y.p(args),
+            }
+            .p(")");
+        }
+    }
+
+    impl<T: CLangify> CLangify for Option<T> {
+        fn print(&self, y: &mut CLangifier) {
+            if let Some(v) = self {
+                y.p(v);
+            }
+        }
+    }
+    impl<T: CLangify> CLangify for Box<T> {
+        fn print(&self, y: &mut CLangifier) {
+            y.p(&**self);
+        }
+    }
+    impl<T: CLangify> CLangify for Vec<T> {
+        fn print(&self, y: &mut CLangifier) {
+            for thing in self {
+                y.p(thing);
+            }
+        }
+    }
+    impl<T: CLangify> CLangify for [T] {
+        fn print(&self, y: &mut CLangifier) {
+            for thing in self {
+                y.p(thing);
+            }
+        }
+    }
+    impl CLangify for () {
+        fn print(&self, _y: &mut CLangifier) {
+            // TODO: C has no language support for zst
+        }
+    }
+
+    impl<T: CLangify> CLangify for &T {
+        fn print(&self, y: &mut CLangifier) {
+            (*self).print(y)
+        }
+    }
+
+    impl CLangify for std::fmt::Arguments<'_> {
+        fn print(&self, _y: &mut CLangifier) {
+            print!("{self}")
+        }
+    }
+    macro_rules! scalar {
+        ($($t:ty),*$(,)?) => {
+            $(impl CLangify for $t {
+                fn print(&self, _y: &mut CLangifier) {
+                    print!("{self}");
+                }
+            })*
+        };
+    }
+
+    scalar! {
+        bool, char, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize, str, &str, String
+    }
+}

compiler/cl-repl/examples/yaml.rs

@@ -0,0 +1,768 @@
+//! Pretty prints a conlang AST in yaml
+
+use cl_ast::Stmt;
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use repline::{Repline, error::Error as RlError};
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let mut rl = Repline::new("\x1b[33m", "cl>", "? >");
+    loop {
+        let line = match rl.read() {
+            Err(RlError::CtrlC(_)) => break,
+            Err(RlError::CtrlD(line)) => {
+                rl.deny();
+                line
+            }
+            Ok(line) => line,
+            Err(e) => Err(e)?,
+        };
+
+        let mut parser = Parser::new("", Lexer::new(&line));
+        let code = match parser.parse::<Stmt>() {
+            Ok(code) => {
+                rl.accept();
+                code
+            }
+            Err(e) => {
+                print!("\x1b[40G\x1bJ\x1b[91m{e}\x1b[0m");
+                continue;
+            }
+        };
+        print!("\x1b[G\x1b[J\x1b[A");
+        Yamler::new().yaml(&code);
+        println!();
+    }
+    Ok(())
+}
+
+pub use yamler::Yamler;
+pub mod yamler {
+    use crate::yamlify::Yamlify;
+    use std::{
+        io::Write,
+        ops::{Deref, DerefMut},
+    };
+    #[derive(Debug, Default)]
+    pub struct Yamler {
+        depth: usize,
+    }
+
+    impl Yamler {
+        pub fn new() -> Self {
+            Self::default()
+        }
+
+        pub fn indent(&mut self) -> Section<'_> {
+            Section::new(self)
+        }
+
+        /// Prints a [Yamlify] value
+        #[inline]
+        pub fn yaml<T: Yamlify>(&mut self, yaml: &T) -> &mut Self {
+            yaml.yaml(self);
+            self
+        }
+
+        fn increase(&mut self) {
+            self.depth += 1;
+        }
+
+        fn decrease(&mut self) {
+            self.depth -= 1;
+        }
+
+        fn print_indentation(&self, writer: &mut impl Write) {
+            for _ in 0..self.depth {
+                let _ = write!(writer, "  ");
+            }
+        }
+
+        /// Prints a section header and increases indentation
+        pub fn key(&mut self, name: impl Yamlify) -> Section<'_> {
+            println!();
+            self.print_indentation(&mut std::io::stdout().lock());
+            print!("  ");
+            name.yaml(self);
+            print!(":");
+            self.indent()
+        }
+
+        /// Prints a yaml key value pair: `- name: "value"`
+        pub fn pair<D: Yamlify, T: Yamlify>(&mut self, name: D, value: T) -> &mut Self {
+            self.key(name).value(value);
+            self
+        }
+
+        /// Prints a yaml scalar value: `"name"``
+        pub fn value<D: Yamlify>(&mut self, value: D) -> &mut Self {
+            print!(" ");
+            value.yaml(self);
+            self
+        }
+
+        pub fn list<D: Yamlify>(&mut self, list: &[D]) -> &mut Self {
+            for value in list {
+                println!();
+                self.print_indentation(&mut std::io::stdout().lock());
+                self.yaml(&"- ").yaml(value);
+            }
+            self
+        }
+    }
+
+    /// Tracks the start and end of an indented block (a "section")
+    pub struct Section<'y> {
+        yamler: &'y mut Yamler,
+    }
+
+    impl<'y> Section<'y> {
+        pub fn new(yamler: &'y mut Yamler) -> Self {
+            yamler.increase();
+            Self { yamler }
+        }
+    }
+
+    impl Deref for Section<'_> {
+        type Target = Yamler;
+        fn deref(&self) -> &Self::Target {
+            self.yamler
+        }
+    }
+    impl DerefMut for Section<'_> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.yamler
+        }
+    }
+
+    impl Drop for Section<'_> {
+        fn drop(&mut self) {
+            let Self { yamler } = self;
+            yamler.decrease();
+        }
+    }
+}
+
+pub mod yamlify {
+    use super::yamler::Yamler;
+    use cl_ast::*;
+
+    pub trait Yamlify {
+        fn yaml(&self, y: &mut Yamler);
+    }
+
+    impl Yamlify for File {
+        fn yaml(&self, y: &mut Yamler) {
+            let File { name, items } = self;
+            y.key("File").pair("name", name).yaml(items);
+        }
+    }
+    impl Yamlify for Visibility {
+        fn yaml(&self, y: &mut Yamler) {
+            if let Visibility::Public = self {
+                y.pair("vis", "pub");
+            }
+        }
+    }
+    impl Yamlify for Mutability {
+        fn yaml(&self, y: &mut Yamler) {
+            if let Mutability::Mut = self {
+                y.pair("mut", true);
+            }
+        }
+    }
+
+    impl Yamlify for Attrs {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { meta } = self;
+            y.key("Attrs").yaml(meta);
+        }
+    }
+    impl Yamlify for Meta {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, kind } = self;
+            y.key("Meta").pair("name", name).yaml(kind);
+        }
+    }
+    impl Yamlify for MetaKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                MetaKind::Plain => y,
+                MetaKind::Equals(value) => y.pair("equals", value),
+                MetaKind::Func(args) => y.pair("args", args),
+            };
+        }
+    }
+
+    impl Yamlify for Item {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { span: _, attrs, vis, kind } = self;
+            y.key("Item").yaml(attrs).yaml(vis).yaml(kind);
+        }
+    }
+    impl Yamlify for ItemKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                ItemKind::Alias(f) => y.yaml(f),
+                ItemKind::Const(f) => y.yaml(f),
+                ItemKind::Static(f) => y.yaml(f),
+                ItemKind::Module(f) => y.yaml(f),
+                ItemKind::Function(f) => y.yaml(f),
+                ItemKind::Struct(f) => y.yaml(f),
+                ItemKind::Enum(f) => y.yaml(f),
+                ItemKind::Impl(f) => y.yaml(f),
+                ItemKind::Use(f) => y.yaml(f),
+            };
+        }
+    }
+    impl Yamlify for Generics {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { vars } = self;
+            y.key("Generics").value(vars);
+        }
+    }
+    impl Yamlify for Alias {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, from } = self;
+            y.key("Alias").pair("to", name).pair("from", from);
+        }
+    }
+    impl Yamlify for Const {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, ty, init } = self;
+            y.key("Const")
+                .pair("name", name)
+                .pair("ty", ty)
+                .pair("init", init);
+        }
+    }
+    impl Yamlify for Static {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { mutable, name, ty, init } = self;
+            y.key(name).yaml(mutable).pair("ty", ty).pair("init", init);
+        }
+    }
+    impl Yamlify for Module {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, file } = self;
+            y.key("Module").pair("name", name).yaml(file);
+        }
+    }
+    impl Yamlify for Function {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, gens, sign, bind, body } = self;
+            y.key("Function")
+                .pair("name", name)
+                .pair("gens", gens)
+                .pair("sign", sign)
+                .pair("bind", bind)
+                .pair("body", body);
+        }
+    }
+    impl Yamlify for Struct {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, gens, kind } = self;
+            y.key("Struct")
+                .pair("gens", gens)
+                .pair("name", name)
+                .yaml(kind);
+        }
+    }
+    impl Yamlify for StructKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                StructKind::Empty => y,
+                StructKind::Tuple(k) => y.yaml(k),
+                StructKind::Struct(k) => y.yaml(k),
+            };
+        }
+    }
+    impl Yamlify for StructMember {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { vis, name, ty } = self;
+            y.key("StructMember").yaml(vis).pair("name", name).yaml(ty);
+        }
+    }
+    impl Yamlify for Enum {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, gens, variants: kind } = self;
+            y.key("Enum")
+                .pair("gens", gens)
+                .pair("name", name)
+                .yaml(kind);
+        }
+    }
+    impl Yamlify for Variant {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, kind, body } = self;
+            y.key("Variant")
+                .pair("name", name)
+                .pair("kind", kind)
+                .pair("body", body);
+        }
+    }
+    impl Yamlify for Impl {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { gens, target, body } = self;
+            y.key("Impl")
+                .pair("gens", gens)
+                .pair("target", target)
+                .pair("body", body);
+        }
+    }
+    impl Yamlify for ImplKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                ImplKind::Type(t) => y.value(t),
+                ImplKind::Trait { impl_trait, for_type } => {
+                    y.pair("trait", impl_trait).pair("for_type", for_type)
+                }
+            };
+        }
+    }
+    impl Yamlify for Use {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { absolute, tree } = self;
+            y.key("Use").pair("absolute", absolute).yaml(tree);
+        }
+    }
+    impl Yamlify for UseTree {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                UseTree::Tree(trees) => y.pair("trees", trees),
+                UseTree::Path(path, tree) => y.pair("path", path).pair("tree", tree),
+                UseTree::Alias(from, to) => y.pair("from", from).pair("to", to),
+                UseTree::Name(name) => y.pair("name", name),
+                UseTree::Glob => y.value("Glob"),
+            };
+        }
+    }
+    impl Yamlify for Block {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { stmts } = self;
+            y.key("Block").yaml(stmts);
+        }
+    }
+    impl Yamlify for Stmt {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { span: _, kind, semi } = self;
+            y.key("Stmt").value(kind).yaml(semi);
+        }
+    }
+    impl Yamlify for Semi {
+        fn yaml(&self, y: &mut Yamler) {
+            if let Semi::Terminated = self {
+                y.pair("terminated", true);
+            }
+        }
+    }
+    impl Yamlify for StmtKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                StmtKind::Empty => y,
+                StmtKind::Item(s) => y.yaml(s),
+                StmtKind::Expr(s) => y.yaml(s),
+            };
+        }
+    }
+    impl Yamlify for Expr {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { span: _, kind } = self;
+            y.yaml(kind);
+        }
+    }
+    impl Yamlify for ExprKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                ExprKind::Closure(k) => k.yaml(y),
+                ExprKind::Quote(k) => k.yaml(y),
+                ExprKind::Let(k) => k.yaml(y),
+                ExprKind::Match(k) => k.yaml(y),
+                ExprKind::Assign(k) => k.yaml(y),
+                ExprKind::Modify(k) => k.yaml(y),
+                ExprKind::Binary(k) => k.yaml(y),
+                ExprKind::Unary(k) => k.yaml(y),
+                ExprKind::Cast(k) => k.yaml(y),
+                ExprKind::Member(k) => k.yaml(y),
+                ExprKind::Index(k) => k.yaml(y),
+                ExprKind::Structor(k) => k.yaml(y),
+                ExprKind::Path(k) => k.yaml(y),
+                ExprKind::Literal(k) => k.yaml(y),
+                ExprKind::Array(k) => k.yaml(y),
+                ExprKind::ArrayRep(k) => k.yaml(y),
+                ExprKind::AddrOf(k) => k.yaml(y),
+                ExprKind::Block(k) => k.yaml(y),
+                ExprKind::Empty => {}
+                ExprKind::Group(k) => k.yaml(y),
+                ExprKind::Tuple(k) => k.yaml(y),
+                ExprKind::While(k) => k.yaml(y),
+                ExprKind::If(k) => k.yaml(y),
+                ExprKind::For(k) => k.yaml(y),
+                ExprKind::Break(k) => k.yaml(y),
+                ExprKind::Return(k) => k.yaml(y),
+                ExprKind::Continue => {
+                    y.key("Continue");
+                }
+            }
+        }
+    }
+    impl Yamlify for Closure {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { arg, body } = self;
+            y.key("Closure").pair("arg", arg).pair("body", body);
+        }
+    }
+    impl Yamlify for Quote {
+        fn yaml(&self, y: &mut Yamler) {
+            y.key("Quote").value(self);
+        }
+    }
+    impl Yamlify for Let {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { mutable, name, ty, init } = self;
+            y.key("Let")
+                .pair("name", name)
+                .yaml(mutable)
+                .pair("ty", ty)
+                .pair("init", init);
+        }
+    }
+
+    impl Yamlify for Pattern {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                Pattern::Name(name) => y.value(name),
+                Pattern::Path(path) => y.value(path),
+                Pattern::Literal(literal) => y.value(literal),
+                Pattern::Rest(name) => y.pair("Rest", name),
+                Pattern::Ref(mutability, pattern) => y.yaml(mutability).pair("Pat", pattern),
+                Pattern::RangeInc(head, tail) => {
+                    y.key("RangeInc").pair("head", head).pair("tail", tail);
+                    y
+                }
+                Pattern::RangeExc(head, tail) => {
+                    y.key("RangeExc").pair("head", head).pair("tail", tail);
+                    y
+                }
+                Pattern::Tuple(patterns) => y.key("Tuple").list(patterns),
+                Pattern::Array(patterns) => y.key("Array").list(patterns),
+                Pattern::Struct(path, items) => {
+                    {
+                        let mut y = y.key("Struct");
+                        y.yaml(path);
+                        for (name, item) in items {
+                            y.pair(name, item);
+                        }
+                    }
+                    y
+                }
+                Pattern::TupleStruct(path, items) => {
+                    y.key("TupleStruct").yaml(path).list(items);
+                    y
+                }
+            };
+        }
+    }
+    impl Yamlify for Match {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { scrutinee, arms } = self;
+            y.key("Match")
+                .pair("scrutinee", scrutinee)
+                .pair("arms", arms);
+        }
+    }
+
+    impl Yamlify for MatchArm {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self(pat, expr) = self;
+            y.pair("pat", pat).pair("expr", expr);
+        }
+    }
+    impl Yamlify for Assign {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { parts } = self;
+            y.key("Assign")
+                .pair("head", &parts.0)
+                .pair("tail", &parts.1);
+        }
+    }
+    impl Yamlify for Modify {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { kind, parts } = self;
+            y.key("Modify")
+                .pair("kind", kind)
+                .pair("head", &parts.0)
+                .pair("tail", &parts.1);
+        }
+    }
+    impl Yamlify for Binary {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { kind, parts } = self;
+            y.key("Binary")
+                .pair("kind", kind)
+                .pair("head", &parts.0)
+                .pair("tail", &parts.1);
+        }
+    }
+    impl Yamlify for Unary {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { kind, tail } = self;
+            y.key("Unary").pair("kind", kind).pair("tail", tail);
+        }
+    }
+    impl Yamlify for Cast {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { head, ty } = self;
+            y.key("Cast").pair("head", head).pair("ty", ty);
+        }
+    }
+    impl Yamlify for Member {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { head, kind } = self;
+            y.key("Member").pair("head", head).pair("kind", kind);
+        }
+    }
+    impl Yamlify for MemberKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                MemberKind::Call(id, args) => y.pair("id", id).pair("args", args),
+                MemberKind::Struct(id) => y.pair("id", id),
+                MemberKind::Tuple(id) => y.pair("id", id),
+            };
+        }
+    }
+    impl Yamlify for Tuple {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { exprs } = self;
+            y.key("Tuple").list(exprs);
+        }
+    }
+    impl Yamlify for Index {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { head, indices } = self;
+            y.key("Index")
+                .pair("head", head)
+                .key("indices")
+                .list(indices);
+        }
+    }
+    impl Yamlify for Structor {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { to, init } = self;
+            y.key("Structor").pair("to", to).list(init);
+        }
+    }
+    impl Yamlify for Fielder {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, init } = self;
+            y.key("Fielder").pair("name", name).pair("init", init);
+        }
+    }
+    impl Yamlify for Array {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { values } = self;
+            y.key("Array").list(values);
+        }
+    }
+    impl Yamlify for ArrayRep {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { value, repeat } = self;
+            y.key("ArrayRep")
+                .pair("value", value)
+                .pair("repeat", repeat);
+        }
+    }
+    impl Yamlify for AddrOf {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { mutable, expr } = self;
+            y.key("AddrOf").yaml(mutable).pair("expr", expr);
+        }
+    }
+    impl Yamlify for Group {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { expr } = self;
+            y.key("Group").yaml(expr);
+        }
+    }
+    impl Yamlify for While {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { cond, pass, fail } = self;
+            y.key("While")
+                .pair("cond", cond)
+                .pair("pass", pass)
+                .yaml(fail);
+        }
+    }
+    impl Yamlify for Else {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("fail").yaml(body);
+        }
+    }
+    impl Yamlify for If {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { cond, pass, fail } = self;
+            y.key("If").pair("cond", cond).pair("pass", pass).yaml(fail);
+        }
+    }
+    impl Yamlify for For {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { bind, cond, pass, fail } = self;
+            y.key("For")
+                .pair("bind", bind)
+                .pair("cond", cond)
+                .pair("pass", pass)
+                .yaml(fail);
+        }
+    }
+    impl Yamlify for Break {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("Break").yaml(body);
+        }
+    }
+    impl Yamlify for Return {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("Return").yaml(body);
+        }
+    }
+    impl Yamlify for Literal {
+        fn yaml(&self, _y: &mut Yamler) {
+            match self {
+                Literal::Bool(v) => print!("{v}"),
+                Literal::Char(v) => print!("'{}'", v.escape_debug()),
+                Literal::Int(v) => print!("{v}"),
+                Literal::Float(v) => print!("{v}"),
+                Literal::String(v) => print!("{}", v.escape_debug()),
+            }
+        }
+    }
+    impl Yamlify for Ty {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { span: _, kind, gens } = self;
+            y.key("Ty").yaml(kind).yaml(gens);
+        }
+    }
+    impl Yamlify for TyKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                TyKind::Never => y.value("Never"),
+                TyKind::Infer => y.value("_"),
+                TyKind::Path(t) => y.yaml(t),
+                TyKind::Tuple(t) => y.yaml(t),
+                TyKind::Ref(t) => y.yaml(t),
+                TyKind::Ptr(t) => y.yaml(t),
+                TyKind::Fn(t) => y.yaml(t),
+                TyKind::Slice(t) => y.yaml(t),
+                TyKind::Array(t) => y.yaml(t),
+            };
+        }
+    }
+    impl Yamlify for Path {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { absolute, parts } = self;
+            let mut y = y.key("Path");
+            if *absolute {
+                y.pair("absolute", absolute);
+            }
+            y.yaml(parts);
+        }
+    }
+    impl Yamlify for PathPart {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                PathPart::SuperKw => y.value("super"),
+                PathPart::SelfTy => y.value("Self"),
+                PathPart::Ident(i) => y.yaml(i),
+            };
+        }
+    }
+    impl Yamlify for TyArray {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { ty, count } = self;
+            y.key("TyArray").pair("ty", ty).pair("count", count);
+        }
+    }
+    impl Yamlify for TySlice {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { ty } = self;
+            y.key("TyArray").pair("ty", ty);
+        }
+    }
+    impl Yamlify for TyTuple {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { types } = self;
+            let mut y = y.key("TyTuple");
+            for ty in types {
+                y.yaml(ty);
+            }
+        }
+    }
+    impl Yamlify for TyRef {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { count, mutable, to } = self;
+            y.key("TyRef")
+                .pair("count", count)
+                .yaml(mutable)
+                .pair("to", to);
+        }
+    }
+    impl Yamlify for TyPtr {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { to } = self;
+            y.key("TyPtr").pair("to", to);
+        }
+    }
+    impl Yamlify for TyFn {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { args, rety } = self;
+            y.key("TyFn").pair("args", args).pair("rety", rety);
+        }
+    }
+
+    impl<T: Yamlify> Yamlify for Option<T> {
+        fn yaml(&self, y: &mut Yamler) {
+            if let Some(v) = self {
+                y.yaml(v);
+            } else {
+                y.value("");
+            }
+        }
+    }
+    impl<T: Yamlify> Yamlify for Box<T> {
+        fn yaml(&self, y: &mut Yamler) {
+            y.yaml(&**self);
+        }
+    }
+    impl<T: Yamlify> Yamlify for Vec<T> {
+        fn yaml(&self, y: &mut Yamler) {
+            y.list(self);
+        }
+    }
+    impl Yamlify for () {
+        fn yaml(&self, _y: &mut Yamler) {}
+    }
+
+    impl<T: Yamlify> Yamlify for &T {
+        fn yaml(&self, y: &mut Yamler) {
+            (*self).yaml(y)
+        }
+    }
+
+    macro_rules! scalar {
+        ($($t:ty),*$(,)?) => {
+            $(impl Yamlify for $t {
+                fn yaml(&self, _y: &mut Yamler) {
+                    print!("{self}");
+                }
+            })*
+        };
+    }
+
+    scalar! {
+        bool, char, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize, &str, String,
+        BinaryKind, UnaryKind, ModifyKind, Sym,
+    }
+}

compiler/cl-repl/src/ansi.rs

@@ -0,0 +1,14 @@
+//! ANSI escape sequences
+
+pub const RED: &str = "\x1b[31m";
+pub const GREEN: &str = "\x1b[32m"; // the color of type checker mode
+pub const CYAN: &str = "\x1b[36m";
+pub const BRIGHT_GREEN: &str = "\x1b[92m";
+pub const BRIGHT_BLUE: &str = "\x1b[94m";
+pub const BRIGHT_MAGENTA: &str = "\x1b[95m";
+pub const BRIGHT_CYAN: &str = "\x1b[96m";
+pub const RESET: &str = "\x1b[0m";
+pub const OUTPUT: &str = "\x1b[38;5;117m";
+
+pub const CLEAR_LINES: &str = "\x1b[G\x1b[J";
+pub const CLEAR_ALL: &str = "\x1b[H\x1b[2J\x1b[3J";

compiler/cl-repl/src/args.rs

@@ -0,0 +1,68 @@
+//! Handles argument parsing (currently using the [argwerk] crate)
+
+use std::{io::IsTerminal, path::PathBuf, str::FromStr};
+
+argwerk::define! {
+    ///
+    ///The Conlang prototype debug interface
+    #[usage = "conlang [<file>] [-I <include...>] [-m <mode>] [-r <repl>]"]
+    #[derive(Clone, PartialEq, Eq, PartialOrd, Ord)]
+    pub struct Args {
+        pub file: Option<PathBuf>,
+        pub include: Vec<PathBuf>,
+        pub mode: Mode,
+        pub repl: bool = is_terminal(),
+    }
+
+    ///files to include
+    ["-I" | "--include", path] => {
+        include.push(path.into());
+    }
+    ///the CLI operating mode (`f`mt | `l`ex | `r`un)
+    ["-m" | "--mode", flr] => {
+        mode = flr.parse()?;
+    }
+    ///whether to start the repl (`true` or `false`)
+    ["-r" | "--repl", bool] => {
+        repl = bool.parse()?;
+    }
+    ///display usage information
+    ["-h" | "--help"] => {
+        println!("{}", Args::help());
+        if true { std::process::exit(0); }
+    }
+    ///the main source file
+    [#[option] path] if file.is_none() => {
+        file = path.map(Into::into);
+    }
+
+    [path] if file.is_some() => {
+        include.push(path.into());
+    }
+}
+
+/// gets whether stdin AND stdout are a terminal, for pipelining
+pub fn is_terminal() -> bool {
+    std::io::stdin().is_terminal() && std::io::stdout().is_terminal()
+}
+
+/// The CLI's operating mode
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Mode {
+    Lex,
+    Fmt,
+    #[default]
+    Run,
+}
+
+impl FromStr for Mode {
+    type Err = &'static str;
+    fn from_str(s: &str) -> Result<Self, &'static str> {
+        Ok(match s {
+            "f" | "fmt" | "p" | "pretty" => Mode::Fmt,
+            "l" | "lex" | "tokenize" | "token" => Mode::Lex,
+            "r" | "run" => Mode::Run,
+            _ => Err("Recognized modes are: 'r' \"run\", 'f' \"fmt\", 'l' \"lex\"")?,
+        })
+    }
+}

compiler/cl-repl/src/bin/conlang.rs

@@ -0,0 +1,5 @@
+use cl_repl::{args, cli::run};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    run(args::Args::args()?)
+}

