stdlib: Update num.cl with eased name resolution restrictions

- Perform heirarchical resolution through "transparent" nodes
- Reparenting impls broke relative path traversal entirely. To impl something, it must already be in scope anyway.
- TODO: well-formedness checks?

.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 +1,10 @@
+
+# Visual Studio Code config
+.vscode
+
+# Rust
 **/Cargo.lock
 target
+
+# Pest files generated by Grammatical
 *.p*st

Cargo.toml

@@ -1,11 +1,25 @@
 [workspace]
-members = ["libconlang", "cl-repl"]
+members = [
+    "compiler/cl-repl",
+    "compiler/cl-typeck",
+    "compiler/cl-interpret",
+    "compiler/cl-structures",
+    "compiler/cl-token",
+    "compiler/cl-ast",
+    "compiler/cl-parser",
+    "compiler/cl-lexer",
+    "compiler/cl-arena",
+    "repline",
+]
 resolver = "2"
 
 [workspace.package]
 repository = "https://git.soft.fish/j/Conlang"
-version = "0.0.3"
+version = "0.0.5"
 authors = ["John Breaux <j@soft.fish>"]
 edition = "2021"
 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-arena/Cargo.toml

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

compiler/cl-arena/src/dropless_arena/tests.rs

@@ -0,0 +1,42 @@
+use super::DroplessArena;
+    extern crate std;
+    use core::alloc::Layout;
+    use std::{prelude::rust_2021::*, vec};
+
+    #[test]
+    fn alloc_raw() {
+        let arena = DroplessArena::new();
+        let bytes = arena.alloc_raw(Layout::for_value(&0u128));
+        let byte2 = arena.alloc_raw(Layout::for_value(&0u128));
+
+        assert_ne!(bytes, byte2);
+    }
+
+    #[test]
+    fn alloc() {
+        let arena = DroplessArena::new();
+        let mut allocations = vec![];
+        for i in 0..0x400 {
+            allocations.push(arena.alloc(i));
+        }
+    }
+
+    #[test]
+    fn alloc_strings() {
+        const KW: &[&str] = &["pub", "mut", "fn", "mod", "conlang", "sidon", "🦈"];
+        let arena = DroplessArena::new();
+        let mut allocations = vec![];
+        for _ in 0..100 {
+            for kw in KW {
+                allocations.push(arena.alloc_str(kw));
+            }
+        }
+    }
+
+    #[test]
+    #[should_panic]
+    fn alloc_zsts() {
+        struct Zst;
+        let arena = DroplessArena::new();
+        arena.alloc(Zst);
+    }

compiler/cl-arena/src/lib.rs

@@ -0,0 +1,396 @@
+//! Typed and dropless arena allocation, paraphrased from [the Rust Compiler's `rustc_arena`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_arena/src/lib.rs). See [LICENSE][1].
+//!
+//! An Arena Allocator is a type of allocator which provides stable locations for allocations within
+//! itself for the entire duration of its lifetime.
+//!
+//! [1]: https://raw.githubusercontent.com/rust-lang/rust/master/LICENSE-MIT
+
+#![feature(dropck_eyepatch, new_uninit, strict_provenance)]
+#![no_std]
+
+extern crate alloc;
+
+pub(crate) mod constants {
+    //! Size constants for arena chunk growth
+    pub(crate) const MIN_CHUNK: usize = 4096;
+    pub(crate) const MAX_CHUNK: usize = 2 * 1024 * 1024;
+}
+
+mod chunk {
+    //! An [ArenaChunk] contains a block of raw memory for use in arena allocators.
+    use alloc::boxed::Box;
+    use core::{
+        mem::{self, MaybeUninit},
+        ptr::{self, NonNull},
+    };
+
+    pub struct ArenaChunk<T> {
+        pub(crate) mem: NonNull<[MaybeUninit<T>]>,
+        pub(crate) filled: usize,
+    }
+
+    impl<T: Sized> ArenaChunk<T> {
+        pub fn new(cap: usize) -> Self {
+            let slice = Box::new_uninit_slice(cap);
+            Self { mem: NonNull::from(Box::leak(slice)), filled: 0 }
+        }
+
+        /// Drops all elements inside self, and resets the filled count to 0
+        ///
+        /// # Safety
+        ///
+        /// The caller must ensure that `self.filled` elements of self are currently initialized
+        pub unsafe fn drop_elements(&mut self) {
+            if mem::needs_drop::<T>() {
+                // Safety: the caller has ensured that `filled` elements are initialized
+                unsafe {
+                    let slice = self.mem.as_mut();
+                    for t in slice[..self.filled].iter_mut() {
+                        t.assume_init_drop();
+                    }
+                }
+                self.filled = 0;
+            }
+        }
+
+        /// Gets a pointer to the start of the arena
+        pub fn start(&mut self) -> *mut T {
+            self.mem.as_ptr() as _
+        }
+
+        /// Gets a pointer to the end of the arena
+        pub fn end(&mut self) -> *mut T {
+            if mem::size_of::<T>() == 0 {
+                ptr::without_provenance_mut(usize::MAX) // pointers to ZSTs must be unique
+            } else {
+                unsafe { self.start().add(self.mem.len()) }
+            }
+        }
+    }
+
+    impl<T> Drop for ArenaChunk<T> {
+        fn drop(&mut self) {
+            let _ = unsafe { Box::from_raw(self.mem.as_ptr()) };
+        }
+    }
+}
+
+pub mod typed_arena {
+    //! A [TypedArena] can hold many instances of a single type, and will properly [Drop] them.
+    #![allow(clippy::mut_from_ref)]
+
+    use crate::{chunk::ArenaChunk, constants::*};
+    use alloc::vec::Vec;
+    use core::{
+        cell::{Cell, RefCell},
+        marker::PhantomData,
+        mem, ptr, slice,
+    };
+
+    /// A [TypedArena] can hold many instances of a single type, and will properly [Drop] them when
+    /// it falls out of scope.
+    pub struct TypedArena<'arena, T> {
+        _lives: PhantomData<&'arena T>,
+        _drops: PhantomData<T>,
+        chunks: RefCell<Vec<ArenaChunk<T>>>,
+        head: Cell<*mut T>,
+        tail: Cell<*mut T>,
+    }
+
+    impl<'arena, T> Default for TypedArena<'arena, T> {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<'arena, T> TypedArena<'arena, T> {
+        pub const fn new() -> Self {
+            Self {
+                _lives: PhantomData,
+                _drops: PhantomData,
+                chunks: RefCell::new(Vec::new()),
+                head: Cell::new(ptr::null_mut()),
+                tail: Cell::new(ptr::null_mut()),
+            }
+        }
+
+        pub fn alloc(&'arena self, value: T) -> &'arena mut T {
+            if self.head == self.tail {
+                self.grow(1);
+            }
+
+            let out = if mem::size_of::<T>() == 0 {
+                self.head
+                    .set(ptr::without_provenance_mut(self.head.get().addr() + 1));
+                ptr::NonNull::<T>::dangling().as_ptr()
+            } else {
+                let out = self.head.get();
+                self.head.set(unsafe { out.add(1) });
+                out
+            };
+
+            unsafe {
+                ptr::write(out, value);
+                &mut *out
+            }
+        }
+
+        fn can_allocate(&self, len: usize) -> bool {
+            len <= unsafe { self.tail.get().offset_from(self.head.get()) as usize }
+        }
+
+        /// # Panics
+        /// Panics if size_of::<T> == 0 || len == 0
+        #[inline]
+        fn alloc_raw_slice(&self, len: usize) -> *mut T {
+            assert!(mem::size_of::<T>() != 0);
+            assert!(len != 0);
+
+            if !self.can_allocate(len) {
+                self.grow(len)
+            }
+
+            let out = self.head.get();
+
+            unsafe { self.head.set(out.add(len)) };
+            out
+        }
+
+        pub fn alloc_from_iter<I>(&'arena self, iter: I) -> &'arena mut [T]
+        where I: IntoIterator<Item = T> {
+            // Collect them all into a buffer so they're allocated contiguously
+            let mut buf = iter.into_iter().collect::<Vec<_>>();
+            if buf.is_empty() {
+                return &mut [];
+            }
+
+            let len = buf.len();
+            // If T is a ZST, calling alloc_raw_slice will panic
+            let slice = if mem::size_of::<T>() == 0 {
+                self.head
+                    .set(ptr::without_provenance_mut(self.head.get().addr() + len));
+                ptr::NonNull::dangling().as_ptr()
+            } else {
+                self.alloc_raw_slice(len)
+            };
+
+            unsafe {
+                buf.as_ptr().copy_to_nonoverlapping(slice, len);
+                buf.set_len(0);
+                slice::from_raw_parts_mut(slice, len)
+            }
+        }
+
+        #[cold]
+        #[inline(never)]
+        fn grow(&self, len: usize) {
+            let size = mem::size_of::<T>().max(1);
+
+            let mut chunks = self.chunks.borrow_mut();
+
+            let capacity = if let Some(last) = chunks.last_mut() {
+                last.filled = self.get_filled_of_chunk(last);
+                last.mem.len().min(MAX_CHUNK / size) * 2
+            } else {
+                MIN_CHUNK / size
+            }
+            .max(len);
+
+            let mut chunk = ArenaChunk::<T>::new(capacity);
+
+            self.head.set(chunk.start());
+            self.tail.set(chunk.end());
+            chunks.push(chunk);
+        }
+
+        fn get_filled_of_chunk(&self, chunk: &mut ArenaChunk<T>) -> usize {
+            let Self { head: tail, .. } = self;
+            let head = chunk.start();
+            if mem::size_of::<T>() == 0 {
+                tail.get().addr() - head.addr()
+            } else {
+                unsafe { tail.get().offset_from(head) as usize }
+            }
+        }
+    }
+
+    unsafe impl<'arena, T: Send> Send for TypedArena<'arena, T> {}
+
+    unsafe impl<'arena, #[may_dangle] T> Drop for TypedArena<'arena, T> {
+        fn drop(&mut self) {
+            let mut chunks = self.chunks.borrow_mut();
+
+            if let Some(last) = chunks.last_mut() {
+                last.filled = self.get_filled_of_chunk(last);
+                self.tail.set(self.head.get());
+            }
+
+            for chunk in chunks.iter_mut() {
+                unsafe { chunk.drop_elements() }
+            }
+        }
+    }
+
+    #[cfg(test)]
+    mod tests;
+}
+
+pub mod dropless_arena {
+    //! A [DroplessArena] can hold *any* combination of types as long as they don't implement
+    //! [Drop].
+    use crate::{chunk::ArenaChunk, constants::*};
+    use alloc::vec::Vec;
+    use core::{
+        alloc::Layout,
+        cell::{Cell, RefCell},
+        marker::PhantomData,
+        mem, ptr, slice,
+    };
+
+    pub struct DroplessArena<'arena> {
+        _lives: PhantomData<&'arena u8>,
+        chunks: RefCell<Vec<ArenaChunk<u8>>>,
+        head: Cell<*mut u8>,
+        tail: Cell<*mut u8>,
+    }
+
+    impl Default for DroplessArena<'_> {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<'arena> DroplessArena<'arena> {
+        pub const fn new() -> Self {
+            Self {
+                _lives: PhantomData,
+                chunks: RefCell::new(Vec::new()),
+                head: Cell::new(ptr::null_mut()),
+                tail: Cell::new(ptr::null_mut()),
+            }
+        }
+
+        /// Allocates a `T` in the [DroplessArena], and returns a mutable reference to it.
+        ///
+        /// # Panics
+        /// - Panics if T implements [Drop]
+        /// - Panics if T is zero-sized
+        #[allow(clippy::mut_from_ref)]
+        pub fn alloc<T>(&'arena self, value: T) -> &'arena mut T {
+            assert!(!mem::needs_drop::<T>());
+            assert!(mem::size_of::<T>() != 0);
+
+            let out = self.alloc_raw(Layout::new::<T>()) as *mut T;
+
+            unsafe {
+                ptr::write(out, value);
+                &mut *out
+            }
+        }
+
+        /// Allocates a slice of `T`s`, copied from the given slice, returning a mutable reference
+        /// to it.
+        ///
+        /// # Panics
+        /// - Panics if T implements [Drop]
+        /// - Panics if T is zero-sized
+        /// - Panics if the slice is empty
+        #[allow(clippy::mut_from_ref)]
+        pub fn alloc_slice<T: Copy>(&'arena self, slice: &[T]) -> &'arena mut [T] {
+            assert!(!mem::needs_drop::<T>());
+            assert!(mem::size_of::<T>() != 0);
+            assert!(!slice.is_empty());
+
+            let mem = self.alloc_raw(Layout::for_value::<[T]>(slice)) as *mut T;
+
+            unsafe {
+                mem.copy_from_nonoverlapping(slice.as_ptr(), slice.len());
+                slice::from_raw_parts_mut(mem, slice.len())
+            }
+        }
+
+        /// Allocates a copy of the given [`&str`](str), returning a reference to the allocation.
+        ///
+        /// # Panics
+        /// Panics if the string is empty.
+        pub fn alloc_str(&'arena self, string: &str) -> &'arena str {
+            let slice = self.alloc_slice(string.as_bytes());
+
+            // Safety: This is a clone of the input string, which was valid
+            unsafe { core::str::from_utf8_unchecked(slice) }
+        }
+
+        /// Allocates some [bytes](u8) based on the given [Layout].
+        ///
+        /// # Panics
+        /// Panics if the provided [Layout] has size 0
+        pub fn alloc_raw(&'arena self, layout: Layout) -> *mut u8 {
+            /// Rounds the given size (or pointer value) *up* to the given alignment
+            fn align_up(size: usize, align: usize) -> usize {
+                (size + align - 1) & !(align - 1)
+            }
+            /// Rounds the given size (or pointer value) *down* to the given alignment
+            fn align_down(size: usize, align: usize) -> usize {
+                size & !(align - 1)
+            }
+
+            assert!(layout.size() != 0);
+            loop {
+                let Self { head, tail, .. } = self;
+                let start = head.get().addr();
+                let end = tail.get().addr();
+
+                let align = 8.max(layout.align());
+
+                let bytes = align_up(layout.size(), align);
+
+                if let Some(end) = end.checked_sub(bytes) {
+                    let end = align_down(end, layout.align());
+
+                    if start <= end {
+                        tail.set(tail.get().with_addr(end));
+                        return tail.get();
+                    }
+                }
+
+                self.grow(layout.size());
+            }
+        }
+
+        /// Grows the allocator, doubling the chunk size until it reaches [MAX_CHUNK].
+        #[cold]
+        #[inline(never)]
+        fn grow(&self, len: usize) {
+            let mut chunks = self.chunks.borrow_mut();
+
+            let capacity = if let Some(last) = chunks.last_mut() {
+                last.mem.len().min(MAX_CHUNK / 2) * 2
+            } else {
+                MIN_CHUNK
+            }
+            .max(len);
+
+            let mut chunk = ArenaChunk::<u8>::new(capacity);
+
+            self.head.set(chunk.start());
+            self.tail.set(chunk.end());
+            chunks.push(chunk);
+        }
+
+        /// Checks whether the given slice is allocated in this arena
+        pub fn contains_slice<T>(&self, slice: &[T]) -> bool {
+            let ptr = slice.as_ptr().cast::<u8>().cast_mut();
+            for chunk in self.chunks.borrow_mut().iter_mut() {
+                if chunk.start() <= ptr && ptr <= chunk.end() {
+                    return true;
+                }
+            }
+            false
+        }
+    }
+
+    unsafe impl<'arena> Send for DroplessArena<'arena> {}
+
+    #[cfg(test)]
+    mod tests;
+}

compiler/cl-arena/src/typed_arena/tests.rs

@@ -0,0 +1,61 @@
+use super::TypedArena;
+    extern crate std;
+    use std::{prelude::rust_2021::*, print, vec};
+    #[test]
+    fn pushing_to_arena() {
+        let arena = TypedArena::new();
+        let foo = arena.alloc("foo");
+        let bar = arena.alloc("bar");
+        let baz = arena.alloc("baz");
+
+        assert_eq!("foo", *foo);
+        assert_eq!("bar", *bar);
+        assert_eq!("baz", *baz);
+    }
+
+    #[test]
+    fn pushing_vecs_to_arena() {
+        let arena = TypedArena::new();
+
+        let foo = arena.alloc(vec!["foo"]);
+        let bar = arena.alloc(vec!["bar"]);
+        let baz = arena.alloc(vec!["baz"]);
+
+        assert_eq!("foo", foo[0]);
+        assert_eq!("bar", bar[0]);
+        assert_eq!("baz", baz[0]);
+    }
+
+    #[test]
+    fn pushing_zsts() {
+        struct ZeroSized;
+        impl Drop for ZeroSized {
+            fn drop(&mut self) {
+                print!("")
+            }
+        }
+
+        let arena = TypedArena::new();
+
+        for _ in 0..0x100 {
+            arena.alloc(ZeroSized);
+        }
+    }
+
+    #[test]
+    fn pushing_nodrop_zsts() {
+        struct ZeroSized;
+        let arena = TypedArena::new();
+
+        for _ in 0..0x1000 {
+            arena.alloc(ZeroSized);
+        }
+    }
+    #[test]
+    fn resize() {
+        let arena = TypedArena::new();
+
+        for _ in 0..0x780 {
+            arena.alloc(0u128);
+        }
+    }

compiler/cl-ast/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "cl-ast"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+cl-structures = { path = "../cl-structures" }

compiler/cl-ast/src/ast.rs

@@ -0,0 +1,614 @@
+//! # 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
+//! - [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 [Literal]: 0x42, 1e123, 2.4, "Hello"
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Literal {
+    Bool(bool),
+    Char(char),
+    Int(u128),
+    String(String),
+}
+
+/// A list of [Item]s
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct File {
+    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 extents: 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: Import declaration ("use") item
+    // 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),
+}
+
+/// An alias to another [Ty]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Alias {
+    pub to: 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>,
+}
+
+/// An ordered collection of [Items](Item)
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Module {
+    pub name: Sym,
+    pub kind: ModuleKind,
+}
+
+/// The contents of a [Module], if they're in the same file
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum ModuleKind {
+    Inline(File),
+    Outline,
+}
+
+/// Code, and the interface to that code
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Function {
+    pub name: Sym,
+    pub sign: TyFn,
+    pub bind: Vec<Param>,
+    pub body: Option<Block>,
+}
+
+/// A single parameter for a [Function]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Param {
+    pub mutability: Mutability,
+    pub name: Sym,
+}
+
+/// A user-defined product type
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Struct {
+    pub name: Sym,
+    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 kind: EnumKind,
+}
+
+/// An [Enum]'s [Variant]s, if it has a variant block
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum EnumKind {
+    /// Represents an enum with no variants
+    NoVariants,
+    Variants(Vec<Variant>),
+}
+
+/// A single [Enum] variant
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Variant {
+    pub name: Sym,
+    pub kind: VariantKind,
+}
+
+/// Whether the [Variant] has a C-like constant value, a tuple, or [StructMember]s
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum VariantKind {
+    Plain,
+    CLike(u128),
+    Tuple(Ty),
+    Struct(Vec<StructMember>),
+}
+
+/// Sub-[items](Item) (associated functions, etc.) for a [Ty]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Impl {
+    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 extents: Span,
+    pub kind: TyKind,
+}
+
+/// Information about a [Ty]pe expression
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum TyKind {
+    Never,
+    Empty,
+    Path(Path),
+    Array(TyArray),
+    Slice(TySlice),
+    Tuple(TyTuple),
+    Ref(TyRef),
+    Fn(TyFn),
+    // TODO: slice, array types
+}
+
+/// An array of [`T`](Ty)
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyArray {
+    pub ty: Box<TyKind>,
+    pub count: usize,
+}
+
+/// A [Ty]pe slice expression: `[T]`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TySlice {
+    pub ty: Box<TyKind>,
+}
+
+/// A tuple of [Ty]pes
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyTuple {
+    pub types: Vec<TyKind>,
+}
+
+/// 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: Path,
+}
+
+/// The args and return value for a function pointer [Ty]pe
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TyFn {
+    pub args: Box<TyKind>,
+    pub rety: Option<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, Debug, PartialEq, Eq, Hash)]
+pub enum PathPart {
+    SuperKw,
+    SelfKw,
+    SelfTy,
+    Ident(Sym),
+}
+
+/// An abstract statement, and associated metadata
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Stmt {
+    pub extents: 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,
+    Local(Let),
+    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,
+}
+
+/// A local variable declaration [Stmt]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Let {
+    pub mutable: Mutability,
+    pub name: Sym,
+    pub ty: Option<Box<Ty>>,
+    pub init: Option<Box<Expr>>,
+}
+
+/// An expression, the beating heart of the language
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Expr {
+    pub extents: 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,
+    /// 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 [Struct creation](Structor) expression: [Path] `{` ([Fielder] `,`)* [Fielder]? `}`
+    Structor(Structor),
+    /// A [path expression](Path): `::`? [PathPart] (`::` [PathPart])*
+    Path(Path),
+    /// A [Literal]: 0x42, 1e123, 2.4, "Hello"
+    Literal(Literal),
+    /// 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 [Block] expression: `{` [`Stmt`]\* [`Expr`]? `}`
+    Block(Block),
+    /// A [Grouping](Group) expression `(` [`Expr`] `)`
+    Group(Group),
+    /// A [Tuple] expression: `(` [`Expr`] (`,` [`Expr`])+ `)`
+    Tuple(Tuple),
+    /// A [Loop] expression: `loop` [`Block`]
+    Loop(Loop),
+    /// 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(Continue),
+}
+
+/// An [Assign]ment expression: [`Expr`] ([`ModifyKind`] [`Expr`])\+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Assign {
+    pub parts: Box<(ExprKind, ExprKind)>,
+}
+
+/// A [Modify]-assignment expression: [`Expr`] ([`ModifyKind`] [`Expr`])\+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Modify {
+    pub kind: ModifyKind,
+    pub parts: Box<(ExprKind, ExprKind)>,
+}
+
+#[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<(ExprKind, ExprKind)>,
+}
+
+/// 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<ExprKind>,
+}
+
+/// A [Unary] operator
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum UnaryKind {
+    Deref,
+    Neg,
+    Not,
+    /// Unused
+    At,
+    /// Unused
+    Tilde,
+}
+
+/// A [Member] access expression: [`Expr`] [`MemberKind`]\*
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Member {
+    pub head: Box<ExprKind>,
+    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<ExprKind>,
+    pub indices: 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<ExprKind>,
+    pub repeat: Box<ExprKind>,
+}
+
+/// An address-of expression: `&` `mut`? [`Expr`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct AddrOf {
+    pub count: usize,
+    pub mutable: Mutability,
+    pub expr: Box<ExprKind>,
+}
+
+/// A [Block] expression: `{` [`Stmt`]\* [`Expr`]? `}`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Block {
+    pub stmts: Vec<Stmt>,
+}
+
+/// A [Grouping](Group) expression `(` [`Expr`] `)`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Group {
+    pub expr: Box<ExprKind>,
+}
+
+/// A [Tuple] expression: `(` [`Expr`] (`,` [`Expr`])+ `)`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Tuple {
+    pub exprs: Vec<Expr>,
+}
+
+/// A [Loop] expression: `loop` [`Block`]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Loop {
+    pub body: Box<Expr>,
+}
+
+/// 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: Sym, // TODO: Patterns?
+    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>>,
+}
+
+/// A continue expression: `continue`
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+pub struct Continue;

compiler/cl-ast/src/ast_impl.rs

@@ -3,52 +3,24 @@ use super::*;
 
 mod display {
     //! Implements [Display] for [AST](super::super) Types
+
     use super::*;
-    pub use delimiters::*;
-    use std::fmt::{Display, Write};
-    mod delimiters {
-        #![allow(dead_code)]
-        #[derive(Clone, Copy, Debug)]
-        pub struct Delimiters<'t> {
-            pub open: &'t str,
-            pub close: &'t str,
-        }
-        /// 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: "]" };
-    }
-    fn delimit<'a>(
-        func: impl Fn(&mut std::fmt::Formatter<'_>) -> std::fmt::Result + 'a,
-        delim: Delimiters<'a>,
-    ) -> impl Fn(&mut std::fmt::Formatter<'_>) -> std::fmt::Result + 'a {
-        move |f| {
-            write!(f, "{}", delim.open)?;
-            func(f)?;
-            write!(f, "{}", delim.close)
-        }
-    }
-    fn separate<'iterable, I>(
-        iterable: &'iterable [I],
-        sep: impl Display + 'iterable,
-    ) -> impl Fn(&mut std::fmt::Formatter<'_>) -> std::fmt::Result + 'iterable
-    where
-        I: Display,
-    {
-        move |f| {
-            for (idx, item) in iterable.iter().enumerate() {
+    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 {
-                    write!(f, "{sep}")?;
+                    f.write_str(sep)?;
                 }
-                item.fmt(f)?;
+                write!(f, "{item}")?;
             }
             Ok(())
         }
@@ -62,6 +34,7 @@ mod display {
             }
         }
     }
+
     impl Display for Visibility {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
@@ -71,9 +44,20 @@ mod display {
         }
     }
 
+    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}'"),
+                Literal::Int(v) => v.fmt(f),
+                Literal::String(v) => write!(f, "\"{v}\""),
+            }
+        }
+    }
+
     impl Display for File {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            separate(&self.items, "\n")(f)
+            separate(&self.items, "\n\n")(f)
         }
     }
 
@@ -84,22 +68,24 @@ mod display {
                 return Ok(());
             }
             "#".fmt(f)?;
-            delimit(separate(meta, ", "), INLINE_SQUARE)(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) => delimit(separate(args, ", "), INLINE_PARENS)(f),
+                MetaKind::Func(args) => separate(args, ", ")(f.delimit(INLINE_PARENS)),
             }
         }
     }
@@ -109,7 +95,13 @@ mod display {
             let Self { extents: _, attrs, vis, kind } = self;
             attrs.fmt(f)?;
             vis.fmt(f)?;
-            match kind {
+            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),
@@ -118,9 +110,11 @@ mod display {
                 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 Alias {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { to, from } = self;
@@ -130,40 +124,63 @@ mod display {
             }
         }
     }
+
     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, kind } = self;
             write!(f, "mod {name}{kind}")
         }
     }
+
     impl Display for ModuleKind {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
                 ModuleKind::Inline(items) => {
                     ' '.fmt(f)?;
-                    delimit(|f| items.fmt(f), BRACES)(f)
+                    write!(f.delimit(BRACES), "{items}")
                 }
                 ModuleKind::Outline => ';'.fmt(f),
             }
         }
     }
+
     impl Display for Function {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { name, args, body, rety } = self;
+            let Self { name, sign: sign @ TyFn { args, rety }, bind, body } = self;
+            let types = match **args {
+                TyKind::Tuple(TyTuple { ref types }) => types.as_slice(),
+                TyKind::Empty => Default::default(),
+                _ => {
+                    write!(f, "Invalid function signature: {sign}")?;
+                    Default::default()
+                }
+            };
+
+            debug_assert_eq!(bind.len(), types.len());
             write!(f, "fn {name} ")?;
-            delimit(separate(args, ", "), INLINE_PARENS)(f)?;
+            {
+                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 Some(rety) = rety {
                 write!(f, " -> {rety}")?;
             }
@@ -173,98 +190,162 @@ mod display {
             }
         }
     }
+
     impl Display for Param {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { mutability, name, ty } = self;
-            write!(f, "{mutability}{name}: {ty}")
+            let Self { mutability, name } = self;
+            write!(f, "{mutability}{name}")
         }
     }
+
     impl Display for Struct {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { name, kind } = self;
             write!(f, "struct {name}{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) => delimit(separate(v, ", "), INLINE_PARENS)(f),
-                StructKind::Struct(v) => {
-                    delimit(separate(v, ",\n"), Delimiters { open: " {\n", ..BRACES })(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, kind } = self;
             write!(f, "enum {name}{kind}")
         }
     }
+
     impl Display for EnumKind {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
-                EnumKind::NoVariants => todo!(),
-                EnumKind::Variants(v) => separate(v, ", ")(f),
+                EnumKind::NoVariants => ';'.fmt(f),
+                EnumKind::Variants(v) => separate(v, ",\n")(f.delimit(SPACED_BRACES)),
             }
         }
     }
+
     impl Display for Variant {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { name, kind } = self;
             write!(f, "{name}{kind}")
         }
     }
+
     impl Display for VariantKind {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
                 VariantKind::Plain => Ok(()),
-                VariantKind::CLike(n) => n.fmt(f),
-                VariantKind::Tuple(v) => delimit(separate(v, ", "), INLINE_PARENS)(f),
-                VariantKind::Struct(v) => delimit(separate(v, ",\n"), BRACES)(f),
+                VariantKind::CLike(n) => write!(f, " = {n}"),
+                VariantKind::Tuple(v) => v.fmt(f),
+                VariantKind::Struct(v) => separate(v, ", ")(f.delimit(INLINE_BRACES)),
             }
         }
     }
+
     impl Display for Impl {
-        fn fmt(&self, _f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            todo!("impl Display for Impl")
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { target, body } = self;
+            write!(f, "impl {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 {
-            match &self.kind {
+            self.kind.fmt(f)
+        }
+    }
+
+    impl Display for TyKind {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            match self {
                 TyKind::Never => "!".fmt(f),
                 TyKind::Empty => "()".fmt(f),
-                TyKind::SelfTy => "Self".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::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 {
-            delimit(separate(&self.types, ", "), INLINE_PARENS)(f)
+            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: _, to } = self;
-            for _ in 0..self.count {
+            let &Self { count, mutable, ref to } = self;
+            for _ in 0..count {
                 f.write_char('&')?;
             }
-            write!(f, "{to}")
+            write!(f, "{mutable}{to}")
         }
     }
+
     impl Display for TyFn {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { args, rety } = self;
@@ -276,21 +357,54 @@ mod display {
         }
     }
 
+    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::SelfKw => "self".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 { extents: _, kind, semi } = self;
-            match kind {
+            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::Local(v) => v.fmt(f),
                 StmtKind::Item(v) => v.fmt(f),
                 StmtKind::Expr(v) => v.fmt(f),
-            }?;
-            match semi {
+            }
+        }
+    }
+
+    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 Let {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             let Self { mutable, name, ty, init } = self;
@@ -307,22 +421,30 @@ mod display {
 
     impl Display for Expr {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            match &self.kind {
+            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::Assign(v) => v.fmt(f),
+                ExprKind::Modify(v) => v.fmt(f),
                 ExprKind::Binary(v) => v.fmt(f),
                 ExprKind::Unary(v) => v.fmt(f),
-                ExprKind::Index(v) => v.fmt(f),
-                ExprKind::Call(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::Empty => "()".fmt(f),
                 ExprKind::Group(v) => v.fmt(f),
                 ExprKind::Tuple(v) => v.fmt(f),
+                ExprKind::Loop(v) => v.fmt(f),
                 ExprKind::While(v) => v.fmt(f),
                 ExprKind::If(v) => v.fmt(f),
                 ExprKind::For(v) => v.fmt(f),
@@ -332,40 +454,50 @@ mod display {
             }
         }
     }
+
     impl Display for Assign {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { head, op, tail } = self;
-            write!(f, "{head} {op} {tail}")
+            let Self { parts } = self;
+            write!(f, "{} = {}", parts.0, parts.1)
         }
     }
-    impl Display for AssignKind {
+
+    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 {
-                AssignKind::Plain => "=",
-                AssignKind::Mul => "*=",
-                AssignKind::Div => "/=",
-                AssignKind::Rem => "%=",
-                AssignKind::Add => "+=",
-                AssignKind::Sub => "-=",
-                AssignKind::And => "&=",
-                AssignKind::Or => "|=",
-                AssignKind::Xor => "^=",
-                AssignKind::Shl => "<<=",
-                AssignKind::Shr => ">>=",
+                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 { head, tail } = self;
-            write!(f, "{head}")?;
-            for (kind, expr) in tail {
-                write!(f, " {kind} {expr}")?;
+            let Self { kind, parts } = self;
+            let (head, tail) = parts.borrow();
+            match kind {
+                BinaryKind::Call => write!(f, "{head}{tail}"),
+                _ => write!(f, "{head} {kind} {tail}"),
             }
-            Ok(())
         }
     }
+
     impl Display for BinaryKind {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
@@ -390,20 +522,19 @@ mod display {
                 BinaryKind::Mul => "*",
                 BinaryKind::Div => "/",
                 BinaryKind::Rem => "%",
-                BinaryKind::Dot => ".",
+                BinaryKind::Call => "()",
             }
             .fmt(f)
         }
     }
+
     impl Display for Unary {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { ops: kinds, tail } = self;
-            for kind in kinds {
-                kind.fmt(f)?
-            }
-            tail.fmt(f)
+            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 {
@@ -416,88 +547,64 @@ mod display {
             .fmt(f)
         }
     }
-    impl Display for Call {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { callee, args } = self;
-            callee.fmt(f)?;
-            for args in args {
-                args.fmt(f)?;
-            }
-            Ok(())
-        }
-    }
-    impl Display for Tuple {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            delimit(separate(&self.exprs, ", "), INLINE_PARENS)(f)
-        }
-    }
+
     impl Display for Member {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { head: parent, tail: children } = self;
-            write!(f, "{parent}.")?;
-            separate(children, ".")(f)?;
-            Ok(())
+            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}")?;
-            for indices in indices {
-                indices.fmt(f)?;
+            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 Indices {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            delimit(separate(&self.exprs, ", "), INLINE_SQUARE)(f)
-        }
-    }
-    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::SelfKw => "self".fmt(f),
-                PathPart::Ident(id) => id.fmt(f),
-            }
-        }
-    }
-    impl Display for Identifier {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            self.0.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}'"),
-                Literal::Int(v) => v.fmt(f),
-                Literal::String(v) => write!(f, "\"{v}\""),
-            }
-        }
-    }
+
     impl Display for Array {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            delimit(separate(&self.values, ", "), INLINE_SQUARE)(f)
+            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 { count, mutable, expr } = self;
@@ -507,34 +614,53 @@ mod display {
             write!(f, "{mutable}{expr}")
         }
     }
+
     impl Display for Block {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            delimit(separate(&self.stmts, "\n"), BRACES)(f)
+            separate(&self.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 {
+            separate(&self.exprs, ", ")(f.delimit(INLINE_PARENS))
+        }
+    }
+
+    impl Display for Loop {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { body } = self;
+            write!(f, "loop {body}")
+        }
+    }
+
     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 {
@@ -543,6 +669,7 @@ mod display {
             }
         }
     }
+
     impl Display for Break {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             write!(f, "break")?;
@@ -552,6 +679,7 @@ mod display {
             }
         }
     }
+
     impl Display for Return {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             write!(f, "return")?;
@@ -561,105 +689,10 @@ mod display {
             }
         }
     }
-}
 
-pub mod format {
-    //! Code formatting for the [AST](super::super)
-
-    use std::{
-        io::{Result, Write as IoWrite},
-        ops::{Deref, DerefMut},
-    };
-
-    /// Trait which adds a function to [Writers](IoWrite) to turn them into [Prettifier]
-    pub trait Pretty {
-        /// Indents code according to the number of matched curly braces
-        fn pretty(self) -> Prettifier<'static, Self>
-        where Self: IoWrite + Sized;
-    }
-    impl<W: IoWrite> Pretty for W {
-        fn pretty(self) -> Prettifier<'static, Self>
-        where Self: IoWrite + Sized {
-            Prettifier::new(self)
-        }
-    }
-
-    pub struct Prettifier<'i, T: IoWrite> {
-        level: isize,
-        indent: &'i str,
-        writer: T,
-    }
-    impl<'i, W: IoWrite> Prettifier<'i, W> {
-        pub fn new(writer: W) -> Self {
-            Self { level: 0, indent: "    ", writer }
-        }
-        pub fn with_indent(indent: &'i str, writer: W) -> Self {
-            Self { level: 0, indent, writer }
-        }
-        pub fn indent<'scope>(&'scope mut self) -> Indent<'scope, 'i, W> {
-            Indent::new(self)
-        }
-        fn write_indentation(&mut self) -> Result<usize> {
-            let Self { level, indent, writer } = self;
-            let mut count = 0;
-            for _ in 0..*level {
-                count += writer.write(indent.as_bytes())?;
-            }
-            Ok(count)
-        }
-    }
-    impl<W: IoWrite> From<W> for Prettifier<'static, W> {
-        fn from(value: W) -> Self {
-            Self::new(value)
-        }
-    }
-    impl<'i, W: IoWrite> IoWrite for Prettifier<'i, W> {
-        fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
-            let mut size = 0;
-            for buf in buf.split_inclusive(|b| b"{}".contains(b)) {
-                match buf.last() {
-                    Some(b'{') => self.level += 1,
-                    Some(b'}') => self.level -= 1,
-                    _ => (),
-                }
-                for buf in buf.split_inclusive(|b| b'\n' == *b) {
-                    size += self.writer.write(buf)?;
-                    if let Some(b'\n') = buf.last() {
-                        self.write_indentation()?;
-                    }
-                }
-            }
-            Ok(size)
-        }
-
-        fn flush(&mut self) -> std::io::Result<()> {
-            self.writer.flush()
-        }
-    }
-
-    pub struct Indent<'scope, 'i, T: IoWrite> {
-        formatter: &'scope mut Prettifier<'i, T>,
-    }
-    impl<'s, 'i, T: IoWrite> Indent<'s, 'i, T> {
-        pub fn new(formatter: &'s mut Prettifier<'i, T>) -> Self {
-            formatter.level += 1;
-            Self { formatter }
-        }
-    }
-    impl<'s, 'i, T: IoWrite> Deref for Indent<'s, 'i, T> {
-        type Target = Prettifier<'i, T>;
-        fn deref(&self) -> &Self::Target {
-            self.formatter
-        }
-    }
-    impl<'s, 'i, T: IoWrite> DerefMut for Indent<'s, 'i, T> {
-        fn deref_mut(&mut self) -> &mut Self::Target {
-            self.formatter
-        }
-    }
-    impl<'s, 'i, T: IoWrite> Drop for Indent<'s, 'i, T> {
-        fn drop(&mut self) {
-            self.formatter.level -= 1;
+    impl Display for Continue {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            "continue".fmt(f)
         }
     }
 }
@@ -668,9 +701,13 @@ mod convert {
     //! Converts between major enums and enum variants
     use super::*;
 
-    impl<T: AsRef<str>> From<T> for Identifier {
+    impl<T: AsRef<str>> From<T> for PathPart {
         fn from(value: T) -> Self {
-            Identifier(value.as_ref().into())
+            match value.as_ref() {
+                "self" => PathPart::SelfKw,
+                "super" => PathPart::SuperKw,
+                ident => PathPart::Ident(ident.into()),
+            }
         }
     }
 
@@ -697,6 +734,7 @@ mod convert {
             Struct => ItemKind::Struct,
             Enum => ItemKind::Enum,
             Impl => ItemKind::Impl,
+            Use => ItemKind::Use,
         }
         impl From for StructKind {
             Vec<Ty> => StructKind::Tuple,
@@ -707,7 +745,7 @@ mod convert {
         }
         impl From for VariantKind {
             u128 => VariantKind::CLike,
-            Vec<Ty> => VariantKind::Tuple,
+            Ty => VariantKind::Tuple,
             // TODO: enum struct variants
         }
         impl From for TyKind {
@@ -723,9 +761,9 @@ mod convert {
         }
         impl From for ExprKind {
             Assign => ExprKind::Assign,
+            Modify => ExprKind::Modify,
             Binary => ExprKind::Binary,
             Unary => ExprKind::Unary,
-            Call => ExprKind::Call,
             Member => ExprKind::Member,
             Index => ExprKind::Index,
             Path => ExprKind::Path,
@@ -736,6 +774,7 @@ mod convert {
             Block => ExprKind::Block,
             Group => ExprKind::Group,
             Tuple => ExprKind::Tuple,
+            Loop => ExprKind::Loop,
             While => ExprKind::While,
             If => ExprKind::If,
             For => ExprKind::For,
@@ -747,18 +786,7 @@ mod convert {
             bool => Literal::Bool,
             char => Literal::Char,
             u128 => Literal::Int,
-            &str => Literal::String,
-        }
-    }
-
-    impl From<Tuple> for Indices {
-        fn from(value: Tuple) -> Self {
-            Self { exprs: value.exprs }
-        }
-    }
-    impl From<Indices> for Tuple {
-        fn from(value: Indices) -> Self {
-            Self { exprs: value.exprs }
+            String => Literal::String,
         }
     }
 
@@ -773,3 +801,34 @@ mod convert {
         }
     }
 }
+
+mod path {
+    //! Utils for [Path]
+    use crate::{ast::Path, PathPart, Sym};
+
+    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
+            }
+        }
+    }
+    impl PathPart {
+        pub fn from_sym(ident: Sym) -> Self {
+            Self::Ident(ident)
+        }
+    }
+}

compiler/cl-ast/src/ast_visitor.rs

@@ -0,0 +1,8 @@
+//! 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 use fold::Fold;
+pub use visit::Visit;

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

@@ -0,0 +1,566 @@
+//! 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, extents: Span) -> Span {
+        extents
+    }
+    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_string(&mut self, s: String) -> String {
+        s
+    }
+    fn fold_file(&mut self, f: File) -> File {
+        let File { items } = f;
+        File { 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 { extents, attrs, vis, kind } = i;
+        Item {
+            extents: self.fold_span(extents),
+            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_alias(&mut self, a: Alias) -> Alias {
+        let Alias { to, from } = a;
+        Alias { to: self.fold_sym(to), 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, kind } = m;
+        Module { name: self.fold_sym(name), kind: self.fold_module_kind(kind) }
+    }
+    fn fold_module_kind(&mut self, m: ModuleKind) -> ModuleKind {
+        match m {
+            ModuleKind::Inline(f) => ModuleKind::Inline(self.fold_file(f)),
+            ModuleKind::Outline => ModuleKind::Outline,
+        }
+    }
+    fn fold_function(&mut self, f: Function) -> Function {
+        let Function { name, sign, bind, body } = f;
+        Function {
+            name: self.fold_sym(name),
+            sign: self.fold_ty_fn(sign),
+            bind: bind.into_iter().map(|p| self.fold_param(p)).collect(),
+            body: body.map(|b| self.fold_block(b)),
+        }
+    }
+    fn fold_param(&mut self, p: Param) -> Param {
+        let Param { mutability, name } = p;
+        Param { mutability: self.fold_mutability(mutability), name: self.fold_sym(name) }
+    }
+    fn fold_struct(&mut self, s: Struct) -> Struct {
+        let Struct { name, kind } = s;
+        Struct { name: self.fold_sym(name), 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, kind } = e;
+        Enum { name: self.fold_sym(name), kind: self.fold_enum_kind(kind) }
+    }
+    fn fold_enum_kind(&mut self, kind: EnumKind) -> EnumKind {
+        or_fold_enum_kind(self, kind)
+    }
+    fn fold_variant(&mut self, v: Variant) -> Variant {
+        let Variant { name, kind } = v;
+
+        Variant { name: self.fold_sym(name), kind: self.fold_variant_kind(kind) }
+    }
+    fn fold_variant_kind(&mut self, kind: VariantKind) -> VariantKind {
+        or_fold_variant_kind(self, kind)
+    }
+    fn fold_impl(&mut self, i: Impl) -> Impl {
+        let Impl { target, body } = i;
+        Impl { 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 { extents, kind } = t;
+        Ty { extents: self.fold_span(extents), kind: self.fold_ty_kind(kind) }
+    }
+    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_kind(*ty)), count }
+    }
+    fn fold_ty_slice(&mut self, s: TySlice) -> TySlice {
+        let TySlice { ty } = s;
+        TySlice { ty: Box::new(self.fold_ty_kind(*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(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: self.fold_path(to) }
+    }
+    fn fold_ty_fn(&mut self, t: TyFn) -> TyFn {
+        let TyFn { args, rety } = t;
+        TyFn {
+            args: Box::new(self.fold_ty_kind(*args)),
+            rety: rety.map(|t| Box::new(self.fold_ty(*t))),
+        }
+    }
+    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::SelfKw => PathPart::SelfKw,
+            PathPart::SelfTy => PathPart::SelfTy,
+            PathPart::Ident(i) => PathPart::Ident(self.fold_sym(i)),
+        }
+    }
+    fn fold_stmt(&mut self, s: Stmt) -> Stmt {
+        let Stmt { extents, kind, semi } = s;
+        Stmt {
+            extents: self.fold_span(extents),
+            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_let(&mut self, l: Let) -> Let {
+        let Let { mutable, name, ty, init } = l;
+        Let {
+            mutable: self.fold_mutability(mutable),
+            name: self.fold_sym(name),
+            ty: ty.map(|t| Box::new(self.fold_ty(*t))),
+            init: init.map(|e| Box::new(self.fold_expr(*e))),
+        }
+    }
+    fn fold_expr(&mut self, e: Expr) -> Expr {
+        let Expr { extents, kind } = e;
+        Expr { extents: self.fold_span(extents), kind: self.fold_expr_kind(kind) }
+    }
+    fn fold_expr_kind(&mut self, kind: ExprKind) -> ExprKind {
+        or_fold_expr_kind(self, kind)
+    }
+    fn fold_assign(&mut self, a: Assign) -> Assign {
+        let Assign { parts } = a;
+        let (head, tail) = *parts;
+        Assign { parts: Box::new((self.fold_expr_kind(head), self.fold_expr_kind(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_kind(head), self.fold_expr_kind(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_kind(head), self.fold_expr_kind(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_kind(*tail)) }
+    }
+    fn fold_unary_kind(&mut self, kind: UnaryKind) -> UnaryKind {
+        kind
+    }
+    fn fold_member(&mut self, m: Member) -> Member {
+        let Member { head, kind } = m;
+        Member { head: Box::new(self.fold_expr_kind(*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_kind(*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_kind(*value)),
+            repeat: Box::new(self.fold_expr_kind(*repeat)),
+        }
+    }
+    fn fold_addrof(&mut self, a: AddrOf) -> AddrOf {
+        let AddrOf { count, mutable, expr } = a;
+        AddrOf {
+            count,
+            mutable: self.fold_mutability(mutable),
+            expr: Box::new(self.fold_expr_kind(*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_kind(*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_loop(&mut self, l: Loop) -> Loop {
+        let Loop { body } = l;
+        Loop { body: Box::new(self.fold_expr(*body)) }
+    }
+    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_sym(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))) }
+    }
+    fn fold_continue(&mut self, c: Continue) -> Continue {
+        let Continue = c;
+        Continue
+    }
+}
+
+#[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::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 [ModuleKind] in the default way
+pub fn or_fold_module_kind<F: Fold + ?Sized>(folder: &mut F, kind: ModuleKind) -> ModuleKind {
+    match kind {
+        ModuleKind::Inline(f) => ModuleKind::Inline(folder.fold_file(f)),
+        ModuleKind::Outline => ModuleKind::Outline,
+    }
+}
+
+#[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 [EnumKind] in the default way
+pub fn or_fold_enum_kind<F: Fold + ?Sized>(folder: &mut F, kind: EnumKind) -> EnumKind {
+    match kind {
+        EnumKind::NoVariants => EnumKind::NoVariants,
+        EnumKind::Variants(v) => {
+            EnumKind::Variants(v.into_iter().map(|v| folder.fold_variant(v)).collect())
+        }
+    }
+}
+
+#[inline]
+/// Folds a [VariantKind] in the default way
+pub fn or_fold_variant_kind<F: Fold + ?Sized>(folder: &mut F, kind: VariantKind) -> VariantKind {
+    match kind {
+        VariantKind::Plain => VariantKind::Plain,
+        VariantKind::CLike(n) => VariantKind::CLike(n),
+        VariantKind::Tuple(t) => VariantKind::Tuple(folder.fold_ty(t)),
+        VariantKind::Struct(mem) => VariantKind::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::Empty => TyKind::Empty,
+        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::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::Local(l) => StmtKind::Local(folder.fold_let(l)),
+        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::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::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::Loop(l) => ExprKind::Loop(folder.fold_loop(l)),
+        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(c) => ExprKind::Continue(folder.fold_continue(c)),
+    }
+}
+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 +1,488 @@
+//! A [visitor](Visit) (implementer of the [Visit] trait) walks the immutable AST, mutating itself.
+
+use crate::ast::*;
+use cl_structures::span::Span;
+
+/// Immutably walks the entire AST
+///
+/// Each method acts as a customization point.
+///
+/// There are a set of default implementations for enums
+/// under the name [`or_visit_`*](or_visit_expr_kind),
+/// provided for ease of use.
+///
+/// For all other nodes, traversal is *explicit*.
+pub trait Visit<'a>: Sized {
+    fn visit_span(&mut self, _extents: &'a Span) {}
+    fn visit_mutability(&mut self, _mutable: &'a Mutability) {}
+    fn visit_visibility(&mut self, _vis: &'a Visibility) {}
+    fn visit_sym(&mut self, _name: &'a Sym) {}
+    fn visit_literal(&mut self, l: &'a Literal) {
+        or_visit_literal(self, l)
+    }
+    fn visit_bool(&mut self, _b: &'a bool) {}
+    fn visit_char(&mut self, _c: &'a char) {}
+    fn visit_int(&mut self, _i: &'a u128) {}
+    fn visit_string(&mut self, _s: &'a str) {}
+    fn visit_file(&mut self, f: &'a File) {
+        let File { items } = f;
+        items.iter().for_each(|i| self.visit_item(i));
+    }
+    fn visit_attrs(&mut self, a: &'a Attrs) {
+        let Attrs { meta } = a;
+        meta.iter().for_each(|m| self.visit_meta(m));
+    }
+    fn visit_meta(&mut self, m: &'a Meta) {
+        let Meta { name, kind } = m;
+        self.visit_sym(name);
+        self.visit_meta_kind(kind);
+    }
+    fn visit_meta_kind(&mut self, kind: &'a MetaKind) {
+        or_visit_meta_kind(self, kind)
+    }
+    fn visit_item(&mut self, i: &'a Item) {
+        let Item { extents, attrs, vis, kind } = i;
+        self.visit_span(extents);
+        self.visit_attrs(attrs);
+        self.visit_visibility(vis);
+        self.visit_item_kind(kind);
+    }
+    fn visit_item_kind(&mut self, kind: &'a ItemKind) {
+        or_visit_item_kind(self, kind)
+    }
+    fn visit_alias(&mut self, a: &'a Alias) {
+        let Alias { to, from } = a;
+        self.visit_sym(to);
+        if let Some(t) = from {
+            self.visit_ty(t)
+        }
+    }
+    fn visit_const(&mut self, c: &'a Const) {
+        let Const { name, ty, init } = c;
+        self.visit_sym(name);
+        self.visit_ty(ty);
+        self.visit_expr(init);
+    }
+    fn visit_static(&mut self, s: &'a Static) {
+        let Static { mutable, name, ty, init } = s;
+        self.visit_mutability(mutable);
+        self.visit_sym(name);
+        self.visit_ty(ty);
+        self.visit_expr(init);
+    }
+    fn visit_module(&mut self, m: &'a Module) {
+        let Module { name, kind } = m;
+        self.visit_sym(name);
+        self.visit_module_kind(kind);
+    }
+    fn visit_module_kind(&mut self, kind: &'a ModuleKind) {
+        or_visit_module_kind(self, kind)
+    }
+    fn visit_function(&mut self, f: &'a Function) {
+        let Function { name, sign, bind, body } = f;
+        self.visit_sym(name);
+        self.visit_ty_fn(sign);
+        bind.iter().for_each(|p| self.visit_param(p));
+        if let Some(b) = body {
+            self.visit_block(b)
+        }
+    }
+    fn visit_param(&mut self, p: &'a Param) {
+        let Param { mutability, name } = p;
+        self.visit_mutability(mutability);
+        self.visit_sym(name);
+    }
+    fn visit_struct(&mut self, s: &'a Struct) {
+        let Struct { name, kind } = s;
+        self.visit_sym(name);
+        self.visit_struct_kind(kind);
+    }
+    fn visit_struct_kind(&mut self, kind: &'a StructKind) {
+        or_visit_struct_kind(self, kind)
+    }
+    fn visit_struct_member(&mut self, m: &'a StructMember) {
+        let StructMember { vis, name, ty } = m;
+        self.visit_visibility(vis);
+        self.visit_sym(name);
+        self.visit_ty(ty);
+    }
+    fn visit_enum(&mut self, e: &'a Enum) {
+        let Enum { name, kind } = e;
+        self.visit_sym(name);
+        self.visit_enum_kind(kind);
+    }
+    fn visit_enum_kind(&mut self, kind: &'a EnumKind) {
+        or_visit_enum_kind(self, kind)
+    }
+    fn visit_variant(&mut self, v: &'a Variant) {
+        let Variant { name, kind } = v;
+        self.visit_sym(name);
+        self.visit_variant_kind(kind);
+    }
+    fn visit_variant_kind(&mut self, kind: &'a VariantKind) {
+        or_visit_variant_kind(self, kind)
+    }
+    fn visit_impl(&mut self, i: &'a Impl) {
+        let Impl { target, body } = i;
+        self.visit_impl_kind(target);
+        self.visit_file(body);
+    }
+    fn visit_impl_kind(&mut self, target: &'a ImplKind) {
+        or_visit_impl_kind(self, target)
+    }
+    fn visit_use(&mut self, u: &'a Use) {
+        let Use { absolute: _, tree } = u;
+        self.visit_use_tree(tree);
+    }
+    fn visit_use_tree(&mut self, tree: &'a UseTree) {
+        or_visit_use_tree(self, tree)
+    }
+    fn visit_ty(&mut self, t: &'a Ty) {
+        let Ty { extents, kind } = t;
+        self.visit_span(extents);
+        self.visit_ty_kind(kind);
+    }
+    fn visit_ty_kind(&mut self, kind: &'a TyKind) {
+        or_visit_ty_kind(self, kind)
+    }
+    fn visit_ty_array(&mut self, a: &'a TyArray) {
+        let TyArray { ty, count: _ } = a;
+        self.visit_ty_kind(ty);
+    }
+    fn visit_ty_slice(&mut self, s: &'a TySlice) {
+        let TySlice { ty } = s;
+        self.visit_ty_kind(ty)
+    }
+    fn visit_ty_tuple(&mut self, t: &'a TyTuple) {
+        let TyTuple { types } = t;
+        types.iter().for_each(|kind| self.visit_ty_kind(kind))
+    }
+    fn visit_ty_ref(&mut self, t: &'a TyRef) {
+        let TyRef { mutable, count: _, to } = t;
+        self.visit_mutability(mutable);
+        self.visit_path(to);
+    }
+    fn visit_ty_fn(&mut self, t: &'a TyFn) {
+        let TyFn { args, rety } = t;
+        self.visit_ty_kind(args);
+        if let Some(rety) = rety {
+            self.visit_ty(rety);
+        }
+    }
+    fn visit_path(&mut self, p: &'a Path) {
+        let Path { absolute: _, parts } = p;
+        parts.iter().for_each(|p| self.visit_path_part(p))
+    }
+    fn visit_path_part(&mut self, p: &'a PathPart) {
+        match p {
+            PathPart::SuperKw => {}
+            PathPart::SelfKw => {}
+            PathPart::SelfTy => {}
+            PathPart::Ident(i) => self.visit_sym(i),
+        }
+    }
+    fn visit_stmt(&mut self, s: &'a Stmt) {
+        let Stmt { extents, kind, semi } = s;
+        self.visit_span(extents);
+        self.visit_stmt_kind(kind);
+        self.visit_semi(semi);
+    }
+    fn visit_stmt_kind(&mut self, kind: &'a StmtKind) {
+        or_visit_stmt_kind(self, kind)
+    }
+    fn visit_semi(&mut self, _s: &'a Semi) {}
+    fn visit_let(&mut self, l: &'a Let) {
+        let Let { mutable, name, ty, init } = l;
+        self.visit_mutability(mutable);
+        self.visit_sym(name);
+        if let Some(ty) = ty {
+            self.visit_ty(ty);
+        }
+        if let Some(init) = init {
+            self.visit_expr(init)
+        }
+    }
+    fn visit_expr(&mut self, e: &'a Expr) {
+        let Expr { extents, kind } = e;
+        self.visit_span(extents);
+        self.visit_expr_kind(kind)
+    }
+    fn visit_expr_kind(&mut self, e: &'a ExprKind) {
+        or_visit_expr_kind(self, e)
+    }
+    fn visit_assign(&mut self, a: &'a Assign) {
+        let Assign { parts } = a;
+        let (head, tail) = parts.as_ref();
+        self.visit_expr_kind(head);
+        self.visit_expr_kind(tail);
+    }
+    fn visit_modify(&mut self, m: &'a Modify) {
+        let Modify { kind, parts } = m;
+        let (head, tail) = parts.as_ref();
+        self.visit_modify_kind(kind);
+        self.visit_expr_kind(head);
+        self.visit_expr_kind(tail);
+    }
+    fn visit_modify_kind(&mut self, _kind: &'a ModifyKind) {}
+    fn visit_binary(&mut self, b: &'a Binary) {
+        let Binary { kind, parts } = b;
+        let (head, tail) = parts.as_ref();
+        self.visit_binary_kind(kind);
+        self.visit_expr_kind(head);
+        self.visit_expr_kind(tail);
+    }
+    fn visit_binary_kind(&mut self, _kind: &'a BinaryKind) {}
+    fn visit_unary(&mut self, u: &'a Unary) {
+        let Unary { kind, tail } = u;
+        self.visit_unary_kind(kind);
+        self.visit_expr_kind(tail);
+    }
+    fn visit_unary_kind(&mut self, _kind: &'a UnaryKind) {}
+    fn visit_member(&mut self, m: &'a Member) {
+        let Member { head, kind } = m;
+        self.visit_expr_kind(head);
+        self.visit_member_kind(kind);
+    }
+    fn visit_member_kind(&mut self, kind: &'a MemberKind) {
+        or_visit_member_kind(self, kind)
+    }
+    fn visit_index(&mut self, i: &'a Index) {
+        let Index { head, indices } = i;
+        self.visit_expr_kind(head);
+        indices.iter().for_each(|e| self.visit_expr(e));
+    }
+    fn visit_structor(&mut self, s: &'a Structor) {
+        let Structor { to, init } = s;
+        self.visit_path(to);
+        init.iter().for_each(|e| self.visit_fielder(e))
+    }
+    fn visit_fielder(&mut self, f: &'a Fielder) {
+        let Fielder { name, init } = f;
+        self.visit_sym(name);
+        if let Some(init) = init {
+            self.visit_expr(init);
+        }
+    }
+    fn visit_array(&mut self, a: &'a Array) {
+        let Array { values } = a;
+        values.iter().for_each(|e| self.visit_expr(e))
+    }
+    fn visit_array_rep(&mut self, a: &'a ArrayRep) {
+        let ArrayRep { value, repeat } = a;
+        self.visit_expr_kind(value);
+        self.visit_expr_kind(repeat);
+    }
+    fn visit_addrof(&mut self, a: &'a AddrOf) {
+        let AddrOf { count: _, mutable, expr } = a;
+        self.visit_mutability(mutable);
+        self.visit_expr_kind(expr);
+    }
+    fn visit_block(&mut self, b: &'a Block) {
+        let Block { stmts } = b;
+        stmts.iter().for_each(|s| self.visit_stmt(s));
+    }
+    fn visit_group(&mut self, g: &'a Group) {
+        let Group { expr } = g;
+        self.visit_expr_kind(expr)
+    }
+    fn visit_tuple(&mut self, t: &'a Tuple) {
+        let Tuple { exprs } = t;
+        exprs.iter().for_each(|e| self.visit_expr(e))
+    }
+    fn visit_loop(&mut self, l: &'a Loop) {
+        let Loop { body } = l;
+        self.visit_expr(body)
+    }
+    fn visit_while(&mut self, w: &'a While) {
+        let While { cond, pass, fail } = w;
+        self.visit_expr(cond);
+        self.visit_block(pass);
+        self.visit_else(fail);
+    }
+    fn visit_if(&mut self, i: &'a If) {
+        let If { cond, pass, fail } = i;
+        self.visit_expr(cond);
+        self.visit_block(pass);
+        self.visit_else(fail);
+    }
+    fn visit_for(&mut self, f: &'a For) {
+        let For { bind, cond, pass, fail } = f;
+        self.visit_sym(bind);
+        self.visit_expr(cond);
+        self.visit_block(pass);
+        self.visit_else(fail);
+    }
+    fn visit_else(&mut self, e: &'a Else) {
+        let Else { body } = e;
+        if let Some(body) = body {
+            self.visit_expr(body)
+        }
+    }
+    fn visit_break(&mut self, b: &'a Break) {
+        let Break { body } = b;
+        if let Some(body) = body {
+            self.visit_expr(body)
+        }
+    }
+    fn visit_return(&mut self, r: &'a Return) {
+        let Return { body } = r;
+        if let Some(body) = body {
+            self.visit_expr(body)
+        }
+    }
+    fn visit_continue(&mut self, c: &'a Continue) {
+        let Continue = c;
+    }
+}
+
+pub fn or_visit_literal<'a, V: Visit<'a>>(visitor: &mut V, l: &'a Literal) {
+    match l {
+        Literal::Bool(b) => visitor.visit_bool(b),
+        Literal::Char(c) => visitor.visit_char(c),
+        Literal::Int(i) => visitor.visit_int(i),
+        Literal::String(s) => visitor.visit_string(s),
+    }
+}
+
+pub fn or_visit_meta_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a MetaKind) {
+    match kind {
+        MetaKind::Plain => {}
+        MetaKind::Equals(l) => visitor.visit_literal(l),
+        MetaKind::Func(lits) => lits.iter().for_each(|l| visitor.visit_literal(l)),
+    }
+}
+
+pub fn or_visit_item_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a ItemKind) {
+    match kind {
+        ItemKind::Module(m) => visitor.visit_module(m),
+        ItemKind::Alias(a) => visitor.visit_alias(a),
+        ItemKind::Enum(e) => visitor.visit_enum(e),
+        ItemKind::Struct(s) => visitor.visit_struct(s),
+        ItemKind::Const(c) => visitor.visit_const(c),
+        ItemKind::Static(s) => visitor.visit_static(s),
+        ItemKind::Function(f) => visitor.visit_function(f),
+        ItemKind::Impl(i) => visitor.visit_impl(i),
+        ItemKind::Use(u) => visitor.visit_use(u),
+    }
+}
+
+pub fn or_visit_module_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a ModuleKind) {
+    match kind {
+        ModuleKind::Inline(f) => visitor.visit_file(f),
+        ModuleKind::Outline => {}
+    }
+}
+
+pub fn or_visit_struct_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a StructKind) {
+    match kind {
+        StructKind::Empty => {}
+        StructKind::Tuple(ty) => ty.iter().for_each(|t| visitor.visit_ty(t)),
+        StructKind::Struct(m) => m.iter().for_each(|m| visitor.visit_struct_member(m)),
+    }
+}
+
+pub fn or_visit_enum_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a EnumKind) {
+    match kind {
+        EnumKind::NoVariants => {}
+        EnumKind::Variants(variants) => variants.iter().for_each(|v| visitor.visit_variant(v)),
+    }
+}
+
+pub fn or_visit_variant_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a VariantKind) {
+    match kind {
+        VariantKind::Plain => {}
+        VariantKind::CLike(_) => {}
+        VariantKind::Tuple(t) => visitor.visit_ty(t),
+        VariantKind::Struct(m) => m.iter().for_each(|m| visitor.visit_struct_member(m)),
+    }
+}
+
+pub fn or_visit_impl_kind<'a, V: Visit<'a>>(visitor: &mut V, target: &'a ImplKind) {
+    match target {
+        ImplKind::Type(t) => visitor.visit_ty(t),
+        ImplKind::Trait { impl_trait, for_type } => {
+            visitor.visit_path(impl_trait);
+            visitor.visit_ty(for_type)
+        }
+    }
+}
+
+pub fn or_visit_use_tree<'a, V: Visit<'a>>(visitor: &mut V, tree: &'a UseTree) {
+    match tree {
+        UseTree::Tree(tree) => {
+            tree.iter().for_each(|tree| visitor.visit_use_tree(tree));
+        }
+        UseTree::Path(path, rest) => {
+            visitor.visit_path_part(path);
+            visitor.visit_use_tree(rest)
+        }
+        UseTree::Alias(path, name) => {
+            visitor.visit_sym(path);
+            visitor.visit_sym(name);
+        }
+        UseTree::Name(name) => {
+            visitor.visit_sym(name);
+        }
+        UseTree::Glob => {}
+    }
+}
+
+pub fn or_visit_ty_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a TyKind) {
+    match kind {
+        TyKind::Never => {}
+        TyKind::Empty => {}
+        TyKind::Path(p) => visitor.visit_path(p),
+        TyKind::Array(t) => visitor.visit_ty_array(t),
+        TyKind::Slice(t) => visitor.visit_ty_slice(t),
+        TyKind::Tuple(t) => visitor.visit_ty_tuple(t),
+        TyKind::Ref(t) => visitor.visit_ty_ref(t),
+        TyKind::Fn(t) => visitor.visit_ty_fn(t),
+    }
+}
+
+pub fn or_visit_stmt_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a StmtKind) {
+    match kind {
+        StmtKind::Empty => {}
+        StmtKind::Local(l) => visitor.visit_let(l),
+        StmtKind::Item(i) => visitor.visit_item(i),
+        StmtKind::Expr(e) => visitor.visit_expr(e),
+    }
+}
+
+pub fn or_visit_expr_kind<'a, V: Visit<'a>>(visitor: &mut V, e: &'a ExprKind) {
+    match e {
+        ExprKind::Empty => {}
+        ExprKind::Assign(a) => visitor.visit_assign(a),
+        ExprKind::Modify(m) => visitor.visit_modify(m),
+        ExprKind::Binary(b) => visitor.visit_binary(b),
+        ExprKind::Unary(u) => visitor.visit_unary(u),
+        ExprKind::Member(m) => visitor.visit_member(m),
+        ExprKind::Index(i) => visitor.visit_index(i),
+        ExprKind::Structor(s) => visitor.visit_structor(s),
+        ExprKind::Path(p) => visitor.visit_path(p),
+        ExprKind::Literal(l) => visitor.visit_literal(l),
+        ExprKind::Array(a) => visitor.visit_array(a),
+        ExprKind::ArrayRep(a) => visitor.visit_array_rep(a),
+        ExprKind::AddrOf(a) => visitor.visit_addrof(a),
+        ExprKind::Block(b) => visitor.visit_block(b),
+        ExprKind::Group(g) => visitor.visit_group(g),
+        ExprKind::Tuple(t) => visitor.visit_tuple(t),
+        ExprKind::Loop(l) => visitor.visit_loop(l),
+        ExprKind::While(w) => visitor.visit_while(w),
+        ExprKind::If(i) => visitor.visit_if(i),
+        ExprKind::For(f) => visitor.visit_for(f),
+        ExprKind::Break(b) => visitor.visit_break(b),
+        ExprKind::Return(r) => visitor.visit_return(r),
+        ExprKind::Continue(c) => visitor.visit_continue(c),
+    }
+}
+pub fn or_visit_member_kind<'a, V: Visit<'a>>(visitor: &mut V, kind: &'a MemberKind) {
+    match kind {
+        MemberKind::Call(field, args) => {
+            visitor.visit_sym(field);
+            visitor.visit_tuple(args);
+        }
+        MemberKind::Struct(field) => visitor.visit_sym(field),
+        MemberKind::Tuple(field) => visitor.visit_literal(field),
+    }
+}

compiler/cl-ast/src/desugar.rs

@@ -0,0 +1,9 @@
+//! Desugaring passes for Conlang
+
+pub mod path_absoluter;
+pub mod squash_groups;
+pub mod while_else;
+
+pub use path_absoluter::NormalizePaths;
+pub use squash_groups::SquashGroups;
+pub use while_else::WhileElseDesugar;