compiler/cl-repl/src/cli.rs

@@ -0,0 +1,171 @@
+//! Implement's the command line interface
+use crate::{
+    args::{Args, Mode},
+    ctx::Context,
+    menu,
+    tools::print_token,
+};
+use cl_ast::File;
+use cl_interpret::{builtin::builtins, convalue::ConValue, env::Environment, interpret::Interpret};
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use std::{borrow::Cow, error::Error, path::Path};
+
+/// Run the command line interface
+pub fn run(args: Args) -> Result<(), Box<dyn Error>> {
+    let Args { file, include, mode, repl } = args;
+
+    let mut env = Environment::new();
+
+    env.add_builtins(&builtins! {
+        /// Lexes, parses, and evaluates an expression in the current env
+        fn eval(string) @env {
+            use cl_interpret::error::Error;
+            let string = match string {
+                ConValue::Str(string) => string.to_ref(),
+                ConValue::String(string) => string.as_str(),
+                ConValue::Ref(v) => {
+                    let string = env.get_id(*v).cloned().unwrap_or_default();
+                    return eval(env, &[string])
+                }
+                _ => Err(Error::TypeError())?
+            };
+            match Parser::new("eval", Lexer::new(string)).parse::<cl_ast::Stmt>() {
+                Err(e) => Ok(ConValue::Str(format!("{e}").into())),
+                Ok(v) => v.interpret(env),
+            }
+        }
+
+        /// Executes a file
+        fn import(path) @env {
+            use cl_interpret::error::Error;
+            match path {
+                ConValue::Str(path) => load_file(env, &**path).or(Ok(ConValue::Empty)),
+                ConValue::String(path) => load_file(env, &**path).or(Ok(ConValue::Empty)),
+                _ => Err(Error::TypeError())
+            }
+        }
+
+        fn putchar(ConValue::Char(c)) {
+            print!("{c}");
+            Ok(ConValue::Empty)
+        }
+
+        /// Gets a line of input from stdin
+        fn get_line(prompt) {
+            use cl_interpret::error::Error;
+            let prompt = match prompt {
+                ConValue::Str(prompt) => prompt.to_ref(),
+                ConValue::String(prompt) => prompt.as_str(),
+                _ => Err(Error::TypeError())?,
+            };
+            match repline::Repline::new("", prompt, "").read() {
+                Ok(line) => Ok(ConValue::String(line)),
+                Err(repline::Error::CtrlD(line)) => Ok(ConValue::String(line)),
+                Err(repline::Error::CtrlC(_)) => Err(cl_interpret::error::Error::Break(ConValue::Empty)),
+                Err(e) => Ok(ConValue::Str(e.to_string().into())),
+            }
+        }
+    });
+
+    for path in include {
+        load_file(&mut env, path)?;
+    }
+
+    if repl {
+        if let Some(file) = file
+            && let Err(e) = load_file(&mut env, file)
+        {
+            eprintln!("{e}")
+        }
+        let mut ctx = Context::with_env(env);
+        menu::main_menu(mode, &mut ctx)?;
+    } else {
+        let path = format_path_for_display(file.as_deref());
+        let code = match &file {
+            Some(file) => std::fs::read_to_string(file)?,
+            None => std::io::read_to_string(std::io::stdin())?,
+        };
+
+        match mode {
+            Mode::Lex => lex_code(&path, &code),
+            Mode::Fmt => fmt_code(&path, &code),
+            Mode::Run => run_code(&path, &code, &mut env),
+        }?;
+    }
+    Ok(())
+}
+
+fn format_path_for_display(path: Option<&Path>) -> Cow<'_, str> {
+    match path {
+        Some(file) => file
+            .to_str()
+            .map(Cow::Borrowed)
+            .unwrap_or_else(|| Cow::Owned(file.display().to_string())),
+        None => Cow::Borrowed(""),
+    }
+}
+
+fn load_file(env: &mut Environment, path: impl AsRef<Path>) -> Result<ConValue, Box<dyn Error>> {
+    let path = path.as_ref();
+    let inliner = cl_parser::inliner::ModuleInliner::new(path.with_extension(""));
+    let file = std::fs::read_to_string(path)?;
+    let code = Parser::new(path.display().to_string(), Lexer::new(&file)).parse()?;
+    let code = match inliner.inline(code) {
+        Ok(a) => a,
+        Err((code, io_errs, parse_errs)) => {
+            for (file, err) in io_errs {
+                eprintln!("{}:{err}", file.display());
+            }
+            for (file, err) in parse_errs {
+                eprintln!("{}:{err}", file.display());
+            }
+            code
+        }
+    };
+    use cl_ast::WeightOf;
+    eprintln!("File {} weighs {} units", code.name, code.weight_of());
+
+    match env.eval(&code) {
+        Ok(v) => Ok(v),
+        Err(e) => {
+            eprintln!("{e}");
+            Ok(ConValue::Empty)
+        }
+    }
+}
+
+fn lex_code(path: &str, code: &str) -> Result<(), Box<dyn Error>> {
+    for token in Lexer::new(code) {
+        if !path.is_empty() {
+            print!("{}:", path);
+        }
+        match token {
+            Ok(token) => print_token(&token),
+            Err(e) => println!("{e}"),
+        }
+    }
+    Ok(())
+}
+
+fn fmt_code(path: &str, code: &str) -> Result<(), Box<dyn Error>> {
+    let code = Parser::new(path, Lexer::new(code)).parse::<File>()?;
+    println!("{code}");
+    Ok(())
+}
+
+fn run_code(path: &str, code: &str, env: &mut Environment) -> Result<(), Box<dyn Error>> {
+    let code = Parser::new(path, Lexer::new(code)).parse::<File>()?;
+    match code.interpret(env)? {
+        ConValue::Empty => {}
+        ret => println!("{ret}"),
+    }
+    if env.get("main".into()).is_ok() {
+        match env.call("main".into(), &[]) {
+            Ok(ConValue::Empty) => {}
+            Ok(ret) => println!("{ret}"),
+            Err(e) => println!("Error: {e}"),
+        }
+    }
+    Ok(())
+}

compiler/cl-repl/src/ctx.rs

@@ -0,0 +1,24 @@
+use cl_interpret::{convalue::ConValue, env::Environment, error::IResult, interpret::Interpret};
+
+#[derive(Clone, Debug)]
+pub struct Context {
+    pub env: Environment,
+}
+
+impl Context {
+    pub fn new() -> Self {
+        Self { env: Environment::new() }
+    }
+    pub fn with_env(env: Environment) -> Self {
+        Self { env }
+    }
+    pub fn run(&mut self, code: &impl Interpret) -> IResult<ConValue> {
+        code.interpret(&mut self.env)
+    }
+}
+
+impl Default for Context {
+    fn default() -> Self {
+        Self::new()
+    }
+}

compiler/cl-repl/src/lib.rs

@@ -0,0 +1,11 @@
+//! The Conlang REPL, based on [repline]
+//!
+//! Uses [argwerk] for argument parsing.
+#![warn(clippy::all)]
+
+pub mod ansi;
+pub mod args;
+pub mod cli;
+pub mod ctx;
+pub mod menu;
+pub mod tools;

compiler/cl-repl/src/menu.rs

@@ -0,0 +1,126 @@
+use std::error::Error;
+
+use crate::{ansi, args::Mode, ctx};
+use cl_ast::Stmt;
+use cl_interpret::convalue::ConValue;
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use repline::{Error as RlError, error::ReplResult, prebaked::*};
+
+pub fn clear() {
+    print!("{}", ansi::CLEAR_ALL);
+    banner()
+}
+
+pub fn banner() {
+    println!("--- conlang v{} 💪🦈 ---", env!("CARGO_PKG_VERSION"))
+}
+
+type ReplCallback = fn(&mut ctx::Context, &str) -> Result<Response, Box<dyn Error>>;
+type ReplMode = (&'static str, &'static str, &'static str, ReplCallback);
+
+#[rustfmt::skip]
+const MODES: &[ReplMode] = &[
+    (ansi::CYAN,            ".>", " >", mode_run),
+    (ansi::BRIGHT_BLUE,     "l>", " >", mode_lex),
+    (ansi::BRIGHT_MAGENTA,  "f>", " >", mode_fmt),
+];
+
+const fn get_mode(mode: Mode) -> ReplMode {
+    match mode {
+        Mode::Lex => MODES[1],
+        Mode::Fmt => MODES[2],
+        Mode::Run => MODES[0],
+    }
+}
+
+/// Presents a selection interface to the user
+pub fn main_menu(mode: Mode, ctx: &mut ctx::Context) -> ReplResult<()> {
+    let mut mode = get_mode(mode);
+    banner();
+
+    let mut rl = repline::Repline::new(mode.0, mode.1, mode.2);
+    loop {
+        rl.set_prompt(mode.0, mode.1, mode.2);
+
+        let line = match rl.read() {
+            Err(RlError::CtrlC(_)) => return Ok(()),
+            Err(RlError::CtrlD(line)) => {
+                rl.deny();
+                line
+            }
+            Ok(line) => line,
+            Err(e) => Err(e)?,
+        };
+        print!("\x1b[G\x1b[J");
+        match line.trim() {
+            "" => continue,
+            "clear" => clear(),
+            "mode run" => mode = get_mode(Mode::Run),
+            "mode lex" => mode = get_mode(Mode::Lex),
+            "mode fmt" => mode = get_mode(Mode::Fmt),
+            "quit" => return Ok(()),
+            "help" => println!(
+                "Valid commands
+    help     : Print this list
+    clear    : Clear the screen
+    quit     : Exit the program
+    mode lex : Lex the input
+    mode fmt : Format the input
+    mode run : Evaluate some expressions"
+            ),
+            _ => match mode.3(ctx, &line) {
+                Ok(Response::Accept) => {
+                    rl.accept();
+                    continue;
+                }
+                Ok(Response::Deny) => {}
+                Ok(Response::Break) => return Ok(()),
+                Ok(Response::Continue) => continue,
+                Err(e) => rl.print_inline(format_args!("\t\x1b[91m{e}\x1b[0m"))?,
+            },
+        }
+        rl.deny();
+    }
+}
+
+pub fn mode_run(ctx: &mut ctx::Context, line: &str) -> Result<Response, Box<dyn Error>> {
+    use cl_ast::ast_visitor::Fold;
+    use cl_parser::inliner::ModuleInliner;
+
+    if line.trim().is_empty() {
+        return Ok(Response::Deny);
+    }
+    let code = Parser::new("", Lexer::new(line)).parse::<Stmt>()?;
+    let code = ModuleInliner::new(".").fold_stmt(code);
+
+    print!("{}", ansi::OUTPUT);
+    match ctx.run(&code) {
+        Ok(ConValue::Empty) => print!("{}", ansi::RESET),
+        Ok(v) => println!("{}{v}", ansi::RESET),
+        Err(e) => println!("{}! > {e}{}", ansi::RED, ansi::RESET),
+    }
+    Ok(Response::Accept)
+}
+
+pub fn mode_lex(_ctx: &mut ctx::Context, line: &str) -> Result<Response, Box<dyn Error>> {
+    for token in Lexer::new(line) {
+        match token {
+            Ok(token) => crate::tools::print_token(&token),
+            Err(e) => eprintln!("! > {}{e}{}", ansi::RED, ansi::RESET),
+        }
+    }
+
+    Ok(Response::Accept)
+}
+
+pub fn mode_fmt(_ctx: &mut ctx::Context, line: &str) -> Result<Response, Box<dyn Error>> {
+    let mut p = Parser::new("", Lexer::new(line));
+
+    match p.parse::<Stmt>() {
+        Ok(code) => println!("{}{code}{}", ansi::OUTPUT, ansi::RESET),
+        Err(e) => Err(e)?,
+    }
+
+    Ok(Response::Accept)
+}

compiler/cl-repl/src/tools.rs

@@ -0,0 +1,11 @@
+use cl_token::Token;
+/// Prints a token in the particular way [cl-repl](crate) does
+pub fn print_token(t: &Token) {
+    println!(
+        "{:02}:{:02}: {:#19} │{}│",
+        t.line(),
+        t.col(),
+        t.ty(),
+        t.data(),
+    )
+}

compiler/cl-structures/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "cl-structures"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-arena = { version = "0", registry = "soft-fish" }

compiler/cl-structures/src/index_map.rs

@@ -0,0 +1,219 @@
+//! Trivially-copyable, easily comparable typed [indices](MapIndex),
+//! and an [IndexMap] to contain them.
+//!
+//! # Examples
+//!
+//! ```rust
+//! # use cl_structures::index_map::*;
+//! // first, create a new MapIndex type (this ensures type safety)
+//! make_index! {
+//!     Number
+//! }
+//!
+//! // then, create a map with that type
+//! let mut numbers: IndexMap<Number, i32> = IndexMap::new();
+//! let first = numbers.insert(1);
+//! let second = numbers.insert(2);
+//! let third = numbers.insert(3);
+//!
+//! // You can access elements immutably with `get`
+//! assert_eq!(Some(&3), numbers.get(third));
+//! assert_eq!(Some(&2), numbers.get(second));
+//! // or by indexing
+//! assert_eq!(1, numbers[first]);
+//!
+//! // Or mutably
+//! *numbers.get_mut(first).unwrap() = 100000;
+//!
+//! assert_eq!(Some(&100000), numbers.get(first));
+//! ```
+
+/// Creates newtype indices over [`usize`] for use as [IndexMap] keys.
+///
+/// Generated key types implement [Clone], [Copy],
+/// [Debug](core::fmt::Debug), [PartialEq], [Eq], [PartialOrd], [Ord], [Hash](core::hash::Hash),
+/// and [MapIndex].
+#[macro_export]
+macro_rules! make_index {($($(#[$meta:meta])* $name:ident),*$(,)?) => {$(
+    $(#[$meta])*
+    #[repr(transparent)]
+    #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    pub struct $name(usize);
+
+    impl $crate::index_map::MapIndex for $name {
+        #[doc = concat!("Constructs a [`", stringify!($name), "`] from a [`usize`] without checking bounds.\n")]
+        /// The provided value should be within the bounds of its associated container
+        #[inline]
+        fn from_usize(value: usize) -> Self {
+            Self(value)
+        }
+        #[inline]
+        fn get(&self) -> usize {
+            self.0
+        }
+    }
+
+    impl From< $name > for usize {
+        fn from(value: $name) -> Self {
+            value.0
+        }
+    }
+)*}}
+
+use self::iter::MapIndexIter;
+use std::{
+    ops::{Index, IndexMut},
+    slice::GetDisjointMutError,
+};
+
+pub use make_index;
+
+/// An index into a [IndexMap]. For full type-safety,
+/// there should be a unique [MapIndex] for each [IndexMap].
+pub trait MapIndex: std::fmt::Debug {
+    /// Constructs an [`MapIndex`] from a [`usize`] without checking bounds.
+    ///
+    /// The provided value should be within the bounds of its associated container.
+    fn from_usize(value: usize) -> Self;
+    /// Gets the index of the [`MapIndex`] by value
+    fn get(&self) -> usize;
+}
+
+/// It's an array. Lmao.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct IndexMap<K: MapIndex, V> {
+    map: Vec<V>,
+    id_type: std::marker::PhantomData<K>,
+}
+
+impl<V, K: MapIndex> IndexMap<K, V> {
+    /// Constructs an empty IndexMap.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Gets a reference to the value in slot `index`.
+    pub fn get(&self, index: K) -> Option<&V> {
+        self.map.get(index.get())
+    }
+
+    /// Gets a mutable reference to the value in slot `index`.
+    pub fn get_mut(&mut self, index: K) -> Option<&mut V> {
+        self.map.get_mut(index.get())
+    }
+
+    /// Returns mutable references to many indices at once.
+    ///
+    /// Returns an error if any index is out of bounds, or if the same index was passed twice.
+    pub fn get_disjoint_mut<const N: usize>(
+        &mut self,
+        indices: [K; N],
+    ) -> Result<[&mut V; N], GetDisjointMutError> {
+        self.map.get_disjoint_mut(indices.map(|id| id.get()))
+    }
+
+    /// Returns an iterator over the IndexMap.
+    pub fn values(&self) -> impl Iterator<Item = &V> {
+        self.map.iter()
+    }
+
+    /// Returns an iterator that allows modifying each value.
+    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut V> {
+        self.map.iter_mut()
+    }
+
+    /// Returns an iterator over all keys in the IndexMap.
+    pub fn keys(&self) -> iter::MapIndexIter<K> {
+        // Safety: IndexMap currently has map.len() entries, and data cannot be removed
+        MapIndexIter::new(0..self.map.len())
+    }
+
+    /// Constructs an [ID](MapIndex) from a [usize], if it's within bounds
+    #[doc(hidden)]
+    pub fn try_key_from(&self, value: usize) -> Option<K> {
+        (value < self.map.len()).then(|| K::from_usize(value))
+    }
+
+    /// Inserts a new item into the IndexMap, returning the key associated with it.
+    pub fn insert(&mut self, value: V) -> K {
+        let id = self.map.len();
+        self.map.push(value);
+
+        // Safety: value was pushed to `self.map[id]`
+        K::from_usize(id)
+    }
+
+    /// Replaces a value in the IndexMap, returning the old value.
+    pub fn replace(&mut self, key: K, value: V) -> V {
+        std::mem::replace(&mut self[key], value)
+    }
+}
+
+impl<K: MapIndex, V> Default for IndexMap<K, V> {
+    fn default() -> Self {
+        Self { map: vec![], id_type: std::marker::PhantomData }
+    }
+}
+
+impl<K: MapIndex, V> Index<K> for IndexMap<K, V> {
+    type Output = V;
+
+    fn index(&self, index: K) -> &Self::Output {
+        match self.map.get(index.get()) {
+            None => panic!("Index {:?} out of bounds in IndexMap!", index),
+            Some(value) => value,
+        }
+    }
+}
+
+impl<K: MapIndex, V> IndexMut<K> for IndexMap<K, V> {
+    fn index_mut(&mut self, index: K) -> &mut Self::Output {
+        match self.map.get_mut(index.get()) {
+            None => panic!("Index {:?} out of bounds in IndexMap!", index),
+            Some(value) => value,
+        }
+    }
+}
+
+mod iter {
+    //! Iterators for [IndexMap](super::IndexMap)
+    use super::MapIndex;
+    use std::{marker::PhantomData, ops::Range};
+
+    /// Iterates over the keys of an [IndexMap](super::IndexMap), independently of the map.
+    ///
+    /// This is guaranteed to never overrun the length of the map, but is *NOT* guaranteed
+    /// to iterate over all elements of the map if the map is extended during iteration.
+    #[derive(Clone, Debug, PartialEq, Eq, Hash)]
+    pub struct MapIndexIter<K: MapIndex> {
+        range: Range<usize>,
+        _id: PhantomData<K>,
+    }
+
+    impl<K: MapIndex> MapIndexIter<K> {
+        /// Creates a new [MapIndexIter] producing the given [MapIndex]
+        pub(super) fn new(range: Range<usize>) -> Self {
+            Self { range, _id: PhantomData }
+        }
+    }
+
+    impl<ID: MapIndex> Iterator for MapIndexIter<ID> {
+        type Item = ID;
+
+        fn next(&mut self) -> Option<Self::Item> {
+            Some(ID::from_usize(self.range.next()?))
+        }
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            self.range.size_hint()
+        }
+    }
+
+    impl<ID: MapIndex> DoubleEndedIterator for MapIndexIter<ID> {
+        fn next_back(&mut self) -> Option<Self::Item> {
+            // Safety: see above
+            Some(ID::from_usize(self.range.next_back()?))
+        }
+    }
+
+    impl<ID: MapIndex> ExactSizeIterator for MapIndexIter<ID> {}
+}

compiler/cl-structures/src/intern.rs

@@ -0,0 +1,319 @@
+//! Interners for [strings](string_interner) and arbitrary [types](typed_interner).
+//!
+//! An object is [Interned][1] if it is allocated within one of the interners
+//! in this module. [Interned][1] values have referential equality semantics, and
+//! [Deref](std::ops::Deref) to the value within their respective intern pool.
+//!
+//! This means, of course, that the same value interned in two different pools will be
+//! considered *not equal* by [Eq] and [Hash](std::hash::Hash).
+//!
+//! [1]: interned::Interned
+
+pub mod interned {
+    //! An [Interned] reference asserts its wrapped value has referential equality.
+    use super::string_interner::StringInterner;
+    use std::{
+        fmt::{Debug, Display},
+        hash::Hash,
+        ops::Deref,
+    };
+
+    /// An [Interned] value is one that is *referentially comparable*.
+    /// That is, the interned value is unique in memory, simplifying
+    /// its equality and hashing implementation.
+    ///
+    /// Comparing [Interned] values via [PartialOrd] or [Ord] will still
+    /// dereference to the wrapped pointers, and as such, may produce
+    /// results inconsistent with [PartialEq] or [Eq].
+    #[repr(transparent)]
+    pub struct Interned<'a, T: ?Sized> {
+        value: &'a T,
+    }
+
+    impl<'a, T: ?Sized> Interned<'a, T> {
+        /// Gets the internal value as a pointer
+        pub fn as_ptr(interned: &Self) -> *const T {
+            interned.value
+        }
+
+        /// Gets the internal value as a reference with the interner's lifetime
+        pub fn to_ref(&self) -> &'a T {
+            self.value
+        }
+    }
+
+    impl<T: ?Sized + Debug> Debug for Interned<'_, T> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "~")?;
+            self.value.fmt(f)
+        }
+    }
+    impl<'a, T: ?Sized> Interned<'a, T> {
+        pub(super) fn new(value: &'a T) -> Self {
+            Self { value }
+        }
+    }
+    impl<T: ?Sized> Deref for Interned<'_, T> {
+        type Target = T;
+        fn deref(&self) -> &Self::Target {
+            self.value
+        }
+    }
+    impl<T: ?Sized> Copy for Interned<'_, T> {}
+    impl<T: ?Sized> Clone for Interned<'_, T> {
+        fn clone(&self) -> Self {
+            *self
+        }
+    }
+    // TODO: These implementations are subtly incorrect, as they do not line up with `eq`
+    // impl<'a, T: ?Sized + PartialOrd> PartialOrd for Interned<'a, T> {
+    //     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+    //         match self == other {
+    //             true => Some(std::cmp::Ordering::Equal),
+    //             false => self.value.partial_cmp(other.value),
+    //         }
+    //     }
+    // }
+    // impl<'a, T: ?Sized + Ord> Ord for Interned<'a, T> {
+    //     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+    //         match self == other {
+    //             true => std::cmp::Ordering::Equal,
+    //             false => self.value.cmp(other.value),
+    //         }
+    //     }
+    // }
+
+    impl<T: ?Sized> Eq for Interned<'_, T> {}
+    impl<T: ?Sized> PartialEq for Interned<'_, T> {
+        fn eq(&self, other: &Self) -> bool {
+            std::ptr::eq(self.value, other.value)
+        }
+    }
+    impl<T: ?Sized> Hash for Interned<'_, T> {
+        fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+            Self::as_ptr(self).hash(state)
+        }
+    }
+    impl<T: ?Sized + Display> Display for Interned<'_, T> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            self.value.fmt(f)
+        }
+    }
+
+    impl<T: AsRef<str>> From<T> for Interned<'static, str> {
+        /// Types which implement [`AsRef<str>`] will be stored in the global [StringInterner]
+        fn from(value: T) -> Self {
+            from_str(value.as_ref())
+        }
+    }
+    fn from_str(value: &str) -> Interned<'static, str> {
+        let global_interner = StringInterner::global();
+        global_interner.get_or_insert(value)
+    }
+}
+
+pub mod string_interner {
+    //! A [StringInterner] hands out [Interned] copies of each unique string given to it.
+
+    use super::interned::Interned;
+    use cl_arena::dropless_arena::DroplessArena;
+    use std::{
+        collections::HashSet,
+        sync::{OnceLock, RwLock},
+    };
+
+    /// A string interner hands out [Interned] copies of each unique string given to it.
+    #[derive(Default)]
+    pub struct StringInterner<'a> {
+        arena: DroplessArena<'a>,
+        keys: RwLock<HashSet<&'a str>>,
+    }
+
+    impl StringInterner<'static> {
+        /// Gets a reference to a global string interner whose [Interned] strings are `'static`
+        pub fn global() -> &'static Self {
+            static GLOBAL_INTERNER: OnceLock<StringInterner<'static>> = OnceLock::new();
+
+            // SAFETY: The RwLock within the interner's `keys` protects the arena
+            // from being modified concurrently.
+            GLOBAL_INTERNER.get_or_init(|| StringInterner {
+                arena: DroplessArena::new(),
+                keys: Default::default(),
+            })
+        }
+    }
+
+    impl<'a> StringInterner<'a> {
+        /// Creates a new [StringInterner] backed by the provided [DroplessArena]
+        pub fn new(arena: DroplessArena<'a>) -> Self {
+            Self { arena, keys: RwLock::new(HashSet::new()) }
+        }
+
+        /// Returns an [Interned] copy of the given string,
+        /// allocating a new one if it doesn't already exist.
+        ///
+        /// # Blocks
+        /// This function blocks when the interner is held by another thread.
+        pub fn get_or_insert(&'a self, value: &str) -> Interned<'a, str> {
+            let Self { arena, keys } = self;
+
+            // Safety: Holding this write guard for the entire duration of this
+            // function enforces a safety invariant. See StringInterner::global.
+            let mut keys = keys.write().expect("should not be poisoned");
+
+            Interned::new(match keys.get(value) {
+                Some(value) => value,
+                None => {
+                    let value = match value {
+                        "" => "", // Arena will panic if passed an empty string
+                        _ => arena.alloc_str(value),
+                    };
+                    keys.insert(value);
+                    value
+                }
+            })
+        }
+        /// Gets a reference to the interned copy of the given value, if it exists
+        /// # Blocks
+        /// This function blocks when the interner is held by another thread.
+        pub fn get(&'a self, value: &str) -> Option<Interned<'a, str>> {
+            let keys = self.keys.read().expect("should not be poisoned");
+            keys.get(value).copied().map(Interned::new)
+        }
+    }
+
+    impl std::fmt::Debug for StringInterner<'_> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            f.debug_struct("Interner")
+                .field("keys", &self.keys)
+                .finish()
+        }
+    }
+
+    impl std::fmt::Display for StringInterner<'_> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Ok(keys) = self.keys.read() else {
+                return write!(f, "Could not lock StringInterner key map.");
+            };
+            let mut keys: Vec<_> = keys.iter().collect();
+            keys.sort();
+
+            writeln!(f, "Keys:")?;
+            for (idx, key) in keys.iter().enumerate() {
+                writeln!(f, "{idx}:\t\"{key}\"")?
+            }
+            writeln!(f, "Count: {}", keys.len())?;
+
+            Ok(())
+        }
+    }
+
+    // # Safety:
+    // This is fine because StringInterner::get_or_insert(v) holds a RwLock
+    // for its entire duration, and doesn't touch the non-(Send+Sync) arena
+    // unless the lock is held by a write guard.
+    unsafe impl Send for StringInterner<'_> {}
+    unsafe impl Sync for StringInterner<'_> {}
+
+    #[cfg(test)]
+    mod tests {
+        use super::StringInterner;
+
+        macro_rules! ptr_eq {
+        ($a: expr, $b: expr $(, $($t:tt)*)?) => {
+            assert_eq!(std::ptr::addr_of!($a), std::ptr::addr_of!($b) $(, $($t)*)?)
+        };
+    }
+        macro_rules! ptr_ne {
+        ($a: expr, $b: expr $(, $($t:tt)*)?) => {
+            assert_ne!(std::ptr::addr_of!($a), std::ptr::addr_of!($b) $(, $($t)*)?)
+        };
+    }
+
+        #[test]
+        fn empties_is_unique() {
+            let interner = StringInterner::global();
+            let empty = interner.get_or_insert("");
+            let empty2 = interner.get_or_insert("");
+            ptr_eq!(*empty, *empty2);
+        }
+        #[test]
+        fn non_empty_is_unique() {
+            let interner = StringInterner::global();
+            let nonempty1 = interner.get_or_insert("not empty!");
+            let nonempty2 = interner.get_or_insert("not empty!");
+            let different = interner.get_or_insert("different!");
+            ptr_eq!(*nonempty1, *nonempty2);
+            ptr_ne!(*nonempty1, *different);
+        }
+    }
+}
+
+pub mod typed_interner {
+    //! A [TypedInterner] hands out [Interned] references for arbitrary types.
+    //!
+    //! Note: It is a *logic error* to modify the returned reference via interior mutability
+    //! in a way that changes the values produced by [Eq] and [Hash].
+    //!
+    //! See the standard library [HashSet] for more details.
+    use super::interned::Interned;
+    use cl_arena::typed_arena::TypedArena;
+    use std::{collections::HashSet, hash::Hash, sync::RwLock};
+
+    /// A [TypedInterner] hands out [Interned] references for arbitrary types.
+    ///
+    /// See the [module-level documentation](self) for more information.
+    pub struct TypedInterner<'a, T: Eq + Hash> {
+        arena: TypedArena<'a, T>,
+        keys: RwLock<HashSet<&'a T>>,
+    }
+
+    impl<'a, T: Eq + Hash> Default for TypedInterner<'a, T> {
+        fn default() -> Self {
+            Self { arena: Default::default(), keys: Default::default() }
+        }
+    }
+
+    impl<'a, T: Eq + Hash> TypedInterner<'a, T> {
+        /// Creates a new [TypedInterner] backed by the provided [TypedArena]
+        pub fn new(arena: TypedArena<'a, T>) -> Self {
+            Self { arena, keys: RwLock::new(HashSet::new()) }
+        }
+
+        /// Converts the given value into an [Interned] value.
+        ///
+        /// # Blocks
+        /// This function blocks when the interner is held by another thread.
+        pub fn get_or_insert(&'a self, value: T) -> Interned<'a, T> {
+            let Self { arena, keys } = self;
+
+            // Safety: Locking the keyset for the entire duration of this function
+            // enforces a safety invariant when the interner is stored in a global.
+            let mut keys = keys.write().expect("should not be poisoned");
+
+            Interned::new(match keys.get(&value) {
+                Some(value) => value,
+                None => {
+                    let value = arena.alloc(value);
+                    keys.insert(value);
+                    value
+                }
+            })
+        }
+        /// Returns the [Interned] copy of the given value, if one already exists
+        ///
+        /// # Blocks
+        /// This function blocks when the interner is being written to by another thread.
+        pub fn get(&self, value: &T) -> Option<Interned<'a, T>> {
+            let keys = self.keys.read().expect("should not be poisoned");
+            keys.get(value).copied().map(Interned::new)
+        }
+    }
+
+    /// # Safety
+    /// This should be safe because references yielded by
+    /// [get_or_insert](TypedInterner::get_or_insert) are unique, and the function uses
+    /// the [RwLock] around the [HashSet] to ensure mutual exclusion
+    unsafe impl<'a, T: Eq + Hash + Send> Send for TypedInterner<'a, T> where &'a T: Send {}
+    unsafe impl<T: Eq + Hash + Send + Sync> Sync for TypedInterner<'_, T> {}
+}

compiler/cl-structures/src/lib.rs

@@ -0,0 +1,24 @@
+//! # Universally useful structures
+//! - [Span](struct@span::Span): Stores a start and end [Loc](struct@span::Loc)
+//! - [Loc](struct@span::Loc): Stores the index in a stream
+//! - [TypedInterner][ti] & [StringInterner][si]: Provies stable, unique allocations
+//! - [Stack](stack::Stack): Contiguous collections with constant capacity
+//! - [IndexMap][im]: A map from [map indices][mi] to values
+//!
+//! [ti]: intern::typed_interner::TypedInterner
+//! [si]: intern::string_interner::StringInterner
+//! [im]: index_map::IndexMap
+//! [mi]: index_map::MapIndex
+#![warn(clippy::all)]
+#![feature(dropck_eyepatch, decl_macro)]
+#![deny(unsafe_op_in_unsafe_fn)]
+
+pub mod intern;
+
+pub mod span;
+
+pub mod tree;
+
+pub mod stack;
+
+pub mod index_map;

compiler/cl-structures/src/span.rs

@@ -1,8 +1,6 @@
-//! # Universally useful structures
 //! - [struct@Span]: Stores the start and end [struct@Loc] of a notable AST node
 //! - [struct@Loc]: Stores the line/column of a notable AST node
 #![allow(non_snake_case)]
-use crate::lexer::Lexer;
 
 /// Stores the start and end [locations](struct@Loc) within the token stream
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -10,24 +8,33 @@ pub struct Span {
     pub head: Loc,
     pub tail: Loc,
 }
-pub fn Span(head: Loc, tail: Loc) -> Span {
+pub const fn Span(head: Loc, tail: Loc) -> Span {
     Span { head, tail }
 }
 
+impl Span {
+    pub const fn dummy() -> Self {
+        Span { head: Loc::dummy(), tail: Loc::dummy() }
+    }
+}
+
 /// Stores a read-only (line, column) location in a token stream
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Loc {
     line: u32,
     col: u32,
 }
-pub fn Loc(line: u32, col: u32) -> Loc {
+pub const fn Loc(line: u32, col: u32) -> Loc {
     Loc { line, col }
 }
 impl Loc {
-    pub fn line(self) -> u32 {
+    pub const fn dummy() -> Self {
+        Loc { line: 0, col: 0 }
+    }
+    pub const fn line(self) -> u32 {
         self.line
     }
-    pub fn col(self) -> u32 {
+    pub const fn col(self) -> u32 {
         self.col
     }
 }
@@ -35,12 +42,6 @@ impl Loc {
 impl std::fmt::Display for Loc {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Loc { line, col } = self;
-        write!(f, "{line}:{col}:")
-    }
-}
-
-impl<'t> From<&Lexer<'t>> for Loc {
-    fn from(value: &Lexer<'t>) -> Self {
-        Loc(value.line(), value.col())
+        write!(f, "{line}:{col}")
     }
 }

compiler/cl-structures/src/stack.rs

@@ -0,0 +1,777 @@
+//! A contiguous collection with constant capacity.
+//!
+//! Since the capacity of a [Stack] may be [*known at compile time*](Sized),
+//! it may live on the call stack.
+//!
+//!
+//! # Examples
+//!
+//! Unlike a [Vec], the [Stack] doesn't grow when it reaches capacity.
+//! ```should_panic
+//! # use cl_structures::stack::*;
+//! let mut v = stack![1];
+//! v.push("This should work");
+//! v.push("This will panic!");
+//! ```
+//! To get around this limitation, the methods [try_push](Stack::try_push) and
+//! [try_insert](Stack::try_insert) are provided:
+//! ```
+//! # use cl_structures::stack::*;
+//! let mut v = stack![1];
+//! v.push("This should work");
+//! v.try_push("This should produce an err").unwrap_err();
+//! ```
+//!
+//! As the name suggests, a [Stack] enforces a stack discipline:
+//! ```
+//! # use cl_structures::stack::*;
+//! let mut v = stack![100];
+//!
+//! assert_eq!(100, v.capacity());
+//! assert_eq!(0, v.len());
+//!
+//! // Elements are pushed one at a time onto the stack
+//! v.push("foo");
+//! v.push("bar");
+//! assert_eq!(2, v.len());
+//!
+//! // The stack can be used anywhere a slice is expected
+//! assert_eq!(Some(&"foo"), v.get(0));
+//! assert_eq!(Some(&"bar"), v.last());
+//!
+//! // Elements are popped from the stack in reverse order
+//! assert_eq!(Some("bar"), v.pop());
+//! assert_eq!(Some("foo"), v.pop());
+//! assert_eq!(None, v.pop());
+//! ```
+
+// yar har! here there be unsafe code! Tread carefully.
+
+use core::slice;
+use std::{
+    fmt::Debug,
+    marker::PhantomData,
+    mem::{ManuallyDrop, MaybeUninit},
+    ops::{Deref, DerefMut},
+    ptr,
+};
+
+/// Creates a [`stack`] containing the arguments
+///
+/// # Examples
+///
+/// Creates a *full* [`Stack`] containing a list of elements
+/// ```
+/// # use cl_structures::stack::stack;
+/// let mut v = stack![1, 2, 3];
+///
+/// assert_eq!(Some(3), v.pop());
+/// assert_eq!(Some(2), v.pop());
+/// assert_eq!(Some(1), v.pop());
+/// assert_eq!(None, v.pop());
+/// ```
+///
+/// Creates a *full* [`Stack`] from a given element and size
+/// ```
+/// # use cl_structures::stack::stack;
+/// let mut v = stack![1; 2];
+///
+/// assert_eq!(Some(1), v.pop());
+/// assert_eq!(Some(1), v.pop());
+/// assert_eq!(None, v.pop());
+/// ```
+///
+/// Creates an *empty* [`Stack`] from a given size
+/// ```
+/// # use cl_structures::stack::{Stack, stack};
+/// let mut v = stack![10];
+///
+/// assert_eq!(0, v.len());
+/// assert_eq!(10, v.capacity());
+///
+/// v.push(10);
+/// assert_eq!(Some(&10), v.last());
+/// ```
+pub macro stack {
+    ($capacity:literal) => {
+        Stack::<_, $capacity>::new()
+    },
+    ($value:expr ; $count:literal) => {{
+        let mut stack: Stack<_, $count> = Stack::new();
+        for _ in 0..$count {
+            stack.push($value)
+        }
+        stack
+    }},
+    ($value:expr ; $count:literal ; $capacity:literal) => {{
+        let mut stack: Stack<_, $capacity> = Stack::new();
+        for _ in 0..$count {
+            stack.push($value)
+        }
+        stack
+    }},
+    ($($values:expr),* $(,)?) => {
+        Stack::from([$($values),*])
+    }
+}
+
+/// A contiguous collection with constant capacity
+pub struct Stack<T, const N: usize> {
+    _data: PhantomData<T>,
+    buf: [MaybeUninit<T>; N],
+    len: usize,
+}
+
+impl<T: Clone, const N: usize> Clone for Stack<T, N> {
+    fn clone(&self) -> Self {
+        let mut new = Self::new();
+        for value in self.iter() {
+            new.push(value.clone())
+        }
+        new
+    }
+}
+
+impl<T: Debug, const N: usize> Debug for Stack<T, N> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_list().entries(self.iter()).finish()
+    }
+}
+
+impl<T, const N: usize> Default for Stack<T, N> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T, const N: usize> Deref for Stack<T, N> {
+    type Target = [T];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.as_slice()
+    }
+}
+
+impl<T, const N: usize> DerefMut for Stack<T, N> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.as_mut_slice()
+    }
+}
+
+// requires dropck-eyepatch for elements with contravariant lifetimes
+unsafe impl<#[may_dangle] T, const N: usize> Drop for Stack<T, N> {
+    #[inline]
+    fn drop(&mut self) {
+        // Safety: Elements in [0..self.len] are initialized
+        if std::mem::needs_drop::<T>() {
+            unsafe { core::ptr::drop_in_place(self.as_mut_slice()) };
+        }
+    }
+}
+
+impl<T, const N: usize> Extend<T> for Stack<T, N> {
+    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
+        for value in iter {
+            self.push(value)
+        }
+    }
+}
+
+impl<T, const N: usize> From<[T; N]> for Stack<T, N> {
+    fn from(value: [T; N]) -> Self {
+        let value = ManuallyDrop::new(value);
+        if std::mem::size_of::<[T; N]>() == 0 {
+            // Safety: since [T; N] is zero-sized, and there are no other fields,
+            // it should be okay to interpret N as Self
+            unsafe { ptr::read(&N as *const _ as *const _) }
+        } else {
+            // Safety:
+            // - `value` is ManuallyDrop, so its destructor won't run
+            // - All elements are assumed to be initialized (so len is N)
+            Self {
+                buf: unsafe { ptr::read(&value as *const _ as *const _) },
+                len: N,
+                ..Default::default()
+            }
+        }
+    }
+}
+
+impl<T, const N: usize> Stack<T, N> {
+    /// Constructs a new, empty [Stack]
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v: Stack<_, 3> = Stack::new();
+    ///
+    /// v.try_push(1).unwrap();
+    /// v.try_push(2).unwrap();
+    /// v.try_push(3).unwrap();
+    /// // Trying to push a 4th element will fail, and return the failed element
+    /// assert_eq!(4, v.try_push(4).unwrap_err());
+    ///
+    /// assert_eq!(Some(3), v.pop());
+    /// ```
+    pub const fn new() -> Self {
+        Self { buf: [const { MaybeUninit::uninit() }; N], len: 0, _data: PhantomData }
+    }
+
+    /// Constructs a new [Stack] from an array of [`MaybeUninit<T>`] and an initialized length
+    ///
+    /// # Safety
+    ///
+    /// - Elements from `0..len` must be initialized
+    /// - len must not exceed the length of the array
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// # use core::mem::MaybeUninit;
+    /// let mut v = unsafe { Stack::from_raw_parts([MaybeUninit::new(100)], 1) };
+    ///
+    /// assert_eq!(1, v.len());
+    /// assert_eq!(1, v.capacity());
+    /// assert_eq!(Some(100), v.pop());
+    /// assert_eq!(None, v.pop());
+    /// ```
+    pub const unsafe fn from_raw_parts(buf: [MaybeUninit<T>; N], len: usize) -> Self {
+        Self { buf, len, _data: PhantomData }
+    }
+
+    /// Converts a [Stack] into an array of [`MaybeUninit<T>`] and the initialized length
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v: Stack<_, 10> = Stack::new();
+    /// v.push(0);
+    /// v.push(1);
+    ///
+    /// let (buf, len) = v.into_raw_parts();
+    ///
+    /// assert_eq!(0, unsafe { buf[0].assume_init() });
+    /// assert_eq!(1, unsafe { buf[1].assume_init() });
+    /// assert_eq!(2, len);
+    /// ```
+    #[inline]
+    pub fn into_raw_parts(self) -> ([MaybeUninit<T>; N], usize) {
+        let this = ManuallyDrop::new(self);
+        // Safety: since
+        (unsafe { ptr::read(&this.buf) }, this.len)
+    }
+
+    /// Returns a raw pointer to the stack's buffer
+    pub const fn as_ptr(&self) -> *const T {
+        self.buf.as_ptr().cast()
+    }
+
+    /// Returns an unsafe mutable pointer to the stack's buffer
+    pub const fn as_mut_ptr(&mut self) -> *mut T {
+        self.buf.as_mut_ptr().cast()
+    }
+
+    /// Extracts a slice containing the entire vector
+    pub const fn as_slice(&self) -> &[T] {
+        // Safety:
+        // - We have ensured all elements from 0 to len have been initialized
+        // - self.elem[0] came from a reference, and so is aligned to T
+        // unsafe { &*(&self.buf[0..self.len] as *const [_] as *const [T]) }
+        unsafe { slice::from_raw_parts(self.buf.as_ptr().cast(), self.len) }
+    }
+
+    /// Extracts a mutable slice containing the entire vector
+    pub const fn as_mut_slice(&mut self) -> &mut [T] {
+        // Safety:
+        // - See Stack::as_slice
+        unsafe { slice::from_raw_parts_mut(self.buf.as_mut_ptr().cast(), self.len) }
+    }
+
+    /// Returns the total number of elements the stack can hold
+    pub const fn capacity(&self) -> usize {
+        N
+    }
+
+    /// Moves an existing stack into an allocation of a (potentially) different size,
+    /// truncating if necessary.
+    ///
+    /// This can be used to easily construct a half-empty stack
+    ///
+    /// # Examples
+    ///
+    /// You can grow a stack to fit more elements
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let v = Stack::from([0, 1, 2, 3, 4]);
+    /// assert_eq!(5, v.capacity());
+    ///
+    /// let mut v = v.resize::<10>();
+    /// assert_eq!(10, v.capacity());
+    ///
+    /// v.push(5);
+    /// ```
+    ///
+    /// You can truncate a stack, dropping elements off the end
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let v = Stack::from([0, 1, 2, 3, 4, 5, 6, 7]);
+    /// assert_eq!(8, v.capacity());
+    ///
+    /// let v = v.resize::<5>();
+    /// assert_eq!(5, v.capacity());
+    /// ```
+    pub fn resize<const M: usize>(mut self) -> Stack<T, M> {
+        // Drop elements until new length is reached
+        while self.len > M {
+            drop(self.pop());
+        }
+        let (old, len) = self.into_raw_parts();
+        let mut new: Stack<T, M> = Stack::new();
+
+        // Safety:
+        // - new and old are separate allocations
+        // - len <= M
+        unsafe {
+            ptr::copy_nonoverlapping(old.as_ptr(), new.buf.as_mut_ptr(), len);
+        }
+
+        new.len = len;
+        new
+    }
+
+    /// Push a new element onto the end of the stack
+    ///
+    /// # May Panic
+    ///
+    /// Panics if the new length exceeds capacity
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v: Stack<_, 4> = Stack::new();
+    ///
+    /// v.push(0);
+    /// v.push(1);
+    /// v.push(2);
+    /// v.push(3);
+    /// assert_eq!(&[0, 1, 2, 3], v.as_slice());
+    /// ```
+    pub const fn push(&mut self, value: T) {
+        if self.len >= N {
+            panic!("Attempted to push into full stack")
+        }
+        // Safety: len is confirmed to be less than capacity
+        unsafe { self.push_unchecked(value) };
+    }
+
+    /// Push a new element onto the end of the stack
+    ///
+    /// Returns [`Err(value)`](Result::Err) if the new length would exceed capacity
+    pub const fn try_push(&mut self, value: T) -> Result<(), T> {
+        if self.len >= N {
+            return Err(value);
+        }
+        // Safety: len is confirmed to be less than capacity
+        unsafe { self.push_unchecked(value) };
+        Ok(())
+    }
+
+    /// Push a new element onto the end of the stack, without checking capacity
+    ///
+    /// # Safety
+    ///
+    /// len after push must not exceed capacity N
+    #[inline]
+    const unsafe fn push_unchecked(&mut self, value: T) {
+        unsafe {
+            // self.buf.get_unchecked_mut(self.len).write(value); // TODO: This is non-const
+            ptr::write(self.as_mut_ptr().add(self.len), value)
+        }
+        self.len += 1; // post inc
+    }
+
+    /// Pops the last element off the end of the stack, and returns it
+    ///
+    /// Returns None if the stack is empty
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v = Stack::from([0, 1, 2, 3]);
+    ///
+    /// assert_eq!(Some(3), v.pop());
+    /// assert_eq!(Some(2), v.pop());
+    /// assert_eq!(Some(1), v.pop());
+    /// assert_eq!(Some(0), v.pop());
+    /// assert_eq!(None, v.pop());
+    /// ```
+    pub const fn pop(&mut self) -> Option<T> {
+        if self.len == 0 {
+            None
+        } else {
+            self.len -= 1;
+            // Safety: MaybeUninit<T> implies ManuallyDrop<T>,
+            // therefore should not get dropped twice
+            // Some(unsafe { self.buf.get_unchecked_mut(self.len).assume_init_read() })
+            Some(unsafe { ptr::read(self.as_ptr().add(self.len).cast()) })
+        }
+    }
+
+    /// Removes and returns the element at the given index,
+    /// shifting other elements toward the start
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v = Stack::from([0, 1, 2, 3, 4]);
+    ///
+    /// assert_eq!(2, v.remove(2));
+    /// assert_eq!(&[0, 1, 3, 4], v.as_slice());
+    /// ```
+    pub fn remove(&mut self, index: usize) -> T {
+        if index >= self.len {
+            panic!("Index {index} exceeded length {}", self.len)
+        }
+        let len = self.len - 1;
+        let base = self.as_mut_ptr();
+        let out = unsafe { ptr::read(base.add(index)) };
+
+        unsafe { ptr::copy(base.add(index + 1), base.add(index), len - index) };
+        self.len = len;
+        out
+    }
+
+    /// Removes and returns the element at the given index,
+    /// swapping it with the last element.
+    ///
+    /// # May Panic
+    ///
+    /// Panics if `index >= len`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v = Stack::from([0, 1, 2, 3, 4]);
+    ///
+    /// assert_eq!(2, v.swap_remove(2));
+    ///
+    /// assert_eq!(&[0, 1, 4, 3], v.as_slice());
+    /// ```
+    pub fn swap_remove(&mut self, index: usize) -> T {
+        if index >= self.len {
+            panic!("Index {index} exceeds length {}", self.len);
+        }
+        let len = self.len - 1;
+        let ptr = self.as_mut_ptr();
+        let out = unsafe { ptr::read(ptr.add(index)) };
+
+        unsafe { ptr::copy(ptr.add(len), ptr.add(index), 1) };
+        self.len = len;
+        out
+    }
+
+    /// Inserts an element at position `index` in the stack,
+    /// shifting all elements after it to the right.
+    ///
+    /// # May Panic
+    ///
+    /// Panics if `index > len` or [`self.is_full()`](Stack::is_full)
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    /// let mut v = Stack::from([0, 1, 2, 3, 4]).resize::<6>();
+    ///
+    /// v.insert(3, 0xbeef);
+    /// assert_eq!(&[0, 1, 2, 0xbeef, 3, 4], v.as_slice());
+    /// ```
+    pub fn insert(&mut self, index: usize, data: T) {
+        if index > self.len {
+            panic!("Index {index} exceeded length {}", self.len)
+        }
+        if self.is_full() {
+            panic!("Attempted to insert into full stack")
+        }
+        unsafe { self.insert_unchecked(index, data) };
+    }
+
+    /// Attempts to insert an element at position `index` in the stack,
+    /// shifting all elements after it to the right.
+    ///
+    /// If the stack is at capacity, returns the original element and an [InsertFailed] error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use cl_structures::stack::Stack;
+    /// let mut v: Stack<_, 2> = Stack::new();
+    ///
+    /// assert_eq!(Ok(()), v.try_insert(0, 0));
+    /// ```
+    pub const fn try_insert(&mut self, index: usize, data: T) -> Result<(), (T, InsertFailed<N>)> {
+        if index > self.len {
+            return Err((data, InsertFailed::Bounds(index)));
+        }
+        if self.is_full() {
+            return Err((data, InsertFailed::Full));
+        }
+        // Safety: index < self.len && !self.is_full()
+        unsafe { self.insert_unchecked(index, data) };
+        Ok(())
+    }
+
+    /// # Safety:
+    /// - index must be less than self.len
+    /// - length after insertion must be <= N
+    #[inline]
+    const unsafe fn insert_unchecked(&mut self, index: usize, data: T) {
+        let base = self.as_mut_ptr();
+
+        unsafe { ptr::copy(base.add(index), base.add(index + 1), self.len - index) }
+
+        self.len += 1;
+        self.buf[index] = MaybeUninit::new(data);
+    }
+
+    /// Clears the stack
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::Stack;
+    ///
+    /// let mut v = Stack::from([0, 1, 2, 3, 4]);
+    /// assert_eq!(v.as_slice(), &[0, 1, 2, 3, 4]);
+    ///
+    /// v.clear();
+    /// assert_eq!(v.as_slice(), &[]);
+    /// ```
+    pub fn clear(&mut self) {
+        // Hopefully copy elision takes care of this lmao
+        while !self.is_empty() {
+            drop(self.pop());
+        }
+    }
+
+    /// Returns the number of elements in the stack
+    /// ```
+    /// # use cl_structures::stack::*;
+    /// let v = Stack::from([0, 1, 2, 3, 4]);
+    ///
+    /// assert_eq!(5, v.len());
+    /// ```
+    pub const fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Returns true if the stack is at (or over) capacity
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::*;
+    /// let v = Stack::from([(); 10]);
+    ///
+    /// assert!(v.is_full());
+    /// ```
+    #[inline]
+    pub const fn is_full(&self) -> bool {
+        self.len >= N
+    }
+
+    /// Returns true if the stack contains no elements
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use cl_structures::stack::*;
+    /// let v: Stack<(), 10> = Stack::new();
+    ///
+    /// assert!(v.is_empty());
+    /// ```
+    #[inline]
+    pub const fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum InsertFailed<const N: usize> {
+    Bounds(usize),
+    Full,
+}
+impl<const N: usize> std::error::Error for InsertFailed<N> {}
+impl<const N: usize> std::fmt::Display for InsertFailed<N> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            InsertFailed::Bounds(idx) => write!(f, "Index {idx} exceeded length {N}"),
+            InsertFailed::Full => {
+                write!(f, "Attempt to insert into full stack (length {N})")
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn zero_sized() {
+        let v: Stack<(), { usize::MAX }> = Stack::new();
+        assert_eq!(usize::MAX, v.capacity());
+        assert_eq!(std::mem::size_of::<usize>(), std::mem::size_of_val(&v))
+    }
+    #[test]
+    fn from_usize_max_zst_array() {
+        let mut v = Stack::from([(); usize::MAX]);
+        assert_eq!(v.len(), usize::MAX);
+        v.pop();
+        assert_eq!(v.len(), usize::MAX - 1);
+    }
+
+    #[test]
+    fn new() {
+        let v: Stack<(), 255> = Stack::new();
+        assert_eq!(0, v.len());
+        assert_eq!(255, v.capacity());
+    }
+
+    #[test]
+    fn push() {
+        let mut v: Stack<_, 64> = Stack::new();
+        v.push(10);
+    }
+
+    #[test]
+    #[should_panic = "Attempted to push into full stack"]
+    fn push_overflow() {
+        let mut v = Stack::from([]);
+        v.push(10);
+    }
+
+    #[test]
+    fn pop() {
+        let mut v = Stack::from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        assert_eq!(Some(9), v.pop());
+        assert_eq!(Some(8), v.pop());
+        assert_eq!(Some(7), v.pop());
+        assert_eq!(Some(6), v.pop());
+        assert_eq!(Some(5), v.pop());
+        assert_eq!(Some(4), v.pop());
+        assert_eq!(Some(3), v.pop());
+        assert_eq!(Some(2), v.pop());
+        assert_eq!(Some(1), v.pop());
+        assert_eq!(None, v.pop());
+    }
+
+    #[test]
+    fn resize_smaller() {
+        let v = Stack::from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        let mut v = v.resize::<2>();
+
+        assert_eq!(2, v.capacity());
+
+        assert_eq!(Some(2), v.pop());
+        assert_eq!(Some(1), v.pop());
+        assert_eq!(None, v.pop());
+    }
+
+    #[test]
+    fn resize_bigger() {
+        let v = Stack::from([1, 2, 3, 4]);
+        let mut v: Stack<_, 10> = v.resize();
+
+        assert_eq!(Some(4), v.pop());
+        assert_eq!(Some(3), v.pop());
+        assert_eq!(Some(2), v.pop());
+        assert_eq!(Some(1), v.pop());
+        assert_eq!(None, v.pop());
+    }
+    #[test]
+    fn dangle() {
+        let mut v: Stack<_, 2> = Stack::new();
+        let a = 0;
+        let b = 1;
+        v.push(&a);
+        v.push(&b);
+        println!("{v:?}");
+    }
+    #[test]
+    fn remove() {
+        let mut v = Stack::from([0, 1, 2, 3, 4, 5]);
+
+        assert_eq!(3, v.remove(3));
+        assert_eq!(4, v.remove(3));
+        assert_eq!(5, v.remove(3));
+        assert_eq!(Some(2), v.pop());
+        assert_eq!(Some(1), v.pop());
+        assert_eq!(Some(0), v.pop());
+        assert_eq!(None, v.pop());
+    }
+
+    #[test]
+    fn swap_remove() {
+        let mut v = Stack::from([0, 1, 2, 3, 4, 5]);
+        assert_eq!(3, v.swap_remove(3));
+        assert_eq!(&[0, 1, 2, 5, 4], v.as_slice());
+    }
+    #[test]
+    fn swap_remove_last() {
+        let mut v = Stack::from([0, 1, 2, 3, 4, 5]);
+        assert_eq!(5, v.swap_remove(5));
+        assert_eq!(&[0, 1, 2, 3, 4], v.as_slice())
+    }
+
+    #[test]
+    fn insert() {
+        let mut v = Stack::from([0, 1, 2, 4, 5, 0x41414141]);
+        v.pop();
+        v.insert(3, 3);
+
+        assert_eq!(&[0, 1, 2, 3, 4, 5], v.as_slice())
+    }
+
+    #[test]
+    #[should_panic = "Attempted to insert into full stack"]
+    fn insert_overflow() {
+        let mut v = Stack::from([0]);
+        v.insert(0, 1);
+    }
+
+    #[test]
+    fn drop() {
+        let v = Stack::from([
+            Box::new(0),
+            Box::new(1),
+            Box::new(2),
+            Box::new(3),
+            Box::new(4),
+        ]);
+        std::mem::drop(std::hint::black_box(v));
+    }
+
+    #[test]
+    fn drop_zst() {
+        struct Droppable;
+        impl Drop for Droppable {
+            fn drop(&mut self) {
+                use std::sync::atomic::{AtomicU32, Ordering};
+                static V: AtomicU32 = AtomicU32::new(1);
+                eprintln!("{}", V.fetch_add(1, Ordering::Relaxed));
+            }
+        }
+
+        let v = Stack::from([const { Droppable }; 10]);
+        std::mem::drop(v);
+    }
+}