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

@@ -0,0 +1,54 @@
+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, kind } = m;
+        self.path.push(PathPart::Ident(name));
+
+        let (name, kind) = (self.fold_sym(name), self.fold_module_kind(kind));
+
+        self.path.pop();
+        Module { name, kind }
+    }
+
+    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.clone(), 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_kind(*expr),
+            _ => or_fold_expr_kind(self, kind),
+        }
+    }
+}

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

@@ -0,0 +1,34 @@
+//! 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 { extents, kind } = e;
+        let kind = desugar_while(extents, kind);
+        Expr { extents: self.fold_span(extents), kind: self.fold_expr_kind(kind) }
+    }
+}
+
+/// Desugars while(-else) expressions into loop-if-else-break expressions
+fn desugar_while(extents: 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 extents, if present, or use the parent's extents
+            let fail_span = body.as_ref().map(|body| body.extents).unwrap_or(extents);
+            let break_expr = Expr { extents: fail_span, kind: ExprKind::Break(Break { body }) };
+
+            let loop_body = If { cond, pass, fail: Else { body: Some(Box::new(break_expr)) } };
+            let loop_body = Expr { extents, kind: ExprKind::If(loop_body) };
+            ExprKind::Loop(Loop { body: Box::new(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, F: Write + ?Sized> Write for Indent<'f, 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, F: Write + ?Sized> Drop for Delimit<'f, F> {
+    fn drop(&mut self) {
+        let Self { f: Indent { f, .. }, delim } = self;
+        let _ = f.write_str(delim.close);
+    }
+}
+
+impl<'f, F: Write + ?Sized> Write for Delimit<'f, 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 +1,21 @@
+//! # 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
+//! - [Path]: Path expressions
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+
+pub use ast::*;
+
+pub mod ast;
+pub mod ast_impl;
+pub mod ast_visitor;
+pub mod desugar;
+pub mod format;

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/fib.rs

@@ -1,12 +1,13 @@
 // Calculate Fibonacci numbers
 
-fn main() -> i128 {
-    let num = 10;
-    print("fib(", num, "): ", fib(num));
+fn main() {
+    for num in 0..=30 {
+        println!("fib({num}) = {}", fib(num))
+    }
 }
 
 /// Implements the classic recursive definition of fib()
-fn fib(a: i128) -> i128 {
+fn fib(a: i64) -> i64 {
     if a > 1 {
         fib(a - 1) + fib(a - 2)
     } else {

compiler/cl-interpret/src/builtin.rs

@@ -0,0 +1,284 @@
+//! Implementations of built-in functions
+
+use super::{
+    convalue::ConValue,
+    env::Environment,
+    error::{Error, IResult},
+    BuiltIn, Callable,
+};
+use cl_ast::Sym;
+use std::{
+    io::{stdout, Write},
+    rc::Rc,
+};
+
+builtins! {
+    const MISC;
+    /// Unstable variadic format function
+    pub fn format<_, args> () -> IResult<ConValue> {
+        use std::fmt::Write;
+        let mut out = String::new();
+        for arg in args {
+            write!(out, "{arg}").ok();
+        }
+        Ok(ConValue::String(out.into()))
+    }
+
+    /// Unstable variadic print function
+    pub fn print<_, args> () -> IResult<ConValue> {
+        let mut out = stdout().lock();
+        for arg in args {
+            write!(out, "{arg}").ok();
+        }
+        Ok(ConValue::Empty)
+    }
+
+    /// Unstable variadic println function
+    pub fn println<_, args> () -> IResult<ConValue> {
+        let mut out = stdout().lock();
+        for arg in args {
+            write!(out, "{arg}").ok();
+        }
+        writeln!(out).ok();
+        Ok(ConValue::Empty)
+    }
+
+    /// Prints the [Debug](std::fmt::Debug) version of the input values
+    pub fn dbg<_, args> () -> IResult<ConValue> {
+        let mut out = stdout().lock();
+        for arg in args {
+            writeln!(out, "{arg:?}").ok();
+        }
+        Ok(args.into())
+    }
+
+    /// Dumps info from the environment
+    pub fn dump<env, _>() -> IResult<ConValue> {
+        println!("{}", *env);
+        Ok(ConValue::Empty)
+    }
+}
+builtins! {
+    const BINARY;
+    /// Multiplication `a * b`
+    pub fn mul(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn div(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn rem(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn add(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a + b),
+            (ConValue::String(a), ConValue::String(b)) => (a.to_string() + &b.to_string()).into(),
+            _ => Err(Error::TypeError)?
+        })
+    }
+
+    /// Subtraction `a - b`
+    pub fn sub(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn shl(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn shr(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn and(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn or(lhs, rhs) -> IResult<ConValue> {
+        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`
+    pub fn xor(lhs, rhs) -> IResult<ConValue> {
+        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)?,
+        })
+    }
+
+    /// Tests whether `a < b`
+    pub fn lt(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, <)
+    }
+
+    /// Tests whether `a <= b`
+    pub fn lt_eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, <=)
+    }
+
+    /// Tests whether `a == b`
+    pub fn eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, ==)
+    }
+
+    /// Tests whether `a != b`
+    pub fn neq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, !=)
+    }
+
+    /// Tests whether `a <= b`
+    pub fn gt_eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, >=)
+    }
+
+    /// Tests whether `a < b`
+    pub fn gt(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, >)
+    }
+}
+builtins! {
+    const RANGE;
+    /// Exclusive Range `a..b`
+    pub fn range_exc(lhs, rhs) -> IResult<ConValue> {
+        let (&ConValue::Int(lhs), &ConValue::Int(rhs)) = (lhs, rhs) else {
+            Err(Error::TypeError)?
+        };
+        Ok(ConValue::RangeExc(lhs, rhs.saturating_sub(1)))
+    }
+
+    /// Inclusive Range `a..=b`
+    pub fn range_inc(lhs, rhs) -> IResult<ConValue> {
+        let (&ConValue::Int(lhs), &ConValue::Int(rhs)) = (lhs, rhs) else {
+            Err(Error::TypeError)?
+        };
+        Ok(ConValue::RangeInc(lhs, rhs))
+    }
+}
+builtins! {
+    const UNARY;
+    /// Negates the ConValue
+    pub fn neg(tail) -> IResult<ConValue> {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(v.wrapping_neg()),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    /// Inverts the ConValue
+    pub fn not(tail) -> IResult<ConValue> {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(!v),
+            ConValue::Bool(v) => ConValue::Bool(!v),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    pub fn deref(tail) -> IResult<ConValue> {
+        Ok(match tail {
+            ConValue::Ref(v) => Rc::as_ref(v).clone(),
+            _ => tail.clone(),
+        })
+    }
+}
+
+/// Turns an argument slice into an array with the (inferred) correct number of elements
+pub fn to_args<const N: usize>(args: &[ConValue]) -> IResult<&[ConValue; N]> {
+    args.try_into()
+        .map_err(|_| Error::ArgNumber { want: N, got: args.len() })
+}
+
+/// Turns function definitions into ZSTs which implement [Callable] and [BuiltIn]
+macro builtins (
+    $(prefix = $prefix:literal)?
+    const $defaults:ident $( = [$($additional_builtins:expr),*$(,)?])?;
+    $(
+        $(#[$meta:meta])*$vis:vis fn $name:ident$(<$env:tt, $args:tt>)? ( $($($arg:tt),+$(,)?)? ) $(-> $rety:ty)?
+            $body:block
+    )*
+) {
+    /// Builtins to load when a new interpreter is created
+    pub const $defaults: &[&dyn BuiltIn] = &[$(&$name,)* $($additional_builtins)*];
+    $(
+        $(#[$meta])* #[allow(non_camel_case_types)] #[derive(Clone, Debug)]
+        /// ```rust,ignore
+        #[doc = stringify!(builtin! fn $name($($($arg),*)?) $(-> $rety)? $body)]
+        /// ```
+        $vis struct $name;
+        impl BuiltIn for $name {
+            fn description(&self) -> &str { concat!("builtin ", stringify!($name), stringify!(($($($arg),*)?) )) }
+        }
+        impl Callable for $name {
+            #[allow(unused)]
+            fn call(&self, env: &mut Environment, args: &[ConValue]) $(-> $rety)? {
+                // println!("{}", stringify!($name), );
+                $(let $env = env;
+                let $args = args;)?
+                $(let [$($arg),*] = to_args(args)?;)?
+                $body
+            }
+            fn name(&self) -> Sym { stringify!($name).into() }
+        }
+    )*
+}
+
+/// Templates comparison functions for [ConValue]
+macro cmp ($a:expr, $b:expr, $empty:literal, $op:tt) {
+    match ($a, $b) {
+        (ConValue::Empty, ConValue::Empty) => Ok(ConValue::Bool($empty)),
+        (ConValue::Int(a), ConValue::Int(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::Bool(a), ConValue::Bool(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::Char(a), ConValue::Char(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::String(a), ConValue::String(b)) => Ok(ConValue::Bool(&**a $op &**b)),
+        _ => Err(Error::TypeError)
+    }
+}

compiler/cl-interpret/src/interpret.rs

@@ -0,0 +1,559 @@
+//! A work-in-progress tree walk interpreter for Conlang
+//!
+//! Currently, major parts of the interpreter are not yet implemented, and major parts will never be
+//! implemented in its current form. Namely, since no [ConValue] has a stable location, it's
+//! meaningless to get a pointer to one, and would be undefined behavior to dereference a pointer to
+//! one in any situation.
+
+use std::{borrow::Borrow, rc::Rc};
+
+use super::*;
+use cl_ast::*;
+/// A work-in-progress tree walk interpreter for Conlang
+pub trait Interpret {
+    /// Interprets this thing in the given [`Environment`].
+    ///
+    /// Everything returns a value!™
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue>;
+}
+
+impl Interpret for File {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        for item in &self.items {
+            item.interpret(env)?;
+        }
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Item {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        match &self.kind {
+            ItemKind::Alias(item) => item.interpret(env),
+            ItemKind::Const(item) => item.interpret(env),
+            ItemKind::Static(item) => item.interpret(env),
+            ItemKind::Module(item) => item.interpret(env),
+            ItemKind::Function(item) => item.interpret(env),
+            ItemKind::Struct(item) => item.interpret(env),
+            ItemKind::Enum(item) => item.interpret(env),
+            ItemKind::Impl(item) => item.interpret(env),
+            ItemKind::Use(_) => todo!("namespaces and imports in the interpreter"),
+        }
+    }
+}
+impl Interpret for Alias {
+    fn interpret(&self, _env: &mut Environment) -> IResult<ConValue> {
+        println!("TODO: {self}");
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Const {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Const { name, ty: _, init } = self;
+
+        let init = init.as_ref().interpret(env)?;
+        env.insert(*name, Some(init));
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Static {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Static { mutable: _, name, ty: _, init } = self;
+
+        let init = init.as_ref().interpret(env)?;
+        env.insert(*name, Some(init));
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Module {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { name, kind } = self;
+        // TODO: Enter this module's namespace
+        match kind {
+            ModuleKind::Inline(file) => file.interpret(env),
+            ModuleKind::Outline => Err(Error::Outlined(*name)),
+        }
+    }
+}
+impl Interpret for Function {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        // register the function in the current environment
+        env.insert_fn(self);
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Struct {
+    fn interpret(&self, _env: &mut Environment) -> IResult<ConValue> {
+        println!("TODO: {self}");
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Enum {
+    fn interpret(&self, _env: &mut Environment) -> IResult<ConValue> {
+        println!("TODO: {self}");
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Impl {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        println!("TODO: {self}");
+        let Self { target: _, body } = self;
+        body.interpret(env)
+    }
+}
+impl Interpret for Stmt {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { extents: _, kind, semi } = self;
+        let out = match kind {
+            StmtKind::Empty => ConValue::Empty,
+            StmtKind::Local(stmt) => stmt.interpret(env)?,
+            StmtKind::Item(stmt) => stmt.interpret(env)?,
+            StmtKind::Expr(stmt) => stmt.interpret(env)?,
+        };
+        Ok(match semi {
+            Semi::Terminated => ConValue::Empty,
+            Semi::Unterminated => out,
+        })
+    }
+}
+impl Interpret for Let {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Let { mutable: _, name, ty: _, init } = self;
+        let init = init.as_ref().map(|i| i.interpret(env)).transpose()?;
+        env.insert(*name, init);
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Expr {
+    #[inline]
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { extents: _, kind } = self;
+        kind.interpret(env)
+    }
+}
+impl Interpret for ExprKind {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        match self {
+            ExprKind::Empty => Ok(ConValue::Empty),
+            ExprKind::Assign(v) => v.interpret(env),
+            ExprKind::Modify(v) => v.interpret(env),
+            ExprKind::Binary(v) => v.interpret(env),
+            ExprKind::Unary(v) => v.interpret(env),
+            ExprKind::Member(v) => v.interpret(env),
+            ExprKind::Index(v) => v.interpret(env),
+            ExprKind::Structor(v) => v.interpret(env),
+            ExprKind::Path(v) => v.interpret(env),
+            ExprKind::Literal(v) => v.interpret(env),
+            ExprKind::Array(v) => v.interpret(env),
+            ExprKind::ArrayRep(v) => v.interpret(env),
+            ExprKind::AddrOf(v) => v.interpret(env),
+            ExprKind::Block(v) => v.interpret(env),
+            ExprKind::Group(v) => v.interpret(env),
+            ExprKind::Tuple(v) => v.interpret(env),
+            ExprKind::Loop(v) => v.interpret(env),
+            ExprKind::While(v) => v.interpret(env),
+            ExprKind::If(v) => v.interpret(env),
+            ExprKind::For(v) => v.interpret(env),
+            ExprKind::Break(v) => v.interpret(env),
+            ExprKind::Return(v) => v.interpret(env),
+            ExprKind::Continue(v) => v.interpret(env),
+        }
+    }
+}
+
+fn evaluate_place_expr<'e>(
+    env: &'e mut Environment,
+    expr: &ExprKind,
+) -> IResult<(&'e mut Option<ConValue>, Sym)> {
+    match expr {
+        ExprKind::Path(Path { parts, .. }) if parts.len() == 1 => {
+            match parts.last().expect("parts should not be empty") {
+                PathPart::SuperKw => Err(Error::NotAssignable),
+                PathPart::SelfKw => todo!("Assignment to `self`"),
+                PathPart::SelfTy => todo!("What does it mean to assign to capital-S Self?"),
+                PathPart::Ident(s) => env.get_mut(*s).map(|v| (v, *s)),
+            }
+        }
+        ExprKind::Index(_) => todo!("Assignment to an index operation"),
+        ExprKind::Path(_) => todo!("Path expression resolution (IMPORTANT)"),
+        ExprKind::Empty | ExprKind::Group(_) | ExprKind::Tuple(_) => {
+            todo!("Pattern Destructuring?")
+        }
+        _ => Err(Error::NotAssignable),
+    }
+}
+
+impl Interpret for Assign {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Assign { parts } = self;
+        let (head, tail) = parts.borrow();
+        let init = tail.interpret(env)?;
+        // Resolve the head pattern
+        let target = evaluate_place_expr(env, head)?;
+        use std::mem::discriminant as variant;
+        // runtime typecheck
+        match target.0 {
+            Some(value) if variant(value) == variant(&init) => {
+                *value = init;
+            }
+            value @ None => *value = Some(init),
+            _ => Err(Error::TypeError)?,
+        }
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Modify {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Modify { kind: op, parts } = self;
+        let (head, tail) = parts.borrow();
+        // Get the initializer and the tail
+        let init = tail.interpret(env)?;
+        // Resolve the head pattern
+        let target = evaluate_place_expr(env, head)?;
+        let (Some(target), _) = target else {
+            return Err(Error::NotInitialized(target.1));
+        };
+
+        match op {
+            ModifyKind::Add => target.add_assign(init),
+            ModifyKind::Sub => target.sub_assign(init),
+            ModifyKind::Mul => target.mul_assign(init),
+            ModifyKind::Div => target.div_assign(init),
+            ModifyKind::Rem => target.rem_assign(init),
+            ModifyKind::And => target.bitand_assign(init),
+            ModifyKind::Or => target.bitor_assign(init),
+            ModifyKind::Xor => target.bitxor_assign(init),
+            ModifyKind::Shl => target.shl_assign(init),
+            ModifyKind::Shr => target.shr_assign(init),
+        }?;
+        Ok(ConValue::Empty)
+    }
+}
+impl Interpret for Binary {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Binary { kind, parts } = self;
+        let (head, tail) = parts.borrow();
+
+        let head = head.interpret(env)?;
+
+        // Short-circuiting ops
+        match kind {
+            BinaryKind::LogAnd => {
+                return if head.truthy()? {
+                    tail.interpret(env)
+                } else {
+                    Ok(head)
+                }; // Short circuiting
+            }
+            BinaryKind::LogOr => {
+                return if !head.truthy()? {
+                    tail.interpret(env)
+                } else {
+                    Ok(head)
+                }; // Short circuiting
+            }
+            BinaryKind::LogXor => {
+                return Ok(ConValue::Bool(
+                    head.truthy()? ^ tail.interpret(env)?.truthy()?,
+                ));
+            }
+            _ => {}
+        }
+        let tail = tail.interpret(env)?;
+        match kind {
+            BinaryKind::Lt => head.lt(&tail),
+            BinaryKind::LtEq => head.lt_eq(&tail),
+            BinaryKind::Equal => head.eq(&tail),
+            BinaryKind::NotEq => head.neq(&tail),
+            BinaryKind::GtEq => head.gt_eq(&tail),
+            BinaryKind::Gt => head.gt(&tail),
+            BinaryKind::RangeExc => head.range_exc(tail),
+            BinaryKind::RangeInc => head.range_inc(tail),
+            BinaryKind::BitAnd => head & tail,
+            BinaryKind::BitOr => head | tail,
+            BinaryKind::BitXor => head ^ tail,
+            BinaryKind::Shl => head << tail,
+            BinaryKind::Shr => head >> tail,
+            BinaryKind::Add => head + tail,
+            BinaryKind::Sub => head - tail,
+            BinaryKind::Mul => head * tail,
+            BinaryKind::Div => head / tail,
+            BinaryKind::Rem => head % tail,
+            BinaryKind::Call => match tail {
+                ConValue::Empty => head.call(env, &[]),
+                ConValue::Tuple(args) => head.call(env, &args),
+                _ => Err(Error::TypeError),
+            },
+            _ => Ok(head),
+        }
+
+        // // Temporarily disabled, to avoid function dispatch overhead while I screw around
+        // // Not like it helped much in the first place!
+        // match kind {
+        //     BinaryKind::Mul => env.call("mul", &[head, tail]),
+        //     BinaryKind::Div => env.call("div", &[head, tail]),
+        //     BinaryKind::Rem => env.call("rem", &[head, tail]),
+        //     BinaryKind::Add => env.call("add", &[head, tail]),
+        //     BinaryKind::Sub => env.call("sub", &[head, tail]),
+        //     BinaryKind::Shl => env.call("shl", &[head, tail]),
+        //     BinaryKind::Shr => env.call("shr", &[head, tail]),
+        //     BinaryKind::BitAnd => env.call("and", &[head, tail]),
+        //     BinaryKind::BitOr => env.call("or", &[head, tail]),
+        //     BinaryKind::BitXor => env.call("xor", &[head, tail]),
+        //     BinaryKind::RangeExc => env.call("range_exc", &[head, tail]),
+        //     BinaryKind::RangeInc => env.call("range_inc", &[head, tail]),
+        //     BinaryKind::Lt => env.call("lt", &[head, tail]),
+        //     BinaryKind::LtEq => env.call("lt_eq", &[head, tail]),
+        //     BinaryKind::Equal => env.call("eq", &[head, tail]),
+        //     BinaryKind::NotEq => env.call("neq", &[head, tail]),
+        //     BinaryKind::GtEq => env.call("gt_eq", &[head, tail]),
+        //     BinaryKind::Gt => env.call("gt", &[head, tail]),
+        //     BinaryKind::Dot => todo!("search within a type's namespace!"),
+        //     BinaryKind::Call => match tail {
+        //         ConValue::Empty => head.call(env, &[]),
+        //         ConValue::Tuple(args) => head.call(env, &args),
+        //         _ => Err(Error::TypeError),
+        //     },
+        //     _ => Ok(head),
+        // }
+    }
+}
+
+impl Interpret for Unary {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Unary { kind, tail } = self;
+        let operand = tail.interpret(env)?;
+        match kind {
+            UnaryKind::Deref => env.call("deref".into(), &[operand]),
+            UnaryKind::Neg => env.call("neg".into(), &[operand]),
+            UnaryKind::Not => env.call("not".into(), &[operand]),
+            UnaryKind::At => {
+                println!("{operand}");
+                Ok(operand)
+            }
+            UnaryKind::Tilde => unimplemented!("Tilde operator"),
+        }
+    }
+}
+impl Interpret for Member {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Member { head, kind } = self;
+        let head = head.interpret(env)?;
+        match (head, kind) {
+            (ConValue::Tuple(v), MemberKind::Tuple(Literal::Int(id))) => v
+                .get(*id as usize)
+                .cloned()
+                .ok_or(Error::OobIndex(*id as usize, v.len())),
+            (head, MemberKind::Call(name, args)) => {
+                let mut values = vec![head];
+                for arg in &args.exprs {
+                    values.push(arg.interpret(env)?);
+                }
+                env.call(*name, &values)
+            }
+            _ => Err(Error::TypeError)?,
+        }
+    }
+}
+impl Interpret for Index {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { head, indices } = self;
+        let mut head = head.interpret(env)?;
+        for index in indices {
+            head = head.index(&index.interpret(env)?)?;
+        }
+        Ok(head)
+    }
+}
+impl Interpret for Structor {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        todo!("struct construction in {env}")
+    }
+}
+impl Interpret for Path {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { absolute: _, parts } = self;
+
+        if parts.len() == 1 {
+            match parts.last().expect("parts should not be empty") {
+                PathPart::SuperKw | PathPart::SelfKw => todo!("Path navigation"),
+                PathPart::SelfTy => todo!("Path navigation to Self"),
+                PathPart::Ident(name) => env.get(*name),
+            }
+        } else {
+            todo!("Path navigation!")
+        }
+    }
+}
+impl Interpret for Literal {
+    fn interpret(&self, _env: &mut Environment) -> IResult<ConValue> {
+        Ok(match self {
+            Literal::String(value) => ConValue::from(value.as_str()),
+            Literal::Char(value) => ConValue::Char(*value),
+            Literal::Bool(value) => ConValue::Bool(*value),
+            // Literal::Float(value) => todo!("Float values in interpreter: {value:?}"),
+            Literal::Int(value) => ConValue::Int(*value as _),
+        })
+    }
+}
+impl Interpret for Array {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { values } = self;
+        let mut out = vec![];
+        for expr in values {
+            out.push(expr.interpret(env)?)
+        }
+        Ok(ConValue::Array(out.into()))
+    }
+}
+impl Interpret for ArrayRep {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { value, repeat } = self;
+        let repeat = match repeat.interpret(env)? {
+            ConValue::Int(v) => v,
+            _ => Err(Error::TypeError)?,
+        };
+        let value = value.interpret(env)?;
+        Ok(ConValue::Array(vec![value; repeat as usize].into()))
+    }
+}
+impl Interpret for AddrOf {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { count: _, mutable: _, expr } = self;
+        match expr.as_ref() {
+            ExprKind::Index(_) => todo!("AddrOf array index"),
+            // ExprKind::Path(Path { absolute: false, parts }) => match parts.as_slice() {
+            //     [PathPart::Ident(id)] => env.get_ref(id),
+            //     _ => todo!("Path traversal in addrof"),
+            // },
+            ExprKind::Path(_) => todo!("Path traversal in addrof"),
+            _ => Ok(ConValue::Ref(Rc::new(expr.interpret(env)?))),
+        }
+    }
+}
+impl Interpret for Block {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { stmts } = self;
+        let mut env = env.frame("block");
+        let mut out = ConValue::Empty;
+        for stmt in stmts {
+            out = stmt.interpret(&mut env)?;
+        }
+        Ok(out)
+    }
+}
+impl Interpret for Group {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { expr } = self;
+        expr.interpret(env)
+    }
+}
+impl Interpret for Tuple {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { exprs } = self;
+        Ok(ConValue::Tuple(
+            exprs
+                .iter()
+                .try_fold(vec![], |mut out, element| {
+                    out.push(element.interpret(env)?);
+                    Ok(out)
+                })?
+                .into(),
+        ))
+    }
+}
+impl Interpret for Loop {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        loop {
+            match body.interpret(env) {
+                Err(Error::Break(value)) => return Ok(value),
+                Err(Error::Continue) => continue,
+                e => e?,
+            };
+        }
+    }
+}
+impl Interpret for While {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { cond, pass, fail } = self;
+        loop {
+            if cond.interpret(env)?.truthy()? {
+                match pass.interpret(env) {
+                    Err(Error::Break(value)) => return Ok(value),
+                    Err(Error::Continue) => continue,
+                    e => e?,
+                };
+            } else {
+                break fail.interpret(env);
+            }
+        }
+    }
+}
+impl Interpret for If {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { cond, pass, fail } = self;
+        if cond.interpret(env)?.truthy()? {
+            pass.interpret(env)
+        } else {
+            fail.interpret(env)
+        }
+    }
+}
+impl Interpret for For {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { bind: name, cond, pass, fail } = self;
+        // TODO: A better iterator model
+        let mut bounds = match cond.interpret(env)? {
+            ConValue::RangeExc(a, b) => a..=b,
+            ConValue::RangeInc(a, b) => a..=b,
+            _ => Err(Error::TypeError)?,
+        };
+        loop {
+            let mut env = env.frame("loop variable");
+            if let Some(loop_var) = bounds.next() {
+                env.insert(*name, Some(loop_var.into()));
+                match pass.interpret(&mut env) {
+                    Err(Error::Break(value)) => return Ok(value),
+                    Err(Error::Continue) => continue,
+                    result => result?,
+                };
+            } else {
+                break fail.interpret(&mut env);
+            }
+        }
+    }
+}
+impl Interpret for Else {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        match body {
+            Some(body) => body.interpret(env),
+            None => Ok(ConValue::Empty),
+        }
+    }
+}
+impl Interpret for Continue {
+    fn interpret(&self, _env: &mut Environment) -> IResult<ConValue> {
+        Err(Error::Continue)
+    }
+}
+impl Interpret for Return {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        Err(Error::Return(
+            body.as_ref()
+                .map(|body| body.interpret(env))
+                .unwrap_or(Ok(ConValue::Empty))?,
+        ))
+    }
+}
+impl Interpret for Break {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        Err(Error::Break(
+            body.as_ref()
+                .map(|body| body.interpret(env))
+                .unwrap_or(Ok(ConValue::Empty))?,
+        ))
+    }
+}