compiler/cl-structures/src/tree.rs

@@ -0,0 +1,221 @@
+//! An insert-only unordered tree, backed by a [Vec]
+//!
+//! # Examples
+//! ```
+//! use cl_structures::tree::{Tree, Node};
+//! // A tree can be created
+//! let mut tree = Tree::new();
+//! // Provided with a root node
+//! let root = tree.root("This is the root node").unwrap();
+//!
+//! // Nodes can be accessed by indexing
+//! assert_eq!(*tree[root].as_ref(), "This is the root node");
+//! // Nodes' data can be accessed directly by calling `get`/`get_mut`
+//! assert_eq!(tree.get(root).unwrap(), &"This is the root node")
+//! ```
+
+// TODO: implement an Entry-style API for doing traversal algorithms
+
+pub use self::tree_ref::Ref;
+use std::ops::{Index, IndexMut};
+
+pub mod tree_ref;
+
+/// An insert-only unordered tree, backed by a [Vec]
+#[derive(Debug)]
+pub struct Tree<T> {
+    nodes: Vec<Node<T>>,
+}
+
+impl<T> Default for Tree<T> {
+    fn default() -> Self {
+        Self { nodes: Default::default() }
+    }
+}
+
+/// Getters
+impl<T> Tree<T> {
+    pub fn get(&self, index: Ref<T>) -> Option<&T> {
+        self.get_node(index).map(|node| &node.value)
+    }
+    pub fn get_mut(&mut self, index: Ref<T>) -> Option<&mut T> {
+        self.get_node_mut(index).map(|node| &mut node.value)
+    }
+    pub fn get_node(&self, index: Ref<T>) -> Option<&Node<T>> {
+        self.nodes.get(usize::from(index))
+    }
+    pub fn get_node_mut(&mut self, index: Ref<T>) -> Option<&mut Node<T>> {
+        self.nodes.get_mut(usize::from(index))
+    }
+}
+
+/// Tree operations
+impl<T> Tree<T> {
+    pub fn new() -> Self {
+        Self { nodes: Default::default() }
+    }
+
+    /// Creates a new root for the tree.
+    ///
+    /// If the tree already has a root, the value will be returned.
+    pub fn root(&mut self, value: T) -> Result<Ref<T>, T> {
+        if self.is_empty() {
+            // Create an index for the new node
+            let node = Ref::new_unchecked(self.nodes.len());
+            // add child to tree
+            self.nodes.push(Node::from(value));
+            Ok(node)
+        } else {
+            Err(value)
+        }
+    }
+
+    pub fn get_root(&mut self) -> Option<Ref<T>> {
+        match self.nodes.is_empty() {
+            true => None,
+            false => Some(Ref::new_unchecked(0)),
+        }
+    }
+
+    /// Insert a value into the tree as a child of the parent node
+    ///
+    /// # Panics
+    /// May panic if the node [Ref] is from a different tree
+    pub fn insert(&mut self, value: T, parent: Ref<T>) -> Ref<T> {
+        let child = Ref::new_unchecked(self.nodes.len());
+        // add child to tree before parent
+        self.nodes.push(Node::with_parent(value, parent));
+        // add child to parent
+        self[parent].children.push(child);
+
+        child
+    }
+
+    /// Gets the depth of a node
+    ///
+    /// # Panics
+    /// May panic if the node [Ref] is from a different tree
+    pub fn depth(&self, node: Ref<T>) -> usize {
+        match self[node].parent {
+            Some(node) => self.depth(node) + 1,
+            None => 0,
+        }
+    }
+
+    /// Gets the number of branches in the tree
+    pub fn branches(&self) -> usize {
+        self.nodes.iter().fold(0, |edges, node| edges + node.len())
+    }
+}
+
+/// Standard data structure functions
+impl<T> Tree<T> {
+    pub fn len(&self) -> usize {
+        self.nodes.len()
+    }
+    pub fn is_empty(&self) -> bool {
+        self.nodes.is_empty()
+    }
+}
+
+impl<T> Index<Ref<T>> for Tree<T> {
+    type Output = Node<T>;
+    fn index(&self, index: Ref<T>) -> &Self::Output {
+        self.get_node(index).expect("Ref should be inside Tree")
+    }
+}
+impl<T> IndexMut<Ref<T>> for Tree<T> {
+    fn index_mut(&mut self, index: Ref<T>) -> &mut Self::Output {
+        self.get_node_mut(index).expect("Ref should be inside Tree")
+    }
+}
+
+/// A node in a [Tree]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Node<T> {
+    value: T,
+    /// The parent
+    parent: Option<Ref<T>>,
+    /// The children
+    children: Vec<Ref<T>>,
+}
+
+impl<T> Node<T> {
+    pub const fn new(value: T) -> Self {
+        Self { value, parent: None, children: vec![] }
+    }
+    pub const fn with_parent(value: T, parent: Ref<T>) -> Self {
+        Self { value, parent: Some(parent), children: vec![] }
+    }
+
+    pub fn get(&self) -> &T {
+        self.as_ref()
+    }
+    pub fn get_mut(&mut self) -> &mut T {
+        self.as_mut()
+    }
+    pub fn swap(&mut self, value: T) -> T {
+        std::mem::replace(&mut self.value, value)
+    }
+
+    pub fn parent(&self) -> Option<Ref<T>> {
+        self.parent
+    }
+    pub fn children(&self) -> &[Ref<T>] {
+        &self.children
+    }
+
+    pub fn len(&self) -> usize {
+        self.children.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.children.is_empty()
+    }
+}
+
+impl<T> AsRef<T> for Node<T> {
+    fn as_ref(&self) -> &T {
+        &self.value
+    }
+}
+impl<T> AsMut<T> for Node<T> {
+    fn as_mut(&mut self) -> &mut T {
+        &mut self.value
+    }
+}
+
+impl<T> From<T> for Node<T> {
+    #[inline]
+    fn from(value: T) -> Self {
+        Self::new(value)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[allow(unused)]
+    use super::*;
+
+    #[test]
+    fn add_children() {
+        let mut tree = Tree::new();
+        let root = tree.root(0).unwrap();
+        let one = tree.insert(1, root);
+        let two = tree.insert(2, root);
+        assert_eq!([one, two].as_slice(), tree[root].children());
+    }
+    #[test]
+    fn nest_children() {
+        let mut tree = Tree::new();
+        let root = tree.root(0).unwrap();
+        let one = tree.insert(1, root);
+        let two = tree.insert(2, one);
+        assert_eq!(&[one], tree[root].children());
+        assert_eq!(&[two], tree[one].children());
+        assert_eq!(tree[two].children(), &[]);
+    }
+
+    #[test]
+    fn compares_equal() {}
+}

compiler/cl-structures/src/tree/tree_ref.rs

@@ -0,0 +1,70 @@
+//! An element in a [Tree](super::Tree)
+///
+/// Contains a niche, and as such, [`Option<TreeRef<T>>`] is free :D
+use std::{marker::PhantomData, num::NonZeroUsize};
+
+/// An element of in a [Tree](super::Tree).
+//? The index of the node is stored as a [NonZeroUsize] for space savings
+//? Making Refs T-specific helps the user keep track of which Refs belong to which trees.
+//? This isn't bulletproof, of course, but it'll keep Ref<Foo> from being used on Tree<Bar>
+pub struct Ref<T: ?Sized>(NonZeroUsize, PhantomData<T>);
+
+impl<T: ?Sized> Ref<T> {
+    /// Constructs a new [Ref] with the given index
+    pub fn new_unchecked(index: usize) -> Self {
+        // Safety: index cannot be zero because we use saturating addition on unsigned type.
+        Self(
+            unsafe { NonZeroUsize::new_unchecked(index.saturating_add(1)) },
+            PhantomData,
+        )
+    }
+}
+
+impl<T: ?Sized> From<Ref<T>> for usize {
+    fn from(value: Ref<T>) -> Self {
+        usize::from(value.0) - 1
+    }
+}
+
+/* --- implementations of derivable traits, because we don't need bounds here --- */
+
+impl<T: ?Sized> std::fmt::Debug for Ref<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_tuple("TreeRef").field(&self.0).finish()
+    }
+}
+
+impl<T: ?Sized> std::hash::Hash for Ref<T> {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.0.hash(state);
+        self.1.hash(state);
+    }
+}
+
+impl<T: ?Sized> PartialEq for Ref<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0 && self.1 == other.1
+    }
+}
+
+impl<T: ?Sized> Eq for Ref<T> {}
+
+impl<T: ?Sized> PartialOrd for Ref<T> {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl<T: ?Sized> Ord for Ref<T> {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.0.cmp(&other.0)
+    }
+}
+
+impl<T: ?Sized> Clone for Ref<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: ?Sized> Copy for Ref<T> {}

compiler/cl-token/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "cl-token"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]

compiler/cl-token/src/lib.rs

@@ -0,0 +1,13 @@
+//! # Token
+//!
+//! Stores a component of a file as a [TokenKind], some [TokenData], and a line and column number
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+
+pub mod token;
+pub mod token_data;
+pub mod token_type;
+
+pub use token::Token;
+pub use token_data::TokenData;
+pub use token_type::TokenKind;

compiler/cl-token/src/token.rs

@@ -0,0 +1,42 @@
+//! A [Token] contains a single unit of lexical information, and an optional bit of [TokenData]
+use super::{TokenData, TokenKind};
+
+/// Contains a single unit of lexical information,
+/// and an optional bit of [TokenData]
+#[derive(Clone, Debug, PartialEq)]
+pub struct Token {
+    pub ty: TokenKind,
+    pub data: TokenData,
+    pub line: u32,
+    pub col: u32,
+}
+impl Token {
+    /// Creates a new [Token] out of a [TokenKind], [TokenData], line, and column.
+    pub fn new(ty: TokenKind, data: impl Into<TokenData>, line: u32, col: u32) -> Self {
+        Self { ty, data: data.into(), line, col }
+    }
+    /// Casts this token to a new [TokenKind]
+    pub fn cast(self, ty: TokenKind) -> Self {
+        Self { ty, ..self }
+    }
+    /// Returns the [TokenKind] of this token
+    pub fn ty(&self) -> TokenKind {
+        self.ty
+    }
+    /// Returns a reference to this token's [TokenData]
+    pub fn data(&self) -> &TokenData {
+        &self.data
+    }
+    /// Converts this token into its inner [TokenData]
+    pub fn into_data(self) -> TokenData {
+        self.data
+    }
+    /// Returns the line where this token originated
+    pub fn line(&self) -> u32 {
+        self.line
+    }
+    /// Returns the column where this token originated
+    pub fn col(&self) -> u32 {
+        self.col
+    }
+}

compiler/cl-token/src/token_data.rs

@@ -1,11 +1,9 @@
 //! Additional data stored within a [Token](super::Token),
-//! external to its [Type](super::token_type::Type)
+//! external to its [TokenKind](super::token_type::TokenKind)
 /// Additional data stored within a [Token](super::Token),
-/// external to its [Type](super::token_type::Type)
+/// external to its [TokenKind](super::token_type::TokenKind)
 #[derive(Clone, Debug, PartialEq)]
-pub enum Data {
-    /// [Token](super::Token) contains an [identifier](str)
-    Identifier(Box<str>),
+pub enum TokenData {
     /// [Token](super::Token) contains a [String]
     String(String),
     /// [Token](super::Token) contains a [character](char)
@@ -18,7 +16,6 @@ pub enum Data {
     None,
 }
 from! {
-    value: &str => Self::Identifier(value.into()),
     value: String => Self::String(value),
     value: u128 => Self::Integer(value),
     value: f64 => Self::Float(value),
@@ -27,19 +24,18 @@ from! {
 }
 /// Implements [From] for an enum
 macro from($($value:ident: $src:ty => $dst:expr),*$(,)?) {
-    $(impl From<$src> for Data {
+    $(impl From<$src> for TokenData {
         fn from($value: $src) -> Self { $dst }
     })*
 }
-impl std::fmt::Display for Data {
+impl std::fmt::Display for TokenData {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Data::Identifier(v) => v.fmt(f),
-            Data::String(v) => write!(f, "\"{v}\""),
-            Data::Character(v) => write!(f, "'{v}'"),
-            Data::Integer(v) => v.fmt(f),
-            Data::Float(v) => v.fmt(f),
-            Data::None => "None".fmt(f),
+            TokenData::String(v) => write!(f, "\"{v}\""),
+            TokenData::Character(v) => write!(f, "'{v}'"),
+            TokenData::Integer(v) => v.fmt(f),
+            TokenData::Float(v) => v.fmt(f),
+            TokenData::None => "None".fmt(f),
         }
     }
 }

compiler/cl-token/src/token_type.rs

@@ -0,0 +1,232 @@
+//! Stores a [Token's](super::Token) lexical information
+use std::{fmt::Display, str::FromStr};
+
+/// Stores a [Token's](super::Token) lexical information
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum TokenKind {
+    /// Invalid sequence
+    Invalid,
+    /// Any kind of comment
+    Comment,
+    /// Any tokenizable literal (See [TokenData](super::TokenData))
+    Literal,
+    /// A non-keyword identifier
+    Identifier,
+    // A keyword
+    As,       // as
+    Break,    // "break"
+    Cl,       // "cl"
+    Const,    // "const"
+    Continue, // "continue"
+    Else,     // "else"
+    Enum,     // "enum"
+    False,    // "false"
+    Fn,       // "fn"
+    For,      // "for"
+    If,       // "if"
+    Impl,     // "impl"
+    In,       // "in"
+    Let,      // "let"
+    Loop,     // "loop"
+    Match,    // "match"
+    Mod,      // "mod"
+    Mut,      // "mut"
+    Pub,      // "pub"
+    Return,   // "return"
+    SelfTy,   // "Self"
+    Static,   // "static"
+    Struct,   // "struct"
+    Super,    // "super"
+    True,     // "true"
+    Type,     // "type"
+    Use,      // "use"
+    While,    // "while"
+    // Delimiter or punctuation
+    LCurly,     // {
+    RCurly,     // }
+    LBrack,     // [
+    RBrack,     // ]
+    LParen,     // (
+    RParen,     // )
+    Amp,        // &
+    AmpAmp,     // &&
+    AmpEq,      // &=
+    Arrow,      // ->
+    At,         // @
+    Backslash,  // \
+    Bang,       // !
+    BangBang,   // !!
+    BangEq,     // !=
+    Bar,        // |
+    BarBar,     // ||
+    BarEq,      // |=
+    Colon,      // :
+    ColonColon, // ::
+    Comma,      // ,
+    Dot,        // .
+    DotDot,     // ..
+    DotDotEq,   // ..=
+    Eq,         // =
+    EqEq,       // ==
+    FatArrow,   // =>
+    Grave,      // `
+    Gt,         // >
+    GtEq,       // >=
+    GtGt,       // >>
+    GtGtEq,     // >>=
+    Hash,       // #
+    HashBang,   // #!
+    Lt,         // <
+    LtEq,       // <=
+    LtLt,       // <<
+    LtLtEq,     // <<=
+    Minus,      // -
+    MinusEq,    // -=
+    Plus,       // +
+    PlusEq,     // +=
+    Question,   // ?
+    Rem,        // %
+    RemEq,      // %=
+    Semi,       // ;
+    Slash,      // /
+    SlashEq,    // /=
+    Star,       // *
+    StarEq,     // *=
+    Tilde,      // ~
+    Xor,        // ^
+    XorEq,      // ^=
+    XorXor,     // ^^
+}
+
+impl Display for TokenKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TokenKind::Invalid => "invalid".fmt(f),
+            TokenKind::Comment => "comment".fmt(f),
+            TokenKind::Literal => "literal".fmt(f),
+            TokenKind::Identifier => "identifier".fmt(f),
+
+            TokenKind::As => "as".fmt(f),
+            TokenKind::Break => "break".fmt(f),
+            TokenKind::Cl => "cl".fmt(f),
+            TokenKind::Const => "const".fmt(f),
+            TokenKind::Continue => "continue".fmt(f),
+            TokenKind::Else => "else".fmt(f),
+            TokenKind::Enum => "enum".fmt(f),
+            TokenKind::False => "false".fmt(f),
+            TokenKind::Fn => "fn".fmt(f),
+            TokenKind::For => "for".fmt(f),
+            TokenKind::If => "if".fmt(f),
+            TokenKind::Impl => "impl".fmt(f),
+            TokenKind::In => "in".fmt(f),
+            TokenKind::Let => "let".fmt(f),
+            TokenKind::Loop => "loop".fmt(f),
+            TokenKind::Match => "match".fmt(f),
+            TokenKind::Mod => "mod".fmt(f),
+            TokenKind::Mut => "mut".fmt(f),
+            TokenKind::Pub => "pub".fmt(f),
+            TokenKind::Return => "return".fmt(f),
+            TokenKind::SelfTy => "Self".fmt(f),
+            TokenKind::Static => "static".fmt(f),
+            TokenKind::Struct => "struct".fmt(f),
+            TokenKind::Super => "super".fmt(f),
+            TokenKind::True => "true".fmt(f),
+            TokenKind::Type => "type".fmt(f),
+            TokenKind::Use => "use".fmt(f),
+            TokenKind::While => "while".fmt(f),
+
+            TokenKind::LCurly => "{".fmt(f),
+            TokenKind::RCurly => "}".fmt(f),
+            TokenKind::LBrack => "[".fmt(f),
+            TokenKind::RBrack => "]".fmt(f),
+            TokenKind::LParen => "(".fmt(f),
+            TokenKind::RParen => ")".fmt(f),
+            TokenKind::Amp => "&".fmt(f),
+            TokenKind::AmpAmp => "&&".fmt(f),
+            TokenKind::AmpEq => "&=".fmt(f),
+            TokenKind::Arrow => "->".fmt(f),
+            TokenKind::At => "@".fmt(f),
+            TokenKind::Backslash => "\\".fmt(f),
+            TokenKind::Bang => "!".fmt(f),
+            TokenKind::BangBang => "!!".fmt(f),
+            TokenKind::BangEq => "!=".fmt(f),
+            TokenKind::Bar => "|".fmt(f),
+            TokenKind::BarBar => "||".fmt(f),
+            TokenKind::BarEq => "|=".fmt(f),
+            TokenKind::Colon => ":".fmt(f),
+            TokenKind::ColonColon => "::".fmt(f),
+            TokenKind::Comma => ",".fmt(f),
+            TokenKind::Dot => ".".fmt(f),
+            TokenKind::DotDot => "..".fmt(f),
+            TokenKind::DotDotEq => "..=".fmt(f),
+            TokenKind::Eq => "=".fmt(f),
+            TokenKind::EqEq => "==".fmt(f),
+            TokenKind::FatArrow => "=>".fmt(f),
+            TokenKind::Grave => "`".fmt(f),
+            TokenKind::Gt => ">".fmt(f),
+            TokenKind::GtEq => ">=".fmt(f),
+            TokenKind::GtGt => ">>".fmt(f),
+            TokenKind::GtGtEq => ">>=".fmt(f),
+            TokenKind::Hash => "#".fmt(f),
+            TokenKind::HashBang => "#!".fmt(f),
+            TokenKind::Lt => "<".fmt(f),
+            TokenKind::LtEq => "<=".fmt(f),
+            TokenKind::LtLt => "<<".fmt(f),
+            TokenKind::LtLtEq => "<<=".fmt(f),
+            TokenKind::Minus => "-".fmt(f),
+            TokenKind::MinusEq => "-=".fmt(f),
+            TokenKind::Plus => "+".fmt(f),
+            TokenKind::PlusEq => "+=".fmt(f),
+            TokenKind::Question => "?".fmt(f),
+            TokenKind::Rem => "%".fmt(f),
+            TokenKind::RemEq => "%=".fmt(f),
+            TokenKind::Semi => ";".fmt(f),
+            TokenKind::Slash => "/".fmt(f),
+            TokenKind::SlashEq => "/=".fmt(f),
+            TokenKind::Star => "*".fmt(f),
+            TokenKind::StarEq => "*=".fmt(f),
+            TokenKind::Tilde => "~".fmt(f),
+            TokenKind::Xor => "^".fmt(f),
+            TokenKind::XorEq => "^=".fmt(f),
+            TokenKind::XorXor => "^^".fmt(f),
+        }
+    }
+}
+impl FromStr for TokenKind {
+    /// [FromStr] can only fail when an identifier isn't a keyword
+    type Err = ();
+    /// Parses a string s to return a Keyword
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(match s {
+            "as" => Self::As,
+            "break" => Self::Break,
+            "cl" => Self::Cl,
+            "const" => Self::Const,
+            "continue" => Self::Continue,
+            "else" => Self::Else,
+            "enum" => Self::Enum,
+            "false" => Self::False,
+            "fn" => Self::Fn,
+            "for" => Self::For,
+            "if" => Self::If,
+            "impl" => Self::Impl,
+            "in" => Self::In,
+            "let" => Self::Let,
+            "loop" => Self::Loop,
+            "match" => Self::Match,
+            "mod" => Self::Mod,
+            "mut" => Self::Mut,
+            "pub" => Self::Pub,
+            "return" => Self::Return,
+            "Self" => Self::SelfTy,
+            "static" => Self::Static,
+            "struct" => Self::Struct,
+            "super" => Self::Super,
+            "true" => Self::True,
+            "type" => Self::Type,
+            "use" => Self::Use,
+            "while" => Self::While,
+            _ => Err(())?,
+        })
+    }
+}

compiler/cl-typeck/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "cl-typeck"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-ast = { path = "../cl-ast" }
+cl-structures = { path = "../cl-structures" }
+
+[dev-dependencies]
+repline = { version = "*", registry = "soft-fish" }
+cl-lexer = { path = "../cl-lexer" }
+cl-parser = { path = "../cl-parser" }