compiler/cl-interpret/src/lib.rs

@@ -0,0 +1,632 @@
+//! 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, IResult};
+use interpret::Interpret;
+
+/// Callable types can be called from within a Conlang program
+pub trait Callable: std::fmt::Debug {
+    /// 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;
+}
+
+/// [BuiltIn]s are [Callable]s with bespoke definitions
+pub trait BuiltIn: std::fmt::Debug + Callable {
+    fn description(&self) -> &str;
+}
+
+pub mod convalue {
+    //! Values in the dynamically typed AST interpreter.
+    //!
+    //! The most permanent fix is a temporary one.
+    use cl_ast::Sym;
+
+    use super::{
+        error::{Error, IResult},
+        function::Function,
+        BuiltIn, Callable, Environment,
+    };
+    use std::{ops::*, rc::Rc};
+
+    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 boolean
+        Bool(bool),
+        /// A unicode character
+        Char(char),
+        /// A string
+        String(Sym),
+        /// A reference
+        Ref(Rc<ConValue>),
+        /// An Array
+        Array(Rc<[ConValue]>),
+        /// A tuple
+        Tuple(Rc<[ConValue]>),
+        /// An exclusive range
+        RangeExc(Integer, Integer),
+        /// An inclusive range
+        RangeInc(Integer, Integer),
+        /// A callable thing
+        Function(Function),
+        /// A built-in function
+        BuiltIn(&'static dyn 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 range_exc(self, other: Self) -> IResult<Self> {
+            let (Self::Int(a), Self::Int(b)) = (self, other) else {
+                Err(Error::TypeError)?
+            };
+            Ok(Self::RangeExc(a, b.saturating_sub(1)))
+        }
+        pub fn range_inc(self, other: Self) -> IResult<Self> {
+            let (Self::Int(a), Self::Int(b)) = (self, other) else {
+                Err(Error::TypeError)?
+            };
+            Ok(Self::RangeInc(a, b))
+        }
+        pub fn index(&self, index: &Self) -> IResult<ConValue> {
+            let Self::Int(index) = index else {
+                Err(Error::TypeError)?
+            };
+            let Self::Array(arr) = self else {
+                Err(Error::TypeError)?
+            };
+            arr.get(*index as usize)
+                .cloned()
+                .ok_or(Error::OobIndex(*index as usize, arr.len()))
+        }
+        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::BuiltIn(func) => func.name(),
+                _ => "".into(),
+            }
+        }
+        fn call(&self, interpreter: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
+            match self {
+                Self::Function(func) => func.call(interpreter, args),
+                Self::BuiltIn(func) => func.call(interpreter, 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::Bool(a), Self::Bool(b)) => Ok(Self::Bool(a $op b)),
+                (Self::Char(a), Self::Char(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 { $v(value.into()) }
+        })*
+    }
+    impl From<&Sym> for ConValue {
+        fn from(value: &Sym) -> Self {
+            ConValue::String(*value)
+        }
+    }
+    from! {
+        Integer => ConValue::Int,
+        bool => ConValue::Bool,
+        char => ConValue::Char,
+        Sym => ConValue::String,
+        &str => ConValue::String,
+        String => ConValue::String,
+        Rc<str> => ConValue::String,
+        Function => ConValue::Function,
+        Vec<ConValue> => ConValue::Tuple,
+        &'static dyn BuiltIn => ConValue::BuiltIn,
+    }
+    impl From<()> for ConValue {
+        fn from(_: ()) -> Self {
+            Self::Empty
+        }
+    }
+    impl From<&[ConValue]> for ConValue {
+        fn from(value: &[ConValue]) -> Self {
+            match value.len() {
+                0 => Self::Empty,
+                1 => value[0].clone(),
+                _ => Self::Tuple(value.into()),
+            }
+        }
+    }
+
+    /// Implements binary [std::ops] traits for [ConValue]
+    ///
+    /// TODO: Desugar operators into function calls
+    macro ops($($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::String(a), ConValue::String(b)) => (a.to_string() + &b.to_string()).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>().into())
+            }
+            _ => 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
+            })),
+            _ => Err(Error::TypeError)?
+        ]
+        Mul: mul = [
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a.wrapping_mul(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(|| {
+                eprintln!("Warning: Divide by zero in {a} % {b}"); a
+            })),
+            _ => 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)),
+            _ => 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::Bool(v) => v.fmt(f),
+                ConValue::Char(v) => v.fmt(f),
+                ConValue::String(v) => v.fmt(f),
+                ConValue::Ref(v) => write!(f, "&{v}"),
+                ConValue::Array(array) => {
+                    '['.fmt(f)?;
+                    for (idx, element) in array.iter().enumerate() {
+                        if idx > 0 {
+                            ", ".fmt(f)?
+                        }
+                        element.fmt(f)?
+                    }
+                    ']'.fmt(f)
+                }
+                ConValue::RangeExc(a, b) => write!(f, "{a}..{}", b + 1),
+                ConValue::RangeInc(a, b) => write!(f, "{a}..={b}"),
+                ConValue::Tuple(tuple) => {
+                    '('.fmt(f)?;
+                    for (idx, element) in tuple.iter().enumerate() {
+                        if idx > 0 {
+                            ", ".fmt(f)?
+                        }
+                        element.fmt(f)?
+                    }
+                    ')'.fmt(f)
+                }
+                ConValue::Function(func) => {
+                    write!(f, "{}", func.decl())
+                }
+                ConValue::BuiltIn(func) => {
+                    write!(f, "{}", func.description())
+                }
+            }
+        }
+    }
+}
+
+pub mod interpret;
+
+pub mod function {
+    //! Represents a block of code which lives inside the Interpreter
+
+    use super::{Callable, ConValue, Environment, Error, IResult, Interpret};
+    use cl_ast::{Function as FnDecl, Param, Sym};
+    use std::rc::Rc;
+    /// 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 the enclosing scope of the function
+        // env: Box<Environment>,
+    }
+
+    impl Function {
+        pub fn new(decl: &FnDecl) -> Self {
+            Self { decl: decl.clone().into() }
+        }
+        pub fn decl(&self) -> &FnDecl {
+            &self.decl
+        }
+    }
+
+    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, bind, body, sign: _ } = &*self.decl;
+            // Check arg mapping
+            if args.len() != bind.len() {
+                return Err(Error::ArgNumber { want: bind.len(), got: args.len() });
+            }
+            let Some(body) = body else {
+                return Err(Error::NotDefined(*name));
+            };
+            // TODO: completely refactor data storage
+            let mut frame = env.frame("fn args");
+            for (Param { mutability: _, name }, value) in bind.iter().zip(args) {
+                frame.insert(*name, Some(value.clone()));
+            }
+            match body.interpret(&mut frame) {
+                Err(Error::Return(value)) => Ok(value),
+                Err(Error::Break(value)) => Err(Error::BadBreak(value)),
+                result => result,
+            }
+        }
+    }
+}
+
+pub mod builtin;
+
+pub mod env {
+    //! Lexical and non-lexical scoping for variables
+    use super::{
+        builtin::{BINARY, MISC, RANGE, UNARY},
+        convalue::ConValue,
+        error::{Error, IResult},
+        function::Function,
+        BuiltIn, Callable, Interpret,
+    };
+    use cl_ast::{Function as FnDecl, Sym};
+    use std::{
+        collections::HashMap,
+        fmt::Display,
+        ops::{Deref, DerefMut},
+    };
+
+    type StackFrame = HashMap<Sym, Option<ConValue>>;
+
+    /// Implements a nested lexical scope
+    #[derive(Clone, Debug)]
+    pub struct Environment {
+        frames: Vec<(StackFrame, &'static str)>,
+    }
+
+    impl Display for Environment {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            for (frame, name) in self.frames.iter().rev() {
+                writeln!(f, "--- {name} ---")?;
+                for (var, val) in frame {
+                    write!(f, "{var}: ")?;
+                    match val {
+                        Some(value) => writeln!(f, "\t{value}"),
+                        None => writeln!(f, "<undefined>"),
+                    }?
+                }
+            }
+            Ok(())
+        }
+    }
+    impl Default for Environment {
+        fn default() -> Self {
+            Self {
+                frames: vec![
+                    (to_hashmap(RANGE), "range ops"),
+                    (to_hashmap(UNARY), "unary ops"),
+                    (to_hashmap(BINARY), "binary ops"),
+                    (to_hashmap(MISC), "builtins"),
+                    (HashMap::new(), "globals"),
+                ],
+            }
+        }
+    }
+    fn to_hashmap(from: &[&'static dyn BuiltIn]) -> HashMap<Sym, Option<ConValue>> {
+        from.iter().map(|&v| (v.name(), Some(v.into()))).collect()
+    }
+
+    impl Environment {
+        pub fn new() -> Self {
+            Self::default()
+        }
+        /// Creates an [Environment] with no [builtins](super::builtin)
+        pub fn no_builtins(name: &'static str) -> Self {
+            Self { frames: vec![(Default::default(), name)] }
+        }
+
+        pub fn eval(&mut self, node: &impl Interpret) -> IResult<ConValue> {
+            node.interpret(self)
+        }
+
+        /// Calls a function inside the interpreter's scope,
+        /// and returns the result
+        pub fn call(&mut self, name: Sym, args: &[ConValue]) -> IResult<ConValue> {
+            // FIXME: Clone to satisfy the borrow checker
+            let function = self.get(name)?.clone();
+            function.call(self, args)
+        }
+        /// 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)
+        }
+        /// Resolves a variable mutably.
+        ///
+        /// Returns a mutable reference to the variable's record, if it exists.
+        pub fn get_mut(&mut self, id: Sym) -> IResult<&mut Option<ConValue>> {
+            for (frame, _) in self.frames.iter_mut().rev() {
+                if let Some(var) = frame.get_mut(&id) {
+                    return Ok(var);
+                }
+            }
+            Err(Error::NotDefined(id))
+        }
+        /// Resolves a variable immutably.
+        ///
+        /// Returns a reference to the variable's contents, if it is defined and initialized.
+        pub fn get(&self, id: Sym) -> IResult<ConValue> {
+            for (frame, _) in self.frames.iter().rev() {
+                match frame.get(&id) {
+                    Some(Some(var)) => return Ok(var.clone()),
+                    Some(None) => return Err(Error::NotInitialized(id)),
+                    _ => (),
+                }
+            }
+            Err(Error::NotDefined(id))
+        }
+        /// Inserts a new [ConValue] into this [Environment]
+        pub fn insert(&mut self, id: Sym, value: Option<ConValue>) {
+            if let Some((frame, _)) = self.frames.last_mut() {
+                frame.insert(id, value);
+            }
+        }
+        /// 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, Some(Function::new(decl).into()));
+            if let Some((frame, _)) = self.frames.last_mut() {
+                frame.insert(*name, function);
+            }
+        }
+    }
+
+    /// Functions which aid in the implementation of [`Frame`]
+    impl Environment {
+        /// Enters a scope, creating a new namespace for variables
+        fn enter(&mut self, name: &'static str) -> &mut Self {
+            self.frames.push((Default::default(), name));
+            self
+        }
+
+        /// Exits the scope, destroying all local variables and
+        /// returning the outer scope, if there is one
+        fn exit(&mut self) -> &mut Self {
+            if self.frames.len() > 2 {
+                self.frames.pop();
+            }
+            self
+        }
+    }
+
+    /// 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 {
+            Self { scope: scope.enter(name) }
+        }
+    }
+    impl<'scope> Deref for Frame<'scope> {
+        type Target = Environment;
+        fn deref(&self) -> &Self::Target {
+            self.scope
+        }
+    }
+    impl<'scope> DerefMut for Frame<'scope> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.scope
+        }
+    }
+    impl<'scope> Drop for Frame<'scope> {
+        fn drop(&mut self) {
+            self.scope.exit();
+        }
+    }
+}
+
+pub mod error {
+    //! The [Error] type represents any error thrown by the [Environment](super::Environment)
+
+    use cl_ast::Sym;
+
+    use super::convalue::ConValue;
+
+    pub type IResult<T> = Result<T, Error>;
+
+    /// Represents any error thrown by the [Environment](super::Environment)
+    #[derive(Clone, Debug)]
+    pub enum Error {
+        /// 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,
+        /// 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,
+        },
+        Outlined(Sym),
+    }
+
+    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::Return(value) => write!(f, "return {value}"),
+                Error::Break(value) => write!(f, "break {value}"),
+                Error::BadBreak(value) => write!(f, "rogue break: {value}"),
+                Error::Continue => "continue".fmt(f),
+                Error::StackUnderflow => "Stack underflow".fmt(f),
+                Error::ScopeExit => "Exited the last scope. This is a logic bug.".fmt(f),
+                Error::TypeError => "Incompatible types".fmt(f),
+                Error::NotIterable => "`in` clause of `for` loop did not yield an iterable".fmt(f),
+                Error::NotIndexable => {
+                    write!(f, "expression cannot be indexed")
+                }
+                Error::OobIndex(idx, len) => {
+                    write!(f, "Index out of bounds: index was {idx}. but len is {len}")
+                }
+                Error::NotAssignable => {
+                    write!(f, "expression is not assignable")
+                }
+                Error::NotDefined(value) => {
+                    write!(f, "{value} not bound. Did you mean `let {value};`?")
+                }
+                Error::NotInitialized(value) => {
+                    write!(f, "{value} bound, but not initialized")
+                }
+                Error::NotCallable(value) => {
+                    write!(f, "{value} is not callable.")
+                }
+                Error::ArgNumber { want, got } => {
+                    write!(
+                        f,
+                        "Expected {want} argument{}, got {got}",
+                        if *want == 1 { "" } else { "s" }
+                    )
+                }
+                Error::Outlined(name) => {
+                    write!(f, "Module {name} specified, but not imported.")
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;

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::{env::Environment, convalue::ConValue, Interpret};
+use cl_ast::*;
+use cl_lexer::Lexer;
+use cl_parser::Parser;
 pub use macros::*;
 
 mod macros {
@@ -49,7 +47,7 @@ mod macros {
     //! env_eq!(env.x, 10); // like assert_eq! for Environments
     //! ```
     #![allow(unused_macros)]
-    use crate::interpreter::IResult;
+    use crate::IResult;
 
     use super::*;
 
@@ -129,7 +127,7 @@ 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 +135,7 @@ 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))
@@ -189,10 +187,10 @@ mod fn_declarations {
         assert_eval!(env, fn empty_fn() {});
         // TODO: true equality for functions
         assert_eq!(
-            "fn empty_fn",
+            "fn empty_fn () {\n    \n}",
             format!(
                 "{}",
-                env.get("empty_fn")
+                env.get("empty_fn".into())
                     .expect(stringify!(empty_fn should be defined and initialized))
             )
         )
@@ -212,7 +210,7 @@ mod fn_declarations {
 }
 
 mod operators {
-    use crate::ast::Tuple;
+    use cl_ast::Tuple;
 
     use super::*;
     #[test]

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

@@ -1,10 +1,16 @@
 //! Converts a text file into tokens
-use crate::token::preamble::*;
+#![warn(clippy::all)]
+#![feature(decl_macro)]
+use cl_structures::span::Loc;
+use cl_token::{TokenKind as Kind, *};
 use std::{
     iter::Peekable,
     str::{Chars, FromStr},
 };
-use unicode_xid::UnicodeXID;
+use unicode_ident::*;
+
+#[cfg(test)]
+mod tests;
 
 pub mod lexer_iter {
     //! Iterator over a [`Lexer`], returning [`LResult<Token>`]s
@@ -45,7 +51,8 @@ pub mod lexer_iter {
 ///
 /// # Examples
 /// ```rust
-/// # use conlang::lexer::Lexer;
+/// # use cl_lexer::Lexer;
+/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
 /// // Read in your code from somewhere
 /// let some_code = "
 /// fn main () {
@@ -55,16 +62,17 @@ pub mod lexer_iter {
 /// // Create a lexer over your code
 /// let mut lexer = Lexer::new(some_code);
 /// // Scan for a single token
-/// let first_token = lexer.scan().unwrap();
+/// 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.unwrap());
+/// #   let token: Result<_,()> = Ok(token?);
 ///     match token {
 ///         Ok(token) => println!("{token:?}"),
 ///         Err(e) => eprintln!("{e:?}"),
 ///     }
 /// }
+/// # Ok(()) }
 /// ```
 #[derive(Clone, Debug)]
 pub struct Lexer<'t> {
@@ -89,40 +97,40 @@ impl<'t> Lexer<'t> {
     /// Scans through the text, searching for the next [Token]
     pub fn scan(&mut self) -> LResult<Token> {
         match self.skip_whitespace().peek()? {
-            '{' => self.consume()?.produce(Type::LCurly, ()),
-            '}' => self.consume()?.produce(Type::RCurly, ()),
-            '[' => self.consume()?.produce(Type::LBrack, ()),
-            ']' => self.consume()?.produce(Type::RBrack, ()),
-            '(' => self.consume()?.produce(Type::LParen, ()),
-            ')' => self.consume()?.produce(Type::RParen, ()),
+            '{' => self.consume()?.produce_op(Punct::LCurly),
+            '}' => self.consume()?.produce_op(Punct::RCurly),
+            '[' => self.consume()?.produce_op(Punct::LBrack),
+            ']' => self.consume()?.produce_op(Punct::RBrack),
+            '(' => self.consume()?.produce_op(Punct::LParen),
+            ')' => self.consume()?.produce_op(Punct::RParen),
             '&' => self.consume()?.amp(),
-            '@' => self.consume()?.produce(Type::At, ()),
-            '\\' => self.consume()?.produce(Type::Backslash, ()),
+            '@' => self.consume()?.produce_op(Punct::At),
+            '\\' => self.consume()?.produce_op(Punct::Backslash),
             '!' => self.consume()?.bang(),
             '|' => self.consume()?.bar(),
             ':' => self.consume()?.colon(),
-            ',' => self.consume()?.produce(Type::Comma, ()),
+            ',' => self.consume()?.produce_op(Punct::Comma),
             '.' => self.consume()?.dot(),
             '=' => self.consume()?.equal(),
-            '`' => self.consume()?.produce(Type::Grave, ()),
+            '`' => self.consume()?.produce_op(Punct::Grave),
             '>' => self.consume()?.greater(),
             '#' => self.consume()?.hash(),
             '<' => self.consume()?.less(),
             '-' => self.consume()?.minus(),
             '+' => self.consume()?.plus(),
-            '?' => self.consume()?.produce(Type::Question, ()),
+            '?' => self.consume()?.produce_op(Punct::Question),
             '%' => self.consume()?.rem(),
-            ';' => self.consume()?.produce(Type::Semi, ()),
+            ';' => self.consume()?.produce_op(Punct::Semi),
             '/' => self.consume()?.slash(),
             '*' => self.consume()?.star(),
-            '~' => self.consume()?.produce(Type::Tilde, ()),
+            '~' => self.consume()?.produce_op(Punct::Tilde),
             '^' => self.consume()?.xor(),
             '0' => self.consume()?.int_with_base(),
             '1'..='9' => self.digits::<10>(),
             '"' => self.consume()?.string(),
             '\'' => self.consume()?.character(),
             '_' => self.identifier(),
-            i if i.is_xid_start() => self.identifier(),
+            i if is_xid_start(i) => self.identifier(),
             e => {
                 let err = Err(Error::unexpected_char(e, self.line(), self.col()));
                 let _ = self.consume();
@@ -149,11 +157,14 @@ impl<'t> Lexer<'t> {
             .copied()
             .ok_or(Error::end_of_file(self.line(), self.col()))
     }
-    fn produce(&mut self, ty: Type, data: impl Into<Data>) -> LResult<Token> {
+    fn produce(&mut self, kind: TokenKind, data: impl Into<TokenData>) -> LResult<Token> {
         let loc = self.start_loc;
         self.start_loc = self.current_loc;
         self.start = self.current;
-        Ok(Token::new(ty, data, loc.0, loc.1))
+        Ok(Token::new(kind, data, loc.0, loc.1))
+    }
+    fn produce_op(&mut self, kind: Punct) -> LResult<Token> {
+        self.produce(TokenKind::Punct(kind), ())
     }
     fn skip_whitespace(&mut self) -> &mut Self {
         while let Ok(c) = self.peek() {
@@ -184,120 +195,120 @@ impl<'t> Lexer<'t> {
 impl<'t> Lexer<'t> {
     fn amp(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('&') => self.consume()?.produce(Type::AmpAmp, ()),
-            Ok('=') => self.consume()?.produce(Type::AmpEq, ()),
-            _ => self.produce(Type::Amp, ()),
+            Ok('&') => self.consume()?.produce_op(Punct::AmpAmp),
+            Ok('=') => self.consume()?.produce_op(Punct::AmpEq),
+            _ => self.produce_op(Punct::Amp),
         }
     }
     fn bang(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('!') => self.consume()?.produce(Type::BangBang, ()),
-            Ok('=') => self.consume()?.produce(Type::BangEq, ()),
-            _ => self.produce(Type::Bang, ()),
+            Ok('!') => self.consume()?.produce_op(Punct::BangBang),
+            Ok('=') => self.consume()?.produce_op(Punct::BangEq),
+            _ => self.produce_op(Punct::Bang),
         }
     }
     fn bar(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('|') => self.consume()?.produce(Type::BarBar, ()),
-            Ok('=') => self.consume()?.produce(Type::BarEq, ()),
-            _ => self.produce(Type::Bar, ()),
+            Ok('|') => self.consume()?.produce_op(Punct::BarBar),
+            Ok('=') => self.consume()?.produce_op(Punct::BarEq),
+            _ => self.produce_op(Punct::Bar),
         }
     }
     fn colon(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok(':') => self.consume()?.produce(Type::ColonColon, ()),
-            _ => self.produce(Type::Colon, ()),
+            Ok(':') => self.consume()?.produce_op(Punct::ColonColon),
+            _ => self.produce_op(Punct::Colon),
         }
     }
     fn dot(&mut self) -> LResult<Token> {
         match self.peek() {
             Ok('.') => {
                 if let Ok('=') = self.consume()?.peek() {
-                    self.consume()?.produce(Type::DotDotEq, ())
+                    self.consume()?.produce_op(Punct::DotDotEq)
                 } else {
-                    self.produce(Type::DotDot, ())
+                    self.produce_op(Punct::DotDot)
                 }
             }
-            _ => self.produce(Type::Dot, ()),
+            _ => self.produce_op(Punct::Dot),
         }
     }
     fn equal(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::EqEq, ()),
-            Ok('>') => self.consume()?.produce(Type::FatArrow, ()),
-            _ => self.produce(Type::Eq, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::EqEq),
+            Ok('>') => self.consume()?.produce_op(Punct::FatArrow),
+            _ => self.produce_op(Punct::Eq),
         }
     }
     fn greater(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::GtEq, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::GtEq),
             Ok('>') => {
                 if let Ok('=') = self.consume()?.peek() {
-                    self.consume()?.produce(Type::GtGtEq, ())
+                    self.consume()?.produce_op(Punct::GtGtEq)
                 } else {
-                    self.produce(Type::GtGt, ())
+                    self.produce_op(Punct::GtGt)
                 }
             }
-            _ => self.produce(Type::Gt, ()),
+            _ => self.produce_op(Punct::Gt),
         }
     }
     fn hash(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('!') => self.consume()?.produce(Type::HashBang, ()),
-            _ => self.produce(Type::Hash, ()),
+            Ok('!') => self.consume()?.produce_op(Punct::HashBang),
+            _ => self.produce_op(Punct::Hash),
         }
     }
     fn less(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::LtEq, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::LtEq),
             Ok('<') => {
                 if let Ok('=') = self.consume()?.peek() {
-                    self.consume()?.produce(Type::LtLtEq, ())
+                    self.consume()?.produce_op(Punct::LtLtEq)
                 } else {
-                    self.produce(Type::LtLt, ())
+                    self.produce_op(Punct::LtLt)
                 }
             }
-            _ => self.produce(Type::Lt, ()),
+            _ => self.produce_op(Punct::Lt),
         }
     }
     fn minus(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::MinusEq, ()),
-            Ok('>') => self.consume()?.produce(Type::Arrow, ()),
-            _ => self.produce(Type::Minus, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::MinusEq),
+            Ok('>') => self.consume()?.produce_op(Punct::Arrow),
+            _ => self.produce_op(Punct::Minus),
         }
     }
     fn plus(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::PlusEq, ()),
-            _ => self.produce(Type::Plus, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::PlusEq),
+            _ => self.produce_op(Punct::Plus),
         }
     }
     fn rem(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::RemEq, ()),
-            _ => self.produce(Type::Rem, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::RemEq),
+            _ => self.produce_op(Punct::Rem),
         }
     }
     fn slash(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::SlashEq, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::SlashEq),
             Ok('/') => self.consume()?.line_comment(),
             Ok('*') => self.consume()?.block_comment(),
-            _ => self.produce(Type::Slash, ()),
+            _ => self.produce_op(Punct::Slash),
         }
     }
     fn star(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::StarEq, ()),
-            _ => self.produce(Type::Star, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::StarEq),
+            _ => self.produce_op(Punct::Star),
         }
     }
     fn xor(&mut self) -> LResult<Token> {
         match self.peek() {
-            Ok('=') => self.consume()?.produce(Type::XorEq, ()),
-            Ok('^') => self.consume()?.produce(Type::XorXor, ()),
-            _ => self.produce(Type::Xor, ()),
+            Ok('=') => self.consume()?.produce_op(Punct::XorEq),
+            Ok('^') => self.consume()?.produce_op(Punct::XorXor),
+            _ => self.produce_op(Punct::Xor),
         }
     }
 }
@@ -307,7 +318,7 @@ impl<'t> Lexer<'t> {
         while Ok('\n') != self.peek() {
             self.consume()?;
         }
-        self.produce(Type::Comment, ())
+        self.produce(Kind::Comment, ())
     }
     fn block_comment(&mut self) -> LResult<Token> {
         while let Ok(c) = self.next() {
@@ -315,7 +326,7 @@ impl<'t> Lexer<'t> {
                 break;
             }
         }
-        self.produce(Type::Comment, ())
+        self.produce(Kind::Comment, ())
     }
 }
 /// Identifiers
@@ -325,15 +336,15 @@ impl<'t> Lexer<'t> {
         while let Ok(c) = self.xid_continue() {
             out.push(c)
         }
-        if let Ok(keyword) = Keyword::from_str(&out) {
-            self.produce(Type::Keyword(keyword), ())
+        if let Ok(keyword) = Kind::from_str(&out) {
+            self.produce(keyword, ())
         } else {
-            self.produce(Type::Identifier, Data::Identifier(out.into()))
+            self.produce(Kind::Identifier, TokenData::String(out))
         }
     }
     fn xid_start(&mut self) -> LResult<char> {
         match self.peek()? {
-            xid if xid == '_' || xid.is_xid_start() => {
+            xid if xid == '_' || is_xid_start(xid) => {
                 self.consume()?;
                 Ok(xid)
             }
@@ -342,7 +353,7 @@ impl<'t> Lexer<'t> {
     }
     fn xid_continue(&mut self) -> LResult<char> {
         match self.peek()? {
-            xid if xid.is_xid_continue() => {
+            xid if is_xid_continue(xid) => {
                 self.consume()?;
                 Ok(xid)
             }
@@ -359,7 +370,7 @@ impl<'t> Lexer<'t> {
             Ok('o') => self.consume()?.digits::<8>(),
             Ok('b') => self.consume()?.digits::<2>(),
             Ok('0'..='9') => self.digits::<10>(),
-            _ => self.produce(Type::Integer, 0),
+            _ => self.produce(Kind::Literal, 0),
         }
     }
     fn digits<const B: u32>(&mut self) -> LResult<Token> {
@@ -367,7 +378,7 @@ impl<'t> Lexer<'t> {
         while let Ok(true) = self.peek().as_ref().map(char::is_ascii_alphanumeric) {
             value = value * B as u128 + self.digit::<B>()? as u128;
         }
-        self.produce(Type::Integer, value)
+        self.produce(Kind::Literal, value)
     }
     fn digit<const B: u32>(&mut self) -> LResult<u32> {
         let digit = self.peek()?;
@@ -388,12 +399,12 @@ impl<'t> Lexer<'t> {
         {
             value.push(self.unescape()?)
         }
-        self.consume()?.produce(Type::String, value)
+        self.consume()?.produce(Kind::Literal, value)
     }
     fn character(&mut self) -> LResult<Token> {
         let out = self.unescape()?;
         match self.peek()? {
-            '\'' => self.consume()?.produce(Type::Character, out),
+            '\'' => self.consume()?.produce(Kind::Literal, out),
             _ => Err(Error::unmatched_delimiters('\'', self.line(), self.col())),
         }
     }
@@ -445,6 +456,12 @@ impl<'t> Lexer<'t> {
     }
 }
 
+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)
@@ -463,7 +480,7 @@ pub mod error {
     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 [Type](crate::token::token_type::Type)
+        /// Found a character that doesn't belong to any [TokenKind](cl_token::TokenKind)
         UnexpectedChar(char),
         /// Found a character that's not valid in identifiers while looking for an identifier
         NotIdentifier(char),

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($op:ident) {
+        TokenKind::Punct(Punct::$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 +1,229 @@
+use super::*;
+
+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 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,
+    },
+    /// 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,
+    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,
+    Assign,
+    AssignKind,
+    Binary,
+    BinaryKind,
+    Unary,
+    UnaryKind,
+    Index,
+    Structor,
+    Fielder,
+    Call,
+    Member,
+    Array,
+    ArrayRep,
+    AddrOf,
+    Block,
+    Group,
+    Tuple,
+    Loop,
+    While,
+    If,
+    For,
+    Else,
+    Break,
+    Return,
+    Continue,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { reason, while_parsing, loc } = self;
+        match reason {
+            // TODO entries are debug-printed
+            ErrorKind::Todo(_) => write!(f, "{loc} {reason} {while_parsing:?}"),
+            // lexical errors print their own higher-resolution loc info
+            ErrorKind::Lexical(e) => write!(f, "{e} (while parsing {while_parsing})"),
+            _ => 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::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::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::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::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",
+        }
+        .fmt(f)
+    }
+}

compiler/cl-parser/src/inliner.rs

@@ -0,0 +1,98 @@
+//! 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) -> ModuleKind {
+        self.io_errs.push((self.path.clone(), error));
+        ModuleKind::Outline
+    }
+
+    /// Records a [parse error](crate::error::Error) for later
+    fn handle_parse_error(&mut self, error: crate::error::Error) -> ModuleKind {
+        self.parse_errs.push((self.path.clone(), error));
+        ModuleKind::Outline
+    }
+}
+
+impl Fold for ModuleInliner {
+    /// Traverses down the module tree, entering ever nested directories
+    fn fold_module(&mut self, m: Module) -> Module {
+        let Module { name, kind } = m;
+        self.path.push(&*name); // cd ./name
+
+        let kind = self.fold_module_kind(kind);
+
+        self.path.pop(); // cd ..
+        Module { name, kind }
+    }
+
+    /// Attempts to read and parse a file for every module in the tree
+    fn fold_module_kind(&mut self, m: ModuleKind) -> ModuleKind {
+        if let ModuleKind::Inline(f) = m {
+            return ModuleKind::Inline(self.fold_file(f));
+        }
+        // cd path/mod.cl
+        self.path.set_extension("cl");
+
+        let file = match std::fs::read_to_string(&self.path) {
+            Err(error) => return self.handle_io_error(error),
+            Ok(file) => file,
+        };
+
+        let kind = match Parser::new(Lexer::new(&file)).file() {
+            Err(e) => return self.handle_parse_error(e),
+            Ok(file) => ModuleKind::Inline(file),
+        };
+        // cd path/mod
+        self.path.set_extension("");
+
+        // The newly loaded module may need further inlining
+        self.fold_module_kind(kind)
+    }
+}

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-repl/Cargo.toml

@@ -10,5 +10,10 @@ 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-ast = { path = "../cl-ast" }
+cl-lexer = { path = "../cl-lexer" }
+cl-token = { path = "../cl-token" }
+cl-parser = { path = "../cl-parser" }
+cl-interpret = { path = "../cl-interpret" }
+repline = { path = "../../repline" }
+argwerk = "0.20.4"

compiler/cl-repl/examples/identify_tokens.rs

@@ -1,6 +1,7 @@
 //! 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},
@@ -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/yaml.rs

@@ -0,0 +1,725 @@
+//! Pretty prints a conlang AST in yaml
+
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use repline::{error::Error as RlError, Repline};
+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.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::{
+        fmt::Display,
+        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 Display) -> Section {
+            println!();
+            self.print_indentation(&mut std::io::stdout().lock());
+            print!("- {name}:");
+            self.indent()
+        }
+
+        /// Prints a yaml key value pair: `- name: "value"`
+        pub fn pair<D: Display, T: Yamlify>(&mut self, name: D, value: T) -> &mut Self {
+            self.key(name).yaml(&value);
+            self
+        }
+
+        /// Prints a yaml scalar value: `"name"``
+        pub fn value<D: Display>(&mut self, value: D) -> &mut Self {
+            print!(" {value}");
+            self
+        }
+
+        pub fn list<D: Yamlify>(&mut self, list: &[D]) -> &mut Self {
+            for (idx, value) in list.iter().enumerate() {
+                self.pair(idx, 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<'y> Deref for Section<'y> {
+        type Target = Yamler;
+        fn deref(&self) -> &Self::Target {
+            self.yamler
+        }
+    }
+    impl<'y> DerefMut for Section<'y> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.yamler
+        }
+    }
+
+    impl<'y> Drop for Section<'y> {
+        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 { items } = self;
+            y.key("File").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 { extents: _, 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 Alias {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { to, from } = self;
+            y.key("Alias").pair("to", to).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, kind } = self;
+            y.key("Module").pair("name", name).yaml(kind);
+        }
+    }
+    impl Yamlify for ModuleKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                ModuleKind::Inline(f) => y.yaml(f),
+                ModuleKind::Outline => y,
+            };
+        }
+    }
+    impl Yamlify for Function {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, sign, bind, body } = self;
+            y.key("Function")
+                .pair("name", name)
+                .pair("sign", sign)
+                .pair("bind", bind)
+                .pair("body", body);
+        }
+    }
+    impl Yamlify for Struct {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, kind } = self;
+            y.key("Struct").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, kind } = self;
+            y.key("Enum").pair("name", name).yaml(kind);
+        }
+    }
+    impl Yamlify for EnumKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                EnumKind::NoVariants => y,
+                EnumKind::Variants(v) => y.yaml(v),
+            };
+        }
+    }
+    impl Yamlify for Variant {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name, kind } = self;
+            y.key("Variant").pair("name", name).yaml(kind);
+        }
+    }
+    impl Yamlify for VariantKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                VariantKind::Plain => y,
+                VariantKind::CLike(v) => y.yaml(v),
+                VariantKind::Tuple(v) => y.yaml(v),
+                VariantKind::Struct(v) => y.yaml(v),
+            };
+        }
+    }
+    impl Yamlify for Impl {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { target, body } = self;
+            y.key("Impl").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 { extents: _, kind, semi } = self;
+            y.key("Stmt").yaml(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::Local(s) => y.yaml(s),
+                StmtKind::Item(s) => y.yaml(s),
+                StmtKind::Expr(s) => y.yaml(s),
+            };
+        }
+    }
+    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 Expr {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { extents: _, kind } = self;
+            y.yaml(kind);
+        }
+    }
+    impl Yamlify for ExprKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                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::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::Loop(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(k) => k.yaml(y),
+            }
+        }
+    }
+    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 ModifyKind {
+        fn yaml(&self, y: &mut Yamler) {
+            y.value(self);
+        }
+    }
+    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 BinaryKind {
+        fn yaml(&self, y: &mut Yamler) {
+            y.value(self);
+        }
+    }
+    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 UnaryKind {
+        fn yaml(&self, y: &mut Yamler) {
+            y.value(self);
+        }
+    }
+    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).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 { count, mutable, expr } = self;
+            y.key("AddrOf")
+                .pair("count", count)
+                .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 Loop {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("Loop").yaml(body);
+        }
+    }
+    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("Else").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 Continue {
+        fn yaml(&self, y: &mut Yamler) {
+            y.key("Continue");
+        }
+    }
+    impl Yamlify for Literal {
+        fn yaml(&self, y: &mut Yamler) {
+            y.value(format_args!("\"{self}\""));
+        }
+    }
+    impl Yamlify for Sym {
+        fn yaml(&self, y: &mut Yamler) {
+            y.value(self);
+        }
+    }
+    impl Yamlify for Param {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { mutability, name } = self;
+            y.key("Param").yaml(mutability).pair("name", name);
+        }
+    }
+    impl Yamlify for Ty {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { extents: _, kind } = self;
+            y.key("Ty").yaml(kind);
+        }
+    }
+    impl Yamlify for TyKind {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                TyKind::Never => y.value("Never"),
+                TyKind::Empty => y.value("Empty"),
+                TyKind::Path(t) => y.yaml(t),
+                TyKind::Tuple(t) => y.yaml(t),
+                TyKind::Ref(t) => y.yaml(t),
+                TyKind::Fn(t) => y.yaml(t),
+                TyKind::Slice(_) => todo!(),
+                TyKind::Array(_) => todo!(),
+            };
+        }
+    }
+    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);
+            }
+            for part in parts {
+                y.pair("part", part);
+            }
+        }
+    }
+    impl Yamlify for PathPart {
+        fn yaml(&self, y: &mut Yamler) {
+            match self {
+                PathPart::SuperKw => y.value("super"),
+                PathPart::SelfKw => y.value("self"),
+                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 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) {
+            for thing in self {
+                y.yaml(thing);
+            }
+        }
+    }
+    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) {
+                    y.value(self);
+                }
+            })*
+        };
+    }
+
+    scalar! {
+        bool, char, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize, &str, String
+    }
+}

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";

compiler/cl-repl/src/args.rs

@@ -0,0 +1,65 @@
+//! 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);
+    }
+}
+
+/// 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 {
+    #[default]
+    Menu,
+    Lex,
+    Fmt,
+    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 +1,100 @@
+//! Implement's the command line interface
+use crate::{
+    args::{Args, Mode},
+    ctx::Context,
+    menu,
+    tools::print_token,
+};
+use cl_interpret::{convalue::ConValue, env::Environment, interpret::Interpret};
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use std::{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();
+    for path in include {
+        load_file(&mut env, path)?;
+    }
+
+    if repl {
+        if let Some(file) = file {
+            load_file(&mut env, file)?;
+        }
+        let mut ctx = Context::with_env(env);
+        match mode {
+            Mode::Menu => menu::main_menu(&mut ctx)?,
+            Mode::Lex => menu::lex(&mut ctx)?,
+            Mode::Fmt => menu::fmt(&mut ctx)?,
+            Mode::Run => menu::run(&mut ctx)?,
+        }
+    } else {
+        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(&code, file),
+            Mode::Fmt => fmt_code(&code),
+            Mode::Run | Mode::Menu => run_code(&code, &mut env),
+        }?;
+    }
+    Ok(())
+}
+
+fn load_file(env: &mut Environment, path: impl AsRef<Path>) -> Result<ConValue, Box<dyn Error>> {
+    let inliner =
+        cl_parser::inliner::ModuleInliner::new(path.as_ref().parent().unwrap_or(Path::new("")));
+    let file = std::fs::read_to_string(path)?;
+    let code = Parser::new(Lexer::new(&file)).file()?;
+    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
+        }
+    };
+    Ok(env.eval(&code)?)
+}
+
+fn lex_code(code: &str, path: Option<impl AsRef<Path>>) -> Result<(), Box<dyn Error>> {
+    for token in Lexer::new(code) {
+        if let Some(path) = &path {
+            print!("{}:", path.as_ref().display());
+        }
+        match token {
+            Ok(token) => print_token(&token),
+            Err(e) => println!("{e}"),
+        }
+    }
+    Ok(())
+}
+
+fn fmt_code(code: &str) -> Result<(), Box<dyn Error>> {
+    let code = Parser::new(Lexer::new(code)).file()?;
+    println!("{code}");
+    Ok(())
+}
+
+fn run_code(code: &str, env: &mut Environment) -> Result<(), Box<dyn Error>> {
+    let code = Parser::new(Lexer::new(code)).file()?;
+    match code.interpret(env)? {
+        ConValue::Empty => {}
+        ret => println!("{ret}"),
+    }
+    if env.get("main".into()).is_ok() {
+        match env.call("main".into(), &[])? {
+            ConValue::Empty => {}
+            ret => println!("{ret}"),
+        }
+    }
+    Ok(())
+}

compiler/cl-repl/src/ctx.rs

@@ -0,0 +1,26 @@
+use cl_interpret::{
+    env::Environment, error::IResult, interpret::Interpret, convalue::ConValue,
+};
+
+#[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 +1,81 @@
+use crate::{ansi, ctx};
+use cl_lexer::Lexer;
+use cl_parser::Parser;
+use repline::{error::ReplResult, prebaked::*};
+
+fn clear() {
+    println!("{}", ansi::CLEAR_ALL);
+    banner()
+}
+
+pub fn banner() {
+    println!("--- conlang v{} 💪🦈 ---", env!("CARGO_PKG_VERSION"))
+}
+
+/// Presents a selection interface to the user
+pub fn main_menu(ctx: &mut ctx::Context) -> ReplResult<()> {
+    banner();
+    run(ctx)?;
+    read_and(ansi::GREEN, "mu>", " ?>", |line| {
+        match line.trim() {
+            "clear" => clear(),
+            "l" | "lex" => lex(ctx)?,
+            "f" | "fmt" => fmt(ctx)?,
+            "r" | "run" => run(ctx)?,
+            "q" | "quit" => return Ok(Response::Break),
+            "h" | "help" => println!(
+                "Valid commands
+    lex     (l): Spin up a lexer, and lex some lines
+    fmt     (f): Format the input
+    run     (r): Enter the REPL, and evaluate some statements
+    help    (h): Print this list
+    quit    (q): Exit the program"
+            ),
+            _ => Err("Unknown command. Type \"help\" for help")?,
+        }
+        Ok(Response::Accept)
+    })
+}
+
+pub fn run(ctx: &mut ctx::Context) -> ReplResult<()> {
+    use cl_ast::ast_visitor::Fold;
+    use cl_parser::inliner::ModuleInliner;
+
+    read_and(ansi::CYAN, "cl>", " ?>", |line| {
+        let code = Parser::new(Lexer::new(line)).stmt()?;
+        let code = ModuleInliner::new(".").fold_stmt(code);
+
+        print!("{}", ansi::OUTPUT);
+        match ctx.run(&code) {
+            Ok(v) => println!("{}{v}", ansi::RESET),
+            Err(e) => println!("{}! > {e}{}", ansi::RED, ansi::RESET),
+        }
+        Ok(Response::Accept)
+    })
+}
+
+pub fn lex(_ctx: &mut ctx::Context) -> ReplResult<()> {
+    read_and(ansi::BRIGHT_BLUE, "lx>", " ?>", |line| {
+        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 fmt(_ctx: &mut ctx::Context) -> ReplResult<()> {
+    read_and(ansi::BRIGHT_MAGENTA, "cl>", " ?>", |line| {
+        let mut p = Parser::new(Lexer::new(line));
+
+        match p.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 = { path = "../cl-arena" }

compiler/cl-structures/src/index_map.rs

@@ -0,0 +1,217 @@
+//! 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 core::slice::GetManyMutError;
+use std::ops::{Index, IndexMut};
+
+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_many_mut<const N: usize>(
+        &mut self,
+        indices: [K; N],
+    ) -> Result<[&mut V; N], GetManyMutError<N>> {
+        self.map.get_many_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 +1,290 @@
+//! 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
+        }
+    }
+
+    impl<'a, T: ?Sized + Debug> Debug for Interned<'a, T> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            f.debug_struct("Interned")
+                .field("value", &self.value)
+                .finish()
+        }
+    }
+    impl<'a, T: ?Sized> Interned<'a, T> {
+        pub(super) fn new(value: &'a T) -> Self {
+            Self { value }
+        }
+    }
+    impl<'a, T: ?Sized> Deref for Interned<'a, T> {
+        type Target = T;
+        fn deref(&self) -> &Self::Target {
+            self.value
+        }
+    }
+    impl<'a, T: ?Sized> Copy for Interned<'a, T> {}
+    impl<'a, T: ?Sized> Clone for Interned<'a, 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<'a, T: ?Sized> Eq for Interned<'a, T> {}
+    impl<'a, T: ?Sized> PartialEq for Interned<'a, T> {
+        fn eq(&self, other: &Self) -> bool {
+            std::ptr::eq(self.value, other.value)
+        }
+    }
+    impl<'a, T: ?Sized> Hash for Interned<'a, 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.
+    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()
+        }
+    }
+
+    // # 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<'a> Send for StringInterner<'a> {}
+    unsafe impl<'a> Sync for StringInterner<'a> {}
+
+    #[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> 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<'a, T: Eq + Hash + Send + Sync> Sync for TypedInterner<'a, 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, get_many_mut)]
+#![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
     }
 }
@@ -38,9 +45,3 @@ impl std::fmt::Display for Loc {
         write!(f, "{line}:{col}:")
     }
 }
-
-impl<'t> From<&Lexer<'t>> for Loc {
-    fn from(value: &Lexer<'t>) -> Self {
-        Loc(value.line(), value.col())
-    }
-}

compiler/cl-structures/src/stack.rs

@@ -0,0 +1,748 @@
+//! 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 {
+    ($count:literal) => {
+        Stack::<_, $count>::new()
+    },
+    ($value:expr ; $count:literal) => {{
+        let mut stack: Stack<_, $count> = Stack::new();
+        for _ in 0..$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 {
+        // 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) }
+    }
+}
+
+impl<T, const N: usize> DerefMut for Stack<T, N> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        // Safety:
+        // - See Deref
+        unsafe { slice::from_raw_parts_mut(self.buf.as_mut_ptr().cast(), self.len) }
+    }
+}
+
+// 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: We have ensured that all elements in the list are
+        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 fn as_mut_ptr(&mut self) -> *mut T {
+        self.buf.as_mut_ptr().cast()
+    }
+
+    /// Extracts a slice containing the entire vector
+    pub fn as_slice(&self) -> &[T] {
+        self
+    }
+
+    /// Extracts a mutable slice containing the entire vector
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        self
+    }
+
+    /// 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 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 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]
+    unsafe fn push_unchecked(&mut self, value: T) {
+        unsafe { 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 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 { 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 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]
+    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
+        drop(std::mem::take(self))
+    }
+
+    /// 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 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 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 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));
+    }
+}

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::{Punct, 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 +1,246 @@
+//! 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,
+    Break,
+    Cl,
+    Const,
+    Continue,
+    Else,
+    Enum,
+    False,
+    For,
+    Fn,
+    If,
+    Impl,
+    In,
+    Let,
+    Loop,
+    Mod,
+    Mut,
+    Pub,
+    Return,
+    SelfKw,
+    SelfTy,
+    Static,
+    Struct,
+    Super,
+    True,
+    Type,
+    Use,
+    While,
+    /// Delimiter or punctuation
+    Punct(Punct),
+}
+
+/// An operator character (delimiter, punctuation)
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Punct {
+    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::For => "for".fmt(f),
+            TokenKind::Fn => "fn".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::Mod => "mod".fmt(f),
+            TokenKind::Mut => "mut".fmt(f),
+            TokenKind::Pub => "pub".fmt(f),
+            TokenKind::Return => "return".fmt(f),
+            TokenKind::SelfKw => "self".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::Punct(op) => op.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,
+            "for" => Self::For,
+            "fn" => Self::Fn,
+            "if" => Self::If,
+            "impl" => Self::Impl,
+            "in" => Self::In,
+            "let" => Self::Let,
+            "loop" => Self::Loop,
+            "mod" => Self::Mod,
+            "mut" => Self::Mut,
+            "pub" => Self::Pub,
+            "return" => Self::Return,
+            "self" => Self::SelfKw,
+            "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(())?,
+        })
+    }
+}
+
+impl Display for Punct {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Punct::LCurly => "{".fmt(f),
+            Punct::RCurly => "}".fmt(f),
+            Punct::LBrack => "[".fmt(f),
+            Punct::RBrack => "]".fmt(f),
+            Punct::LParen => "(".fmt(f),
+            Punct::RParen => ")".fmt(f),
+            Punct::Amp => "&".fmt(f),
+            Punct::AmpAmp => "&&".fmt(f),
+            Punct::AmpEq => "&=".fmt(f),
+            Punct::Arrow => "->".fmt(f),
+            Punct::At => "@".fmt(f),
+            Punct::Backslash => "\\".fmt(f),
+            Punct::Bang => "!".fmt(f),
+            Punct::BangBang => "!!".fmt(f),
+            Punct::BangEq => "!=".fmt(f),
+            Punct::Bar => "|".fmt(f),
+            Punct::BarBar => "||".fmt(f),
+            Punct::BarEq => "|=".fmt(f),
+            Punct::Colon => ":".fmt(f),
+            Punct::ColonColon => "::".fmt(f),
+            Punct::Comma => ",".fmt(f),
+            Punct::Dot => ".".fmt(f),
+            Punct::DotDot => "..".fmt(f),
+            Punct::DotDotEq => "..=".fmt(f),
+            Punct::Eq => "=".fmt(f),
+            Punct::EqEq => "==".fmt(f),
+            Punct::FatArrow => "=>".fmt(f),
+            Punct::Grave => "`".fmt(f),
+            Punct::Gt => ">".fmt(f),
+            Punct::GtEq => ">=".fmt(f),
+            Punct::GtGt => ">>".fmt(f),
+            Punct::GtGtEq => ">>=".fmt(f),
+            Punct::Hash => "#".fmt(f),
+            Punct::HashBang => "#!".fmt(f),
+            Punct::Lt => "<".fmt(f),
+            Punct::LtEq => "<=".fmt(f),
+            Punct::LtLt => "<<".fmt(f),
+            Punct::LtLtEq => "<<=".fmt(f),
+            Punct::Minus => "-".fmt(f),
+            Punct::MinusEq => "-=".fmt(f),
+            Punct::Plus => "+".fmt(f),
+            Punct::PlusEq => "+=".fmt(f),
+            Punct::Question => "?".fmt(f),
+            Punct::Rem => "%".fmt(f),
+            Punct::RemEq => "%=".fmt(f),
+            Punct::Semi => ";".fmt(f),
+            Punct::Slash => "/".fmt(f),
+            Punct::SlashEq => "/=".fmt(f),
+            Punct::Star => "*".fmt(f),
+            Punct::StarEq => "*=".fmt(f),
+            Punct::Tilde => "~".fmt(f),
+            Punct::Xor => "^".fmt(f),
+            Punct::XorEq => "^=".fmt(f),
+            Punct::XorXor => "^^".fmt(f),
+        }
+    }
+}

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 = { path = "../../repline" }
+cl-lexer = { path = "../cl-lexer" }
+cl-parser = { path = "../cl-parser" }

compiler/cl-typeck/examples/typeck.rs

@@ -0,0 +1,266 @@
+use cl_ast::{
+    ast_visitor::{Fold, Visit},
+    desugar::*,
+};
+use cl_lexer::Lexer;
+use cl_parser::{inliner::ModuleInliner, Parser};
+use cl_typeck::{
+    definition::Def,
+    handle::Handle,
+    name_collector::NameCollector,
+    node::{Node, NodeSource},
+    project::Project,
+    type_resolver::resolve,
+};
+use repline::{error::Error as RlError, prebaked::*};
+use std::{error::Error, path};
+
+// Path to display in standard library errors
+const STDLIB_DISPLAY_PATH: &str = "stdlib/lib.cl";
+// Statically included standard library
+const STDLIB: &str = include_str!("../../../stdlib/lib.cl");
+
+// Colors
+const C_MAIN: &str = "";
+const C_RESV: &str = "\x1b[35m";
+const C_CODE: &str = "\x1b[36m";
+const C_BYID: &str = "\x1b[95m";
+const C_LISTING: &str = "\x1b[38;5;117m";
+
+/// A home for immutable intermediate ASTs
+///
+/// TODO: remove this.
+static mut TREES: TreeManager = TreeManager::new();
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let mut prj = Project::default();
+
+    let mut parser = Parser::new(Lexer::new(STDLIB));
+    let code = match parser.file() {
+        Ok(code) => code,
+        Err(e) => {
+            eprintln!("{STDLIB_DISPLAY_PATH}:{e}");
+            Err(e)?
+        }
+    };
+    let code = inline_modules(code, concat!(env!("PWD"), "/stdlib"));
+    NameCollector::new(&mut prj).visit_file(unsafe { TREES.push(code) });
+
+    main_menu(&mut prj)?;
+    Ok(())
+}
+
+fn main_menu(prj: &mut Project) -> Result<(), RlError> {
+    banner();
+    read_and(C_MAIN, "mu>", "? >", |line| {
+        match line.trim() {
+            "c" | "code" => enter_code(prj)?,
+            "clear" => clear()?,
+            "e" | "exit" => return Ok(Response::Break),
+            "l" | "list" => list_types(prj),
+            "q" | "query" => query_type_expression(prj)?,
+            "i" | "id" => get_by_id(prj)?,
+            "r" | "resolve" => resolve_all(prj)?,
+            "d" | "desugar" => live_desugar()?,
+            "h" | "help" => {
+                println!(
+                    "Valid commands are:
+    code    (c): Enter code to type-check
+    list    (l): List all known types
+    query   (q): Query the type system
+    id      (i): Get a type by its type ID
+    resolve (r): Perform type resolution
+    desugar (d): WIP: Test the experimental desugaring passes
+    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 Project) -> Result<(), RlError> {
+    read_and(C_CODE, "cl>", "? >", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        let code = Parser::new(Lexer::new(line)).file()?;
+        let code = inline_modules(code, "");
+        let code = WhileElseDesugar.fold_file(code);
+        // Safety: this is totally unsafe
+        NameCollector::new(prj).visit_file(unsafe { TREES.push(code) });
+
+        Ok(Response::Accept)
+    })
+}
+
+fn live_desugar() -> Result<(), RlError> {
+    read_and(C_RESV, "se>", "? >", |line| {
+        let code = Parser::new(Lexer::new(line)).stmt()?;
+        println!("Raw, as parsed:\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 query_type_expression(prj: &mut Project) -> Result<(), RlError> {
+    read_and(C_RESV, "ty>", "? >", |line| {
+        if line.trim().is_empty() {
+            return Ok(Response::Break);
+        }
+        // parse it as a path, and convert the path into a borrowed path
+        let ty = Parser::new(Lexer::new(line)).ty()?.kind;
+        let id = prj.evaluate(&ty, prj.root)?.handle_unchecked(prj);
+        pretty_handle(id)?;
+        Ok(Response::Accept)
+    })
+}
+
+fn get_by_id(prj: &mut Project) -> Result<(), RlError> {
+    use cl_structures::index_map::MapIndex;
+    use cl_typeck::handle::DefID;
+    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 parser.literal()? {
+            cl_ast::Literal::Int(int) => int as _,
+            other => Err(format!("Expected integer, got {other}"))?,
+        };
+        let mut path = parser.path().unwrap_or_default();
+        path.absolute = false;
+
+        let Some(handle) = DefID::from_usize(def_id).handle(prj) else {
+            return Ok(Response::Deny);
+        };
+
+        print!("  > {{{C_LISTING}{handle}\x1b[0m}}");
+        if !path.parts.is_empty() {
+            print!("::{path}")
+        }
+        println!();
+
+        let (ty, value) = handle.navigate((&path).into());
+        if let (None, None) = (ty, value) {
+            Err("No results.")?
+        }
+        if let Some(t) = ty {
+            println!("Result in type namespace: {}", t.id());
+            pretty_handle(t)?;
+        }
+        if let Some(v) = value {
+            println!("Result in value namespace: {}", v.id());
+            pretty_handle(v)?;
+        }
+
+        Ok(Response::Accept)
+    })
+}
+
+fn resolve_all(prj: &mut Project) -> Result<(), Box<dyn Error>> {
+    prj.resolve_imports()?;
+    for id in prj.pool.keys() {
+        resolve(prj, id)?;
+    }
+    println!("Types resolved successfully!");
+    Ok(())
+}
+
+fn list_types(prj: &mut Project) {
+    println!("     name\x1b[30G  type");
+    for (idx, key) in prj.pool.keys().enumerate() {
+        let Def { node: Node { vis, kind: source, .. }, .. } = &prj[key];
+        let name = match source.as_ref().map(NodeSource::name) {
+            Some(Some(name)) => name,
+            _ => "".into(),
+        };
+        print!(
+            "{idx:3}: {vis}{name}\x1b[30G = {}",
+            key.handle_unchecked(prj)
+        );
+        println!();
+    }
+}
+
+fn pretty_handle(handle: Handle) -> Result<(), std::io::Error> {
+    use std::io::Write;
+    let mut stdout = std::io::stdout().lock();
+    let Some(Def { module, node: Node { vis, .. }, .. }) = handle.get() else {
+        return writeln!(stdout, "Invalid handle: {handle}");
+    };
+    writeln!(stdout, "{C_LISTING}{vis}{handle}\x1b[0m: {}", handle.id())?;
+    if let Some(parent) = module.parent {
+        writeln!(stdout, "{C_LISTING}Parent\x1b[0m: {}", handle.with(parent))?;
+    }
+    if !module.types.is_empty() {
+        writeln!(stdout, "{C_LISTING}Types:\x1b[0m")?;
+        for (name, def) in &module.types {
+            writeln!(stdout, "- {C_LISTING}{name}\x1b[0m: {}", handle.with(*def))?
+        }
+    }
+    if !module.values.is_empty() {
+        writeln!(stdout, "{C_LISTING}Values:\x1b[0m")?;
+        for (name, def) in &module.values {
+            writeln!(stdout, "- {C_LISTING}{name}\x1b[0m: {}", handle.with(*def))?
+        }
+    }
+    write!(stdout, "\x1b[0m")
+}
+
+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 clear() -> Result<(), Box<dyn Error>> {
+    println!("\x1b[H\x1b[2J");
+    banner();
+    Ok(())
+}
+
+fn banner() {
+    println!(
+        "--- {} v{} 💪🦈 ---",
+        env!("CARGO_BIN_NAME"),
+        env!("CARGO_PKG_VERSION"),
+    );
+}
+
+/// Keeps leaked references to past ASTs, for posterity:tm:
+struct TreeManager {
+    trees: Vec<&'static cl_ast::File>,
+}
+
+impl TreeManager {
+    const fn new() -> Self {
+        Self { trees: vec![] }
+    }
+    fn push(&mut self, tree: cl_ast::File) -> &'static cl_ast::File {
+        let ptr = Box::leak(Box::new(tree));
+        self.trees.push(ptr);
+        ptr
+    }
+}

compiler/cl-typeck/src/definition.rs

@@ -0,0 +1,193 @@
+use crate::{
+    handle::DefID,
+    module::Module,
+    node::{Node, NodeSource},
+};
+use cl_ast::{Meta, Sym, Visibility};
+use std::{fmt::Debug, str::FromStr};
+
+mod display;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Def<'a> {
+    pub node: Node<'a>,
+    pub kind: DefKind,
+    pub module: Module,
+}
+
+impl<'a> Def<'a> {
+    pub fn with_node(node: Node<'a>) -> Self {
+        Self { node, kind: DefKind::Undecided, module: Default::default() }
+    }
+}
+
+impl Def<'_> {
+    pub fn name(&self) -> Option<Sym> {
+        match self.node.kind {
+            Some(source) => source.name(),
+            None => None,
+        }
+    }
+
+    pub fn is_transparent(&self) -> bool {
+        !matches!(self.kind, DefKind::Type(_))
+    }
+}
+
+mod builder_functions {
+    use super::*;
+
+    impl<'a> Def<'a> {
+        pub fn set_vis(&mut self, vis: Visibility) -> &mut Self {
+            self.node.vis = vis;
+            self
+        }
+        pub fn set_meta(&mut self, meta: &'a [Meta]) -> &mut Self {
+            self.node.meta = meta;
+            self
+        }
+        pub fn set_kind(&mut self, kind: DefKind) -> &mut Self {
+            self.kind = kind;
+            self
+        }
+        pub fn set_source(&mut self, source: NodeSource<'a>) -> &mut Self {
+            self.node.kind = Some(source);
+            self
+        }
+        pub fn set_module(&mut self, module: Module) -> &mut Self {
+            self.module = module;
+            self
+        }
+    }
+}
+
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
+pub enum DefKind {
+    /// An unevaluated definition
+    #[default]
+    Undecided,
+    /// An impl block
+    Impl(DefID),
+    /// A use tree, and its parent
+    Use(DefID),
+    /// A type, such as a `type`, `struct`, or `enum`
+    Type(TypeKind),
+    /// A value, such as a `const`, `static`, or `fn`
+    Value(ValueKind),
+}
+
+/// A [ValueKind] represents an item in the Value Namespace
+/// (a component of a [Project](crate::project::Project)).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ValueKind {
+    Const(DefID),
+    Static(DefID),
+    Local(DefID),
+    Fn(DefID),
+}
+/// A [TypeKind] represents an item in the Type Namespace
+/// (a component of a [Project](crate::project::Project)).
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum TypeKind {
+    /// An alias for an already-defined type
+    Alias(Option<DefID>),
+    /// A primitive type, built-in to the compiler
+    Intrinsic(Intrinsic),
+    /// A user-defined aromatic data type
+    Adt(Adt),
+    /// A reference to an already-defined type: &T
+    Ref(u16, DefID),
+    /// A contiguous view of dynamically sized memory
+    Slice(DefID),
+    /// A contiguous view of statically sized memory
+    Array(DefID, usize),
+    /// A tuple of existing types
+    Tuple(Vec<DefID>),
+    /// A function which accepts multiple inputs and produces an output
+    FnSig { args: DefID, rety: DefID },
+    /// The unit type
+    Empty,
+    /// The never type
+    Never,
+    /// 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, Option<DefID>)>),
+    /// A C-like enum
+    CLikeEnum(Vec<(Sym, u128)>),
+    /// An enum with no fields, which can never be constructed
+    FieldlessEnum,
+
+    /// A structural product type with named members
+    Struct(Vec<(Sym, Visibility, DefID)>),
+    /// A structural product type with unnamed members
+    TupleStruct(Vec<(Visibility, DefID)>),
+    /// 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, DefID)>),
+}
+
+/// The set of compiler-intrinsic types.
+/// These primitive types have native implementations of the basic operations.
+#[allow(non_camel_case_types)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Intrinsic {
+    /// An 8-bit signed integer: `#[intrinsic = "i8"]`
+    I8,
+    /// A 16-bit signed integer: `#[intrinsic = "i16"]`
+    I16,
+    /// A 32-bit signed integer: `#[intrinsic = "i32"]`
+    I32,
+    /// A 64-bit signed integer: `#[intrinsic = "i32"]`
+    I64,
+    // /// A 128-bit signed integer: `#[intrinsic = "i32"]`
+    // I128,
+    /// A ptr-len signed integer: `#[intrinsic = "isize"]`
+    Isize,
+    /// An 8-bit unsigned integer: `#[intrinsic = "u8"]`
+    U8,
+    /// A 16-bit unsigned integer: `#[intrinsic = "u16"]`
+    U16,
+    /// A 32-bit unsigned integer: `#[intrinsic = "u32"]`
+    U32,
+    /// A 64-bit unsigned integer: `#[intrinsic = "u64"]`
+    U64,
+    // /// A 128-bit unsigned integer: `#[intrinsic = "u128"]`
+    // U128,
+    /// A ptr-len unsigned integer: `#[intrinsic = "isize"]`
+    Usize,
+    /// A boolean (`true` or `false`): `#[intrinsic = "bool"]`
+    Bool,
+    /// The unicode codepoint type: #[intrinsic = "char"]
+    Char,
+}
+
+impl FromStr for Intrinsic {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(match s {
+            "i8" => Intrinsic::I8,
+            "i16" => Intrinsic::I16,
+            "i32" => Intrinsic::I32,
+            "i64" => Intrinsic::I64,
+            "isize" => Intrinsic::Isize,
+            "u8" => Intrinsic::U8,
+            "u16" => Intrinsic::U16,
+            "u32" => Intrinsic::U32,
+            "u64" => Intrinsic::U64,
+            "usize" => Intrinsic::Usize,
+            "bool" => Intrinsic::Bool,
+            "char" => Intrinsic::Char,
+            _ => Err(())?,
+        })
+    }
+}

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

@@ -0,0 +1,147 @@
+//! [Display] implementations for [TypeKind], [Adt], and [Intrinsic]
+
+use super::{Adt, Def, DefKind, Intrinsic, TypeKind, ValueKind};
+use crate::{format_utils::*, node::Node};
+use cl_ast::format::FmtAdapter;
+use std::fmt::{self, Display, Write};
+
+impl Display for Def<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { module, node: Node { in_path: _, span: _, meta, vis, kind: source }, kind } =
+            self;
+        if !meta.is_empty() {
+            writeln!(f, "#{meta:?}")?;
+        }
+        if let Some(source) = source {
+            if let Some(name) = source.name() {
+                writeln!(f, "{vis}{name}:")?;
+            }
+            writeln!(f.indent(), "source:\n{source}")?;
+        } else {
+            writeln!(f, "{vis}: ")?;
+        }
+        writeln!(f, "kind: {kind}")?;
+        write!(f, "module: {module}")
+    }
+}
+
+impl Display for DefKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            DefKind::Undecided => write!(f, "undecided"),
+            DefKind::Impl(id) => write!(f, "impl {id}"),
+            DefKind::Use(id) => write!(f, "use (inside {id})"),
+            DefKind::Type(kind) => write!(f, "{kind}"),
+            DefKind::Value(kind) => write!(f, "{kind}"),
+        }
+    }
+}
+
+impl std::fmt::Display for ValueKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ValueKind::Const(id) => write!(f, "const ({id})"),
+            ValueKind::Static(id) => write!(f, "static ({id})"),
+            ValueKind::Local(id) => write!(f, "let ({id})"),
+            ValueKind::Fn(id) => write!(f, "fn def ({id})"),
+        }
+    }
+}
+
+impl Display for TypeKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            TypeKind::Alias(def) => match def {
+                Some(def) => write!(f, "alias to #{def}"),
+                None => f.write_str("type"),
+            },
+            TypeKind::Intrinsic(i) => i.fmt(f),
+            TypeKind::Adt(a) => a.fmt(f),
+            TypeKind::Ref(cnt, def) => {
+                for _ in 0..*cnt {
+                    f.write_str("&")?;
+                }
+                def.fmt(f)
+            }
+            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::Empty => f.write_str("()"),
+            TypeKind::Never => f.write_str("!"),
+            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<_>| match def {
+                        Some(def) => write!(f, "{name}: #{def}"),
+                        None => write!(f, "{name}"),
+                    })
+                })(f.delimit_with("enum {", "}"))
+            }
+            Adt::CLikeEnum(variants) => {
+                let mut variants = variants.iter();
+                separate(", ", || {
+                    let (name, descrim) = variants.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{name} = {descrim}"))
+                })(f.delimit_with("enum {", "}"))
+            }
+            Adt::FieldlessEnum => write!(f, "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 Intrinsic {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Intrinsic::I8 => f.write_str("i8"),
+            Intrinsic::I16 => f.write_str("i16"),
+            Intrinsic::I32 => f.write_str("i32"),
+            Intrinsic::I64 => f.write_str("i64"),
+            Intrinsic::Isize => f.write_str("isize"),
+            Intrinsic::U8 => f.write_str("u8"),
+            Intrinsic::U16 => f.write_str("u16"),
+            Intrinsic::U32 => f.write_str("u32"),
+            Intrinsic::U64 => f.write_str("u64"),
+            Intrinsic::Usize => f.write_str("usize"),
+            Intrinsic::Bool => f.write_str("bool"),
+            Intrinsic::Char => f.write_str("char"),
+        }
+    }
+}