compiler/cl-typeck/examples/typeck.rs

@@ -0,0 +1,462 @@
+use cl_typeck::{
+    entry::Entry,
+    stage::{
+        infer::{engine::InferenceEngine, error::InferenceError, inference::Inference},
+        *,
+    },
+    table::Table,
+    type_expression::TypeExpression,
+};
+
+use cl_ast::{
+    Expr, Path, Stmt, Ty,
+    ast_visitor::{Fold, Visit},
+    desugar::*,
+};
+use cl_lexer::Lexer;
+use cl_parser::{Parser, inliner::ModuleInliner};
+use cl_structures::intern::string_interner::StringInterner;
+use repline::{error::Error as RlError, prebaked::*};
+use std::{
+    error::Error,
+    path::{self, PathBuf},
+    sync::LazyLock,
+};
+
+// Path to display in standard library errors
+const STDLIB_DISPLAY_PATH: &str = "stdlib/lib.cl";
+// Statically included standard library
+const PREAMBLE: &str = r"
+pub mod std;
+pub use std::preamble::*;
+";
+
+// Colors
+const C_MAIN: &str = C_LISTING;
+const C_RESV: &str = "\x1b[35m";
+const C_CODE: &str = "\x1b[36m";
+const C_BYID: &str = "\x1b[95m";
+const C_ERROR: &str = "\x1b[31m";
+const C_LISTING: &str = "\x1b[38;5;117m";
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let mut prj = Table::default();
+
+    let mut parser = Parser::new("PREAMBLE", Lexer::new(PREAMBLE));
+    let code = match parser.parse() {
+        Ok(code) => code,
+        Err(e) => {
+            eprintln!("{STDLIB_DISPLAY_PATH}:{e}");
+            Err(e)?
+        }
+    };
+    // This code is special - it gets loaded from a hard-coded project directory (for now)
+    let code = inline_modules(code, concat!(env!("CARGO_MANIFEST_DIR"), "/../../stdlib"));
+    let code = cl_ast::desugar::WhileElseDesugar.fold_file(code);
+    Populator::new(&mut prj).visit_file(interned(code));
+
+    for arg in std::env::args().skip(1) {
+        import_file(&mut prj, arg)?;
+    }
+
+    resolve_all(&mut prj)?;
+
+    main_menu(&mut prj)?;
+    Ok(())
+}
+
+fn main_menu(prj: &mut Table) -> Result<(), RlError> {
+    banner();
+    read_and(C_MAIN, "mu>", "? >", |line| {
+        for line in line.trim().split_ascii_whitespace() {
+            match line {
+                "c" | "code" => enter_code(prj)?,
+                "clear" => clear()?,
+                "dump" => dump(prj)?,
+                "d" | "desugar" => live_desugar()?,
+                "e" | "exit" => return Ok(Response::Break),
+                "f" | "file" => import_files(prj)?,
+                "i" | "id" => get_by_id(prj)?,
+                "l" | "list" => list_types(prj),
+                "q" | "query" => query_type_expression(prj)?,
+                "r" | "resolve" => resolve_all(prj)?,
+                "s" | "strings" => print_strings(),
+                "a" | "all" => infer_all(prj)?,
+                "t" | "test" => infer_expression(prj)?,
+                "h" | "help" | "" => {
+                    println!(
+                        "Valid commands are:
+    clear      : Clear the screen
+    code    (c): Enter code to type-check
+    desugar (d): WIP: Test the experimental desugaring passes
+    file    (f): Load files from disk
+    id      (i): Get a type by its type ID
+    list    (l): List all known types
+    query   (q): Query the type system
+    resolve (r): Perform type resolution
+    help    (h): Print this list
+    exit    (e): Exit the program"
+                    );
+                    return Ok(Response::Deny);
+                }
+                _ => Err(r#"Invalid command. Type "help" to see the list of valid commands."#)?,
+            }
+        }
+        Ok(Response::Accept)
+    })
+}
+
+fn enter_code(prj: &mut Table) -> Result<(), RlError> {
+    read_and(C_CODE, "cl>", "? >", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        let code = Parser::new("", Lexer::new(line)).parse()?;
+        let code = inline_modules(code, "");
+        let code = WhileElseDesugar.fold_file(code);
+
+        Populator::new(prj).visit_file(interned(code));
+        Ok(Response::Accept)
+    })
+}
+
+fn live_desugar() -> Result<(), RlError> {
+    read_and(C_RESV, "se>", "? >", |line| {
+        let code = Parser::new("", Lexer::new(line)).parse::<Stmt>()?;
+        println!("Raw, as parsed:\n{C_LISTING}{code}\x1b[0m");
+
+        let code = ConstantFolder.fold_stmt(code);
+        println!("ConstantFolder\n{C_LISTING}{code}\x1b[0m");
+
+        let code = SquashGroups.fold_stmt(code);
+        println!("SquashGroups\n{C_LISTING}{code}\x1b[0m");
+
+        let code = WhileElseDesugar.fold_stmt(code);
+        println!("WhileElseDesugar\n{C_LISTING}{code}\x1b[0m");
+
+        let code = NormalizePaths::new().fold_stmt(code);
+        println!("NormalizePaths\n{C_LISTING}{code}\x1b[0m");
+
+        Ok(Response::Accept)
+    })
+}
+
+fn print_strings() {
+    println!("{}", StringInterner::global());
+}
+
+fn query_type_expression(prj: &mut Table) -> Result<(), RlError> {
+    read_and(C_RESV, "ty>", "? >", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        // A query is comprised of a Ty and a relative Path
+        let mut p = Parser::new("", Lexer::new(line));
+        let ty: Ty = p.parse()?;
+        let path: Path = p
+            .parse()
+            .map(|p| Path { absolute: false, ..p })
+            .unwrap_or_default();
+        let id = ty.evaluate(prj, prj.root())?;
+        let id = path.evaluate(prj, id)?;
+        pretty_handle(id.to_entry(prj))?;
+        Ok(Response::Accept)
+    })
+}
+
+#[allow(dead_code)]
+fn infer_expression(prj: &mut Table) -> Result<(), RlError> {
+    read_and(C_RESV, "ex>", "!?>", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        let mut p = Parser::new("", Lexer::new(line));
+        let e: Expr = p.parse()?;
+        let mut inf = InferenceEngine::new(prj, prj.root());
+        let ty = match exp_terned(e).infer(&mut inf) {
+            Ok(ty) => ty,
+            Err(e) => match e {
+                InferenceError::Mismatch(a, b) => {
+                    eprintln!("Mismatched types: {}, {}", prj.entry(a), prj.entry(b));
+                    return Ok(Response::Deny);
+                }
+                InferenceError::Recursive(a, b) => {
+                    eprintln!("Recursive types: {}, {}", prj.entry(a), prj.entry(b));
+                    return Ok(Response::Deny);
+                }
+                e => Err(e)?,
+            },
+        };
+        eprintln!("--> {}", prj.entry(ty));
+        Ok(Response::Accept)
+    })
+}
+
+fn get_by_id(prj: &mut Table) -> Result<(), RlError> {
+    use cl_parser::parser::Parse;
+    use cl_structures::index_map::MapIndex;
+    use cl_typeck::handle::Handle;
+    read_and(C_BYID, "id>", "? >", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        let mut parser = Parser::new("", Lexer::new(line));
+        let def_id = match Parse::parse(&mut parser)? {
+            cl_ast::Literal::Int(int) => int as _,
+            other => Err(format!("Expected integer, got {other}"))?,
+        };
+        let mut path = parser.parse::<cl_ast::Path>().unwrap_or_default();
+        path.absolute = false;
+
+        let handle = Handle::from_usize(def_id).to_entry(prj);
+
+        print!("  > {{{C_LISTING}{handle}\x1b[0m}}");
+        if !path.parts.is_empty() {
+            print!("::{path}")
+        }
+        println!();
+
+        let Some(entry) = handle.nav(&path.parts) else {
+            Err("No results.")?
+        };
+
+        pretty_handle(entry)?;
+
+        Ok(Response::Accept)
+    })
+}
+
+fn resolve_all(table: &mut Table) -> Result<(), Box<dyn Error>> {
+    for (id, error) in import(table) {
+        eprintln!("{error} in {} ({id})", id.to_entry(table))
+    }
+    for handle in table.handle_iter() {
+        if let Err(error) = handle.to_entry_mut(table).categorize() {
+            eprintln!("{error}");
+        }
+    }
+
+    for handle in implement(table) {
+        eprintln!("Unable to reparent {} ({handle})", handle.to_entry(table))
+    }
+
+    println!("...Resolved!");
+    Ok(())
+}
+
+fn infer_all(table: &mut Table) -> Result<(), Box<dyn Error>> {
+    for (id, error) in InferenceEngine::new(table, table.root()).infer_all() {
+        match error {
+            InferenceError::Mismatch(a, b) => {
+                eprint!("Mismatched types: {}, {}", table.entry(a), table.entry(b));
+            }
+            InferenceError::Recursive(a, b) => {
+                eprint!("Recursive types: {}, {}", table.entry(a), table.entry(b));
+            }
+            e => eprint!("{e}"),
+        }
+        eprintln!(" in {id}\n({})\n", id.to_entry(table).source().unwrap())
+    }
+
+    println!("...Inferred!");
+    Ok(())
+}
+
+fn list_types(table: &mut Table) {
+    for handle in table.debug_entry_iter() {
+        let id = handle.id();
+        let kind = handle.kind().unwrap();
+        let name = handle.name().unwrap_or("".into());
+        println!("{id:3}: {name:16}| {kind}: {handle}");
+    }
+}
+
+fn import_file(table: &mut Table, path: impl AsRef<std::path::Path>) -> Result<(), Box<dyn Error>> {
+    let Ok(file) = std::fs::read_to_string(path.as_ref()) else {
+        for file in std::fs::read_dir(path)? {
+            println!("{}", file?.path().display())
+        }
+        return Ok(());
+    };
+
+    let mut parser = Parser::new("", Lexer::new(&file));
+    let code = match parser.parse() {
+        Ok(code) => inline_modules(
+            code,
+            PathBuf::from(path.as_ref()).parent().unwrap_or("".as_ref()),
+        ),
+        Err(e) => {
+            eprintln!("{C_ERROR}{}:{e}\x1b[0m", path.as_ref().display());
+            return Ok(());
+        }
+    };
+
+    let code = cl_ast::desugar::WhileElseDesugar.fold_file(code);
+    Populator::new(table).visit_file(interned(code));
+
+    Ok(())
+}
+
+fn import_files(table: &mut Table) -> Result<(), RlError> {
+    read_and(C_RESV, "fi>", "? >", |line| {
+        let line = line.trim();
+        if line.is_empty() {
+            return Ok(Response::Break);
+        }
+        let Ok(file) = std::fs::read_to_string(line) else {
+            for file in std::fs::read_dir(line)? {
+                println!("{}", file?.path().display())
+            }
+            return Ok(Response::Accept);
+        };
+
+        let mut parser = Parser::new("", Lexer::new(&file));
+        let code = match parser.parse() {
+            Ok(code) => inline_modules(code, PathBuf::from(line).parent().unwrap_or("".as_ref())),
+            Err(e) => {
+                eprintln!("{C_ERROR}{line}:{e}\x1b[0m");
+                return Ok(Response::Deny);
+            }
+        };
+
+        Populator::new(table).visit_file(interned(code));
+
+        println!("...Imported!");
+        Ok(Response::Accept)
+    })
+}
+
+fn pretty_handle(entry: Entry) -> Result<(), std::io::Error> {
+    use std::io::Write;
+    let mut out = std::io::stdout().lock();
+    let Some(kind) = entry.kind() else {
+        return writeln!(out, "{entry}");
+    };
+    write!(out, "{C_LISTING}{kind}")?;
+
+    if let Some(name) = entry.name() {
+        write!(out, " {name}")?;
+    }
+    writeln!(out, "\x1b[0m ({}): {entry}", entry.id())?;
+
+    if let Some(parent) = entry.parent() {
+        writeln!(
+            out,
+            "- {C_LISTING}Parent\x1b[0m: {parent} ({})",
+            parent.id()
+        )?;
+    }
+
+    if let Some(span) = entry.span() {
+        writeln!(
+            out,
+            "- {C_LISTING}Span:\x1b[0m ({}, {})",
+            span.head, span.tail
+        )?;
+    }
+
+    match entry.meta() {
+        Some(meta) if !meta.is_empty() => {
+            writeln!(out, "- {C_LISTING}Meta:\x1b[0m")?;
+            for meta in meta {
+                writeln!(out, "  - {meta}")?;
+            }
+        }
+        _ => {}
+    }
+
+    if let Some(children) = entry.children() {
+        writeln!(out, "- {C_LISTING}Children:\x1b[0m")?;
+        for (name, child) in children {
+            writeln!(
+                out,
+                "  - {C_LISTING}{name}\x1b[0m ({child}): {}",
+                entry.with_id(*child)
+            )?
+        }
+    }
+
+    if let Some(imports) = entry.imports() {
+        writeln!(out, "- {C_LISTING}Imports:\x1b[0m")?;
+        for (name, child) in imports {
+            writeln!(
+                out,
+                "  - {C_LISTING}{name}\x1b[0m ({child}): {}",
+                entry.with_id(*child)
+            )?
+        }
+    }
+
+    Ok(())
+}
+
+fn inline_modules(code: cl_ast::File, path: impl AsRef<path::Path>) -> cl_ast::File {
+    match ModuleInliner::new(path).inline(code) {
+        Err((code, io, parse)) => {
+            for (file, error) in io {
+                eprintln!("{}:{error}", file.display());
+            }
+            for (file, error) in parse {
+                eprintln!("{}:{error}", file.display());
+            }
+            code
+        }
+        Ok(code) => code,
+    }
+}
+
+fn dump(table: &Table) -> Result<(), Box<dyn Error>> {
+    fn dump_recursive(
+        name: cl_ast::Sym,
+        entry: Entry,
+        depth: usize,
+        to_file: &mut std::fs::File,
+    ) -> std::io::Result<()> {
+        use std::io::Write;
+        write!(to_file, "{:w$}{name}: {entry}", "", w = depth)?;
+        if let Some(children) = entry.children() {
+            writeln!(to_file, " {{")?;
+            for (name, child) in children {
+                dump_recursive(*name, entry.with_id(*child), depth + 2, to_file)?;
+            }
+            write!(to_file, "{:w$}}}", "", w = depth)?;
+        }
+        writeln!(to_file)
+    }
+
+    let mut file = std::fs::File::create("typeck-table.ron")?;
+    dump_recursive("root".into(), table.root_entry(), 0, &mut file)?;
+    Ok(())
+}
+
+fn clear() -> Result<(), Box<dyn Error>> {
+    println!("\x1b[H\x1b[2J");
+    banner();
+    Ok(())
+}
+
+fn banner() {
+    println!(
+        "--- {} v{} 💪🦈 ---",
+        env!("CARGO_BIN_NAME"),
+        env!("CARGO_PKG_VERSION"),
+    );
+}
+
+/// Interns a [File](cl_ast::File), returning a static reference to it.
+fn interned(file: cl_ast::File) -> &'static cl_ast::File {
+    use cl_structures::intern::typed_interner::TypedInterner;
+    static INTERNER: LazyLock<TypedInterner<'static, cl_ast::File>> =
+        LazyLock::new(Default::default);
+
+    INTERNER.get_or_insert(file).to_ref()
+}
+
+/// Interns an [Expr](cl_ast::Expr), returning a static reference to it.
+fn exp_terned(expr: cl_ast::Expr) -> &'static cl_ast::Expr {
+    use cl_structures::intern::typed_interner::TypedInterner;
+    static INTERNER: LazyLock<TypedInterner<'static, cl_ast::Expr>> =
+        LazyLock::new(Default::default);
+
+    INTERNER.get_or_insert(expr).to_ref()
+}

compiler/cl-typeck/src/entry.rs

@@ -0,0 +1,212 @@
+//! An [Entry] is an accessor for [nodes](Handle) in a [Table].
+//!
+//! There are two kinds of entry:
+//! - [Entry]: Provides getters for an entry's fields, and an implementation of
+//!   [Display](std::fmt::Display)
+//! - [EntryMut]: Provides setters for an entry's fields, and an [`as_ref`](EntryMut::as_ref) method
+//!   to demote to an [Entry].
+
+use std::collections::HashMap;
+
+use cl_ast::{Expr, Meta, PathPart, Sym};
+use cl_structures::span::Span;
+
+use crate::{
+    handle::Handle,
+    source::Source,
+    stage::categorize as cat,
+    table::{NodeKind, Table},
+    type_expression::{self as tex, TypeExpression},
+    type_kind::TypeKind,
+};
+
+mod debug;
+mod display;
+
+impl Handle {
+    pub const fn to_entry<'t, 'a>(self, table: &'t Table<'a>) -> Entry<'t, 'a> {
+        Entry { id: self, table }
+    }
+    pub fn to_entry_mut<'t, 'a>(self, table: &'t mut Table<'a>) -> EntryMut<'t, 'a> {
+        EntryMut { id: self, table }
+    }
+}
+
+pub struct Entry<'t, 'a> {
+    table: &'t Table<'a>,
+    id: Handle,
+}
+
+macro_rules! impl_entry_ {
+    () => {
+        pub const fn id(&self) -> Handle {
+            self.id
+        }
+
+        pub const fn inner(&'t self) -> &'t Table<'a> {
+            self.table
+        }
+
+        pub fn kind(&self) -> Option<&NodeKind> {
+            self.table.kind(self.id)
+        }
+
+        pub const fn root(&self) -> Handle {
+            self.table.root()
+        }
+
+        pub fn children(&self) -> Option<&HashMap<Sym, Handle>> {
+            self.table.children(self.id)
+        }
+
+        pub fn imports(&self) -> Option<&HashMap<Sym, Handle>> {
+            self.table.imports(self.id)
+        }
+
+        pub fn bodies(&self) -> Option<&'a Expr> {
+            self.table.body(self.id)
+        }
+
+        pub fn span(&self) -> Option<&Span> {
+            self.table.span(self.id)
+        }
+
+        pub fn meta(&self) -> Option<&[Meta]> {
+            self.table.meta(self.id)
+        }
+
+        pub fn source(&self) -> Option<&Source<'a>> {
+            self.table.source(self.id)
+        }
+
+        pub fn name(&self) -> Option<Sym> {
+            self.table.name(self.id)
+        }
+    };
+}
+
+impl<'t, 'a> Entry<'t, 'a> {
+    pub const fn new(table: &'t Table<'a>, id: Handle) -> Self {
+        Self { table, id }
+    }
+
+    impl_entry_!();
+
+    pub const fn with_id(&self, id: Handle) -> Entry<'t, 'a> {
+        Self { table: self.table, id }
+    }
+
+    pub fn nav(&self, path: &[PathPart]) -> Option<Entry<'t, 'a>> {
+        Some(Entry { id: self.table.nav(self.id, path)?, table: self.table })
+    }
+
+    pub fn parent(&self) -> Option<Entry<'t, 'a>> {
+        Some(Entry { id: *self.table.parent(self.id)?, ..*self })
+    }
+
+    pub fn ty(&self) -> Option<&'t TypeKind> {
+        self.table.ty(self.id)
+    }
+
+    pub fn impl_target(&self) -> Option<Entry<'_, 'a>> {
+        Some(Entry { id: self.table.impl_target(self.id)?, ..*self })
+    }
+
+    pub fn selfty(&self) -> Option<Entry<'_, 'a>> {
+        Some(Entry { id: self.table.selfty(self.id)?, ..*self })
+    }
+}
+
+#[derive(Debug)]
+pub struct EntryMut<'t, 'a> {
+    table: &'t mut Table<'a>,
+    id: Handle,
+}
+
+impl<'t, 'a> EntryMut<'t, 'a> {
+    pub fn new(table: &'t mut Table<'a>, id: Handle) -> Self {
+        Self { table, id }
+    }
+
+    impl_entry_!();
+
+    pub fn ty(&self) -> Option<&TypeKind> {
+        self.table.ty(self.id)
+    }
+
+    pub fn inner_mut(&mut self) -> &mut Table<'a> {
+        self.table
+    }
+
+    pub fn as_ref(&self) -> Entry<'_, 'a> {
+        Entry { table: self.table, id: self.id }
+    }
+
+    /// Evaluates a [TypeExpression] in this entry's context
+    pub fn evaluate<Out>(&mut self, ty: &impl TypeExpression<Out>) -> Result<Out, tex::Error> {
+        let Self { table, id } = self;
+        ty.evaluate(table, *id)
+    }
+
+    pub fn categorize(&mut self) -> Result<(), cat::Error> {
+        cat::categorize(self.table, self.id)
+    }
+
+    /// Constructs a new Handle with the provided parent [Handle]
+    pub fn with_id(&mut self, parent: Handle) -> EntryMut<'_, 'a> {
+        EntryMut { table: self.table, id: parent }
+    }
+
+    pub fn nav(&mut self, path: &[PathPart]) -> Option<EntryMut<'_, 'a>> {
+        Some(EntryMut { id: self.table.nav(self.id, path)?, table: self.table })
+    }
+
+    pub fn new_entry(&mut self, kind: NodeKind) -> EntryMut<'_, 'a> {
+        let id = self.table.new_entry(self.id, kind);
+        self.with_id(id)
+    }
+
+    pub fn add_child(&mut self, name: Sym, child: Handle) -> Option<Handle> {
+        self.table.add_child(self.id, name, child)
+    }
+
+    pub fn set_body(&mut self, body: &'a Expr) -> Option<&'a Expr> {
+        self.table.set_body(self.id, body)
+    }
+
+    pub fn set_ty(&mut self, kind: TypeKind) -> Option<TypeKind> {
+        self.table.set_ty(self.id, kind)
+    }
+
+    pub fn set_span(&mut self, span: Span) -> Option<Span> {
+        self.table.set_span(self.id, span)
+    }
+
+    pub fn set_meta(&mut self, meta: &'a [Meta]) -> Option<&'a [Meta]> {
+        self.table.set_meta(self.id, meta)
+    }
+
+    pub fn set_source(&mut self, source: Source<'a>) -> Option<Source<'a>> {
+        self.table.set_source(self.id, source)
+    }
+
+    pub fn set_impl_target(&mut self, target: Handle) -> Option<Handle> {
+        self.table.set_impl_target(self.id, target)
+    }
+
+    pub fn mark_unchecked(&mut self) {
+        self.table.mark_unchecked(self.id)
+    }
+
+    pub fn mark_use_item(&mut self) {
+        self.table.mark_use_item(self.id)
+    }
+
+    pub fn mark_impl_item(&mut self) {
+        self.table.mark_impl_item(self.id)
+    }
+
+    pub fn mark_lang_item(&mut self, lang_item: &'static str) {
+        self.table.mark_lang_item(lang_item, self.id)
+    }
+}

compiler/cl-typeck/src/entry/debug.rs

@@ -0,0 +1,33 @@
+//! [std::fmt::Debug] implementation for [Entry]
+
+use super::Entry;
+
+impl std::fmt::Debug for Entry<'_, '_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        // virtual fields
+        let mut ds = f.debug_struct("Entry");
+        if let Some(name) = self.name() {
+            ds.field("name", &name.to_ref());
+        }
+        ds.field("kind", &self.kind());
+        if let Some(ty) = self.ty() {
+            ds.field("type", ty);
+        }
+        if let Some(meta) = self.meta() {
+            ds.field("meta", &meta);
+        }
+        if let Some(body) = self.bodies() {
+            ds.field("body", body);
+        }
+        if let Some(children) = self.children() {
+            ds.field("children", children);
+        }
+        if let Some(imports) = self.imports() {
+            ds.field("imports", imports);
+        }
+        // if let Some(source) = self.source() {
+        //     ds.field("source", source);
+        // }
+        ds.field("implements", &self.impl_target()).finish()
+    }
+}

compiler/cl-typeck/src/entry/display.rs

@@ -0,0 +1,100 @@
+use super::*;
+use crate::{format_utils::*, type_kind::Adt};
+use std::fmt::{self, Write};
+
+/// Printing the name of a named type stops infinite recursion
+fn write_name_or(h: Entry, f: &mut impl Write) -> fmt::Result {
+    match h.name() {
+        Some(name) => write!(f, "{name}"),
+        None => write!(f, "{h}"),
+    }
+}
+
+impl fmt::Display for Entry<'_, '_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Some(&kind) = self.kind() else {
+            return write!(f, "<invalid type: {}>", self.id);
+        };
+
+        if let Some(ty) = self.ty() {
+            match ty {
+                TypeKind::Inferred => write!(f, "<_{}>", self.id),
+                TypeKind::Variable => write!(f, "<?{}>", self.id),
+                TypeKind::Instance(id) => write!(f, "{}", self.with_id(*id)),
+                TypeKind::Primitive(kind) => write!(f, "{kind}"),
+                TypeKind::Adt(adt) => write_adt(adt, self, f),
+                &TypeKind::Ref(id) => {
+                    f.write_str("&")?;
+                    let h_id = self.with_id(id);
+                    write_name_or(h_id, f)
+                }
+                &TypeKind::Ptr(id) => {
+                    f.write_str("*")?;
+                    let h_id = self.with_id(id);
+                    write_name_or(h_id, f)
+                }
+                TypeKind::Slice(id) => {
+                    write_name_or(self.with_id(*id), &mut f.delimit_with("[", "]"))
+                }
+                &TypeKind::Array(t, cnt) => {
+                    let mut f = f.delimit_with("[", "]");
+                    write_name_or(self.with_id(t), &mut f)?;
+                    write!(f, "; {cnt}")
+                }
+                TypeKind::Tuple(ids) => {
+                    let mut f = f.delimit_with("(", ")");
+                    for (index, &id) in ids.iter().enumerate() {
+                        if index > 0 {
+                            write!(f, ", ")?;
+                        }
+                        write_name_or(self.with_id(id), &mut f)?;
+                    }
+                    Ok(())
+                }
+                TypeKind::FnSig { args, rety } => {
+                    write!(f, "fn {} -> ", self.with_id(*args))?;
+                    write_name_or(self.with_id(*rety), f)
+                }
+                TypeKind::Module => write!(f, "module?"),
+            }
+        } else {
+            match kind {
+                NodeKind::Type
+                | NodeKind::Const
+                | NodeKind::Static
+                | NodeKind::Temporary
+                | NodeKind::Let => write!(f, "WARNING: NO TYPE ASSIGNED FOR {}", self.id),
+                _ => write!(f, "{kind}"),
+            }
+        }
+    }
+}
+
+fn write_adt(adt: &Adt, h: &Entry, f: &mut impl Write) -> fmt::Result {
+    match adt {
+        Adt::Enum(variants) => {
+            let mut variants = variants.iter();
+            separate(", ", || {
+                variants.next().map(|(name, def)| {
+                    move |f: &mut Delimit<_>| write!(f, "{name}: {}", h.with_id(*def))
+                })
+            })(f.delimit_with("enum {", "}"))
+        }
+        Adt::Struct(members) => {
+            let mut members = members.iter();
+            separate(", ", || {
+                let (name, vis, id) = members.next()?;
+                Some(move |f: &mut Delimit<_>| write!(f, "{vis}{name}: {}", h.with_id(*id)))
+            })(f.delimit_with("struct {", "}"))
+        }
+        Adt::TupleStruct(members) => {
+            let mut members = members.iter();
+            separate(", ", || {
+                let (vis, def) = members.next()?;
+                Some(move |f: &mut Delimit<_>| write!(f, "{vis}{}", h.with_id(*def)))
+            })(f.delimit_with("struct (", ")"))
+        }
+        Adt::UnitStruct => write!(f, "struct"),
+        Adt::Union(_) => todo!("Display union types"),
+    }
+}

compiler/cl-typeck/src/format_utils.rs

@@ -0,0 +1,20 @@
+pub use cl_ast::format::*;
+use std::{fmt, iter};
+
+/// Separates the items yielded by iterating the provided function
+pub const fn separate<'f, 's, Item, F, W>(sep: &'s str, t: F) -> impl FnOnce(W) -> fmt::Result + 's
+where
+    Item: FnMut(&mut W) -> fmt::Result,
+    F: FnMut() -> Option<Item> + 's,
+    W: fmt::Write,
+{
+    move |mut f| {
+        for (idx, mut disp) in iter::from_fn(t).enumerate() {
+            if idx > 0 {
+                f.write_str(sep)?;
+            }
+            disp(&mut f)?;
+        }
+        Ok(())
+    }
+}

compiler/cl-typeck/src/handle.rs

@@ -0,0 +1,15 @@
+//! A [Handle] uniquely represents an entry in the [Table](crate::table::Table)
+
+use cl_structures::index_map::*;
+
+// define the index types
+make_index! {
+    /// Uniquely represents an entry in the [Table](crate::table::Table)
+    Handle,
+}
+
+impl std::fmt::Display for Handle {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}

compiler/cl-typeck/src/lib.rs

@@ -0,0 +1,74 @@
+//! # The Conlang Type Checker
+//!
+//! As a statically typed language, Conlang requires a robust type checker to enforce correctness.
+//!
+//! This crate is a major work-in-progress.
+//!
+//! # The [Table](table::Table)™
+//! A directed graph of nodes and their dependencies.
+//!
+//! Contains [item definitions](handle) and [type expression](type_expression) information.
+//!
+//! *Every* item is itself a module, and can contain arbitrarily nested items
+//! as part of the item graph
+//!
+//! The table, additionally, has some queues for use in external algorithms,
+//! detailed in the [stage] module.
+//!
+//! # Namespaces
+//! Each item in the graph is given its own namespace, which is further separated into
+//! two distinct parts:
+//! - Children of an item are direct descendents (i.e. their `parent` is a handle to the item)
+//! - Imports of an item are indirect descendents created by `use` or `impl` directives. They are
+//!   shadowed by Children with the same name.
+//!
+//! # Order of operations:
+//! For order-of-operations information, see the [stage] module.
+#![warn(clippy::all)]
+
+pub(crate) mod format_utils;
+
+pub mod table;
+
+pub mod handle;
+
+pub mod entry;
+
+pub mod source;
+
+pub mod type_kind;
+
+pub mod type_expression;
+
+pub mod stage {
+    //! Type collection, evaluation, checking, and inference passes.
+    //!
+    //! # Order of operations
+    //! 1. [mod@populate]: Populate the graph with nodes for every named item.
+    //! 2. [mod@import]: Import the `use` nodes discovered in [Stage 1](populate).
+    //! 3. [mod@categorize]: Categorize the nodes according to textual type information.
+    //!    - Creates anonymous types (`fn(T) -> U`, `&T`, `[T]`, etc.) as necessary to fill in the
+    //!      type graph
+    //!    - Creates a new struct type for every enum struct-variant.
+    //! 4. [mod@implement]: Import members of implementation modules into types.
+
+    pub use populate::Populator;
+    /// Stage 1: Populate the graph with nodes.
+    pub mod populate;
+
+    pub use import::import;
+    /// Stage 2: Import the `use` nodes discovered in Stage 1.
+    pub mod import;
+
+    pub use categorize::categorize;
+    /// Stage 3: Categorize the nodes according to textual type information.
+    pub mod categorize;
+
+    pub use implement::implement;
+    /// Stage 4: Import members of `impl` blocks into their corresponding types.
+    pub mod implement;
+
+    // TODO: Make type inference stage 5
+    // TODO: Use the type information stored in the [table]
+    pub mod infer;
+}

compiler/cl-typeck/src/source.rs

@@ -0,0 +1,87 @@
+//! Holds the [Source] of a definition in the AST
+
+use cl_ast::ast::*;
+use std::fmt;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Source<'a> {
+    Root,
+    Module(&'a Module),
+    Alias(&'a Alias),
+    Enum(&'a Enum),
+    Variant(&'a Variant),
+    Struct(&'a Struct),
+    Const(&'a Const),
+    Static(&'a Static),
+    Function(&'a Function),
+    Local(&'a Let),
+    Impl(&'a Impl),
+    Use(&'a Use),
+    Ty(&'a TyKind),
+}
+
+impl Source<'_> {
+    pub fn name(&self) -> Option<Sym> {
+        match self {
+            Source::Root => None,
+            Source::Module(v) => Some(v.name),
+            Source::Alias(v) => Some(v.name),
+            Source::Enum(v) => Some(v.name),
+            Source::Variant(v) => Some(v.name),
+            Source::Struct(v) => Some(v.name),
+            Source::Const(v) => Some(v.name),
+            Source::Static(v) => Some(v.name),
+            Source::Function(v) => Some(v.name),
+            Source::Local(_) => None,
+            Source::Impl(_) | Source::Use(_) | Source::Ty(_) => None,
+        }
+    }
+
+    /// Returns `true` if this [Source] defines a named value
+    pub fn is_named_value(&self) -> bool {
+        matches!(self, Self::Const(_) | Self::Static(_) | Self::Function(_))
+    }
+
+    /// Returns `true` if this [Source] defines a named type
+    pub fn is_named_type(&self) -> bool {
+        matches!(
+            self,
+            Self::Module(_) | Self::Alias(_) | Self::Enum(_) | Self::Struct(_)
+        )
+    }
+
+    /// Returns `true` if this [Source] refers to a [Ty] with no name
+    pub fn is_anon_type(&self) -> bool {
+        matches!(self, Self::Ty(_))
+    }
+
+    /// Returns `true` if this [Source] refers to an [Impl] block
+    pub fn is_impl(&self) -> bool {
+        matches!(self, Self::Impl(_))
+    }
+
+    /// Returns `true` if this [Source] refers to a [Use] import
+    pub fn is_use_import(&self) -> bool {
+        matches!(self, Self::Use(_))
+    }
+}
+
+impl fmt::Display for Source<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Root => "🌳 root 🌳".fmt(f),
+            Self::Module(arg0) => arg0.fmt(f),
+            Self::Alias(arg0) => arg0.fmt(f),
+            Self::Enum(arg0) => arg0.fmt(f),
+            Self::Variant(arg0) => arg0.fmt(f),
+            Self::Struct(arg0) => arg0.fmt(f),
+            Self::Const(arg0) => arg0.fmt(f),
+            Self::Static(arg0) => arg0.fmt(f),
+            Self::Function(arg0) => arg0.fmt(f),
+            Self::Impl(arg0) => arg0.fmt(f),
+            Self::Use(arg0) => arg0.fmt(f),
+            Self::Ty(arg0) => arg0.fmt(f),
+            Self::Local(arg0) => arg0.fmt(f),
+        }
+    }
+}

compiler/cl-typeck/src/stage/categorize.rs

@@ -0,0 +1,187 @@
+//! Categorizes an entry in a table according to its embedded type information
+#![allow(unused)]
+use crate::{
+    entry::EntryMut,
+    handle::Handle,
+    source::Source,
+    table::{NodeKind, Table},
+    type_expression::{Error as TypeEval, TypeExpression},
+    type_kind::{Adt, TypeKind},
+};
+use cl_ast::*;
+
+/// Ensures a type entry exists for the provided handle in the table
+pub fn categorize(table: &mut Table, node: Handle) -> CatResult<()> {
+    let Some(source) = table.source(node) else {
+        return Ok(());
+    };
+
+    match source {
+        Source::Variant(v) => cat_variant(table, node, v)?,
+        Source::Struct(s) => cat_struct(table, node, s)?,
+        Source::Const(c) => cat_const(table, node, c)?,
+        Source::Static(s) => cat_static(table, node, s)?,
+        Source::Function(f) => cat_function(table, node, f)?,
+        Source::Local(l) => cat_local(table, node, l)?,
+        Source::Impl(i) => cat_impl(table, node, i)?,
+        // Source::Alias(_) => {table.mark_unchecked(node)},
+        _ => return Ok(()),
+    }
+    Ok(())
+}
+
+fn parent(table: &Table, node: Handle) -> Handle {
+    table.parent(node).copied().unwrap_or(node)
+}
+
+fn cat_struct(table: &mut Table, node: Handle, s: &Struct) -> CatResult<()> {
+    let Struct { name: _, gens: _, kind } = s;
+    // TODO: Generics
+    let kind = match kind {
+        StructKind::Empty => TypeKind::Adt(Adt::UnitStruct),
+        StructKind::Tuple(types) => {
+            let mut out = vec![];
+            for ty in types {
+                out.push((Visibility::Public, ty.evaluate(table, node)?))
+            }
+            TypeKind::Adt(Adt::TupleStruct(out))
+        }
+        StructKind::Struct(members) => {
+            let mut out = vec![];
+            for m in members {
+                out.push(cat_member(table, node, m)?)
+            }
+            TypeKind::Adt(Adt::Struct(out))
+        }
+    };
+
+    table.set_ty(node, kind);
+    Ok(())
+}
+
+fn cat_member(
+    table: &mut Table,
+    node: Handle,
+    m: &StructMember,
+) -> CatResult<(Sym, Visibility, Handle)> {
+    let StructMember { vis, name, ty } = m;
+    Ok((*name, *vis, ty.evaluate(table, node)?))
+}
+
+fn cat_enum<'a>(_table: &mut Table<'a>, _node: Handle, e: &'a Enum) -> CatResult<()> {
+    let Enum { name: _, gens: _, variants: _ } = e;
+    // table.set_ty(node, kind);
+    Ok(())
+}
+
+fn cat_variant<'a>(table: &mut Table<'a>, node: Handle, v: &'a Variant) -> CatResult<()> {
+    let Variant { name, kind, body } = v;
+    let parent = table.parent(node).copied().unwrap_or(table.root());
+    match (kind) {
+        (StructKind::Empty) => Ok(()),
+        (StructKind::Empty) => Ok(()),
+        (StructKind::Tuple(ty)) => {
+            let ty = TypeKind::Adt(Adt::TupleStruct(
+                ty.iter()
+                    .map(|ty| ty.evaluate(table, node).map(|ty| (Visibility::Public, ty)))
+                    .collect::<Result<_, _>>()?,
+            ));
+            table.set_ty(node, ty);
+            Ok(())
+        }
+        (StructKind::Struct(members)) => {
+            let mut out = vec![];
+            for StructMember { vis, name, ty } in members {
+                let ty = ty.evaluate(table, node)?;
+                out.push((*name, *vis, ty));
+
+                let mut this = node.to_entry_mut(table);
+                let mut child = this.new_entry(NodeKind::Type);
+                child.set_source(Source::Variant(v));
+                child.set_ty(TypeKind::Instance(ty));
+
+                let child = child.id();
+                this.add_child(*name, child);
+            }
+
+            table.set_ty(node, TypeKind::Adt(Adt::Struct(out)));
+            Ok(())
+        }
+    }
+}
+
+fn cat_const(table: &mut Table, node: Handle, c: &Const) -> CatResult<()> {
+    let parent = parent(table, node);
+    let kind = TypeKind::Instance(
+        c.ty.evaluate(table, parent)
+            .map_err(|e| Error::TypeEval(e, " while categorizing a const"))?,
+    );
+    table.set_ty(node, kind);
+    Ok(())
+}
+
+fn cat_static(table: &mut Table, node: Handle, s: &Static) -> CatResult<()> {
+    let parent = parent(table, node);
+    let kind = TypeKind::Instance(
+        s.ty.evaluate(table, parent)
+            .map_err(|e| Error::TypeEval(e, " while categorizing a static"))?,
+    );
+    table.set_ty(node, kind);
+    Ok(())
+}
+
+fn cat_function(table: &mut Table, node: Handle, f: &Function) -> CatResult<()> {
+    let kind = TypeKind::Instance(
+        f.sign
+            .evaluate(table, node)
+            .map_err(|e| Error::TypeEval(e, " while categorizing a function"))?,
+    );
+    table.set_ty(node, kind);
+    Ok(())
+}
+
+fn cat_local(table: &mut Table, node: Handle, l: &Let) -> CatResult<()> {
+    let parent = parent(table, node);
+    if let Some(ty) = &l.ty {
+        let kind = ty
+            .evaluate(table, parent)
+            .map_err(|e| Error::TypeEval(e, " while categorizing a let binding"))?;
+        table.set_ty(node, TypeKind::Instance(kind));
+    }
+    Ok(())
+}
+
+fn cat_impl(table: &mut Table, node: Handle, i: &Impl) -> CatResult<()> {
+    let parent = parent(table, node);
+    let Impl { gens, target, body: _ } = i;
+    let target = match target {
+        ImplKind::Type(t) => t.evaluate(table, parent),
+        ImplKind::Trait { impl_trait: _, for_type: t } => t.evaluate(table, parent),
+    }?;
+
+    table.set_impl_target(node, target);
+    Ok(())
+}
+
+type CatResult<T> = Result<T, Error>;
+
+#[derive(Clone, Debug)]
+pub enum Error {
+    BadMeta(Meta),
+    TypeEval(TypeEval, &'static str),
+}
+
+impl From<TypeEval> for Error {
+    fn from(value: TypeEval) -> Self {
+        Error::TypeEval(value, "")
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::BadMeta(meta) => write!(f, "Unknown attribute: #[{meta}]"),
+            Error::TypeEval(e, during) => write!(f, "{e}{during}"),
+        }
+    }
+}

compiler/cl-typeck/src/stage/implement.rs

@@ -0,0 +1,23 @@
+use crate::{handle::Handle, table::Table};
+
+pub fn implement(table: &mut Table) -> Vec<Handle> {
+    let pending = std::mem::take(&mut table.impls);
+    let mut errors = vec![];
+    for node in pending {
+        if let Err(e) = impl_one(table, node) {
+            errors.push(e);
+        }
+    }
+    errors
+}
+
+pub fn impl_one(table: &mut Table, node: Handle) -> Result<(), Handle> {
+    let Some(target) = table.impl_target(node) else {
+        Err(node)?
+    };
+    if let Some(children) = table.children.get_mut(&node) {
+        let children = children.clone();
+        table.children.entry(target).or_default().extend(children);
+    }
+    Ok(())
+}

compiler/cl-typeck/src/stage/import.rs

@@ -0,0 +1,158 @@
+//! An algorithm for importing external nodes
+
+use crate::{
+    handle::Handle,
+    source::Source,
+    table::{NodeKind, Table},
+};
+use cl_ast::{PathPart, Sym, Use, UseTree};
+use core::slice;
+use std::{collections::HashSet, mem};
+
+type Seen = HashSet<Handle>;
+
+pub fn import<'a>(table: &mut Table<'a>) -> Vec<(Handle, Error<'a>)> {
+    let pending = mem::take(&mut table.uses);
+
+    let mut seen = Seen::new();
+    let mut failed = vec![];
+    for import in pending {
+        let Err(e) = import_one(table, import, &mut seen) else {
+            continue;
+        };
+        if let Error::NotFound(_, _) = e {
+            table.mark_use_item(import)
+        }
+        failed.push((import, e));
+    }
+    failed
+}
+
+fn import_one<'a>(table: &mut Table<'a>, item: Handle, seen: &mut Seen) -> UseResult<'a, ()> {
+    if !seen.insert(item) {
+        return Ok(());
+    }
+
+    let Some(NodeKind::Use) = table.kind(item) else {
+        Err(Error::ItsNoUse)?
+    };
+    let Some(&dst) = table.parent(item) else {
+        Err(Error::NoParents)?
+    };
+    let Some(code) = table.source(item) else {
+        Err(Error::NoSource)?
+    };
+    let &Source::Use(tree) = code else {
+        Err(Error::BadSource(*code))?
+    };
+    let Use { absolute, tree } = tree;
+
+    import_tree(
+        table,
+        if !absolute { dst } else { table.root() },
+        dst,
+        tree,
+        seen,
+    )
+}
+
+fn import_tree<'a>(
+    table: &mut Table<'a>,
+    src: Handle,
+    dst: Handle,
+    tree: &UseTree,
+    seen: &mut Seen,
+) -> UseResult<'a, ()> {
+    match tree {
+        UseTree::Tree(trees) => trees
+            .iter()
+            .try_for_each(|tree| import_tree(table, src, dst, tree, seen)),
+        UseTree::Path(part, rest) => {
+            let source = table
+                .nav(src, slice::from_ref(part))
+                .ok_or(Error::NotFound(src, *part))?;
+            import_tree(table, source, dst, rest, seen)
+        }
+        UseTree::Alias(src_name, dst_name) => {
+            import_name(table, src, src_name, dst, dst_name, seen)
+        }
+        UseTree::Name(src_name) => import_name(table, src, src_name, dst, src_name, seen),
+        UseTree::Glob => import_glob(table, src, dst, seen),
+    }
+}
+
+fn import_glob<'a>(
+    table: &mut Table<'a>,
+    src: Handle,
+    dst: Handle,
+    seen: &mut Seen,
+) -> UseResult<'a, ()> {
+    let Table { children, imports, .. } = table;
+
+    if let Some(c) = children.get(&src) {
+        imports.entry(dst).or_default().extend(c)
+    }
+
+    import_deps(table, src, seen)?;
+
+    let Table { imports, .. } = table;
+
+    // Importing imports requires some extra work, since we can't `get_many_mut`
+    if let Some(i) = imports.get(&src) {
+        let uses: Vec<_> = i.iter().map(|(&k, &v)| (k, v)).collect();
+        imports.entry(dst).or_default().extend(uses);
+    }
+
+    Ok(())
+}
+
+fn import_name<'a>(
+    table: &mut Table<'a>,
+    src: Handle,
+    src_name: &Sym,
+    dst: Handle,
+    dst_name: &Sym,
+    seen: &mut Seen,
+) -> UseResult<'a, ()> {
+    import_deps(table, src, seen)?;
+    match table.get_by_sym(src, src_name) {
+        // TODO: check for new imports clobbering existing imports
+        Some(src_id) => table.add_import(dst, *dst_name, src_id),
+        None => Err(Error::NotFound(src, PathPart::Ident(*src_name)))?,
+    };
+    Ok(())
+}
+
+/// Imports the dependencies of this node
+fn import_deps<'a>(table: &mut Table<'a>, node: Handle, seen: &mut Seen) -> UseResult<'a, ()> {
+    if let Some(items) = table.use_items.get(&node) {
+        let out = items.clone();
+        for item in out {
+            import_one(table, item, seen)?;
+        }
+    }
+    Ok(())
+}
+
+pub type UseResult<'a, T> = Result<T, Error<'a>>;
+
+#[derive(Debug)]
+pub enum Error<'a> {
+    ItsNoUse,
+    NoParents,
+    NoSource,
+    BadSource(Source<'a>),
+    NotFound(Handle, PathPart),
+}
+
+impl std::fmt::Display for Error<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::ItsNoUse => write!(f, "Entry is not use"),
+            Error::NoParents => write!(f, "Entry has no parents"),
+            Error::NoSource => write!(f, "Entry has no source"),
+            Error::BadSource(s) => write!(f, "Entry incorrectly marked as use item: {s}"),
+            Error::NotFound(id, part) => write!(f, "Could not traverse {id}::{part}"),
+        }
+    }
+}

compiler/cl-typeck/src/stage/infer.rs

@@ -0,0 +1,12 @@
+//! Implements type unification, used by the Hindley-Milner type inference algorithm
+//!
+//! Inspired by [rust-hindley-milner][1] and [hindley-milner-python][2]
+//!
+//! [1]: https://github.com/tcr/rust-hindley-milner/
+//! [2]: https://github.com/rob-smallshire/hindley-milner-python
+
+pub mod engine;
+
+pub mod inference;
+
+pub mod error;