compiler/cl-typeck/src/format_utils.rs

@@ -0,0 +1,23 @@
+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 +1,187 @@
+use crate::{definition::Def, path::Path, project::Project};
+use cl_structures::index_map::*;
+
+// define the index types
+make_index! {
+    /// Uniquely represents a [Def][1] in the [Def][1] [Pool]
+    ///
+    /// [1]: crate::definition::Def
+    DefID,
+}
+
+/// A handle to a certain [Def] within a [Project]
+#[derive(Clone, Copy, Debug)]
+pub struct Handle<'prj, 'code> {
+    id: DefID,
+    prj: &'prj Project<'code>,
+}
+
+impl DefID {
+    /// Constructs a new [Handle] from this DefID and the provided [Project].
+    pub fn handle<'p, 'c>(self, prj: &'p Project<'c>) -> Option<Handle<'p, 'c>> {
+        Handle::new(self, prj)
+    }
+
+    /// Constructs a new [Handle] from this DefID and the provided [Project]
+    pub fn handle_unchecked<'p, 'c>(self, prj: &'p Project<'c>) -> Handle<'p, 'c> {
+        Handle::new_unchecked(self, prj)
+    }
+}
+
+impl<'p, 'c> Handle<'p, 'c> {
+    /// Constructs a new Handle from the provided [DefID] and [Project].
+    /// Returns [Some]\(Handle) if the [DefID] exists in the [Project].
+    pub fn new(id: DefID, prj: &'p Project<'c>) -> Option<Self> {
+        prj.pool.get(id).is_some().then_some(Self { id, prj })
+    }
+
+    /// Constructs a new Handle from the provided [DefID] and [Project] without checking membership.
+    /// Using the handle may cause panics or other unwanted (but defined) behavior.
+    pub fn new_unchecked(id: DefID, prj: &'p Project<'c>) -> Self {
+        Self { id, prj }
+    }
+
+    /// Gets the [Def] this handle points to.
+    pub fn get(self) -> Option<&'p Def<'c>> {
+        self.prj.pool.get(self.id)
+    }
+
+    pub fn navigate(self, path: Path) -> (Option<Self>, Option<Self>) {
+        match self.prj.get(path, self.id) {
+            Some((Some(ty), Some(vl), _)) => (Some(self.with(ty)), Some(self.with(vl))),
+            Some((_, Some(vl), _)) => (None, Some(self.with(vl))),
+            Some((Some(ty), _, _)) => (Some(self.with(ty)), None),
+            _ => (None, None),
+        }
+    }
+
+    /// Gets the [Project] this handle points to.
+    pub fn project(self) -> &'p Project<'c> {
+        self.prj
+    }
+
+    pub fn id(self) -> DefID {
+        self.id
+    }
+
+    // TODO: get parent, children, etc.
+
+    /// Gets a handle to the other ID within the same project
+    pub fn with(self, id: DefID) -> Self {
+        Self { id, ..self }
+    }
+}
+
+mod display {
+    use super::*;
+    use crate::{definition::*, format_utils::*};
+    use std::fmt::{self, Display, Write};
+
+    impl Display for DefID {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            self.0.fmt(f)
+        }
+    }
+
+    impl Display for Handle<'_, '_> {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            let Self { id, prj } = *self;
+            let Some(def) = prj.pool.get(id) else {
+                return write!(f, "<invalid type: {id}>");
+            };
+
+            // Match the type
+            match &def.kind {
+                DefKind::Undecided => write!(f, "<undecided>"),
+                DefKind::Impl(id) => write!(f, "impl {}", self.with(*id)),
+                DefKind::Use(id) => write!(f, "use inside {}", self.with(*id)),
+                DefKind::Type(kind) => match kind {
+                    TypeKind::Alias(None) => write!(f, "type"),
+                    TypeKind::Alias(Some(id)) => write!(f, "{}", self.with(*id)),
+                    TypeKind::Intrinsic(intrinsic) => write!(f, "{intrinsic}"),
+                    TypeKind::Adt(adt) => display_adt(self, adt, f),
+                    TypeKind::Ref(count, id) => {
+                        for _ in 0..*count {
+                            f.write_char('&')?;
+                        }
+                        self.with(*id).fmt(f)
+                    }
+                    TypeKind::Array(id, size) => {
+                        write!(f.delimit_with("[", "]"), "{}; {size}", self.with(*id))
+                    }
+                    TypeKind::Slice(id) => write!(f.delimit_with("[", "]"), "{}", self.with(*id)),
+                    TypeKind::Tuple(ids) => {
+                        let mut ids = ids.iter();
+                        separate(", ", || {
+                            let id = ids.next()?;
+                            Some(move |f: &mut Delimit<_>| write!(f, "{}", self.with(*id)))
+                        })(f.delimit_with("(", ")"))
+                    }
+                    TypeKind::FnSig { args, rety } => {
+                        write!(f, "fn {} -> {}", self.with(*args), self.with(*rety))
+                    }
+                    TypeKind::Empty => write!(f, "()"),
+                    TypeKind::Never => write!(f, "!"),
+                    TypeKind::Module => match def.name() {
+                        Some(name) => write!(f, "mod {name}"),
+                        None => write!(f, "mod"),
+                    },
+                },
+
+                DefKind::Value(kind) => match kind {
+                    ValueKind::Const(id) => write!(f, "const {}", self.with(*id)),
+                    ValueKind::Static(id) => write!(f, "static {}", self.with(*id)),
+                    ValueKind::Local(id) => write!(f, "local {}", self.with(*id)),
+                    ValueKind::Fn(id) => write!(f, "{}", self.with(*id)),
+                },
+            }
+        }
+    }
+
+    /// Formats an ADT: a continuation of [Handle::fmt]
+    fn display_adt(handle: &Handle, adt: &Adt, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match adt {
+            Adt::Enum(variants) => {
+                let mut variants = variants.iter();
+                separate(",", || {
+                    variants.next().map(|(name, def)| {
+                        move |f: &mut Delimit<_>| match def {
+                            Some(def) => write!(f, "\n{name}: {}", handle.with(*def)),
+                            None => write!(f, "\n{name}"),
+                        }
+                    })
+                })(f.delimit_with("enum {", "\n}"))
+            }
+            Adt::CLikeEnum(variants) => {
+                let mut variants = variants.iter();
+                separate(",", || {
+                    let (name, descrim) = variants.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "\n{name} = {descrim}"))
+                })(f.delimit_with("enum {", "\n}"))
+            }
+            Adt::FieldlessEnum => write!(f, "enum"),
+            Adt::Struct(members) => {
+                let mut members = members.iter();
+                separate(",", || {
+                    let (name, vis, id) = members.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "\n{vis}{name}: {}", handle.with(*id)))
+                })(f.delimit_with("struct {", "\n}"))
+            }
+            Adt::TupleStruct(members) => {
+                let mut members = members.iter();
+                separate(", ", || {
+                    let (vis, def) = members.next()?;
+                    Some(move |f: &mut Delimit<_>| write!(f, "{vis}{}", handle.with(*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, "\n{name}: {}", handle.with(*def)))
+                })(f.delimit_with("union {", "\n}"))
+            }
+        }
+    }
+}

compiler/cl-typeck/src/inference.rs

@@ -0,0 +1,248 @@
+//! 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
+
+use cl_ast::Sym;
+use core::fmt;
+use std::{cell::RefCell, rc::Rc};
+
+/*
+    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!
+*/
+
+/// A refcounted [Type]
+pub type RcType = Rc<Type>;
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct Variable {
+    pub instance: RefCell<Option<RcType>>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct Operator {
+    name: Sym,
+    types: RefCell<Vec<RcType>>,
+}
+
+/// A [Type::Variable] or [Type::Operator]:
+/// - A [Type::Variable] can be either bound or unbound (instance: Some(_) | None)
+/// - A [Type::Operator] has a name (used to identify the operator) and a list of types.
+///
+/// A type which contains unbound variables is considered "generic" (see
+/// [`Type::is_generic()`]).
+#[derive(Debug, PartialEq, Eq)]
+pub enum Type {
+    Variable(Variable),
+    Operator(Operator),
+}
+
+impl Type {
+    /// Creates a new unbound [type variable](Type::Variable)
+    pub fn new_var() -> RcType {
+        Rc::new(Self::Variable(Variable { instance: RefCell::new(None) }))
+    }
+    /// Creates a variable that is a new instance of another [Type]
+    pub fn new_inst(of: &RcType) -> RcType {
+        Rc::new(Self::Variable(Variable {
+            instance: RefCell::new(Some(of.clone())),
+        }))
+    }
+    /// Creates a new [type operator](Type::Operator)
+    pub fn new_op(name: Sym, types: &[RcType]) -> RcType {
+        Rc::new(Self::Operator(Operator {
+            name,
+            types: RefCell::new(types.to_vec()),
+        }))
+    }
+    /// Creates a new [type operator](Type::Operator) representing a lambda
+    pub fn new_fn(takes: &RcType, returns: &RcType) -> RcType {
+        Self::new_op("fn".into(), &[takes.clone(), returns.clone()])
+    }
+    /// Creates a new [type operator](Type::Operator) representing a primitive type
+    pub fn new_prim(name: Sym) -> RcType {
+        Self::new_op(name, &[])
+    }
+    /// Creates a new [type operator](Type::Operator) representing a tuple
+    pub fn new_tuple(members: &[RcType]) -> RcType {
+        Self::new_op("tuple".into(), members)
+    }
+
+    /// Sets this type variable to be an instance `of` the other
+    /// # Panics
+    /// Panics if `self` is not a type variable
+    pub fn set_instance(self: &RcType, of: &RcType) {
+        match self.as_ref() {
+            Type::Operator(_) => unimplemented!("Cannot set instance of a type operator"),
+            Type::Variable(Variable { instance }) => *instance.borrow_mut() = Some(of.clone()),
+        }
+    }
+    /// Checks whether there are any unbound type variables in this type.
+    /// ```rust
+    /// # use cl_typeck::inference::*;
+    /// let bool = Type::new_op("bool".into(), &[]);
+    /// let true_v = Type::new_inst(&bool);
+    /// let unbound = Type::new_var();
+    /// let id_fun = Type::new_fn(&unbound, &unbound);
+    /// let truthy = Type::new_fn(&unbound, &bool);
+    /// assert!(!bool.is_generic());   // bool contains no unbound type variables
+    /// assert!(!true_v.is_generic()); // true_v is bound to `bool`
+    /// assert!(unbound.is_generic()); // unbound is an unbound type variable
+    /// assert!(id_fun.is_generic());  // id_fun is a function with unbound type variables
+    /// assert!(truthy.is_generic());  // truthy is a function with one unbound type variable
+    /// ```
+    pub fn is_generic(self: &RcType) -> bool {
+        match self.as_ref() {
+            Type::Variable(Variable { instance }) => match instance.borrow().as_ref() {
+                // base case: self is an unbound type variable (instance is none)
+                None => true,
+                // Variable is bound to a type which may be generic
+                Some(instance) => instance.is_generic(),
+            },
+            Type::Operator(Operator { types, .. }) => {
+                // Operator may have generic args
+                types.borrow().iter().any(Self::is_generic)
+            }
+        }
+    }
+    /// Makes a deep copy of a type expression.
+    ///
+    /// Bound variables are shared, unbound variables are duplicated.
+    pub fn deep_clone(self: &RcType) -> RcType {
+        // If there aren't any unbound variables, it's fine to clone the entire expression
+        if !self.is_generic() {
+            return self.clone();
+        }
+        // There are unbound type variables, so we make a new one
+        match self.as_ref() {
+            Type::Variable { .. } => Self::new_var(),
+            Type::Operator(Operator { name, types }) => Self::new_op(
+                *name,
+                &types
+                    .borrow()
+                    .iter()
+                    .map(Self::deep_clone)
+                    .collect::<Vec<_>>(),
+            ),
+        }
+    }
+    /// Returns the defining instance of `self`,
+    /// collapsing type instances along the way.
+    /// # May panic
+    /// Panics if this type variable's instance field is already borrowed.
+    /// # Examples
+    /// ```rust
+    /// # use cl_typeck::inference::*;
+    /// let t_bool = Type::new_op("bool".into(), &[]);
+    /// let t_nest = Type::new_inst(&Type::new_inst(&Type::new_inst(&t_bool)));
+    /// let pruned = t_nest.prune();
+    /// assert_eq!(pruned, t_bool);
+    /// assert_eq!(t_nest, Type::new_inst(&t_bool));
+    /// ```
+    pub fn prune(self: &RcType) -> RcType {
+        if let Type::Variable(Variable { instance }) = self.as_ref() {
+            if let Some(old_inst) = instance.borrow_mut().as_mut() {
+                let new_inst = old_inst.prune(); // get defining instance
+                *old_inst = new_inst.clone(); // collapse
+                return new_inst;
+            }
+        }
+        self.clone()
+    }
+
+    /// Checks whether a type expression occurs in another type expression
+    ///
+    /// # 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: &RcType, other: &RcType) -> bool {
+        if self == other {
+            return true;
+        }
+        match other.as_ref() {
+            Type::Variable(Variable { instance }) => match instance.borrow().as_ref() {
+                Some(t) => self.occurs_in(t),
+                None => false,
+            },
+            Type::Operator(Operator { types, .. }) => {
+                // Note: this might panic.
+                // Think about whether it panics for only recursive types?
+                types.borrow().iter().any(|other| self.occurs_in(other))
+            }
+        }
+    }
+
+    /// Unifies two type expressions, propagating changes via interior mutability
+    pub fn unify(self: &RcType, other: &RcType) -> Result<(), InferenceError> {
+        let (a, b) = (self.prune(), other.prune()); // trim the hedges
+        match (a.as_ref(), b.as_ref()) {
+            (Type::Variable { .. }, _) if !a.occurs_in(&b) => a.set_instance(&b),
+            (Type::Variable { .. }, _) => Err(InferenceError::Recursive(a, b))?,
+            (Type::Operator { .. }, Type::Variable { .. }) => b.unify(&a)?,
+            (
+                Type::Operator(Operator { name: a_name, types: a_types }),
+                Type::Operator(Operator { name: b_name, types: b_types }),
+            ) => {
+                let (a_types, b_types) = (a_types.borrow(), b_types.borrow());
+                if a_name != b_name || a_types.len() != b_types.len() {
+                    Err(InferenceError::Mismatch(a.clone(), b.clone()))?
+                }
+                for (a, b) in a_types.iter().zip(b_types.iter()) {
+                    a.unify(b)?
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+impl fmt::Display for Type {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Type::Variable(Variable { instance }) => match instance.borrow().as_ref() {
+                Some(instance) => write!(f, "{instance}"),
+                None => write!(f, "_"),
+            },
+            Type::Operator(Operator { name, types }) => {
+                write!(f, "({name}")?;
+                for ty in types.borrow().iter() {
+                    write!(f, " {ty}")?;
+                }
+                f.write_str(")")
+            }
+        }
+    }
+}
+
+/// An error produced during type inference
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum InferenceError {
+    Mismatch(RcType, RcType),
+    Recursive(RcType, RcType),
+}
+
+impl fmt::Display for InferenceError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            InferenceError::Mismatch(a, b) => write!(f, "Type mismatch: {a:?} != {b:?}"),
+            InferenceError::Recursive(_, _) => write!(f, "Recursive type!"),
+        }
+    }
+}

compiler/cl-typeck/src/lib.rs

@@ -0,0 +1,157 @@
+//! # 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 [Project](project::Project)™
+//! Contains [item definitions](definition) and type expression information.
+//!
+//! *Every* definition is itself a module, and can contain arbitrarily nested items
+//! as part of the [Module](module::Module) tree.
+//!
+//! The Project keeps track of a *global intern pool* of definitions, which are
+//! trivially comparable by [DefID](key::DefID). Note that, for item definitions,
+//! identical types in different modules DO NOT COMPARE EQUAL under this constraint.
+//! However, so-called "anonymous" types *do not* follow this rule, as their
+//! definitions are constructed dynamically and ensured to be unique.
+// Note: it's a class invariant that named types are not added
+// to the anon-types list. Please keep it that way. ♥  Thanks!
+//!
+//! # Namespaces
+//! Within a Project, [definitions](definition::Def) are classified into two namespaces:
+//!
+//! ## Type Namespace:
+//! - Modules
+//! - Structs
+//! - Enums
+//! - Type aliases
+//!
+//! ## Value Namespace:
+//! - Functions
+//! - Constants
+//! - Static variables
+//!
+//! There is a *key* distinction between the two namespaces when it comes to
+//! [Path](path::Path) traversal: Only items in the Type Namespace will be considered
+//! as an intermediate path target. This means items in the Value namespace are
+//! entirely *opaque*, and form a one-way barrier. Items outside a Value can be
+//! referred to within the Value, but items inside a Value *cannot* be referred to
+//! outside the Value.
+//!
+//! # Order of operations:
+//! Currently, the process of type resolution goes as follows:
+//!
+//! 1. Traverse the AST, [collecting all Items into item definitions](name_collector)
+//! 2. Eagerly [resolve `use` imports](use_importer)
+//! 3. Traverse all [definitions](definition::Def), and [resolve the types for every
+//!    item](type_resolver)
+//! 4. TODO: Construct a typed AST for expressions, and type-check them
+#![warn(clippy::all)]
+
+/*
+How do I flesh out modules in an incremental way?
+
+1. Visit all *modules* and create nodes in a module tree for them
+- This can be done by holding mutable references to submodules!
+
+
+Module:
+    values: Map(name -> Value),
+    types: Map(name -> Type),
+
+Value: Either
+    function: { signature: Type, body: FunctionBody }
+    static: { Mutability, ty: Type, init: ConstEvaluationResult }
+    const: { ty: Type, init: ConstEvaluationResult }
+
+*/
+
+pub mod handle;
+
+pub mod node;
+
+pub mod definition;
+
+pub mod module;
+
+pub mod path;
+
+pub mod project;
+
+pub mod name_collector;
+
+pub mod use_importer;
+
+pub mod type_resolver;
+
+pub mod inference;
+
+pub(crate) mod format_utils;
+
+/*
+
+LET THERE BE NOTES:
+
+/// What is an inference rule?
+/// An inference rule is a specification with a set of predicates and a judgement
+
+/// Let's give every type an ID
+struct TypeID(usize);
+
+/// Let's give every type some data:
+
+struct TypeDef<'def> {
+    name: String,
+    definition: &'def Item,
+}
+
+and store them in a big vector of type descriptions:
+
+struct TypeMap<'def> {
+    types: Vec<TypeDef<'def>>,
+}
+// todo: insertion of a type should yield a TypeID
+// todo: impl index with TypeID
+
+Let's store type information as either a concrete type or a generic type:
+
+/// The Type struct represents all valid types, and can be trivially equality-compared
+pub struct Type {
+    /// You can only have a pointer chain 65535 pointers long.
+    ref_depth: u16,
+    kind: TKind,
+}
+pub enum TKind {
+    Concrete(TypeID),
+    Generic(usize),
+}
+
+And assume I can specify a rule based on its inputs and outputs:
+
+Rule {
+    operation: If,
+    /// The inputs field is populated by
+    inputs: [Concrete(BOOL), Generic(0), Generic(0)],
+    outputs: Generic(0),
+    /// This rule is compiler-intrinsic!
+    through: None,
+}
+
+Rule {
+    operation: Add,
+    inputs: [Concrete(I32), Concrete(I32)],
+    outputs: Concrete(I32),
+    /// This rule is not compiler-intrinsic (it is overloaded!)
+    through: Some(&ImplAddForI32::Add),
+}
+
+
+
+These rules can be stored in some kind of rule database:
+
+let rules: Hashmap<Operation, Vec<Rule>> {
+
+}
+
+*/

compiler/cl-typeck/src/module.rs

@@ -0,0 +1,71 @@
+//! A [Module] is a node in the Module Tree (a component of a
+//! [Project](crate::project::Project))
+use cl_ast::Sym;
+use cl_structures::index_map::MapIndex;
+
+use crate::handle::DefID;
+use std::collections::HashMap;
+
+/// A [Module] is a node in the Module Tree (a component of a
+/// [Project](crate::project::Project)).
+#[derive(Clone, Debug, Default, PartialEq, Eq)]
+pub struct Module {
+    pub parent: Option<DefID>,
+    pub types: HashMap<Sym, DefID>,
+    pub values: HashMap<Sym, DefID>,
+    pub imports: Vec<DefID>,
+}
+
+impl Module {
+    pub fn new(parent: DefID) -> Self {
+        Self { parent: Some(parent), ..Default::default() }
+    }
+    pub fn with_optional_parent(parent: Option<DefID>) -> Self {
+        Self { parent, ..Default::default() }
+    }
+
+    pub fn get(&self, name: Sym) -> (Option<DefID>, Option<DefID>) {
+        (self.get_type(name), self.get_value(name))
+    }
+    pub fn get_type(&self, name: Sym) -> Option<DefID> {
+        self.types.get(&name).copied()
+    }
+    pub fn get_value(&self, name: Sym) -> Option<DefID> {
+        self.values.get(&name).copied()
+    }
+
+    /// Inserts a type with the provided [name](str) and [id](DefID)
+    pub fn insert_type(&mut self, name: Sym, id: DefID) -> Option<DefID> {
+        self.types.insert(name, id)
+    }
+
+    /// Inserts a value with the provided [name](str) and [id](DefID)
+    pub fn insert_value(&mut self, name: Sym, id: DefID) -> Option<DefID> {
+        self.values.insert(name, id)
+    }
+}
+
+impl std::fmt::Display for Module {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let Self { parent, types, values, imports } = self;
+        if let Some(parent) = parent {
+            writeln!(f, "Parent: {}", parent.get())?;
+        }
+        for (name, table) in [("Types", types), ("Values", values)] {
+            if table.is_empty() {
+                continue;
+            }
+            writeln!(f, "{name}:")?;
+            for (name, id) in table.iter() {
+                writeln!(f, "    {name} => {id}")?;
+            }
+        }
+        if !imports.is_empty() {
+            write!(f, "Imports:")?;
+            for id in imports {
+                write!(f, "{id},")?;
+            }
+        }
+        Ok(())
+    }
+}

compiler/cl-typeck/src/name_collector.rs

@@ -0,0 +1,218 @@
+//! Performs step 1 of type checking: Collecting all the names of things into [Module] units
+use crate::{
+    definition::{Def, DefKind},
+    handle::DefID,
+    module::Module as Mod,
+    node::{Node, NodeSource},
+    project::Project as Prj,
+};
+use cl_ast::{ast_visitor::Visit, *};
+use std::mem;
+
+#[derive(Debug)]
+pub struct NameCollector<'prj, 'a> {
+    path: cl_ast::Path,
+    prj: &'prj mut Prj<'a>,
+    parent: DefID,
+    retval: Option<DefID>,
+}
+
+impl<'prj, 'a> NameCollector<'prj, 'a> {
+    /// Constructs a new [NameCollector] out of a [Project](Prj)
+    pub fn new(prj: &'prj mut Prj<'a>) -> Self {
+        Self { parent: prj.root, prj, path: Default::default(), retval: None }
+    }
+    /// Constructs a new [NameCollector] out of a [Project](Prj) and a parent [DefID]
+    pub fn with_root(prj: &'prj mut Prj<'a>, parent: DefID) -> Self {
+        Self { prj, parent, path: Default::default(), retval: None }
+    }
+    /// Runs the provided function with the given parent
+    pub fn with_parent<F, N>(&mut self, parent: DefID, node: N, f: F)
+    where F: FnOnce(&mut Self, N) {
+        let parent = mem::replace(&mut self.parent, parent);
+        f(self, node);
+        self.parent = parent;
+    }
+    /// Extracts the return value from the provided function
+    pub fn returns<F, N>(&mut self, node: N, f: F) -> Option<DefID>
+    where F: FnOnce(&mut Self, N) {
+        let out = self.retval.take();
+        f(self, node);
+        mem::replace(&mut self.retval, out)
+    }
+}
+
+impl<'prj, 'a> Visit<'a> for NameCollector<'prj, 'a> {
+    fn visit_item(&mut self, i: &'a Item) {
+        let Item { extents: _, attrs, vis, kind } = i;
+        if let Some(def) = self.returns(kind, Self::visit_item_kind) {
+            self.prj[def].set_meta(&attrs.meta).set_vis(*vis);
+        }
+    }
+    fn visit_module(&mut self, m: &'a Module) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Module { name, kind } = m;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Module(m))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_type(*name, id);
+        self.path.push(PathPart::Ident(*name));
+        self.with_parent(id, kind, Self::visit_module_kind);
+        self.path.pop();
+        self.retval = Some(id);
+    }
+    fn visit_alias(&mut self, a: &'a Alias) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Alias { to: name, from: _ } = a;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Alias(a))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_type(*name, id);
+
+        self.retval = Some(id);
+    }
+    fn visit_enum(&mut self, e: &'a Enum) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Enum { name, kind } = e;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Enum(e))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_type(*name, id);
+
+        self.with_parent(id, kind, Self::visit_enum_kind);
+        self.retval = Some(id);
+    }
+    fn visit_variant(&mut self, v: &'a Variant) {
+        let Self { path, prj, parent, retval: _ } = self;
+        let Variant { name, kind } = v;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Variant(v))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_type(*name, id);
+
+        self.with_parent(id, kind, Self::visit_variant_kind);
+        self.retval = Some(id);
+    }
+    fn visit_struct(&mut self, s: &'a Struct) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Struct { name, kind } = s;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Struct(s))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_type(*name, id);
+
+        self.with_parent(id, kind, Self::visit_struct_kind);
+        self.retval = Some(id);
+    }
+    fn visit_const(&mut self, c: &'a Const) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Const { name, ty: _, init } = c;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Const(c))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_value(*name, id);
+
+        self.with_parent(id, &**init, Self::visit_expr);
+        self.retval = Some(id);
+    }
+    fn visit_static(&mut self, s: &'a Static) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Static { name, mutable: _, ty: _, init } = s;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Static(s))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_value(*name, id);
+
+        self.with_parent(id, &**init, Self::visit_expr);
+        self.retval = Some(id);
+    }
+    fn visit_function(&mut self, f: &'a Function) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Function { name, body, .. } = f;
+
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Function(f))),
+        };
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_value(*name, id);
+
+        if let Some(body) = body {
+            self.with_parent(id, body, Self::visit_block);
+        }
+        self.retval = Some(id);
+    }
+    fn visit_impl(&mut self, i: &'a Impl) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Impl { target: _, body } = i;
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Impl(i))),
+        };
+        let id = prj.pool.insert(def);
+
+        // items will get reparented after name collection, when target is available
+        self.with_parent(id, body, Self::visit_file);
+
+        self.retval = Some(id);
+    }
+    fn visit_use(&mut self, u: &'a Use) {
+        let Self { prj, parent, path, retval } = self;
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Use(*parent),
+            node: Node::new(path.clone(), Some(NodeSource::Use(u))),
+        };
+
+        let id = prj.pool.insert(def);
+        prj[*parent].module.imports.push(id);
+
+        *retval = Some(id);
+    }
+    fn visit_let(&mut self, l: &'a Let) {
+        let Self { prj, parent, path, retval: _ } = self;
+        let Let { name, init, .. } = l;
+        let def = Def {
+            module: Mod::new(*parent),
+            kind: DefKind::Undecided,
+            node: Node::new(path.clone(), Some(NodeSource::Local(l))),
+        };
+
+        let id = prj.pool.insert(def);
+        prj[*parent].module.insert_value(*name, id);
+        if let Some(expr) = init {
+            self.visit_expr(expr)
+        }
+        self.retval = Some(id)
+    }
+}

compiler/cl-typeck/src/node.rs

@@ -0,0 +1,214 @@
+//! A [Node] contains the [NodeSource] and [Item] metadata for any
+//! [Def](crate::definition::Def), as well as the [Path] of the
+//! containing [Module].
+//!
+//! [Node]s are collected by the [Node Sorcerer](sorcerer),
+//! an AST visitor that pairs [NodeSource]s with their surrounding
+//! context ([Path], [struct@Span], [Meta], [Visibility])
+
+use cl_ast::ast::*;
+use cl_structures::span::Span;
+use std::fmt;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Node<'a> {
+    pub in_path: Path,
+    pub span: &'a Span,
+    pub meta: &'a [Meta],
+    pub vis: Visibility,
+    pub kind: Option<NodeSource<'a>>,
+}
+
+impl<'a> Node<'a> {
+    pub fn new(path: Path, kind: Option<NodeSource<'a>>) -> Self {
+        const DUMMY_SPAN: Span = Span::dummy();
+        Self { in_path: path, span: &DUMMY_SPAN, meta: &[], vis: Visibility::Public, kind }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum NodeSource<'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<'a> NodeSource<'a> {
+    pub fn name(&self) -> Option<Sym> {
+        match self {
+            NodeSource::Root => None,
+            NodeSource::Module(v) => Some(v.name),
+            NodeSource::Alias(v) => Some(v.to),
+            NodeSource::Enum(v) => Some(v.name),
+            NodeSource::Variant(v) => Some(v.name),
+            NodeSource::Struct(v) => Some(v.name),
+            NodeSource::Const(v) => Some(v.name),
+            NodeSource::Static(v) => Some(v.name),
+            NodeSource::Function(v) => Some(v.name),
+            NodeSource::Local(l) => Some(l.name),
+            NodeSource::Impl(_) | NodeSource::Use(_) | NodeSource::Ty(_) => None,
+        }
+    }
+
+    /// Returns `true` if this [NodeSource] defines a named value
+    pub fn is_named_value(&self) -> bool {
+        matches!(self, Self::Const(_) | Self::Static(_) | Self::Function(_))
+    }
+
+    /// Returns `true` if this [NodeSource] 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 [NodeSource] refers to a [Ty] with no name
+    pub fn is_anon_type(&self) -> bool {
+        matches!(self, Self::Ty(_))
+    }
+
+    /// Returns `true` if this [NodeSource] refers to an [Impl] block
+    pub fn is_impl(&self) -> bool {
+        matches!(self, Self::Impl(_))
+    }
+
+    /// Returns `true` if this [NodeSource] refers to a [Use] import
+    pub fn is_use_import(&self) -> bool {
+        matches!(self, Self::Use(_))
+    }
+}
+
+impl fmt::Display for NodeSource<'_> {
+    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),
+        }
+    }
+}
+
+pub mod sorcerer {
+    //! An [AST](cl_ast) analysis pass that collects [Node] entries.
+
+    use super::{Node, NodeSource};
+    use cl_ast::{ast::*, ast_visitor::visit::*};
+    use cl_structures::span::Span;
+    use std::mem;
+
+    /// An AST analysis pass that collects [Node]s
+    #[derive(Clone, Debug)]
+    pub struct NodeSorcerer<'a> {
+        path: Path,
+        parts: Parts<'a>,
+        defs: Vec<Node<'a>>,
+    }
+
+    type Parts<'a> = (&'a Span, &'a [Meta], Visibility);
+
+    impl<'a> NodeSorcerer<'a> {
+        pub fn into_defs(self) -> Vec<Node<'a>> {
+            self.defs
+        }
+
+        fn with_parts<F>(&mut self, s: &'a Span, a: &'a [Meta], v: Visibility, f: F)
+        where F: FnOnce(&mut Self) {
+            let parts = mem::replace(&mut self.parts, (s, a, v));
+            f(self);
+            self.parts = parts;
+        }
+
+        fn with_only_span<F>(&mut self, span: &'a Span, f: F)
+        where F: FnOnce(&mut Self) {
+            self.with_parts(span, &[], Visibility::Public, f)
+        }
+
+        fn push(&mut self, kind: NodeSource<'a>) {
+            let Self { path, parts, defs } = self;
+            let (span, meta, vis) = *parts;
+
+            defs.push(Node { in_path: path.clone(), span, meta, vis, kind: Some(kind) })
+        }
+    }
+
+    impl Default for NodeSorcerer<'_> {
+        fn default() -> Self {
+            const DPARTS: Parts = (&Span::dummy(), &[], Visibility::Private);
+            Self {
+                path: Path { absolute: true, ..Default::default() },
+                parts: DPARTS,
+                defs: Default::default(),
+            }
+        }
+    }
+
+    impl<'a> Visit<'a> for NodeSorcerer<'a> {
+        fn visit_module(&mut self, m: &'a Module) {
+            let Module { name, kind } = m;
+            self.path.push(PathPart::Ident(*name));
+            self.visit_module_kind(kind);
+            self.path.pop();
+        }
+        fn visit_item(&mut self, i: &'a Item) {
+            let Item { extents, attrs, vis, kind } = i;
+            self.with_parts(extents, &attrs.meta, *vis, |v| {
+                v.visit_item_kind(kind);
+            });
+        }
+        fn visit_ty(&mut self, t: &'a Ty) {
+            let Ty { extents, kind } = t;
+            self.with_only_span(extents, |v| {
+                v.push(NodeSource::Ty(kind));
+                v.visit_ty_kind(kind);
+            });
+        }
+        fn visit_stmt(&mut self, s: &'a Stmt) {
+            let Stmt { extents, kind, semi } = s;
+            self.with_only_span(extents, |d| {
+                d.visit_stmt_kind(kind);
+                d.visit_semi(semi);
+            })
+        }
+        fn visit_item_kind(&mut self, kind: &'a ItemKind) {
+            match kind {
+                ItemKind::Module(i) => self.push(NodeSource::Module(i)),
+                ItemKind::Alias(i) => self.push(NodeSource::Alias(i)),
+                ItemKind::Enum(i) => self.push(NodeSource::Enum(i)),
+                ItemKind::Struct(i) => self.push(NodeSource::Struct(i)),
+                ItemKind::Const(i) => self.push(NodeSource::Const(i)),
+                ItemKind::Static(i) => self.push(NodeSource::Static(i)),
+                ItemKind::Function(i) => self.push(NodeSource::Function(i)),
+                ItemKind::Impl(i) => self.push(NodeSource::Impl(i)),
+                ItemKind::Use(i) => self.push(NodeSource::Use(i)),
+            }
+            or_visit_item_kind(self, kind);
+        }
+        fn visit_stmt_kind(&mut self, kind: &'a StmtKind) {
+            if let StmtKind::Local(l) = kind {
+                self.push(NodeSource::Local(l))
+            }
+            or_visit_stmt_kind(self, kind);
+        }
+    }
+}

compiler/cl-typeck/src/path.rs

@@ -0,0 +1,60 @@
+//! A [Path] is a borrowed view of an [AST Path](AstPath)
+use cl_ast::{Path as AstPath, PathPart};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Path<'p> {
+    pub absolute: bool,
+    pub parts: &'p [PathPart],
+}
+
+impl<'p> Path<'p> {
+    pub fn new(path: &'p AstPath) -> Self {
+        let AstPath { absolute, parts } = path;
+        Self { absolute: *absolute, parts }
+    }
+    pub fn relative(self) -> Self {
+        Self { absolute: false, ..self }
+    }
+    pub fn pop_front(self) -> Option<Self> {
+        let Self { absolute, parts } = self;
+        Some(Self { absolute, parts: parts.get(1..)? })
+    }
+    pub fn front(self) -> Option<Self> {
+        let Self { absolute, parts } = self;
+        Some(Self { absolute, parts: parts.get(..1)? })
+    }
+    pub fn is_empty(&self) -> bool {
+        self.parts.is_empty()
+    }
+    pub fn len(&self) -> usize {
+        self.parts.len()
+    }
+    pub fn first(&self) -> Option<&PathPart> {
+        self.parts.first()
+    }
+}
+
+impl<'p> From<&'p AstPath> for Path<'p> {
+    fn from(value: &'p AstPath) -> Self {
+        Self::new(value)
+    }
+}
+impl AsRef<[PathPart]> for Path<'_> {
+    fn as_ref(&self) -> &[PathPart] {
+        self.parts
+    }
+}
+
+impl std::fmt::Display for Path<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        const SEPARATOR: &str = "::";
+        let Self { absolute, parts } = self;
+        if *absolute {
+            write!(f, "{SEPARATOR}")?
+        }
+        for (idx, part) in parts.iter().enumerate() {
+            write!(f, "{}{part}", if idx > 0 { SEPARATOR } else { "" })?;
+        }
+        Ok(())
+    }
+}