compiler/cl-typeck/src/stage/infer/engine.rs

@@ -0,0 +1,621 @@
+use std::collections::HashSet;
+
+use super::error::InferenceError;
+use crate::{
+    entry::Entry,
+    handle::Handle,
+    source::Source,
+    stage::infer::inference::Inference,
+    table::{NodeKind, Table},
+    type_expression::TypeExpression,
+    type_kind::{Adt, Primitive, TypeKind},
+};
+use cl_ast::Sym;
+
+/*
+    Types in Conlang:
+    - Never type: !
+      - type !
+      - for<A> ! -> A
+    - Primitive types: bool, i32, (), ...
+      - type bool; ...
+    - Reference types: &T, *T
+      - for<T> type ref<T>; for<T> type ptr<T>
+    - Slice type:      [T]
+      - for<T> type slice<T>
+    - Array type:      [T;usize]
+      - for<T> type array<T, instanceof<usize>>
+    - Tuple type:      (T, ...Z)
+      - for<T, ..> type tuple<T, ..>    // on a per-case basis!
+    - Funct type:      fn Tuple -> R
+      - for<T, R> type T -> R           // on a per-case basis!
+*/
+
+type HandleSet<'h> = Option<&'h mut Option<Handle>>;
+
+pub struct InferenceEngine<'table, 'a, 'b, 'r> {
+    pub(super) table: &'table mut Table<'a>,
+    /// The current working node
+    pub(crate) at: Handle,
+    /// The current breakset
+    pub(crate) bset: HandleSet<'b>,
+    /// The current returnset
+    pub(crate) rset: HandleSet<'r>,
+}
+
+impl<'table, 'a, 'b, 'r> InferenceEngine<'table, 'a, 'b, 'r> {
+    /// Infers the type of an object by deferring to [`Inference::infer()`]
+    pub fn infer(&mut self, inferrable: &'a impl Inference<'a>) -> Result<Handle, InferenceError> {
+        inferrable.infer(self)
+    }
+
+    /// Constructs a new [`InferenceEngine`], scoped around a [`Handle`] in a [`Table`].
+    pub fn new(table: &'table mut Table<'a>, at: Handle) -> Self {
+        Self { at, table, bset: Default::default(), rset: Default::default() }
+    }
+
+    /// Constructs an [`InferenceEngine`] that borrows the same table as `self`,
+    /// but with a shortened lifetime.
+    pub fn scoped(&mut self) -> InferenceEngine<'_, 'a, '_, '_> {
+        InferenceEngine {
+            at: self.at,
+            table: self.table,
+            bset: self.bset.as_deref_mut(),
+            rset: self.rset.as_deref_mut(),
+        }
+    }
+
+    pub fn infer_all(&mut self) -> Vec<(Handle, InferenceError)> {
+        let queue = std::mem::take(&mut self.table.unchecked);
+        let mut res = Vec::new();
+        for handle in queue {
+            let mut eng = self.at(handle);
+            let Some(source) = eng.table.source(handle) else {
+                eprintln!("No source found for {handle}");
+                continue;
+            };
+
+            println!("Inferring {source}");
+
+            let ret = match source {
+                Source::Module(v) => v.infer(&mut eng),
+                Source::Alias(v) => v.infer(&mut eng),
+                Source::Enum(v) => v.infer(&mut eng),
+                // Source::Variant(v) => v.infer(&mut eng),
+                Source::Struct(v) => v.infer(&mut eng),
+                Source::Const(v) => v.infer(&mut eng),
+                Source::Static(v) => v.infer(&mut eng),
+                Source::Function(v) => v.infer(&mut eng),
+                Source::Local(v) => v.infer(&mut eng),
+                Source::Impl(v) => v.infer(&mut eng),
+                _ => Ok(eng.empty()),
+            };
+
+            match &ret {
+                Ok(handle) => println!("=> {}", eng.entry(*handle)),
+                Err(err @ InferenceError::AnnotationEval(_)) => eprintln!("=> ERROR: {err}"),
+                Err(InferenceError::FieldCount(h, want, got)) => {
+                    eprintln!("=> ERROR: Field count {want} != {got} in {}", eng.entry(*h))
+                }
+                Err(err @ InferenceError::NotFound(_)) => eprintln!("=> ERROR: {err}"),
+                Err(InferenceError::Mismatch(h1, h2)) => eprintln!(
+                    "=> ERROR: Type mismatch {} != {}",
+                    eng.entry(*h1),
+                    eng.entry(*h2),
+                ),
+                Err(InferenceError::Recursive(h1, h2)) => eprintln!(
+                    "=> ERROR: Cycle found in types {}, {}",
+                    eng.entry(*h1),
+                    eng.entry(*h2),
+                ),
+                Err(InferenceError::NoBreak | InferenceError::NoReturn) => {}
+            }
+            println!();
+
+            if let Err(err) = ret {
+                res.push((handle, err));
+                eng.table.mark_unchecked(handle);
+            }
+        }
+        res
+    }
+
+    /// Constructs a new InferenceEngine with the
+    pub fn at(&mut self, at: Handle) -> InferenceEngine<'_, 'a, '_, '_> {
+        InferenceEngine { at, ..self.scoped() }
+    }
+
+    pub fn open_bset<'ob>(
+        &mut self,
+        bset: &'ob mut Option<Handle>,
+    ) -> InferenceEngine<'_, 'a, 'ob, '_> {
+        InferenceEngine { bset: Some(bset), ..self.scoped() }
+    }
+
+    pub fn open_rset<'or>(
+        &mut self,
+        rset: &'or mut Option<Handle>,
+    ) -> InferenceEngine<'_, 'a, '_, 'or> {
+        InferenceEngine { rset: Some(rset), ..self.scoped() }
+    }
+
+    pub fn bset(&mut self, ty: Handle) -> Result<(), InferenceError> {
+        match self.bset.as_mut() {
+            Some(&mut &mut Some(bset)) => self.unify(ty, bset),
+            Some(none) => {
+                let _ = none.insert(ty);
+                Ok(())
+            }
+            None => Err(InferenceError::NoBreak),
+        }
+    }
+
+    pub fn rset(&mut self, ty: Handle) -> Result<(), InferenceError> {
+        match self.rset.as_mut() {
+            Some(&mut &mut Some(rset)) => self.unify(ty, rset),
+            Some(none) => {
+                let _ = none.insert(ty);
+                Ok(())
+            }
+            None => Err(InferenceError::NoReturn),
+        }
+    }
+
+    /// Constructs an [Entry] out of a [Handle], for ease of use
+    pub fn entry(&self, of: Handle) -> Entry<'_, 'a> {
+        self.table.entry(of)
+    }
+
+    pub fn by_name<Out, N: TypeExpression<Out>>(
+        &mut self,
+        name: &N,
+    ) -> Result<Out, crate::type_expression::Error> {
+        name.evaluate(self.table, self.at)
+    }
+
+    /// Creates a new unbound [type variable](Handle)
+    pub fn new_var(&mut self) -> Handle {
+        self.table.type_variable()
+    }
+
+    pub fn new_inferred(&mut self) -> Handle {
+        self.table.inferred_type()
+    }
+
+    /// Creates a variable that is a new instance of another [Type](Handle)
+    pub fn new_inst(&mut self, of: Handle) -> Handle {
+        self.table.anon_type(TypeKind::Instance(of))
+    }
+
+    /// Gets the defining usage of a type without collapsing intermediates
+    pub fn def_usage(&self, to: Handle) -> Handle {
+        match self.table.entry(to).ty() {
+            Some(TypeKind::Instance(id)) => self.def_usage(*id),
+            _ => to,
+        }
+    }
+
+    pub fn get_fn(&self, at: Handle, name: Sym) -> Option<(Handle, Handle)> {
+        use cl_ast::PathPart;
+        if let Some(&TypeKind::FnSig { args, rety }) = self
+            .entry(at)
+            .nav(&[PathPart::Ident(name)])
+            .as_ref()
+            .and_then(Entry::ty)
+        {
+            Some((args, rety))
+        } else {
+            None
+        }
+    }
+
+    /// Creates a new type variable representing a tuple
+    pub fn new_tuple(&mut self, tys: Vec<Handle>) -> Handle {
+        self.table.anon_type(TypeKind::Tuple(tys))
+    }
+
+    /// Creates a new type variable representing an array
+    pub fn new_array(&mut self, ty: Handle, size: usize) -> Handle {
+        self.table.anon_type(TypeKind::Array(ty, size))
+    }
+
+    /// Creates a new type variable representing a slice of contiguous memory
+    pub fn new_slice(&mut self, ty: Handle) -> Handle {
+        self.table.anon_type(TypeKind::Slice(ty))
+    }
+
+    /// Creates a new reference to a type
+    pub fn new_ref(&mut self, to: Handle) -> Handle {
+        self.table.anon_type(TypeKind::Ref(to))
+    }
+
+    /// All primitives must be predefined in the standard library.
+    pub fn primitive(&self, name: &'static str) -> Handle {
+        // TODO: keep a map of primitives in the table root
+        self.table.get_lang_item(name)
+    }
+
+    pub fn never(&mut self) -> Handle {
+        self.table.get_lang_item("never")
+    }
+
+    pub fn empty(&mut self) -> Handle {
+        self.table.anon_type(TypeKind::Tuple(vec![]))
+    }
+
+    pub fn bool(&self) -> Handle {
+        self.primitive("bool")
+    }
+
+    pub fn char(&self) -> Handle {
+        self.primitive("char")
+    }
+
+    pub fn str(&self) -> Handle {
+        self.primitive("str")
+    }
+
+    pub fn u32(&self) -> Handle {
+        self.primitive("u32")
+    }
+
+    pub fn usize(&self) -> Handle {
+        self.primitive("usize")
+    }
+
+    /// Creates a new inferred-integer literal
+    pub fn integer_literal(&mut self) -> Handle {
+        let h = self.table.new_entry(self.at, NodeKind::Temporary);
+        self.table
+            .set_ty(h, TypeKind::Primitive(Primitive::Integer));
+        h
+    }
+
+    /// Creates a new inferred-float literal
+    pub fn float_literal(&mut self) -> Handle {
+        let h = self.table.new_entry(self.at, NodeKind::Temporary);
+        self.table.set_ty(h, TypeKind::Primitive(Primitive::Float));
+        h
+    }
+
+    /// Enters a new scope
+    pub fn local_scope(&mut self, name: Sym) {
+        let scope = self.table.new_entry(self.at, NodeKind::Scope);
+        self.table.add_child(self.at, name, scope);
+        self.at = scope;
+    }
+
+    /// Creates a new locally-scoped InferenceEngine.
+    pub fn block_scope(&mut self) -> InferenceEngine<'_, 'a, '_, '_> {
+        let scope = self.table.new_entry(self.at, NodeKind::Scope);
+        self.table.add_child(self.at, "".into(), scope);
+        self.at(scope)
+    }
+
+    /// Sets this type variable `to` be an instance `of` the other
+    /// # Panics
+    /// Panics if `to` is not a type variable
+    pub fn set_instance(&mut self, to: Handle, of: Handle) {
+        let mut e = self.table.entry_mut(to);
+        match e.as_ref().ty() {
+            Some(TypeKind::Inferred) => {
+                if let Some(ty) = self.table.ty(of) {
+                    self.table.set_ty(to, ty.clone());
+                }
+                None
+            }
+            Some(TypeKind::Variable)
+            | Some(TypeKind::Primitive(Primitive::Float | Primitive::Integer)) => {
+                e.set_ty(TypeKind::Instance(of))
+            }
+            other => todo!("Cannot set {} to instance of: {other:?}", e.as_ref()),
+        };
+    }
+
+    /// Checks whether there are any unbound type variables in this type
+    pub fn is_generic(&self, ty: Handle) -> bool {
+        fn is_generic_rec(this: &InferenceEngine, ty: Handle, seen: &mut HashSet<Handle>) -> bool {
+            if !seen.insert(ty) {
+                return false;
+            }
+            let entry = this.table.entry(ty);
+            let Some(ty) = entry.ty() else {
+                return false;
+            };
+            match ty {
+                TypeKind::Inferred => false,
+                TypeKind::Variable => true,
+                &TypeKind::Array(ty, _) => is_generic_rec(this, ty, seen),
+                &TypeKind::Instance(ty) => is_generic_rec(this, ty, seen),
+                TypeKind::Primitive(_) => false,
+                TypeKind::Adt(Adt::Enum(tys)) => {
+                    tys.iter().any(|&(_, ty)| is_generic_rec(this, ty, seen))
+                }
+                TypeKind::Adt(Adt::Struct(tys)) => {
+                    tys.iter().any(|&(_, _, ty)| is_generic_rec(this, ty, seen))
+                }
+                TypeKind::Adt(Adt::TupleStruct(tys)) => {
+                    tys.iter().any(|&(_, ty)| is_generic_rec(this, ty, seen))
+                }
+                TypeKind::Adt(Adt::UnitStruct) => false,
+                TypeKind::Adt(Adt::Union(tys)) => {
+                    tys.iter().any(|&(_, ty)| is_generic_rec(this, ty, seen))
+                }
+                &TypeKind::Ref(ty) => is_generic_rec(this, ty, seen),
+                &TypeKind::Ptr(ty) => is_generic_rec(this, ty, seen),
+                &TypeKind::Slice(ty) => is_generic_rec(this, ty, seen),
+                TypeKind::Tuple(tys) => tys.iter().any(|&ty| is_generic_rec(this, ty, seen)),
+                &TypeKind::FnSig { args, rety } => {
+                    is_generic_rec(this, args, seen) || is_generic_rec(this, rety, seen)
+                }
+                TypeKind::Module => false,
+            }
+        }
+        is_generic_rec(self, ty, &mut HashSet::new())
+    }
+
+    /// Makes a deep copy of a type expression.
+    ///
+    /// Bound variables are shared, unbound variables are duplicated.
+    pub fn deep_clone(&mut self, ty: Handle) -> Handle {
+        if !self.is_generic(ty) {
+            return ty;
+        };
+        let entry = self.table.entry(ty);
+        let Some(tykind) = entry.ty().cloned() else {
+            return ty;
+        };
+
+        // TODO: Parent the deep clone into a new "monomorphs" branch of tree
+        match tykind {
+            TypeKind::Variable => self.new_inferred(),
+            TypeKind::Array(h, s) => {
+                let ty = self.deep_clone(h);
+                self.table.anon_type(TypeKind::Array(ty, s))
+            }
+            TypeKind::Instance(h) => {
+                let ty = self.deep_clone(h);
+                self.table.anon_type(TypeKind::Instance(ty))
+            }
+            TypeKind::Adt(Adt::Enum(tys)) => {
+                let tys = tys
+                    .into_iter()
+                    .map(|(name, ty)| (name, self.deep_clone(ty)))
+                    .collect();
+                self.table.anon_type(TypeKind::Adt(Adt::Enum(tys)))
+            }
+            TypeKind::Adt(Adt::Struct(tys)) => {
+                let tys = tys
+                    .into_iter()
+                    .map(|(n, v, ty)| (n, v, self.deep_clone(ty)))
+                    .collect();
+                self.table.anon_type(TypeKind::Adt(Adt::Struct(tys)))
+            }
+            TypeKind::Adt(Adt::TupleStruct(tys)) => {
+                let tys = tys
+                    .into_iter()
+                    .map(|(v, ty)| (v, self.deep_clone(ty)))
+                    .collect();
+                self.table.anon_type(TypeKind::Adt(Adt::TupleStruct(tys)))
+            }
+            TypeKind::Adt(Adt::Union(tys)) => {
+                let tys = tys
+                    .into_iter()
+                    .map(|(n, ty)| (n, self.deep_clone(ty)))
+                    .collect();
+                self.table.anon_type(TypeKind::Adt(Adt::Union(tys)))
+            }
+            TypeKind::Ref(h) => {
+                let ty = self.deep_clone(h);
+                self.table.anon_type(TypeKind::Ref(ty))
+            }
+            TypeKind::Ptr(handle) => {
+                let ty = self.deep_clone(handle);
+                self.table.anon_type(TypeKind::Ptr(ty))
+            }
+            TypeKind::Slice(h) => {
+                let ty = self.deep_clone(h);
+                self.table.anon_type(TypeKind::Slice(ty))
+            }
+            TypeKind::Tuple(tys) => {
+                let tys = tys.into_iter().map(|ty| self.deep_clone(ty)).collect();
+                self.table.anon_type(TypeKind::Tuple(tys))
+            }
+            TypeKind::FnSig { args, rety } => {
+                let args = self.deep_clone(args);
+                let rety = self.deep_clone(rety);
+                self.table.anon_type(TypeKind::FnSig { args, rety })
+            }
+            _ => ty,
+        }
+    }
+
+    /// Returns the defining instance of `self`,
+    /// collapsing type instances along the way.
+    pub fn prune(&mut self, ty: Handle) -> Handle {
+        if let Some(TypeKind::Instance(new_ty)) = self.table.ty(ty) {
+            let new_ty = self.prune(*new_ty);
+            self.table.set_ty(ty, TypeKind::Instance(new_ty));
+            new_ty
+        } else {
+            ty
+        }
+    }
+
+    /// Checks whether a type occurs in another type
+    ///
+    /// # Note:
+    /// - Since the test uses strict equality, `self` should be pruned prior to testing.
+    /// - The test is *not guaranteed to terminate* for recursive types.
+    pub fn occurs_in(&self, this: Handle, other: Handle) -> bool {
+        if this == other {
+            return true;
+        }
+        let Some(ty) = self.table.ty(other) else {
+            return false;
+        };
+        match ty {
+            TypeKind::Instance(other) => self.occurs_in(this, *other),
+            TypeKind::Adt(Adt::Enum(items)) => {
+                items.iter().any(|(_, other)| self.occurs_in(this, *other))
+            }
+            TypeKind::Adt(Adt::Struct(items)) => items
+                .iter()
+                .any(|(_, _, other)| self.occurs_in(this, *other)),
+            TypeKind::Adt(Adt::TupleStruct(items)) => {
+                items.iter().any(|(_, other)| self.occurs_in(this, *other))
+            }
+            TypeKind::Adt(Adt::Union(items)) => {
+                items.iter().any(|(_, other)| self.occurs_in(this, *other))
+            }
+            TypeKind::Ref(_) => false,
+            TypeKind::Ptr(_) => false,
+            TypeKind::Slice(other) => self.occurs_in(this, *other),
+            TypeKind::Array(other, _) => self.occurs_in(this, *other),
+            TypeKind::Tuple(handles) => handles.iter().any(|&other| self.occurs_in(this, other)),
+            TypeKind::FnSig { args, rety } => {
+                self.occurs_in(this, *args) || self.occurs_in(this, *rety)
+            }
+            TypeKind::Inferred
+            | TypeKind::Variable
+            | TypeKind::Adt(Adt::UnitStruct)
+            | TypeKind::Primitive(_)
+            | TypeKind::Module => false,
+        }
+    }
+
+    /// Unifies two types
+    pub fn unify(&mut self, this: Handle, other: Handle) -> Result<(), InferenceError> {
+        let (ah, bh) = (self.prune(this), self.prune(other));
+        if ah == bh {
+            return Ok(());
+        }
+        let (a, b) = (self.table.entry(ah), self.table.entry(bh));
+        let (Some(a), Some(b)) = (a.ty(), b.ty()) else {
+            return Err(InferenceError::Mismatch(ah, bh));
+        };
+
+        match (a, b) {
+            (TypeKind::Variable, TypeKind::Variable) => {
+                self.set_instance(ah, bh);
+                Ok(())
+            }
+            (TypeKind::Inferred, _) => {
+                self.set_instance(ah, bh);
+                Ok(())
+            }
+            (_, TypeKind::Inferred) => self.unify(bh, ah),
+
+            (TypeKind::Variable, _) => Err(InferenceError::Mismatch(ah, bh)),
+            (TypeKind::Instance(a), TypeKind::Instance(b)) if !self.occurs_in(*a, *b) => {
+                self.set_instance(*a, *b);
+                Ok(())
+            }
+            (TypeKind::Instance(_), _) => Err(InferenceError::Recursive(ah, bh)),
+
+            (TypeKind::Primitive(Primitive::Float), TypeKind::Primitive(Primitive::Integer))
+            | (TypeKind::Primitive(Primitive::Integer), TypeKind::Primitive(Primitive::Float)) => {
+                Err(InferenceError::Mismatch(ah, bh))
+            }
+
+            // Primitives have their own set of vars which only unify with primitives.
+            (TypeKind::Primitive(Primitive::Integer), TypeKind::Primitive(i)) if i.is_integer() => {
+                self.set_instance(ah, bh);
+                Ok(())
+            }
+            (TypeKind::Primitive(Primitive::Float), TypeKind::Primitive(f)) if f.is_float() => {
+                self.set_instance(ah, bh);
+                Ok(())
+            }
+
+            (_, TypeKind::Variable)
+            | (_, TypeKind::Instance(_))
+            | (TypeKind::Primitive(_), TypeKind::Primitive(Primitive::Integer))
+            | (TypeKind::Primitive(_), TypeKind::Primitive(Primitive::Float)) => self.unify(bh, ah),
+            (TypeKind::Adt(Adt::Enum(ia)), TypeKind::Adt(Adt::Enum(ib)))
+                if ia.len() == ib.len() =>
+            {
+                for ((na, a), (nb, b)) in ia.clone().into_iter().zip(ib.clone().into_iter()) {
+                    if na != nb {
+                        return Err(InferenceError::Mismatch(ah, bh));
+                    }
+                    self.unify(a, b)?;
+                }
+                Ok(())
+            }
+            (TypeKind::Adt(Adt::Enum(en)), TypeKind::Adt(_)) => {
+                #[allow(unused)]
+                let Some(other_parent) = self.table.parent(bh) else {
+                    Err(InferenceError::Mismatch(ah, bh))?
+                };
+
+                if ah != *other_parent {
+                    Err(InferenceError::Mismatch(ah, *other_parent))?
+                }
+
+                #[allow(unused)]
+                for (sym, handle) in en {
+                    let handle = self.def_usage(*handle);
+                    if handle == bh {
+                        return Ok(());
+                    }
+                }
+
+                Err(InferenceError::Mismatch(ah, bh))
+            }
+            (TypeKind::Adt(Adt::Struct(ia)), TypeKind::Adt(Adt::Struct(ib)))
+                if ia.len() == ib.len() =>
+            {
+                for ((na, va, a), (nb, vb, b)) in ia.clone().into_iter().zip(ib.clone().into_iter())
+                {
+                    if na != nb || va != vb {
+                        return Err(InferenceError::Mismatch(ah, bh));
+                    }
+                    self.unify(a, b)?;
+                }
+                Ok(())
+            }
+            (TypeKind::Adt(Adt::TupleStruct(ia)), TypeKind::Adt(Adt::TupleStruct(ib)))
+                if ia.len() == ib.len() =>
+            {
+                for ((va, a), (vb, b)) in ia.clone().into_iter().zip(ib.clone().into_iter()) {
+                    if va != vb {
+                        return Err(InferenceError::Mismatch(ah, bh));
+                    }
+                    self.unify(a, b)?;
+                }
+                Ok(())
+            }
+            (TypeKind::Adt(Adt::Union(ia)), TypeKind::Adt(Adt::Union(ib)))
+                if ia.len() == ib.len() =>
+            {
+                todo!()
+            }
+            (TypeKind::Ref(a), TypeKind::Ref(b)) => self.unify(*a, *b),
+            (TypeKind::Ptr(a), TypeKind::Ptr(b)) => self.unify(*a, *b),
+            (TypeKind::Slice(a), TypeKind::Slice(b)) => self.unify(*a, *b),
+            // Slice unifies with array
+            (TypeKind::Array(a, _), TypeKind::Slice(b)) => self.unify(*a, *b),
+            (TypeKind::Slice(_), TypeKind::Array(_, _)) => self.unify(bh, ah),
+            (TypeKind::Array(a, sa), TypeKind::Array(b, sb)) if sa == sb => self.unify(*a, *b),
+            (TypeKind::Tuple(a), TypeKind::Tuple(b)) => {
+                if a.len() != b.len() {
+                    return Err(InferenceError::Mismatch(ah, bh));
+                }
+                let (a, b) = (a.clone(), b.clone());
+                for (a, b) in a.iter().zip(b.iter()) {
+                    self.unify(*a, *b)?;
+                }
+                Ok(())
+            }
+            (&TypeKind::FnSig { args: a1, rety: r1 }, &TypeKind::FnSig { args: a2, rety: r2 }) => {
+                self.unify(a1, a2)?;
+                self.unify(r1, r2)
+            }
+            (TypeKind::Primitive(Primitive::Never), _)
+            | (_, TypeKind::Primitive(Primitive::Never)) => Ok(()),
+            (a, b) if a == b => Ok(()),
+            _ => Err(InferenceError::Mismatch(ah, bh)),
+        }
+    }
+}

compiler/cl-typeck/src/stage/infer/error.rs

@@ -0,0 +1,43 @@
+use cl_ast::Path;
+
+use crate::handle::Handle;
+use core::fmt;
+
+/// An error produced during type inference
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum InferenceError {
+    AnnotationEval(crate::type_expression::Error),
+    FieldCount(Handle, usize, usize),
+    NotFound(Path),
+    Mismatch(Handle, Handle),
+    Recursive(Handle, Handle),
+    NoBreak,
+    NoReturn,
+}
+
+impl std::error::Error for InferenceError {}
+#[rustfmt::skip]
+impl fmt::Display for InferenceError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            InferenceError::AnnotationEval(error) => write!(f, "{error}"),
+            InferenceError::FieldCount(name, want, got) => {
+                write!(f, 
+                    "Struct {name} {} fields! Expected {want}, got {got}",
+                    if want < got { "has too many" } else { "is missing" }
+                )
+            }
+            InferenceError::NotFound(p) => write!(f, "Path not visible in scope: {p}"),
+            InferenceError::Mismatch(a, b) => write!(f, "Type mismatch: {a:?} != {b:?}"),
+            InferenceError::Recursive(_, _) => write!(f, "Recursive type!"),
+            InferenceError::NoBreak => write!(f, "Encountered break outside loop!"),
+            InferenceError::NoReturn => write!(f, "Encountered return outside function!"),
+        }
+    }
+}
+
+impl From<crate::type_expression::Error> for InferenceError {
+    fn from(value: crate::type_expression::Error) -> Self {
+        Self::AnnotationEval(value)
+    }
+}

compiler/cl-typeck/src/stage/populate.rs

@@ -0,0 +1,193 @@
+//! The [Populator] populates entries in the sym table, including span info
+use crate::{
+    entry::EntryMut,
+    handle::Handle,
+    source::Source,
+    table::{NodeKind, Table},
+    type_kind::TypeKind,
+};
+use cl_ast::{
+    ItemKind, Literal, Meta, MetaKind, Sym,
+    ast_visitor::{Visit, Walk},
+};
+
+#[derive(Debug)]
+pub struct Populator<'t, 'a> {
+    inner: EntryMut<'t, 'a>,
+    name: Option<Sym>, // this is a hack to get around the Visitor interface
+}
+
+impl<'t, 'a> Populator<'t, 'a> {
+    pub fn new(table: &'t mut Table<'a>) -> Self {
+        Self { inner: table.root_entry_mut(), name: None }
+    }
+    /// Constructs a new Populator with the provided parent Handle
+    pub fn with_id(&mut self, parent: Handle) -> Populator<'_, 'a> {
+        Populator { inner: self.inner.with_id(parent), name: None }
+    }
+
+    pub fn new_entry(&mut self, kind: NodeKind) -> Populator<'_, 'a> {
+        Populator { inner: self.inner.new_entry(kind), name: None }
+    }
+
+    pub fn set_name(&mut self, name: Sym) {
+        self.name = Some(name);
+    }
+}
+
+impl<'a> Visit<'a> for Populator<'_, 'a> {
+    fn visit_item(&mut self, i: &'a cl_ast::Item) {
+        let cl_ast::Item { span, attrs, vis: _, kind } = i;
+        // TODO: this, better, better.
+        let entry_kind = match kind {
+            ItemKind::Alias(_) => NodeKind::Type,
+            ItemKind::Enum(_) => NodeKind::Type,
+            ItemKind::Struct(_) => NodeKind::Type,
+
+            ItemKind::Const(_) => NodeKind::Const,
+            ItemKind::Static(_) => NodeKind::Static,
+            ItemKind::Function(_) => NodeKind::Function,
+
+            ItemKind::Module(_) => NodeKind::Module,
+            ItemKind::Impl(_) => NodeKind::Impl,
+            ItemKind::Use(_) => NodeKind::Use,
+        };
+
+        let mut entry = self.new_entry(entry_kind);
+        entry.inner.set_span(*span);
+        entry.inner.set_meta(&attrs.meta);
+
+        for Meta { name, kind } in &attrs.meta {
+            if let ("lang", MetaKind::Equals(Literal::String(s))) = (name.to_ref(), kind) {
+                if let Ok(prim) = s.parse() {
+                    entry.inner.set_ty(TypeKind::Primitive(prim));
+                }
+                entry.inner.mark_lang_item(Sym::from(s).to_ref());
+            }
+        }
+
+        entry.visit_children(i);
+
+        if let (Some(name), child) = (entry.name, entry.inner.id()) {
+            self.inner.add_child(name, child);
+        }
+    }
+
+    fn visit_generics(&mut self, value: &'a cl_ast::Generics) {
+        let cl_ast::Generics { vars } = value;
+        for var in vars {
+            let mut entry = self.inner.new_entry(NodeKind::Type);
+            entry.set_ty(TypeKind::Variable);
+
+            let id = entry.id();
+            self.inner.add_child(*var, id);
+        }
+    }
+
+    fn visit_alias(&mut self, a: &'a cl_ast::Alias) {
+        let cl_ast::Alias { name, from } = a;
+        self.inner.set_source(Source::Alias(a));
+        self.set_name(*name);
+
+        self.visit(from);
+    }
+
+    fn visit_const(&mut self, c: &'a cl_ast::Const) {
+        let cl_ast::Const { name, ty, init } = c;
+        self.inner.set_source(Source::Const(c));
+        self.inner.set_body(init);
+        self.set_name(*name);
+
+        self.visit(ty);
+        self.visit(init);
+    }
+
+    fn visit_static(&mut self, s: &'a cl_ast::Static) {
+        let cl_ast::Static { name, init, .. } = s;
+        self.inner.set_source(Source::Static(s));
+        self.inner.set_body(init);
+        self.set_name(*name);
+
+        s.children(self);
+    }
+
+    fn visit_function(&mut self, f: &'a cl_ast::Function) {
+        self.inner.set_source(Source::Function(f));
+        self.set_name(f.name);
+
+        if let Some(body) = &f.body {
+            self.inner.set_body(body);
+        }
+
+        f.children(self);
+    }
+
+    fn visit_module(&mut self, m: &'a cl_ast::Module) {
+        self.inner.set_source(Source::Module(m));
+        self.set_name(m.name);
+
+        m.children(self);
+    }
+
+    fn visit_struct(&mut self, s: &'a cl_ast::Struct) {
+        self.inner.set_source(Source::Struct(s));
+        self.set_name(s.name);
+
+        s.children(self);
+    }
+
+    fn visit_enum(&mut self, e: &'a cl_ast::Enum) {
+        let cl_ast::Enum { name, gens, variants } = e;
+        self.inner.set_source(Source::Enum(e));
+        self.set_name(*name);
+
+        self.visit(gens);
+        let mut children = Vec::new();
+        for variant in variants.iter() {
+            let mut entry = self.new_entry(NodeKind::Type);
+            variant.visit_in(&mut entry);
+            let child = entry.inner.id();
+            children.push((variant.name, child));
+
+            self.inner.add_child(variant.name, child);
+        }
+        self.inner
+            .set_ty(TypeKind::Adt(crate::type_kind::Adt::Enum(children)));
+    }
+
+    fn visit_variant(&mut self, value: &'a cl_ast::Variant) {
+        let cl_ast::Variant { name, kind, body } = value;
+        self.inner.set_source(Source::Variant(value));
+        self.set_name(*name);
+        self.visit(kind);
+        match (kind, body) {
+            (cl_ast::StructKind::Empty, None) => {
+                self.inner.set_ty(TypeKind::Inferred);
+            }
+            (cl_ast::StructKind::Empty, Some(body)) => {
+                self.inner.set_body(body);
+            }
+            (cl_ast::StructKind::Tuple(_items), None) => {}
+            (cl_ast::StructKind::Struct(_struct_members), None) => {}
+            (_, Some(body)) => panic!("Unexpected body {body} in enum variant `{value}`"),
+        }
+    }
+
+    fn visit_impl(&mut self, i: &'a cl_ast::Impl) {
+        let cl_ast::Impl { gens: _, target: _, body } = i;
+        self.inner.set_source(Source::Impl(i));
+        self.inner.mark_impl_item();
+
+        // We don't know if target is generic yet -- that's checked later.
+
+        self.visit(body);
+    }
+
+    fn visit_use(&mut self, u: &'a cl_ast::Use) {
+        let cl_ast::Use { absolute: _, tree } = u;
+        self.inner.set_source(Source::Use(u));
+        self.inner.mark_use_item();
+
+        self.visit(tree);
+    }
+}

compiler/cl-typeck/src/table.rs

@@ -0,0 +1,364 @@
+//! The [Table] is a monolithic data structure representing everything the type checker
+//! knows about a program.
+//!
+//! Individual nodes in the table can be queried using the [Entry] API ([Table::entry])
+//! or modified using the [EntryMut] API ([Table::entry_mut]).
+//!
+//! # Contents of a "node"
+//! Always present:
+//! - [NodeKind]: Determines how this node will be treated during the [stages](crate::stage) of
+//!   compilation
+//! - [Parent node](Handle): Arranges this node in the hierarchical graph structure
+//!
+//! Populated as needed:
+//! - Children: An associative array of [names](Sym) to child nodes in the graph. Child nodes are
+//!   arranged in a *strict* tree structure, with no back edges
+//! - Imports: An associative array of [names](Sym) to other nodes in the graph. Not all import
+//!   nodes are back edges, but all back edges *must be* import nodes.
+//! - [Types](TypeKind): Contains type information populated through type checking and inference.
+//!   Nodes with unpopulated types may be considered type variables in the future.
+//! - [Spans][span]: Positional information from the source text. See [cl_structures::span].
+//! - [Metas](Meta): Metadata decorators. These may have an effect throughout the compiler.
+//! - [Sources](Source): Pointers back into the AST, for future analysis.
+//! - Impl Targets: Sparse mapping of `impl` nodes to their corresponding targets.
+//! - etc.
+//!
+//! [span]: struct@Span
+
+use crate::{
+    entry::{Entry, EntryMut},
+    handle::Handle,
+    source::Source,
+    type_kind::TypeKind,
+};
+use cl_ast::{Expr, Meta, PathPart, Sym};
+use cl_structures::{index_map::IndexMap, span::Span};
+use std::collections::HashMap;
+
+// TODO: Cycle detection external to this module
+
+/// The table is a monolithic data structure representing everything the type checker
+/// knows about a program.
+///
+/// See [module documentation](self).
+#[derive(Debug)]
+pub struct Table<'a> {
+    root: Handle,
+    /// This is the source of truth for handles
+    kinds: IndexMap<Handle, NodeKind>,
+    parents: IndexMap<Handle, Handle>,
+    pub(crate) children: HashMap<Handle, HashMap<Sym, Handle>>,
+    pub(crate) imports: HashMap<Handle, HashMap<Sym, Handle>>,
+    pub(crate) use_items: HashMap<Handle, Vec<Handle>>,
+    bodies: HashMap<Handle, &'a Expr>,
+    types: HashMap<Handle, TypeKind>,
+    spans: HashMap<Handle, Span>,
+    metas: HashMap<Handle, &'a [Meta]>,
+    sources: HashMap<Handle, Source<'a>>,
+    impl_targets: HashMap<Handle, Handle>,
+    anon_types: HashMap<TypeKind, Handle>,
+    lang_items: HashMap<&'static str, Handle>,
+
+    // --- Queues for algorithms ---
+    pub(crate) unchecked: Vec<Handle>,
+    pub(crate) impls: Vec<Handle>,
+    pub(crate) uses: Vec<Handle>,
+}
+
+impl<'a> Table<'a> {
+    pub fn new() -> Self {
+        let mut kinds = IndexMap::new();
+        let mut parents = IndexMap::new();
+        let root = kinds.insert(NodeKind::Root);
+        assert_eq!(root, parents.insert(root));
+
+        Self {
+            root,
+            kinds,
+            parents,
+            children: HashMap::new(),
+            imports: HashMap::new(),
+            use_items: HashMap::new(),
+            bodies: HashMap::new(),
+            types: HashMap::new(),
+            spans: HashMap::new(),
+            metas: HashMap::new(),
+            sources: HashMap::new(),
+            impl_targets: HashMap::new(),
+            anon_types: HashMap::new(),
+            lang_items: HashMap::new(),
+            unchecked: Vec::new(),
+            impls: Vec::new(),
+            uses: Vec::new(),
+        }
+    }
+
+    pub fn entry(&self, handle: Handle) -> Entry<'_, 'a> {
+        handle.to_entry(self)
+    }
+
+    pub fn entry_mut(&mut self, handle: Handle) -> EntryMut<'_, 'a> {
+        handle.to_entry_mut(self)
+    }
+
+    pub fn new_entry(&mut self, parent: Handle, kind: NodeKind) -> Handle {
+        let entry = self.kinds.insert(kind);
+        assert_eq!(entry, self.parents.insert(parent));
+        entry
+    }
+
+    pub fn add_child(&mut self, parent: Handle, name: Sym, child: Handle) -> Option<Handle> {
+        self.children.entry(parent).or_default().insert(name, child)
+    }
+
+    pub fn add_import(&mut self, parent: Handle, name: Sym, import: Handle) -> Option<Handle> {
+        self.imports.entry(parent).or_default().insert(name, import)
+    }
+
+    pub fn mark_unchecked(&mut self, item: Handle) {
+        self.unchecked.push(item);
+    }
+
+    pub fn mark_use_item(&mut self, item: Handle) {
+        let parent = self.parents[item];
+        self.use_items.entry(parent).or_default().push(item);
+        self.uses.push(item);
+    }
+
+    pub fn mark_impl_item(&mut self, item: Handle) {
+        self.impls.push(item);
+    }
+
+    pub fn mark_lang_item(&mut self, name: &'static str, item: Handle) {
+        self.lang_items.insert(name, item);
+    }
+
+    pub fn get_lang_item(&self, name: &str) -> Handle {
+        match self.lang_items.get(name).copied() {
+            Some(handle) => handle,
+            None => todo!(),
+        }
+    }
+
+    pub fn handle_iter(&self) -> impl Iterator<Item = Handle> + use<> {
+        self.kinds.keys()
+    }
+
+    /// Returns handles to all nodes sequentially by [Entry]
+    pub fn debug_entry_iter(&self) -> impl Iterator<Item = Entry<'_, 'a>> {
+        self.kinds.keys().map(|key| key.to_entry(self))
+    }
+
+    /// Gets the [Handle] of an anonymous type with the provided [TypeKind].
+    /// If not already present, a new one is created.
+    pub(crate) fn anon_type(&mut self, kind: TypeKind) -> Handle {
+        if let Some(id) = self.anon_types.get(&kind) {
+            return *id;
+        }
+        let entry = self.new_entry(self.root, NodeKind::Type);
+        // Anonymous types require a bijective map (anon_types => Def => types)
+        self.types.insert(entry, kind.clone());
+        self.anon_types.insert(kind, entry);
+        entry
+    }
+
+    pub(crate) fn inferred_type(&mut self) -> Handle {
+        let handle = self.new_entry(self.root, NodeKind::Type);
+        self.types.insert(handle, TypeKind::Inferred);
+        handle
+    }
+
+    pub(crate) fn type_variable(&mut self) -> Handle {
+        let handle = self.new_entry(self.root, NodeKind::Type);
+        self.types.insert(handle, TypeKind::Variable);
+        handle
+    }
+
+    pub const fn root_entry(&self) -> Entry<'_, 'a> {
+        self.root.to_entry(self)
+    }
+
+    pub fn root_entry_mut(&mut self) -> crate::entry::EntryMut<'_, 'a> {
+        self.root.to_entry_mut(self)
+    }
+
+    // --- inherent properties ---
+
+    pub const fn root(&self) -> Handle {
+        self.root
+    }
+
+    pub fn kind(&self, node: Handle) -> Option<&NodeKind> {
+        self.kinds.get(node)
+    }
+
+    pub fn parent(&self, node: Handle) -> Option<&Handle> {
+        self.parents.get(node)
+    }
+
+    pub fn children(&self, node: Handle) -> Option<&HashMap<Sym, Handle>> {
+        self.children.get(&node)
+    }
+
+    pub fn imports(&self, node: Handle) -> Option<&HashMap<Sym, Handle>> {
+        self.imports.get(&node)
+    }
+
+    pub fn body(&self, node: Handle) -> Option<&'a Expr> {
+        self.bodies.get(&node).copied()
+    }
+
+    pub fn ty(&self, node: Handle) -> Option<&TypeKind> {
+        self.types.get(&node)
+    }
+
+    pub fn span(&self, node: Handle) -> Option<&Span> {
+        self.spans.get(&node)
+    }
+
+    pub fn meta(&self, node: Handle) -> Option<&'a [Meta]> {
+        self.metas.get(&node).copied()
+    }
+
+    pub fn source(&self, node: Handle) -> Option<&Source<'a>> {
+        self.sources.get(&node)
+    }
+
+    pub fn impl_target(&self, node: Handle) -> Option<Handle> {
+        self.impl_targets.get(&node).copied()
+    }
+
+    pub fn reparent(&mut self, node: Handle, parent: Handle) -> Handle {
+        self.parents.replace(node, parent)
+    }
+
+    pub fn set_body(&mut self, node: Handle, body: &'a Expr) -> Option<&'a Expr> {
+        self.mark_unchecked(node);
+        self.bodies.insert(node, body)
+    }
+
+    pub fn set_ty(&mut self, node: Handle, kind: TypeKind) -> Option<TypeKind> {
+        self.types.insert(node, kind)
+    }
+
+    pub fn set_span(&mut self, node: Handle, span: Span) -> Option<Span> {
+        self.spans.insert(node, span)
+    }
+
+    pub fn set_meta(&mut self, node: Handle, meta: &'a [Meta]) -> Option<&'a [Meta]> {
+        self.metas.insert(node, meta)
+    }
+
+    pub fn set_source(&mut self, node: Handle, source: Source<'a>) -> Option<Source<'a>> {
+        self.sources.insert(node, source)
+    }
+
+    pub fn set_impl_target(&mut self, node: Handle, target: Handle) -> Option<Handle> {
+        self.impl_targets.insert(node, target)
+    }
+
+    // --- derived properties ---
+
+    /// Gets a handle to the local `Self` type, if one exists
+    pub fn selfty(&self, node: Handle) -> Option<Handle> {
+        match self.kinds.get(node)? {
+            NodeKind::Root | NodeKind::Use => None,
+            NodeKind::Type => Some(node),
+            NodeKind::Impl => self.impl_target(node),
+            _ => self.selfty(*self.parent(node)?),
+        }
+    }
+
+    pub fn super_of(&self, node: Handle) -> Option<Handle> {
+        match self.kinds.get(node)? {
+            NodeKind::Root => None,
+            NodeKind::Module => self.parent(node).copied(),
+            _ => self.super_of(*self.parent(node)?),
+        }
+    }
+
+    pub fn name(&self, node: Handle) -> Option<Sym> {
+        self.source(node).and_then(|s| s.name())
+    }
+
+    pub fn is_transparent(&self, node: Handle) -> bool {
+        !matches!(
+            self.kind(node),
+            None | Some(NodeKind::Root | NodeKind::Module)
+        )
+    }
+
+    pub fn get_child(&self, node: Handle, name: &Sym) -> Option<Handle> {
+        self.children.get(&node).and_then(|c| c.get(name)).copied()
+    }
+
+    pub fn get_import(&self, node: Handle, name: &Sym) -> Option<Handle> {
+        self.imports.get(&node).and_then(|i| i.get(name)).copied()
+    }
+
+    pub fn get_by_sym(&self, node: Handle, name: &Sym) -> Option<Handle> {
+        self.get_child(node, name)
+            .or_else(|| self.get_import(node, name))
+            .or_else(|| {
+                self.is_transparent(node)
+                    .then(|| {
+                        self.parent(node)
+                            .and_then(|node| self.get_by_sym(*node, name))
+                    })
+                    .flatten()
+            })
+    }
+
+    /// Does path traversal relative to the provided `node`.
+    pub fn nav(&self, node: Handle, path: &[PathPart]) -> Option<Handle> {
+        match path {
+            [PathPart::SuperKw, rest @ ..] => self.nav(self.super_of(node)?, rest),
+            [PathPart::SelfTy, rest @ ..] => self.nav(self.selfty(node)?, rest),
+            [PathPart::Ident(name), rest @ ..] => self.nav(self.get_by_sym(node, name)?, rest),
+            [] => Some(node),
+        }
+    }
+}
+
+impl Default for Table<'_> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum NodeKind {
+    Root,
+    Module,
+    Type,
+    Const,
+    Static,
+    Function,
+    Temporary,
+    Let,
+    Scope,
+    Impl,
+    Use,
+}
+
+mod display {
+    use super::*;
+    use std::fmt;
+    impl fmt::Display for NodeKind {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            match self {
+                NodeKind::Root => write!(f, "root"),
+                NodeKind::Module => write!(f, "mod"),
+                NodeKind::Type => write!(f, "type"),
+                NodeKind::Const => write!(f, "const"),
+                NodeKind::Static => write!(f, "static"),
+                NodeKind::Function => write!(f, "fn"),
+                NodeKind::Temporary => write!(f, "temp"),
+                NodeKind::Let => write!(f, "let"),
+                NodeKind::Scope => write!(f, "scope"),
+                NodeKind::Use => write!(f, "use"),
+                NodeKind::Impl => write!(f, "impl"),
+            }
+        }
+    }
+}

compiler/cl-typeck/src/type_expression.rs

@@ -0,0 +1,144 @@
+//! A [TypeExpression] is a [syntactic](cl_ast) representation of a [TypeKind], and is used to
+//! construct type bindings in a [Table]'s typing context.
+
+use crate::{handle::Handle, table::Table, type_kind::TypeKind};
+use cl_ast::{PathPart, Sym, Ty, TyArray, TyFn, TyKind, TyPtr, TyRef, TySlice, TyTuple};
+
+#[derive(Clone, Debug, PartialEq, Eq)] // TODO: impl Display and Error
+pub enum Error {
+    BadPath { parent: Handle, path: Vec<PathPart> },
+}
+
+impl std::error::Error for Error {}
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::BadPath { parent, path } => {
+                write!(f, "No item at path {parent}")?;
+                for part in path {
+                    write!(f, "::{part}")?;
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+/// A [TypeExpression] is a syntactic representation of a [TypeKind], and is used to construct
+/// type bindings in a [Table]'s typing context.
+pub trait TypeExpression<Out = Handle> {
+    /// Evaluates a type expression, recursively creating intermediate bindings.
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Out, Error>;
+}
+
+impl TypeExpression for Ty {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        self.kind.evaluate(table, node)
+    }
+}
+
+impl TypeExpression for TyKind {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        match self {
+            TyKind::Never => Ok(table.get_lang_item("never")),
+            TyKind::Infer => Ok(table.inferred_type()),
+            TyKind::Path(p) => p.evaluate(table, node),
+            TyKind::Array(a) => a.evaluate(table, node),
+            TyKind::Slice(s) => s.evaluate(table, node),
+            TyKind::Tuple(t) => t.evaluate(table, node),
+            TyKind::Ref(r) => r.evaluate(table, node),
+            TyKind::Ptr(r) => r.evaluate(table, node),
+            TyKind::Fn(f) => f.evaluate(table, node),
+        }
+    }
+}
+
+impl TypeExpression for cl_ast::Path {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { absolute, parts } = self;
+        parts.evaluate(table, if *absolute { table.root() } else { node })
+    }
+}
+
+impl TypeExpression for [PathPart] {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        table
+            .nav(node, self)
+            .ok_or_else(|| Error::BadPath { parent: node, path: self.to_owned() })
+    }
+}
+
+impl TypeExpression for Sym {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let path = [PathPart::Ident(*self)];
+        table
+            .nav(node, &path)
+            .ok_or_else(|| Error::BadPath { parent: node, path: path.to_vec() })
+    }
+}
+
+impl TypeExpression for TyArray {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { ty, count } = self;
+        let kind = TypeKind::Array(ty.evaluate(table, node)?, *count);
+        Ok(table.anon_type(kind))
+    }
+}
+
+impl TypeExpression for TySlice {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { ty } = self;
+        let kind = TypeKind::Slice(ty.evaluate(table, node)?);
+        Ok(table.anon_type(kind))
+    }
+}
+
+impl TypeExpression for TyTuple {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { types } = self;
+        let kind = TypeKind::Tuple(types.evaluate(table, node)?);
+        Ok(table.anon_type(kind))
+    }
+}
+
+impl TypeExpression for TyRef {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { mutable: _, count, to } = self;
+        let mut t = to.evaluate(table, node)?;
+        for _ in 0..*count {
+            let kind = TypeKind::Ref(t);
+            t = table.anon_type(kind)
+        }
+        Ok(t)
+    }
+}
+
+impl TypeExpression for TyPtr {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { to } = self;
+        let mut t = to.evaluate(table, node)?;
+        t = table.anon_type(TypeKind::Ptr(t));
+        Ok(t)
+    }
+}
+
+impl TypeExpression for TyFn {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Handle, Error> {
+        let Self { args, rety } = self;
+        let kind = TypeKind::FnSig {
+            args: args.evaluate(table, node)?,
+            rety: rety.evaluate(table, node)?,
+        };
+        Ok(table.anon_type(kind))
+    }
+}
+
+impl<T: TypeExpression<U>, U> TypeExpression<Vec<U>> for [T] {
+    fn evaluate(&self, table: &mut Table, node: Handle) -> Result<Vec<U>, Error> {
+        let mut out = Vec::with_capacity(self.len());
+        for te in self {
+            out.push(te.evaluate(table, node)?) // try_collect is unstable
+        }
+        Ok(out)
+    }
+}

compiler/cl-typeck/src/type_kind.rs

@@ -0,0 +1,125 @@
+//! A [TypeKind] is a node in the [Table](crate::table::Table)'s type graph
+
+use crate::handle::Handle;
+use cl_ast::{Sym, Visibility};
+use std::{fmt::Debug, str::FromStr};
+
+mod display;
+
+/// A [TypeKind] represents an item
+/// (a component of a [Table](crate::table::Table))
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum TypeKind {
+    /// A type that is yet to be inferred!
+    Inferred,
+    /// A type variable, to be monomorphized
+    Variable,
+    /// An alias for an already-defined type
+    Instance(Handle),
+    /// A primitive type, built-in to the compiler
+    Primitive(Primitive),
+    /// A user-defined aromatic data type
+    Adt(Adt),
+    /// A reference to an already-defined type: &T
+    Ref(Handle),
+    /// A raw pointer to an already-defined type: &T
+    Ptr(Handle),
+    /// A contiguous view of dynamically sized memory
+    Slice(Handle),
+    /// A contiguous view of statically sized memory
+    Array(Handle, usize),
+    /// A tuple of existing types
+    Tuple(Vec<Handle>),
+    /// A function which accepts multiple inputs and produces an output
+    FnSig { args: Handle, rety: Handle },
+    /// An untyped module
+    Module,
+}
+
+/// A user-defined Aromatic Data Type
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Adt {
+    /// A union-like enum type
+    Enum(Vec<(Sym, Handle)>),
+
+    /// A structural product type with named members
+    Struct(Vec<(Sym, Visibility, Handle)>),
+    /// A structural product type with unnamed members
+    TupleStruct(Vec<(Visibility, Handle)>),
+    /// A structural product type of neither named nor unnamed members
+    UnitStruct,
+
+    /// A choose your own undefined behavior type
+    /// TODO: should unions be a language feature?
+    Union(Vec<(Sym, Handle)>),
+}
+
+/// The set of compiler-intrinsic types.
+/// These primitive types have native implementations of the basic operations.
+#[rustfmt::skip]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Primitive {
+    I8, I16, I32, I64, I128, Isize, // Signed integers
+    U8, U16, U32, U64, U128, Usize, // Unsigned integers
+    F8, F16, F32, F64, F128, Fsize, // Floating point numbers
+    Integer, Float,                 // Inferred int and float
+    Bool,                           // boolean value
+    Char,                           // Unicode codepoint
+    Str,                            // UTF-8 string
+    Never,                          // The never type
+}
+
+#[rustfmt::skip]
+impl Primitive {
+    /// Checks whether self is an integer
+    pub fn is_integer(self) -> bool {
+        matches!(
+            self, 
+            | Self::I8 | Self::I16 | Self::I32 | Self::I64 | Self::I128 | Self::Isize
+            | Self::U8 | Self::U16 | Self::U32 | Self::U64 | Self::U128 | Self::Usize
+            | Self::Integer
+        )
+    }
+    /// Checks whether self is a floating point number
+    pub fn is_float(self) -> bool {
+        matches!(
+            self, 
+            | Self::F8 | Self::F16 | Self::F32 | Self::F64 | Self::F128 | Self::Fsize
+            | Self::Float
+        )
+    }
+}
+
+// Author's note: the fsize type is a meme
+
+impl FromStr for Primitive {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(match s {
+            "i8" => Primitive::I8,
+            "i16" => Primitive::I16,
+            "i32" => Primitive::I32,
+            "i64" => Primitive::I64,
+            "i128" => Primitive::I128,
+            "isize" => Primitive::Isize,
+            "u8" => Primitive::U8,
+            "u16" => Primitive::U16,
+            "u32" => Primitive::U32,
+            "u64" => Primitive::U64,
+            "u128" => Primitive::U128,
+            "usize" => Primitive::Usize,
+            "f8" => Primitive::F8,
+            "f16" => Primitive::F16,
+            "f32" => Primitive::F32,
+            "f64" => Primitive::F64,
+            "f128" => Primitive::F128,
+            "fsize" => Primitive::Fsize,
+            "bool" => Primitive::Bool,
+            "char" => Primitive::Char,
+            "str" => Primitive::Str,
+            "never" => Primitive::Never,
+            _ => Err(())?,
+        })
+    }
+}

compiler/cl-typeck/src/type_kind/display.rs

@@ -0,0 +1,98 @@
+//! [Display] implementations for [TypeKind], [Adt], and [Intrinsic]
+
+use super::{Adt, Primitive, TypeKind};
+use crate::format_utils::*;
+use cl_ast::format::FmtAdapter;
+use std::fmt::{self, Display, Write};
+
+impl Display for TypeKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            TypeKind::Inferred => write!(f, "_"),
+            TypeKind::Variable => write!(f, "?"),
+            TypeKind::Instance(def) => write!(f, "alias to #{def}"),
+            TypeKind::Primitive(i) => i.fmt(f),
+            TypeKind::Adt(a) => a.fmt(f),
+            TypeKind::Ref(def) => write!(f, "&{def}"),
+            TypeKind::Ptr(def) => write!(f, "*{def}"),
+            TypeKind::Slice(def) => write!(f, "slice [#{def}]"),
+            TypeKind::Array(def, size) => write!(f, "array [#{def}; {size}]"),
+            TypeKind::Tuple(defs) => {
+                let mut defs = defs.iter();
+                separate(", ", || {
+                    let def = defs.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "#{def}"))
+                })(f.delimit_with("tuple (", ")"))
+            }
+            TypeKind::FnSig { args, rety } => write!(f, "fn (#{args}) -> #{rety}"),
+            TypeKind::Module => f.write_str("mod"),
+        }
+    }
+}
+
+impl Display for Adt {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Adt::Enum(variants) => {
+                let mut variants = variants.iter();
+                separate(", ", || {
+                    let (name, def) = variants.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{name}: #{def}"))
+                })(f.delimit_with("enum {", "}"))
+            }
+            Adt::Struct(members) => {
+                let mut members = members.iter();
+                separate(", ", || {
+                    let (name, vis, def) = members.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{vis}{name}: #{def}"))
+                })(f.delimit_with("struct {", "}"))
+            }
+            Adt::TupleStruct(members) => {
+                let mut members = members.iter();
+                separate(", ", || {
+                    let (vis, def) = members.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{vis}#{def}"))
+                })(f.delimit_with("struct (", ")"))
+            }
+            Adt::UnitStruct => write!(f, "struct"),
+            Adt::Union(variants) => {
+                let mut variants = variants.iter();
+                separate(", ", || {
+                    let (name, def) = variants.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{name}: #{def}"))
+                })(f.delimit_with("union {", "}"))
+            }
+        }
+    }
+}
+
+impl Display for Primitive {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Primitive::I8 => f.write_str("i8"),
+            Primitive::I16 => f.write_str("i16"),
+            Primitive::I32 => f.write_str("i32"),
+            Primitive::I64 => f.write_str("i64"),
+            Primitive::I128 => f.write_str("i128"),
+            Primitive::Isize => f.write_str("isize"),
+            Primitive::U8 => f.write_str("u8"),
+            Primitive::U16 => f.write_str("u16"),
+            Primitive::U32 => f.write_str("u32"),
+            Primitive::U64 => f.write_str("u64"),
+            Primitive::U128 => f.write_str("u128"),
+            Primitive::Usize => f.write_str("usize"),
+            Primitive::F8 => f.write_str("f8"),
+            Primitive::F16 => f.write_str("f16"),
+            Primitive::F32 => f.write_str("f32"),
+            Primitive::F64 => f.write_str("f64"),
+            Primitive::F128 => f.write_str("f128"),
+            Primitive::Fsize => f.write_str("fsize"),
+            Primitive::Integer => f.write_str("{integer}"),
+            Primitive::Float => f.write_str("{float}"),
+            Primitive::Bool => f.write_str("bool"),
+            Primitive::Char => f.write_str("char"),
+            Primitive::Str => f.write_str("str"),
+            Primitive::Never => f.write_str("!"),
+        }
+    }
+}

grammar.ebnf

@@ -1,38 +1,38 @@
 (* Conlang Expression Grammar *)
-Start       = File ;
+Start       = File EOI ;
 
 Mutability  = "mut"? ;
 Visibility  = "pub"? ;
 
 
-File        = Item* EOI ;
+File        = Item* ;
 
 
-Attrs       = ('#' '[' (Meta ',') Meta? ']')* ;
+Attrs       = ('#' '[' (Meta ',')* Meta? ']')* ;
 Meta        = Identifier ('=' Literal | '(' (Literal ',')* Literal? ')')? ;
 
 
-Item        = Attrs* Visibility ItemKind ;
+Item        = Attrs Visibility ItemKind ;
 ItemKind    = Const    | Static | Module 
             | Function | Struct | Enum 
-            | Alias    | Impl ;
+            | Alias    | Impl   | Use ;
 
 
 (* item *)
-Const       = "const" Identifier ':' Type = Expr ';' ;
+Const       = "const" Identifier ':' Ty '=' Expr ';' ;
 
-Static      = "static" Mutability Identifier ':' Type = Expr ';' ;
+Static      = "static" Mutability Identifier ':' Ty '=' Expr ';' ;
 
 Module      = "mod" Identifier ModuleKind ;
 ModuleKind  = '{' Item* '}' | ';' ;
 
-Function    = "fn" Identifier '(' (Param ',')* Param? ')' ('->' Type)? Block? ;
-Param       = Mutability Identifier ':' Type ;
+Function    = "fn" Identifier '(' (Param ',')* Param? ')' ('->' Ty)? (Expr | ';') ;
+Param       = Mutability Identifier ':' Ty ;
 
 Struct      = "struct" Identifier (StructTuple | StructBody)?;
 StructBody  = '{' (StructMember ',')* StructMember? '}' ;
 StructTuple = TyTuple ;
-StructMember = Visibility Identifier ':' Type ;
+StructMember = Visibility Identifier ':' Ty ;
 
 Enum        = "enum" Identifier '{' (Variant ',')* Variant? '}' ;
 Variant     = Identifier (VarStruct | VarTuple | VarCLike)? ;
@@ -40,24 +40,31 @@ VarStruct   = '{' (StructMember ',')* StructMember? '}' ;
 VarTuple    = TyTuple ;
 VarCLike    = '=' INTEGER ;
 
-Alias       = "type" Ty ('=' Ty)? ';' ;
+Alias       = "type" Identifier ('=' Ty)? ';' ;
 
 Impl        = "impl" Path '{' Item* '}' ;
 (* TODO: Impl Trait for Target*)
 
+Use         = "use" '::'? UseTree ';' ;
+UseTree     = '*' | '{' (UseTree ',')* UseTree? '}'
+            | PathPart ('::' UseTree | "as" Identifier)? ;
 
 (* type *)
-Ty          = Never | Empty | Path | TyTuple | TyRef | TyFn ;
+Ty          = Never | Empty | Path | TyArray | TySlice | TyTuple | TyRef | TyFn ;
 Never       = '!' ;
 Empty       = '(' ')' ;
 TyTuple     = '(' (Ty ',')* Ty? ')' ;
-TyRef       = ('&' | '&&')* Path ;
-TyFn        = "fn" TyTuple (-> Ty)? ;
+TyArray     = '[' Ty ';' INTEGER ']' ;
+TySlice     = '[' Ty ']' ;
+TyRef       = Amps* Path ;
+Amps        = '&' | '&&' ;
+TyFn        = "fn" TyTuple ('->' Ty)? ;
 
 
 (* path *)
-Path        = '::'? PathPart ('::' PathPart)* ;
-PathPart    = "super" | "self" | Identifier ;
+Path        = PathPart ('::' PathPart)*
+            | '::' (PathPart ('::' PathPart)*)? ;
+PathPart    = "super" | "self" | "Self" | Identifier ;
 Identifier  = IDENTIFIER ;
 
 
@@ -74,51 +81,64 @@ Bool        = "true" | "false" ;
 
 
 (* expr *)
-ExprKind    = Assign  | Compare | Range  | Logic    | Bitwise | Shift
-            | Factor  | Term    | Unary  | Member   | Call    | Index
-            | Path    | Literal | Array  | ArrayRep | AddrOf
-            | Block   | Group    
-            | While   | If      | For    | Break    | Return  | Continue ;
 
 Expr        = Assign ;
 
-Assign      = Path (AssignKind  Assign ) | Compare ;
+Assign      = Path (AssignKind  Assign ) | Modify ;
+Modify      = Path (ModifyKind  Assign ) | Compare ;
 
-Binary      = Compare | Range | Logic  | Bitwise | Shift | Factor | Term ;
+(* Binary      = Compare | Range | Logic | Bitwise | Shift | Factor | Term ; *)
 Compare     = Range    (CompareOp Range  )* ;
 Range       = Logic    (RangeOp   Logic  )* ;
 Logic       = Bitwise  (LogicOp   Bitwise)* ;
 Bitwise     = Shift    (BitwiseOp Shift  )* ;
 Shift       = Factor   (ShiftOp   Factor )* ;
 Factor      = Term     (FactorOp  Term   )* ;
-Term        = Unary    (FactorOp  Unary  )* ;
+Term        = Unary    (TermOp    Unary  )* ;
 
-Unary       = (UnaryKind)* Member ;
+Unary       = (UnaryKind)* Cast ;
 
-Member      = Call ('.' Call)* ;
+Cast        = Member ("as" Ty)? ;
+
+Member      = Call (Access)* ;
+Access      = '.' (Identifier ('(' Tuple? ')')? | Literal) ;
 
 Call        = Index  ('(' Tuple? ')')* ;
 
 Index       = Primary ('[' Indices ']')* ;
 Indices     = (Expr ',')* Expr? ;
 
-Primary     = Literal | Path  | Array | ArrayRep | AddrOf 
-            | Block   | Group 
-            | If      | While | For   | Break    | Return | Continue;
+Primary     = Literal | PathLike | Array | ArrayRep | AddrOf | Block  | Group
+            | Loop    | If       | While | For      | Break  | Return | Continue;
 
 Literal     = STRING | CHARACTER | FLOAT | INTEGER | Bool ;
 
+PathLike    = Path | Structor ;
+Structor    = Path ':' '{' (Fielder ',')* Fielder? '}' ;
+Fielder     = Identifier ('=' Expr)? ;
+
 Array       = '[' (Expr ',')* Expr? ']' ;
 ArrayRep    = '[' Expr ';' Expr ']' ;
 
-AddrOf      = ('&' | '&&')* Mutability? Expr ;
+AddrOf      = Amps Amps* Mutability Expr ;
 
 Block       = '{' Stmt* '}';
 
-Group       = '(' (Empty | Expr | Tuple) ')' ;
+Group       = Empty | '(' (Expr | Tuple) ')' ;
 Tuple       = (Expr ',')* Expr? ;
-Empty       = ;
 
+
+Match       = "match" { (MatchArm ',')* MatchArm? } ;
+MatchArm    = Pattern '=>' Expr ;
+Pattern     = Path
+            | Literal
+            | '&' "mut"? Pattern
+            | '(' (Pattern ',')* (Pattern | '..' )? ')'
+            | '[' (Pattern ',')* (Pattern | '..' Identifier?)? ']'
+            | StructPattern
+            ;
+
+Loop        = "loop"  Block ;
 While       = "while" Expr Block Else ;
 If          = "if"    Expr Block Else ;
 For         = "for"   Identifier "in" Expr Block Else ;
@@ -127,11 +147,9 @@ Break       = "break"  Expr ;
 Return      = "return" Expr ;
 Continue    = "continue" ;
 
-AssignKind  =  '=' | '+=' | '-=' | '*=' | '/=' |
-              '&=' | '|=' | '^=' |'<<=' |'>>=' ;
+AssignKind  =  '=' ;
+ModifyKind  = '+=' | '-=' | '*=' | '/=' | '&=' | '|=' | '^=' |'<<=' |'>>=' ;
 
-BinaryKind  = CompareOp | RangeOp | LogicOp  | BitwiseOp 
-            | ShiftOp   | TermOp  | FactorOp ;
 CompareOp   =  '<' | '<=' | '==' | '!=' | '>=' | '>' ;
 RangeOp     = '..' | '..=' ;
 LogicOp     = '&&' | '||' | '^^' ;