compiler/cl-typeck/src/project.rs

@@ -0,0 +1,376 @@
+//! A [Project] contains a tree of [Def]initions, referred to by their [Path]
+use crate::{
+    definition::{Def, DefKind, TypeKind},
+    handle::DefID,
+    module,
+    node::{Node, NodeSource},
+    path::Path,
+};
+use cl_ast::PathPart;
+use cl_structures::index_map::IndexMap;
+use std::{
+    collections::HashMap,
+    ops::{Index, IndexMut},
+};
+
+use self::evaluate::EvaluableTypeExpression;
+
+#[derive(Clone, Debug)]
+pub struct Project<'a> {
+    pub pool: IndexMap<DefID, Def<'a>>,
+    /// Stores anonymous tuples, function pointer types, etc.
+    pub anon_types: HashMap<TypeKind, DefID>,
+    pub root: DefID,
+}
+
+impl Project<'_> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl Default for Project<'_> {
+    fn default() -> Self {
+        const ROOT_PATH: cl_ast::Path = cl_ast::Path { absolute: true, parts: Vec::new() };
+
+        let mut pool = IndexMap::default();
+        let root = pool.insert(Def {
+            module: Default::default(),
+            kind: DefKind::Type(TypeKind::Module),
+            node: Node::new(ROOT_PATH, Some(NodeSource::Root)),
+        });
+        let never = pool.insert(Def {
+            module: module::Module::new(root),
+            kind: DefKind::Type(TypeKind::Never),
+            node: Node::new(ROOT_PATH, None),
+        });
+        let empty = pool.insert(Def {
+            module: module::Module::new(root),
+            kind: DefKind::Type(TypeKind::Empty),
+            node: Node::new(ROOT_PATH, None),
+        });
+
+        let mut anon_types = HashMap::new();
+        anon_types.insert(TypeKind::Empty, empty);
+        anon_types.insert(TypeKind::Never, never);
+
+        Self { pool, root, anon_types }
+    }
+}
+
+impl<'a> Project<'a> {
+    pub fn parent_of(&self, module: DefID) -> Option<DefID> {
+        self[module].module.parent
+    }
+
+    pub fn root_of(&self, module: DefID) -> DefID {
+        match self.parent_of(module) {
+            Some(module) => self.root_of(module),
+            None => module,
+        }
+    }
+
+    /// Returns the DefID of the Self type within the given DefID's context
+    pub fn selfty_of(&self, node: DefID) -> Option<DefID> {
+        match self[node].kind {
+            DefKind::Impl(id) => Some(id),
+            DefKind::Type(_) => Some(node),
+            _ => self.selfty_of(self.parent_of(node)?),
+        }
+    }
+
+    pub fn get<'p>(
+        &self,
+        path: Path<'p>,
+        within: DefID,
+    ) -> Option<(Option<DefID>, Option<DefID>, Path<'p>)> {
+        if path.absolute {
+            return self.get(path.relative(), self.root_of(within));
+        }
+        match path.as_ref() {
+            [PathPart::SuperKw, ..] => self.get(path.pop_front()?, self.parent_of(within)?),
+            [PathPart::SelfTy, ..] => self.get(path.pop_front()?, self.selfty_of(within)?),
+            [PathPart::SelfKw, ..] => self.get(path.pop_front()?, within),
+            [PathPart::Ident(name)] => {
+                let (ty, val) = self[within].module.get(*name);
+
+                // Transparent nodes can be looked through in reverse
+                if self[within].is_transparent() {
+                    let lookback = self.parent_of(within).and_then(|p| self.get(path, p));
+                    if let Some((subty, subval, path)) = lookback {
+                        return Some((ty.or(subty), val.or(subval), path));
+                    }
+                }
+                Some((ty, val, path.pop_front()?))
+            }
+            [PathPart::Ident(name), ..] => {
+                // TODO: This is currently too permissive, and treats undecided nodes as if they're
+                // always transparent, among other issues.
+                let (tysub, _, _) = match self[within].is_transparent() {
+                    true => self.get(path.front()?, within)?,
+                    false => (None, None, path),
+                };
+                let ty = self[within].module.get_type(*name).or(tysub)?;
+                self.get(path.pop_front()?, ty)
+            }
+            [] => Some((Some(within), None, path)),
+        }
+    }
+
+    /// Resolves a path within a module tree, finding the innermost module.
+    /// Returns the remaining path parts.
+    pub fn get_type<'p>(&self, path: Path<'p>, within: DefID) -> Option<(DefID, Path<'p>)> {
+        if path.absolute {
+            self.get_type(path.relative(), self.root_of(within))
+        } else if let Some(front) = path.first() {
+            let module = &self[within].module;
+            match front {
+                PathPart::SelfKw => self.get_type(path.pop_front()?, within),
+                PathPart::SuperKw => self.get_type(path.pop_front()?, module.parent?),
+                PathPart::SelfTy => self.get_type(path.pop_front()?, self.selfty_of(within)?),
+                PathPart::Ident(name) => match module.types.get(name) {
+                    Some(&submodule) => self.get_type(path.pop_front()?, submodule),
+                    None => Some((within, path)),
+                },
+            }
+        } else {
+            Some((within, path))
+        }
+    }
+
+    /// Inserts the type returned by the provided closure iff the TypeKind doesn't already exist
+    ///
+    /// Assumes `kind` uniquely identifies the type!
+    pub fn insert_anonymous_type(
+        &mut self,
+        kind: TypeKind,
+        def: impl FnOnce() -> Def<'a>,
+    ) -> DefID {
+        *(self
+            .anon_types
+            .entry(kind)
+            .or_insert_with(|| self.pool.insert(def())))
+    }
+
+    pub fn evaluate<T>(&mut self, expr: &T, parent: DefID) -> Result<T::Out, String>
+    where T: EvaluableTypeExpression {
+        expr.evaluate(self, parent)
+    }
+}
+
+impl<'a> Index<DefID> for Project<'a> {
+    type Output = Def<'a>;
+    fn index(&self, index: DefID) -> &Self::Output {
+        &self.pool[index]
+    }
+}
+impl IndexMut<DefID> for Project<'_> {
+    fn index_mut(&mut self, index: DefID) -> &mut Self::Output {
+        &mut self.pool[index]
+    }
+}
+
+pub mod evaluate {
+    //! An [EvaluableTypeExpression] is a component of a type expression tree
+    //! or an intermediate result of expression evaluation.
+
+    use super::*;
+    use crate::module;
+    use cl_ast::{Sym, Ty, TyArray, TyFn, TyKind, TyRef, TySlice, TyTuple};
+
+    /// Things that can be evaluated as a type expression
+    pub trait EvaluableTypeExpression {
+        /// The result of type expression evaluation
+        type Out;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String>;
+    }
+
+    impl EvaluableTypeExpression for Ty {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, id: DefID) -> Result<DefID, String> {
+            self.kind.evaluate(prj, id)
+        }
+    }
+
+    impl EvaluableTypeExpression for TyKind {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<DefID, String> {
+            let id = match self {
+                // TODO: reduce duplication here
+                TyKind::Never => prj.anon_types[&TypeKind::Never],
+                TyKind::Empty => prj.anon_types[&TypeKind::Empty],
+                // TyKind::Path must be looked up explicitly
+                TyKind::Path(path) => path.evaluate(prj, parent)?,
+                TyKind::Slice(slice) => slice.evaluate(prj, parent)?,
+                TyKind::Array(array) => array.evaluate(prj, parent)?,
+                TyKind::Tuple(tup) => tup.evaluate(prj, parent)?,
+                TyKind::Ref(tyref) => tyref.evaluate(prj, parent)?,
+                TyKind::Fn(tyfn) => tyfn.evaluate(prj, parent)?,
+            };
+            // println!("{self} => {id:?}");
+
+            Ok(id)
+        }
+    }
+
+    impl EvaluableTypeExpression for Sym {
+        type Out = DefID;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            prj[parent]
+                .module
+                .types
+                .get(self)
+                .copied()
+                .ok_or_else(|| format!("{self} is not a member of {:?}", prj[parent].name()))
+        }
+    }
+
+    impl EvaluableTypeExpression for TySlice {
+        type Out = DefID;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            let ty = self.ty.evaluate(prj, parent)?;
+            let root = prj.root;
+            let id = prj.insert_anonymous_type(TypeKind::Slice(ty), move || Def {
+                module: module::Module::new(root),
+                node: Node::new(Default::default(), None),
+                kind: DefKind::Type(TypeKind::Slice(ty)),
+            });
+
+            Ok(id)
+        }
+    }
+
+    impl EvaluableTypeExpression for TyArray {
+        type Out = DefID;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            let kind = TypeKind::Array(self.ty.evaluate(prj, parent)?, self.count);
+            let root = prj.root;
+            let id = prj.insert_anonymous_type(kind.clone(), move || Def {
+                module: module::Module::new(root),
+                node: Node::new(Default::default(), None),
+                kind: DefKind::Type(kind),
+            });
+
+            Ok(id)
+        }
+    }
+
+    impl EvaluableTypeExpression for TyTuple {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<DefID, String> {
+            let types = self.types.evaluate(prj, parent)?;
+            let root = prj.root;
+            let id = prj.insert_anonymous_type(TypeKind::Tuple(types.clone()), move || Def {
+                module: module::Module::new(root),
+                node: Node::new(Default::default(), None),
+                kind: DefKind::Type(TypeKind::Tuple(types)),
+            });
+
+            Ok(id)
+        }
+    }
+    impl EvaluableTypeExpression for TyRef {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<DefID, String> {
+            let TyRef { count, mutable: _, to } = self;
+            let to = to.evaluate(prj, parent)?;
+
+            let root = prj.root;
+            let id = prj.insert_anonymous_type(TypeKind::Ref(*count, to), move || Def {
+                module: module::Module::new(root),
+                node: Node::new(Default::default(), None),
+                kind: DefKind::Type(TypeKind::Ref(*count, to)),
+            });
+            Ok(id)
+        }
+    }
+    impl EvaluableTypeExpression for TyFn {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<DefID, String> {
+            let TyFn { args, rety } = self;
+
+            let args = args.evaluate(prj, parent)?;
+            let rety = match rety {
+                Some(rety) => rety.evaluate(prj, parent)?,
+                _ => TyKind::Empty.evaluate(prj, parent)?,
+            };
+
+            let root = prj.root;
+            let id = prj.insert_anonymous_type(TypeKind::FnSig { args, rety }, || Def {
+                module: module::Module::new(root),
+                node: Node::new(Default::default(), None),
+                kind: DefKind::Type(TypeKind::FnSig { args, rety }),
+            });
+            Ok(id)
+        }
+    }
+
+    impl EvaluableTypeExpression for cl_ast::Path {
+        type Out = DefID;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            Path::from(self).evaluate(prj, parent)
+        }
+    }
+    impl EvaluableTypeExpression for PathPart {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            match self {
+                PathPart::SuperKw => prj
+                    .parent_of(parent)
+                    .ok_or_else(|| "Attempt to get super of root".into()),
+                PathPart::SelfKw => Ok(parent),
+                PathPart::SelfTy => prj
+                    .selfty_of(parent)
+                    .ok_or_else(|| "Attempt to get Self outside a Self-able context".into()),
+                PathPart::Ident(name) => name.evaluate(prj, parent),
+            }
+        }
+    }
+    impl<'a> EvaluableTypeExpression for Path<'a> {
+        type Out = DefID;
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            let (tid, vid, path) = prj.get(*self, parent).ok_or("Failed to traverse path")?;
+            if !path.is_empty() {
+                Err(format!("Could not traverse past boundary: {path}"))?;
+            }
+            match (tid, vid) {
+                (Some(ty), _) => Ok(ty),
+                (None, Some(val)) => Ok(val),
+                (None, None) => Err(format!("No type or value found at path {self}")),
+            }
+        }
+    }
+    impl<T: EvaluableTypeExpression> EvaluableTypeExpression for [T] {
+        type Out = Vec<T::Out>;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            let mut types = vec![];
+            for value in self {
+                types.push(value.evaluate(prj, parent)?)
+            }
+
+            Ok(types)
+        }
+    }
+    impl<T: EvaluableTypeExpression> EvaluableTypeExpression for Option<T> {
+        type Out = Option<T::Out>;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            Ok(match self {
+                Some(v) => Some(v.evaluate(prj, parent)?),
+                None => None,
+            })
+        }
+    }
+    impl<T: EvaluableTypeExpression> EvaluableTypeExpression for Box<T> {
+        type Out = T::Out;
+
+        fn evaluate(&self, prj: &mut Project, parent: DefID) -> Result<Self::Out, String> {
+            self.as_ref().evaluate(prj, parent)
+        }
+    }
+}

compiler/cl-typeck/src/type_resolver.rs

@@ -0,0 +1,336 @@
+//! Performs step 2 of type checking: Evaluating type definitions
+
+use crate::{
+    definition::{Adt, Def, DefKind, TypeKind, ValueKind},
+    handle::DefID,
+    node::{Node, NodeSource},
+    project::{evaluate::EvaluableTypeExpression, Project as Prj},
+};
+use cl_ast::*;
+
+/// Evaluate a single ID
+pub fn resolve(prj: &mut Prj, id: DefID) -> Result<(), &'static str> {
+    let Def { node: Node { kind: Some(source), meta, .. }, kind: DefKind::Undecided, .. } = prj[id]
+    else {
+        return Ok(());
+    };
+
+    let kind = match &source {
+        NodeSource::Root => "root",
+        NodeSource::Alias(_) => "type",
+        NodeSource::Module(_) => "mod",
+        NodeSource::Enum(_) => "enum",
+        NodeSource::Variant(_) => "variant",
+        NodeSource::Struct(_) => "struct",
+        NodeSource::Const(_) => "const",
+        NodeSource::Static(_) => "static",
+        NodeSource::Function(_) => "fn",
+        NodeSource::Impl(_) => "impl",
+        NodeSource::Use(_) => "use",
+        NodeSource::Local(_) => "let",
+        NodeSource::Ty(_) => "ty",
+    };
+    let name = prj[id].name().unwrap_or("".into());
+
+    eprintln!("Resolver: \x1b[32mEvaluating\x1b[0m \"\x1b[36m{kind} {name}\x1b[0m\" (`{id:?}`)");
+
+    for Meta { name, kind } in meta {
+        if let ("intrinsic", MetaKind::Equals(Literal::String(s))) = (&**name, kind) {
+            prj[id].kind = DefKind::Type(TypeKind::Intrinsic(
+                s.parse().map_err(|_| "Failed to parse intrinsic")?,
+            ));
+        }
+    }
+    if DefKind::Undecided == prj[id].kind {
+        prj[id].kind = source.resolve_type(prj, id)?;
+    }
+
+    eprintln!("\x1b[33m=> {}\x1b[0m", prj[id].kind);
+
+    Ok(())
+}
+
+/// Resolves a given node
+pub trait TypeResolvable<'a> {
+    /// The return type upon success
+    type Out;
+    /// Resolves type expressions within this node
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str>;
+}
+
+impl<'a> TypeResolvable<'a> for NodeSource<'a> {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        match self {
+            NodeSource::Root => Ok(DefKind::Type(TypeKind::Module)),
+            NodeSource::Module(v) => v.resolve_type(prj, id),
+            NodeSource::Alias(v) => v.resolve_type(prj, id),
+            NodeSource::Enum(v) => v.resolve_type(prj, id),
+            NodeSource::Variant(v) => v.resolve_type(prj, id),
+            NodeSource::Struct(v) => v.resolve_type(prj, id),
+            NodeSource::Const(v) => v.resolve_type(prj, id),
+            NodeSource::Static(v) => v.resolve_type(prj, id),
+            NodeSource::Function(v) => v.resolve_type(prj, id),
+            NodeSource::Local(v) => v.resolve_type(prj, id),
+            NodeSource::Impl(v) => v.resolve_type(prj, id),
+            NodeSource::Use(v) => v.resolve_type(prj, id),
+            NodeSource::Ty(v) => v.resolve_type(prj, id),
+        }
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Meta {
+    type Out = DefKind;
+
+    #[allow(unused_variables)]
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let Meta { name, kind } = self;
+        match (name.as_ref(), kind) {
+            ("intrinsic", MetaKind::Equals(Literal::String(intrinsic))) => Ok(DefKind::Type(
+                TypeKind::Intrinsic(intrinsic.parse().map_err(|_| "unknown intrinsic type")?),
+            )),
+            (_, MetaKind::Plain) => Ok(DefKind::Type(TypeKind::Intrinsic(
+                name.parse().map_err(|_| "Unknown intrinsic type")?,
+            ))),
+            _ => Err("Unknown meta attribute"),
+        }
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Module {
+    type Out = DefKind;
+    #[allow(unused_variables)]
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        Ok(DefKind::Type(TypeKind::Module))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Alias {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let alias = if let Some(ty) = &self.from {
+            Some(
+                ty.evaluate(prj, parent)
+                    .or_else(|_| ty.evaluate(prj, id))
+                    .map_err(|_| "Unresolved type in alias")?,
+            )
+        } else {
+            None
+        };
+
+        Ok(DefKind::Type(TypeKind::Alias(alias)))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Enum {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let Enum { name: _, kind } = self;
+        let EnumKind::Variants(v) = kind else {
+            return Ok(DefKind::Type(TypeKind::Adt(Adt::FieldlessEnum)));
+        };
+        let mut fields = vec![];
+        for Variant { name, kind: _ } in v {
+            let id = prj[id].module.get_type(*name);
+            fields.push((*name, id))
+        }
+        Ok(DefKind::Type(TypeKind::Adt(Adt::Enum(fields))))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Variant {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        // Get the grandparent of this node, for name resolution
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let grandparent = prj.parent_of(parent).unwrap_or(parent);
+        let Variant { name: _, kind } = self;
+
+        Ok(DefKind::Type(match kind {
+            VariantKind::Plain => return Ok(DefKind::Type(TypeKind::Empty)),
+            VariantKind::CLike(_) => return Ok(DefKind::Undecided),
+            VariantKind::Tuple(ty) => match &ty.kind {
+                TyKind::Empty => TypeKind::Tuple(vec![]),
+                TyKind::Tuple(TyTuple { types }) => {
+                    TypeKind::Tuple(types.evaluate(prj, grandparent).map_err(|e| {
+                        eprintln!("{e}");
+                        ""
+                    })?)
+                }
+                _ => Err("Unexpected TyKind in tuple variant")?,
+            },
+            VariantKind::Struct(members) => {
+                TypeKind::Adt(Adt::Struct(members.resolve_type(prj, parent)?))
+            }
+        }))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Struct {
+    type Out = DefKind;
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let Struct { name: _, kind } = self;
+        Ok(match kind {
+            StructKind::Empty => DefKind::Type(TypeKind::Empty),
+            StructKind::Tuple(types) => DefKind::Type(TypeKind::Adt(Adt::TupleStruct({
+                let mut out = vec![];
+                for ty in types {
+                    out.push((
+                        Visibility::Public,
+                        ty.evaluate(prj, parent)
+                            .map_err(|_| "Unresolved type in tuple-struct member")?,
+                    ));
+                }
+                out
+            }))),
+            StructKind::Struct(members) => {
+                DefKind::Type(TypeKind::Adt(Adt::Struct(members.resolve_type(prj, id)?)))
+            }
+        })
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a StructMember {
+    type Out = (Sym, Visibility, DefID);
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let StructMember { name, vis, ty } = self;
+
+        let ty = ty
+            .evaluate(prj, parent)
+            .map_err(|_| "Invalid type while resolving StructMember")?;
+
+        Ok((*name, *vis, ty))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Const {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let Const { ty, .. } = self;
+        let ty = ty
+            .evaluate(prj, id)
+            .map_err(|_| "Invalid type while resolving const")?;
+        Ok(DefKind::Value(ValueKind::Const(ty)))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Static {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let Static { ty, .. } = self;
+        let ty = ty
+            .evaluate(prj, parent)
+            .map_err(|_| "Invalid type while resolving static")?;
+        Ok(DefKind::Value(ValueKind::Static(ty)))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Function {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+        let Function { sign, .. } = self;
+        let sign = sign
+            .evaluate(prj, parent)
+            .map_err(|_| "Invalid type in function signature")?;
+        Ok(DefKind::Value(ValueKind::Fn(sign)))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Let {
+    type Out = DefKind;
+
+    #[allow(unused)]
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let Let { mutable, name, ty, init } = self;
+        Ok(DefKind::Undecided)
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Impl {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let parent = prj.parent_of(id).unwrap_or(id);
+
+        let target = match &self.target {
+            ImplKind::Type(t) => t.evaluate(prj, parent),
+            ImplKind::Trait { for_type, .. } => for_type.evaluate(prj, parent),
+        }
+        .map_err(|_| "Unresolved type in impl target")?;
+
+        match prj.pool.get_many_mut([id, target]) {
+            // TODO: Better error handling
+            Err(_) => Err(concat!(
+                file!(),
+                line!(),
+                column!(),
+                "id and target are same"
+            ))?,
+            Ok([id, target]) => {
+                for (name, def) in &id.module.types {
+                    target.module.insert_type(*name, *def);
+                }
+                for (name, def) in &id.module.values {
+                    target.module.insert_value(*name, *def);
+                }
+            }
+        }
+        Ok(DefKind::Impl(target))
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a Use {
+    type Out = DefKind;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        todo!("Resolve types for {self} with ID {id} in {prj:?}")
+    }
+}
+
+impl<'a> TypeResolvable<'a> for &'a TyKind {
+    type Out = DefKind;
+
+    #[allow(unused)]
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        todo!()
+    }
+}
+
+impl<'a, T> TypeResolvable<'a> for &'a [T]
+where &'a T: TypeResolvable<'a>
+{
+    type Out = Vec<<&'a T as TypeResolvable<'a>>::Out>;
+
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        let mut members = vec![];
+        for member in self {
+            members.push(member.resolve_type(prj, id)?);
+        }
+        Ok(members)
+    }
+}
+
+impl<'a, T> TypeResolvable<'a> for Option<&'a T>
+where &'a T: TypeResolvable<'a>
+{
+    type Out = Option<<&'a T as TypeResolvable<'a>>::Out>;
+    fn resolve_type(self, prj: &mut Prj<'a>, id: DefID) -> Result<Self::Out, &'static str> {
+        match self {
+            Some(t) => Some(t.resolve_type(prj, id)).transpose(),
+            None => Ok(None),
+        }
+    }
+}

compiler/cl-typeck/src/use_importer.rs

@@ -0,0 +1,125 @@
+//! WIP use-item importer. This performs eager import resolution on the AST
+//!
+//! # TODOs:
+//! - [ ] Resolve imports using a graph traversal rather than linear iteration
+//! - [ ] Separate imported items from natively declared items
+//! - [ ] Separate the use-import pass from the project
+//! - [ ] Report errors in a meaningful way
+//! - [ ] Lazy import resolution using graph-edge traversal during name lookup?
+//!     - It doesn't seem to me like the imports in a given scope *can change*.
+
+#![allow(unused)]
+use std::fmt::format;
+
+use cl_ast::*;
+
+use crate::{
+    definition::{Def, DefKind},
+    handle::DefID,
+    node::NodeSource,
+    project::Project,
+};
+
+type UseResult = Result<(), String>;
+
+impl<'a> Project<'a> {
+    pub fn resolve_imports(&mut self) -> UseResult {
+        for id in self.pool.keys() {
+            self.visit_def(id)?;
+        }
+        Ok(())
+    }
+
+    pub fn visit_def(&mut self, id: DefID) -> UseResult {
+        let Def { kind, node, module } = &self.pool[id];
+        if let (DefKind::Use(parent), Some(NodeSource::Use(u))) = (kind, node.kind) {
+            println!("Importing use item {u}");
+            self.visit_use(u, *parent);
+        }
+        Ok(())
+    }
+
+    pub fn visit_use(&mut self, u: &'a Use, parent: DefID) -> UseResult {
+        let Use { absolute, tree } = u;
+
+        self.visit_use_tree(tree, parent, if *absolute { self.root } else { parent })
+    }
+
+    pub fn visit_use_tree(&mut self, tree: &'a UseTree, parent: DefID, c: DefID) -> UseResult {
+        match tree {
+            UseTree::Tree(trees) => {
+                for tree in trees {
+                    self.visit_use_tree(tree, parent, c)?;
+                }
+            }
+            UseTree::Path(part, rest) => {
+                let c = self.evaluate(part, c)?;
+                self.visit_use_tree(rest, parent, c)?;
+            }
+
+            UseTree::Name(name) => self.visit_use_leaf(name, parent, c)?,
+            UseTree::Alias(from, to) => self.visit_use_alias(from, to, parent, c)?,
+            UseTree::Glob => self.visit_use_glob(parent, c)?,
+        }
+        Ok(())
+    }
+
+    pub fn visit_use_path(&mut self) -> UseResult {
+        Ok(())
+    }
+
+    pub fn visit_use_leaf(&mut self, name: &'a Sym, parent: DefID, c: DefID) -> UseResult {
+        self.visit_use_alias(name, name, parent, c)
+    }
+
+    pub fn visit_use_alias(
+        &mut self,
+        from: &Sym,
+        name: &Sym,
+        parent: DefID,
+        c: DefID,
+    ) -> UseResult {
+        let mut imported = false;
+        let c_mod = &self[c].module;
+        let (tid, vid) = (
+            c_mod.types.get(from).copied(),
+            c_mod.values.get(from).copied(),
+        );
+        let parent = &mut self[parent].module;
+
+        if let Some(tid) = tid {
+            parent.types.insert(*name, tid);
+            imported = true;
+        }
+
+        if let Some(vid) = vid {
+            parent.values.insert(*name, vid);
+            imported = true;
+        }
+
+        if imported {
+            Ok(())
+        } else {
+            Err(format!("Identifier {name} not found in module {c}"))
+        }
+    }
+
+    pub fn visit_use_glob(&mut self, parent: DefID, c: DefID) -> UseResult {
+        // Loop over all the items in c, and add them as items in the parent
+        if parent == c {
+            return Ok(());
+        }
+        let [parent, c] = self
+            .pool
+            .get_many_mut([parent, c])
+            .expect("parent and c are not the same");
+
+        for (k, v) in &c.module.types {
+            parent.module.types.entry(*k).or_insert(*v);
+        }
+        for (k, v) in &c.module.values {
+            parent.module.values.entry(*k).or_insert(*v);
+        }
+        Ok(())
+    }
+}

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)? Block? ;
+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 +81,51 @@ 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 ;
 
-Member      = Call ('.' Call)* ;
+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       = ;
 
+Loop        = "loop"  Block ;
 While       = "while" Expr Block Else ;
 If          = "if"    Expr Block Else ;
 For         = "for"   Identifier "in" Expr Block Else ;
@@ -127,11 +134,9 @@ Break       = "break"  Expr ;
 Return      = "return" Expr ;
 Continue    = "continue" ;
 
-AssignKind  =  '=' | '+=' | '-=' | '*=' | '/=' |
-              '&=' | '|=' | '^=' |'<<=' |'>>=' ;
+AssignKind  =  '=' ;
+ModifyKind  = '+=' | '-=' | '*=' | '/=' | '&=' | '|=' | '^=' |'<<=' |'>>=' ;
 
-BinaryKind  = CompareOp | RangeOp | LogicOp  | BitwiseOp 
-            | ShiftOp   | TermOp  | FactorOp ;
 CompareOp   =  '<' | '<=' | '==' | '!=' | '>=' | '>' ;
 RangeOp     = '..' | '..=' ;
 LogicOp     = '&&' | '||' | '^^' ;

libconlang/.gitignore

@@ -1 +0,0 @@
-/target

libconlang/Cargo.toml

@@ -1,15 +0,0 @@
-[package]
-name = "conlang"
-description = "The Conlang Programming Language"
-keywords = ["interpreter", "programming", "language"]
-authors.workspace = true
-version.workspace = true
-edition.workspace = true
-license.workspace = true
-publish.workspace = true
-repository.workspace = true
-
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]
-unicode-xid = "0.2.4"

libconlang/src/ast.rs

@@ -1,515 +0,0 @@
-//! # The Abstract Syntax Tree
-//! Contains definitions of AST Nodes, to be derived by a [parser](super::parser).
-//!
-//! # Notable nodes
-//! - [Item] and [ItemKind]: Top-level constructs
-//! - [Stmt] and [StmtKind]: Statements
-//! - [Expr] and [ExprKind]: Expressions
-//!   - [Assign], [Binary], and [Unary] expressions
-//!   - [AssignKind], [BinaryKind], and [UnaryKind] operators
-//! - [Ty] and [TyKind]: Type qualifiers
-//! - [Path]: Path expressions
-use crate::common::*;
-
-pub mod ast_impl;
-
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-pub enum Mutability {
-    #[default]
-    Not,
-    Mut,
-}
-
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-pub enum Visibility {
-    #[default]
-    Private,
-    Public,
-}
-
-#[derive(Clone, Debug, Default, PartialEq, Eq)]
-pub struct File {
-    pub items: Vec<Item>,
-}
-
-// Metadata decorators
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Attrs {
-    pub meta: Vec<Meta>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Meta {
-    pub name: Identifier,
-    pub kind: MetaKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum MetaKind {
-    Plain,
-    Equals(Literal),
-    Func(Vec<Literal>),
-}
-
-// Items
-/// Stores an [ItemKind] and associated metadata
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Item {
-    pub extents: Span,
-    pub attrs: Attrs,
-    pub vis: Visibility,
-    pub kind: ItemKind,
-}
-
-/// Stores a concrete Item
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum ItemKind {
-    // TODO: Import declaration ("use") item
-    // TODO: Trait declaration ("trait") item?
-    /// A [type alias](Alias)
-    Alias(Alias),
-    /// A [constant](Const)
-    Const(Const),
-    /// A [static](Static) variable
-    Static(Static),
-    /// A [module](Module)
-    Module(Module),
-    /// A [function definition](Function)
-    Function(Function),
-    /// A [structure](Struct)
-    Struct(Struct),
-    /// An [enumerated type](Enum)
-    Enum(Enum),
-    /// An [implementation](Impl)
-    Impl(Impl),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Alias {
-    pub to: Box<Ty>,
-    pub from: Option<Box<Ty>>,
-}
-
-/// Stores a `const` value
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Const {
-    pub name: Identifier,
-    pub ty: Box<Ty>,
-    pub init: Box<Expr>,
-}
-
-/// Stores a `static` variable
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Static {
-    pub mutable: Mutability,
-    pub name: Identifier,
-    pub ty: Box<Ty>,
-    pub init: Box<Expr>,
-}
-
-/// Stores a collection of [Items](Item)
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Module {
-    pub name: Identifier,
-    pub kind: ModuleKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum ModuleKind {
-    Inline(File),
-    Outline,
-}
-
-/// Contains code, and the interface to that code
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Function {
-    pub name: Identifier,
-    pub args: Vec<Param>,
-    pub body: Option<Block>,
-    pub rety: Option<Box<Ty>>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Param {
-    pub mutability: Mutability,
-    pub name: Identifier,
-    pub ty: Box<Ty>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Struct {
-    pub name: Identifier,
-    pub kind: StructKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum StructKind {
-    Empty,
-    Tuple(Vec<Ty>),
-    Struct(Vec<StructMember>),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct StructMember {
-    pub vis: Visibility,
-    pub name: Identifier,
-    pub ty: Ty,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Enum {
-    pub name: Identifier,
-    pub kind: EnumKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum EnumKind {
-    /// Represents an enum with no variants
-    NoVariants,
-    Variants(Vec<Variant>),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Variant {
-    pub name: Identifier,
-    pub kind: VariantKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum VariantKind {
-    Plain,
-    CLike(u128),
-    Tuple(Vec<Ty>),
-    Struct(Vec<StructMember>),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Impl {
-    pub target: Ty,
-    pub body: Vec<Item>,
-}
-
-// TODO: `impl` Trait for <Target> { }
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum ImplKind {
-    Type(Box<Ty>),
-    Trait { impl_trait: Path, for_type: Box<Ty> },
-}
-
-/// # Static Type Information
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Ty {
-    pub extents: Span,
-    pub kind: TyKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum TyKind {
-    Never,
-    Empty,
-    SelfTy,
-    Path(Path),
-    Tuple(TyTuple),
-    Ref(TyRef),
-    Fn(TyFn),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct TyTuple {
-    pub types: Vec<Ty>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct TyRef {
-    pub count: u16,
-    pub to: Path,
-}
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct TyFn {
-    pub args: TyTuple,
-    pub rety: Option<Box<Ty>>,
-}
-
-// Path
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Path {
-    pub absolute: bool,
-    pub parts: Vec<PathPart>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum PathPart {
-    SuperKw,
-    SelfKw,
-    Ident(Identifier),
-}
-
-// TODO: Capture token?
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Identifier(pub String);
-
-/// Stores an abstract statement, and associated metadata
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Stmt {
-    pub extents: Span,
-    pub kind: StmtKind,
-    pub semi: Semi,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum Semi {
-    Terminated,
-    Unterminated,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum StmtKind {
-    Empty,
-    Local(Let),
-    Item(Box<Item>),
-    Expr(Box<Expr>),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Let {
-    pub mutable: Mutability,
-    pub name: Identifier,
-    pub ty: Option<Box<Ty>>,
-    pub init: Option<Box<Expr>>,
-}
-
-/// Stores an abstract expression, and associated metadata
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Expr {
-    pub extents: Span,
-    pub kind: ExprKind,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum ExprKind {
-    /// An [Assign]ment expression: [`Expr`] ([`AssignKind`] [`Expr`])\+
-    Assign(Box<Assign>),
-    /// A [Binary] expression: [`Expr`] ([`BinaryKind`] [`Expr`])\+
-    Binary(Binary),
-    /// A [Unary] expression: [`UnaryKind`]\* [`Expr`]
-    Unary(Unary),
-    /// A [Member] access expression: [`Expr`] (`.` [`Expr`])+
-    Member(Member),
-    /// A [Call] expression, with arguments: a(foo, bar)
-    Call(Call),
-    /// An Array [Index] expression: a[10, 20, 30]
-    Index(Index),
-    /// A [path expression](Path): `::`? [PathPart] (`::` [PathPart])*
-    Path(Path),
-    /// A [Literal]: 0x42, 1e123, 2.4, "Hello"
-    Literal(Literal),
-    /// 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 [Block] expression: `{` [`Stmt`]\* [`Expr`]? `}`
-    Block(Block),
-    /// An empty expression: `(` `)`
-    Empty,
-    /// A [Grouping](Group) expression `(` [`Expr`] `)`
-    Group(Group),
-    /// A [Tuple] expression: `(` [`Expr`] (`,` [`Expr`])+ `)`
-    Tuple(Tuple),
-    /// 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(Continue),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Assign {
-    pub head: Expr,
-    pub op: AssignKind,
-    pub tail: Box<Expr>,
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum AssignKind {
-    /// Standard Assignment with no read-back
-    Plain,
-    And,
-    Or,
-    Xor,
-    Shl,
-    Shr,
-    Add,
-    Sub,
-    Mul,
-    Div,
-    Rem,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Binary {
-    pub head: Box<Expr>,
-    pub tail: Vec<(BinaryKind, Expr)>,
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum BinaryKind {
-    Lt,
-    LtEq,
-    Equal,
-    NotEq,
-    GtEq,
-    Gt,
-    RangeExc,
-    RangeInc,
-    LogAnd,
-    LogOr,
-    LogXor,
-    BitAnd,
-    BitOr,
-    BitXor,
-    Shl,
-    Shr,
-    Add,
-    Sub,
-    Mul,
-    Div,
-    Rem,
-    Dot,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Unary {
-    pub ops: Vec<UnaryKind>,
-    pub tail: Box<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum UnaryKind {
-    Deref,
-    Neg,
-    Not,
-    /// Unused
-    At,
-    /// Unused
-    Tilde,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Member {
-    pub head: Box<Expr>,
-    pub tail: Vec<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum MemberKind {
-    Dot,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Call {
-    pub callee: Box<Expr>,
-    pub args: Vec<Tuple>,
-}
-
-/// Index operator: Member (`[` Expr `]`)*
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Index {
-    pub head: Box<Expr>,
-    pub indices: Vec<Indices>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Indices {
-    pub exprs: Vec<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub enum Literal {
-    Bool(bool),
-    Char(char),
-    Int(u128),
-    String(String),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Array {
-    pub values: Vec<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct ArrayRep {
-    pub value: Box<Expr>,
-    pub repeat: Box<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct AddrOf {
-    pub count: usize,
-    pub mutable: Mutability,
-    pub expr: Box<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Block {
-    pub stmts: Vec<Stmt>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Group {
-    pub expr: Box<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Tuple {
-    pub exprs: Vec<Expr>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct While {
-    pub cond: Box<Expr>,
-    pub pass: Box<Block>,
-    pub fail: Else,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct If {
-    pub cond: Box<Expr>,
-    pub pass: Box<Block>,
-    pub fail: Else,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct For {
-    pub bind: Identifier, // TODO: Patterns?
-    pub cond: Box<Expr>,
-    pub pass: Box<Block>,
-    pub fail: Else,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Else {
-    pub body: Option<Box<Expr>>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Break {
-    pub body: Option<Box<Expr>>,
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Return {
-    pub body: Option<Box<Expr>>,
-}
-
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-pub struct Continue;

libconlang/src/lib.rs

@@ -1,20 +0,0 @@
-//! Conlang is an expression-based programming language with similarities to Rust and Python
-#![warn(clippy::all)]
-#![feature(decl_macro)]
-
-pub mod common;
-
-pub mod token;
-
-pub mod ast;
-
-pub mod lexer;
-
-pub mod parser;
-
-pub mod resolver;
-
-pub mod interpreter;
-
-#[cfg(test)]
-mod tests;

libconlang/src/resolver.rs

@@ -1,916 +0,0 @@
-//! Extremely early WIP of a static type-checker/resolver
-//!
-//! This will hopefully become a fully fledged static resolution pass in the future
-use std::collections::HashMap;
-
-use scopeguard::Scoped;
-pub mod scopeguard {
-    //! Implements a generic RAII scope-guard
-
-    use std::ops::{Deref, DerefMut};
-
-    pub trait Scoped: Sized {
-        fn frame(&mut self) -> Guard<Self> {
-            Guard::new(self)
-        }
-        ///
-        fn enter_scope(&mut self);
-        fn exit_scope(&mut self);
-    }
-
-    pub struct Guard<'scope, T: Scoped> {
-        inner: &'scope mut T,
-    }
-    impl<'scope, T: Scoped> Guard<'scope, T> {
-        pub fn new(inner: &'scope mut T) -> Self {
-            inner.enter_scope();
-            Self { inner }
-        }
-    }
-    impl<'scope, T: Scoped> Deref for Guard<'scope, T> {
-        type Target = T;
-        fn deref(&self) -> &Self::Target {
-            self.inner
-        }
-    }
-    impl<'scope, T: Scoped> DerefMut for Guard<'scope, T> {
-        fn deref_mut(&mut self) -> &mut Self::Target {
-            self.inner
-        }
-    }
-    impl<'scope, T: Scoped> Drop for Guard<'scope, T> {
-        fn drop(&mut self) {
-            self.inner.exit_scope()
-        }
-    }
-}
-
-/// Prints like [println] if `debug_assertions` are enabled
-macro debugln($($t:tt)*) {
-    if cfg!(debug_assertions) {
-        println!($($t)*);
-    }
-}
-macro debug($($t:tt)*) {
-    if cfg!(debug_assertions) {
-        print!($($t)*);
-    }
-}
-
-use ty::Type;
-pub mod ty {
-    //! Describes the type of a [Variable](super::Variable)
-    use std::fmt::Display;
-
-    /// Describes the type of a [Variable](super::Variable)
-    #[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-    pub enum Type {
-        #[default]
-        Empty,
-        Int,
-        Bool,
-        Char,
-        String,
-        Float,
-        Fn {
-            args: Vec<Type>,
-            ret: Box<Type>,
-        },
-        Range(Box<Type>),
-        Tuple(Vec<Type>),
-        Never,
-        /// [Inferred](Type::Inferred) is for error messages. DO NOT CONSTRUCT
-        Inferred,
-        Generic(String),
-        /// A function with a single parameter of [Type::ManyInferred]
-        /// is assumed to always be correct.
-        ManyInferred,
-    }
-    impl Type {
-        fn is_empty(&self) -> bool {
-            self == &Type::Empty
-        }
-    }
-    impl Display for Type {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            match self {
-                Type::Empty => "Empty".fmt(f),
-                Type::Int => "integer".fmt(f),
-                Type::Bool => "bool".fmt(f),
-                Type::Char => "char".fmt(f),
-                Type::String => "String".fmt(f),
-                Type::Float => "float".fmt(f),
-                // TODO: clean this up
-                Type::Fn { args, ret } => {
-                    "fn (".fmt(f)?;
-                    let mut args = args.iter();
-                    if let Some(arg) = args.next() {
-                        arg.fmt(f)?;
-                    }
-                    for arg in args {
-                        write!(f, ", {arg}")?
-                    }
-                    ")".fmt(f)?;
-                    if !ret.is_empty() {
-                        write!(f, " -> {ret}")?;
-                    }
-                    Ok(())
-                }
-                Type::Range(t) => write!(f, "{t}..{t}"),
-                Type::Tuple(t) => {
-                    "(".fmt(f)?;
-                    for (idx, ty) in t.iter().enumerate() {
-                        if idx > 0 {
-                            ", ".fmt(f)?;
-                        }
-                        ty.fmt(f)?;
-                    }
-                    ")".fmt(f)
-                }
-                Type::Never => "!".fmt(f),
-                Type::Inferred => "_".fmt(f),
-                Type::Generic(name) => write!(f, "<{name}>"),
-                Type::ManyInferred => "..".fmt(f),
-            }
-        }
-    }
-}
-
-/// Describes the life-cycle of a [Variable]: Whether it's bound, typed, or initialized
-#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-pub enum Status {
-    #[default]
-    Bound,
-    Uninitialized(Type),
-    Initialized(Type),
-}
-impl Status {
-    /// Performs type-checking for a [Variable] assignment
-    pub fn assign(&mut self, ty: &Type) -> TyResult<()> {
-        match self {
-            // Variable uninitialized: initialize it
-            Status::Bound => {
-                *self = Status::Initialized(ty.clone());
-                Ok(())
-            }
-            // Typecheck ok! Reuse the allocation for t
-            Status::Uninitialized(t) if t == ty => {
-                *self = Status::Initialized(std::mem::take(t));
-                Ok(())
-            }
-            Status::Initialized(t) if t == ty => Ok(()),
-            // Typecheck not ok.
-            Status::Uninitialized(e) | Status::Initialized(e) => {
-                Err(Error::TypeMismatch { want: ty.clone(), got: e.clone() })
-            }
-        }
-    }
-}
-#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-pub struct Variable {
-    /// The unique, global index of this variable
-    pub index: usize,
-    /// The [Status] of this variable
-    pub status: Status,
-    /// The mutability qualifier of this variable
-    pub mutable: bool,
-}
-impl Variable {
-    /// Constructs a new variable with the provided index and mutability
-    pub fn new(index: usize, mutable: bool) -> Self {
-        Self { index, mutable, ..Default::default() }
-    }
-    /// Performs a type-checked assignment on self
-    pub fn assign(&mut self, name: &str, ty: &Type) -> TyResult<()> {
-        let Variable { index, status, mutable } = self;
-        debug!("Typecheck for {name} #{index}: ");
-        let out = match (status, mutable) {
-            // Variable uninitialized: initialize it
-            (Status::Bound, _) => {
-                self.status = Status::Initialized(ty.clone());
-                Ok(())
-            }
-            // Typecheck ok! Reuse the allocation for t
-            (Status::Uninitialized(t), _) if t == ty => {
-                self.status = Status::Initialized(std::mem::take(t));
-                Ok(())
-            }
-            // Reassignment of mutable variable is ok
-            (Status::Initialized(t), true) if t == ty => Ok(()),
-            // Reassignment of immutable variable is not ok
-            (Status::Initialized(_), false) => Err(Error::ImmutableAssign(name.into(), *index)),
-            // Typecheck not ok.
-            (Status::Uninitialized(e) | Status::Initialized(e), _) => {
-                Err(Error::TypeMismatch { want: ty.clone(), got: e.clone() })
-            }
-        };
-        match &out {
-            Ok(_) => debugln!("Ok! ({ty})"),
-            Err(e) => debugln!("Error: {e:?}"),
-        }
-        out
-    }
-    /// Performs the type-checking for a modifying assignment
-    pub fn modify_assign(&self, name: &str, ty: &Type) -> TyResult<()> {
-        let Variable { index, status, mutable } = &self;
-        match (status, mutable) {
-            (Status::Initialized(t), true) if t == ty => Ok(()),
-            (Status::Initialized(t), true) => {
-                Err(Error::TypeMismatch { want: t.clone(), got: ty.clone() })
-            }
-            (Status::Initialized(_), false) => Err(Error::ImmutableAssign(name.into(), *index)),
-            (..) => Err(Error::Uninitialized(name.into(), *index)),
-        }
-    }
-}
-
-/*
-    THE BIG IDEA:
-    - Each `let` statement binds a *different* variable.
-      - Shadowing is a FEATURE
-    - Traversing the tree before program launch allows the Resolver to assign
-      an index to each variable usage in the scope-tree
-    - These indices allow constant-time variable lookup in the interpreter!!!
-    - The added type-checking means fewer type errors!
-
-    REQUIREMENTS FOR FULL TYPE-CHECKING:
-    - Meaningful type expressions in function declarations
-
-    NECESSARY CONSIDERATIONS:
-    - Variable binding happens AFTER the initialization expression is run.
-      - If a variable is *entirely* unbound before being referenced,
-        it'll still error.
-      - This is *intentional*, and ALLOWS shadowing previous variables.
-      - In my experience, this is almost NEVER an error :P
-*/
-
-#[derive(Clone, Debug, Default)]
-pub struct Scope {
-    /// A monotonically increasing counter of variable declarations
-    count: usize,
-    /// A dictionary keeping track of type and lifetime information
-    vars: HashMap<String, Variable>,
-}
-impl Scope {
-    /// Bind a [Variable] in Scope
-    pub fn insert(&mut self, name: &str, index: usize, mutable: bool) {
-        self.count += 1;
-        self.vars
-            .insert(name.to_string(), Variable::new(index, mutable));
-    }
-    /// Returns a reference to a [Variable], if `name` is bound
-    pub fn get(&self, name: &str) -> Option<&Variable> {
-        self.vars.get(name)
-    }
-    /// Returns a mutable reference to a [Variable], if `name` is bound
-    pub fn get_mut(&mut self, name: &str) -> Option<&mut Variable> {
-        self.vars.get_mut(name)
-    }
-}
-/// Implements a dynamically scoped namespace
-#[derive(Clone, Debug, Default)]
-pub struct Module {
-    modules: HashMap<String, Module>,
-    vars: HashMap<String, Variable>,
-}
-impl Module {
-    pub fn insert_var(&mut self, name: &str, index: usize, mutable: bool) -> TyResult<()> {
-        if self
-            .vars
-            .insert(name.into(), Variable::new(index, mutable))
-            .is_some()
-        {
-            Err(Error::NonUniqueInModule(name.into()))?;
-        }
-        Ok(())
-    }
-    pub fn insert_module(&mut self, name: String, module: Module) -> TyResult<()> {
-        if self.modules.insert(name.clone(), module).is_some() {
-            Err(Error::NonUniqueInModule(name + "(module)"))?
-        }
-        Ok(())
-    }
-    /// Returns a reference to a [Variable] in this Module, if `name` is bound
-    pub fn get(&self, name: &str) -> Option<&Variable> {
-        self.vars.get(name)
-    }
-    /// Returns a mutable reference to a [Variable] in this Module, if `name` is bound
-    pub fn get_mut(&mut self, name: &str) -> Option<&mut Variable> {
-        self.vars.get_mut(name)
-    }
-
-    pub fn resolve_get(&self, name: &str, path: &[String]) -> Option<&Variable> {
-        if path.is_empty() {
-            return self.get(name);
-        }
-        let module = self.modules.get(&path[0])?;
-        module
-            .resolve_get(name, &path[1..])
-            .or_else(|| self.get(name))
-    }
-    // Returns a reference to the module at a specified path
-    pub fn resolve(&self, path: &[String]) -> TyResult<&Module> {
-        if path.is_empty() {
-            return Ok(self);
-        }
-        let module = self
-            .modules
-            .get(&path[0])
-            .ok_or_else(|| Error::Unbound(path[0].clone()))?;
-        module.resolve(&path[1..])
-    }
-    /// Returns a mutable reference to a Module if one is bound
-    pub fn resolve_mut(&mut self, path: &[String]) -> TyResult<&mut Module> {
-        if path.is_empty() {
-            return Ok(self);
-        }
-        let module = self
-            .modules
-            .get_mut(&path[0])
-            .ok_or_else(|| Error::Unbound(path[0].clone()))?;
-        module.resolve_mut(&path[1..])
-    }
-}
-
-#[derive(Clone, Debug)]
-pub struct Resolver {
-    /// A monotonically increasing counter of variable declarations
-    count: usize,
-    /// A stack of nested scopes *inside* a function
-    scopes: Vec<Scope>,
-    /// A stack of nested scopes *outside* a function
-    // TODO: Record the name of the module, and keep a stack of the current module
-    // for name resolution
-    modules: Module,
-    /// Describes the current path
-    module: Vec<String>,
-    /// A stack of types
-    types: Vec<Type>,
-}
-
-impl Scoped for Resolver {
-    fn enter_scope(&mut self) {
-        self.enter_scope();
-    }
-    fn exit_scope(&mut self) {
-        self.exit_scope();
-    }
-}
-
-impl Default for Resolver {
-    fn default() -> Self {
-        let mut new = Self {
-            count: Default::default(),
-            scopes: vec![Default::default()],
-            modules: Default::default(),
-            module: Default::default(),
-            types: Default::default(),
-        };
-        new.register_builtin("print", &[], &[Type::ManyInferred], Type::Empty)
-            .expect("print should not be bound in new Resolver");
-        new
-    }
-}
-
-impl Resolver {
-    pub fn new() -> Self {
-        Default::default()
-    }
-    /// Register a built-in function into the top-level module
-    pub fn register_builtin(
-        &mut self,
-        name: &str,
-        path: &[String],
-        args: &[Type],
-        ret: Type,
-    ) -> TyResult<()> {
-        let module = self.modules.resolve_mut(path)?;
-        module.vars.insert(
-            name.into(),
-            Variable {
-                index: 0,
-                status: Status::Initialized(Type::Fn { args: args.into(), ret: ret.into() }),
-                mutable: false,
-            },
-        );
-        Ok(())
-    }
-    /// Enters a Module Scope
-    pub fn enter_module(&mut self, name: &str) -> TyResult<()> {
-        let module = self.modules.resolve_mut(&self.module)?;
-        module.insert_module(name.into(), Default::default())?;
-        self.module.push(name.into());
-        Ok(())
-    }
-    /// Exits a Module Scope
-    pub fn exit_module(&mut self) -> Option<String> {
-        // Modules stay registered
-        self.module.pop()
-    }
-    /// Enters a Block Scope
-    pub fn enter_scope(&mut self) {
-        self.scopes.push(Default::default());
-    }
-    /// Exits a Block Scope, returning the value
-    pub fn exit_scope(&mut self) -> Option<usize> {
-        self.scopes.pop().map(|scope| scope.count)
-    }
-    /// Resolves a name to a [Variable]
-    pub fn get(&self, name: &str) -> TyResult<&Variable> {
-        if let Some(var) = self.scopes.iter().rev().find_map(|s| s.get(name)) {
-            return Ok(var);
-        }
-        self.modules
-            .resolve_get(name, &self.module)
-            .ok_or_else(|| Error::Unbound(name.into()))
-    }
-    /// Mutably resolves a name to a [Variable]
-    pub fn get_mut(&mut self, name: &str) -> TyResult<&mut Variable> {
-        if let Some(var) = self.scopes.iter_mut().rev().find_map(|s| s.get_mut(name)) {
-            return Ok(var);
-        }
-        self.modules
-            .resolve_mut(&self.module)?
-            .get_mut(name)
-            .ok_or_else(|| Error::Unbound(name.into()))
-    }
-    /// Binds a name in the current lexical scope
-    pub fn insert_scope(&mut self, name: &str, mutable: bool) -> TyResult<usize> {
-        self.count += 1;
-        self.scopes
-            .last_mut()
-            .ok_or_else(|| panic!("Stack underflow in resolver?"))?
-            .insert(name, self.count, mutable);
-        Ok(self.count)
-    }
-    /// Binds a name in the current module
-    pub fn insert_module(&mut self, name: &str, mutable: bool) -> TyResult<usize> {
-        self.count += 1;
-        self.modules
-            .resolve_mut(&self.module)?
-            .insert_var(name, self.count, mutable)?;
-        Ok(self.count)
-    }
-    /// Performs scoped type-checking of variables
-    pub fn assign(&mut self, name: &str, ty: &Type) -> TyResult<()> {
-        self.get_mut(name)?.assign(name, ty)
-    }
-}
-#[allow(unused_macros)]
-/// Manages a module scope
-/// ```rust,ignore
-/// macro module(self, name: &str, inner: {...}) -> Result<_, Error>
-/// ```
-macro module($self:ident, $name:tt, $inner:tt) {{
-    $self.enter_module($name)?;
-    #[allow(clippy::redundant_closure_call)]
-    let scope = (|| $inner)(); // This is pretty gross, but hey, try {} syntax is unstable too
-    $self.exit_module();
-    scope
-}}
-
-impl Resolver {
-    pub fn visit_empty(&mut self) -> TyResult<()> {
-        debugln!("Got Empty");
-        self.types.push(Type::Empty);
-        Ok(())
-    }
-}
-
-pub trait Resolve {
-    /// Performs variable resolution on self, and returns the type of self.
-    ///
-    /// For expressions, this is the type of the expression.
-    ///
-    /// For declarations, this is Empty.
-    fn resolve(&mut self, _resolver: &mut Resolver) -> TyResult<Type> {
-        Ok(Type::Empty)
-    }
-}
-mod ast1 {
-    // #![allow(deprecated)]
-    // use super::*;
-    // use crate::ast::preamble::*;
-    // impl Resolve for Start {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Self(program) = self;
-    //         program.resolve(resolver)
-    //     }
-    // }
-    // impl Resolve for Program {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Self(module) = self;
-    //         for decl in module {
-    //             decl.resolve(resolver)?;
-    //         }
-    //         // TODO: record the number of module-level assignments into the AST
-    //         Ok(Type::Empty)
-    //     }
-    // }
-    // impl Resolve for Stmt {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         match self {
-    //             Stmt::Let(value) => value.resolve(resolver),
-    //             Stmt::Fn(value) => value.resolve(resolver),
-    //             Stmt::Expr(value) => value.resolve(resolver),
-    //         }
-    //     }
-    // }
-    // impl Resolve for Let {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Let { name: Name { symbol: Identifier { name, index }, mutable, ty: _ }, init } =
-    //             self;
-    //         debugln!("ty> let {name} ...");
-    //         if let Some(init) = init {
-    //             let ty = init.resolve(resolver)?;
-    //             *index = Some(resolver.insert_scope(name, *mutable)?);
-    //             resolver.get_mut(name)?.assign(name, &ty)?;
-    //         } else {
-    //             resolver.insert_scope(name, *mutable)?;
-    //         }
-    //         Ok(Type::Empty)
-    //     }
-    // }
-    // impl Resolve for FnDecl {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let FnDecl { name: Name { symbol: Identifier { name, index }, .. }, args, body } =
-    // self;         debugln!("ty> fn {name} ...");
-    //         // register the name at module scope
-    //         *index = Some(resolver.insert_module(name, false)?);
-    //         // create a new lexical scope
-    //         let scopes = std::mem::take(&mut resolver.scopes);
-    //         // type-check the function body
-    //         let out = {
-    //             let mut resolver = resolver.frame();
-    //             let mut evaluated_args = vec![];
-    //             for arg in args {
-    //                 evaluated_args.push(arg.resolve(&mut resolver)?)
-    //             }
-    //             let fn_decl = Type::Fn { args: evaluated_args.clone(), ret: Box::new(Type::Empty)
-    // };             resolver.get_mut(name)?.assign(name, &fn_decl)?;
-    //             module!(resolver, name, { body.resolve(&mut resolver) })
-    //         };
-    //         let _ = std::mem::replace(&mut resolver.scopes, scopes);
-    //         out
-    //     }
-    // }
-    // impl Resolve for Name {
-    //     fn resolve(&mut self, _resolver: &mut Resolver) -> TyResult<Type> {
-    //         Ok(Type::Empty)
-    //     }
-    // }
-    // impl Resolve for Block {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Block { let_count: _, statements, expr } = self;
-    //         let mut resolver = resolver.frame();
-    //         for stmt in statements {
-    //             stmt.resolve(&mut resolver)?;
-    //         }
-    //         expr.resolve(&mut resolver)
-    //     }
-    // }
-    // impl Resolve for Expr {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Expr(expr) = self;
-    //         expr.resolve(resolver)
-    //     }
-    // }
-
-    // impl Resolve for Operation {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         match self {
-    //             Operation::Assign(value) => value.resolve(resolver),
-    //             Operation::Binary(value) => value.resolve(resolver),
-    //             Operation::Unary(value) => value.resolve(resolver),
-    //             Operation::Call(value) => value.resolve(resolver),
-    //         }
-    //     }
-    // }
-    // impl Resolve for Assign {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Assign { target, operator, init } = self;
-    //         // Evaluate the initializer expression
-    //         let ty = init.resolve(resolver)?;
-    //         // Resolve the variable
-    //         match (operator, resolver.get_mut(&target.name)?) {
-    //             (
-    //                 operator::Assign::Assign,
-    //                 Variable { status: Status::Initialized(_), mutable: false, index },
-    //             ) => Err(Error::ImmutableAssign(target.name.clone(), *index)),
-    //             // TODO: make typing more expressive for modifying assignment
-    //             (_, variable) => variable
-    //                 .modify_assign(&target.name, &ty)
-    //                 .map(|_| Type::Empty),
-    //         }
-    //     }
-    // }
-
-    // impl Resolve for Binary {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Binary { first, other } = self;
-
-    //         let mut first = first.resolve(resolver)?;
-    //         for (op, other) in other {
-    //             let other = other.resolve(resolver)?;
-    //             first = resolver.resolve_binary_operator(first, other, op)?;
-    //         }
-    //         Ok(first)
-    //     }
-    // }
-    // impl Resolve for Unary {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Unary { operators, operand } = self;
-    //         let mut operand = operand.resolve(resolver)?;
-    //         for op in operators {
-    //             operand = resolver.resolve_unary_operator(operand, op)?;
-    //         }
-    //         Ok(operand)
-    //     }
-    // }
-    // /// Resolve [operator]s
-    // impl Resolver {
-    //     fn resolve_binary_operator(
-    //         &mut self,
-    //         first: Type,
-    //         other: Type,
-    //         op: &operator::Binary,
-    //     ) -> TyResult<Type> {
-    //         // TODO: check type compatibility for binary ops
-    //         // TODO: desugar binary ops into function calls, when member functions are a thing
-    //         eprintln!("Resolve binary operators {first} {op:?} {other}");
-    //         if first != other {
-    //             Err(Error::TypeMismatch { want: first, got: other })
-    //         } else {
-    //             Ok(first)
-    //         }
-    //     }
-    //     fn resolve_unary_operator(
-    //         &mut self,
-    //         operand: Type,
-    //         op: &operator::Unary,
-    //     ) -> TyResult<Type> {
-    //         // TODO: Allow more expressive unary operator type conversions
-    //         todo!("Resolve unary operators {op:?} {operand}")
-    //     }
-    // }
-    // impl Resolve for Call {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         match self {
-    //             Call::FnCall(value) => value.resolve(resolver),
-    //             Call::Primary(value) => value.resolve(resolver),
-    //         }
-    //     }
-    // }
-    // impl Resolve for FnCall {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let FnCall { callee, args } = self;
-    //         let mut callee = callee.resolve(resolver)?;
-    //         for argset in args {
-    //             // arguments should always be a tuple here
-    //             let arguments = argset.resolve(resolver)?;
-    //             let Type::Tuple(arguments) = arguments else {
-    //                 Err(Error::TypeMismatch {
-    //                     want: Type::Tuple(vec![Type::ManyInferred]),
-    //                     got: arguments,
-    //                 })?
-    //             };
-    //             // Verify that the callee is a function, and the arguments match.
-    //             // We need the arguments
-    //             let Type::Fn { args, ret } = callee else {
-    //                 return Err(Error::TypeMismatch {
-    //                     want: Type::Fn { args: arguments, ret: Type::Inferred.into() },
-    //                     got: callee,
-    //                 })?;
-    //             };
-    //             for (want, got) in args.iter().zip(&arguments) {
-    //                 // TODO: verify generics
-    //                 if let Type::Generic(_) = want {
-    //                     continue;
-    //                 }
-    //                 if want != got {
-    //                     return Err(Error::TypeMismatch {
-    //                         want: Type::Fn { args: arguments, ret: Type::Inferred.into() },
-    //                         got: Type::Fn { args, ret },
-    //                     })?;
-    //                 }
-    //             }
-    //             callee = *ret;
-    //         }
-    //         Ok(callee)
-    //     }
-    // }
-    // impl Resolve for Primary {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         match self {
-    //             Primary::Identifier(value) => value.resolve(resolver),
-    //             Primary::Literal(value) => value.resolve(resolver),
-    //             Primary::Block(value) => value.resolve(resolver),
-    //             Primary::Group(value) => value.resolve(resolver),
-    //             Primary::Branch(value) => value.resolve(resolver),
-    //         }
-    //     }
-    // }
-
-    // impl Resolve for Group {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         match self {
-    //             Group::Tuple(tuple) => tuple.resolve(resolver),
-    //             Group::Single(expr) => expr.resolve(resolver),
-    //             Group::Empty => Ok(Type::Empty),
-    //         }
-    //     }
-    // }
-
-    // impl Resolve for Tuple {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Tuple { elements } = self;
-    //         let mut types = vec![];
-    //         for expr in elements.iter_mut() {
-    //             types.push(expr.resolve(resolver)?);
-    //         }
-    //         Ok(Type::Tuple(types))
-    //     }
-    // }
-
-    // impl Resolve for Identifier {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Identifier { name, index: id_index } = self;
-    //         let Variable { index, status, .. } = resolver.get(name)?;
-    //         *id_index = Some(*index);
-    //         let ty = match status {
-    //             Status::Initialized(t) => t,
-    //             _ => Err(Error::Uninitialized(name.to_owned(), *index))?,
-    //         };
-    //         debugln!("ty> Resolved {} #{index}: {ty}", name);
-    //         Ok(ty.to_owned())
-    //     }
-    // }
-    // impl Resolve for Literal {
-    //     fn resolve(&mut self, _resolver: &mut Resolver) -> TyResult<Type> {
-    //         Ok(match self {
-    //             Literal::String(_) => Type::String,
-    //             Literal::Char(_) => Type::Char,
-    //             Literal::Bool(_) => Type::Bool,
-    //             Literal::Float(_) => Type::Float,
-    //             Literal::Int(_) => Type::Int,
-    //         })
-    //     }
-    // }
-
-    // impl Resolve for Flow {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         // TODO: Finish this
-    //         match self {
-    //             Flow::While(value) => value.resolve(resolver),
-    //             Flow::If(value) => value.resolve(resolver),
-    //             Flow::For(value) => value.resolve(resolver),
-    //             Flow::Continue(value) => value.resolve(resolver),
-    //             Flow::Return(value) => value.resolve(resolver),
-    //             Flow::Break(value) => value.resolve(resolver),
-    //         }
-    //     }
-    // }
-    // impl Resolve for While {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         // TODO: Finish this
-    //         // Visit else first, save that to a break-pattern stack in the Resolver,
-    //         // and check it inside Break::resolve()
-    //         let While { cond, body, else_ } = self;
-    //         cond.resolve(resolver)?; // must be Type::Bool
-    //         body.resolve(resolver)?; // discard
-    //         else_.resolve(resolver) // compare with returns inside body
-    //     }
-    // }
-    // impl Resolve for If {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let If { cond, body, else_ } = self;
-    //         let cond = cond.resolve(resolver)?;
-    //         if Type::Bool != cond {
-    //             return Err(Error::TypeMismatch { want: Type::Bool, got: cond });
-    //         }
-    //         let body_ty = body.resolve(resolver)?;
-    //         let else_ty = else_.resolve(resolver)?;
-    //         if body_ty == else_ty {
-    //             Ok(body_ty)
-    //         } else {
-    //             Err(Error::TypeMismatch { want: body_ty, got: else_ty })
-    //         }
-    //     }
-    // }
-
-    // impl Resolve for For {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let For { var: Identifier { name, index }, iter, body, else_ } = self;
-    //         debugln!("> for {name} in ...");
-    //         // Visit the iter expression and get its type
-    //         let range = iter.resolve(resolver)?;
-    //         let ty = match range {
-    //             Type::Range(t) => t,
-    //             got => Err(Error::TypeMismatch { want: Type::Range(Type::Inferred.into()), got
-    // })?,         };
-    //         let body_ty = {
-    //             let mut resolver = resolver.frame();
-    //             // bind the variable in the loop scope
-    //             *index = Some(resolver.insert_scope(name, false)?);
-    //             resolver.get_mut(name)?.assign(name, &ty)?;
-    //             body.resolve(&mut resolver)
-    //         }?;
-    //         // visit the else block
-    //         let else_ty = else_.resolve(resolver)?;
-    //         if body_ty != else_ty {
-    //             Err(Error::TypeMismatch { want: body_ty, got: else_ty })
-    //         } else {
-    //             Ok(body_ty)
-    //         }
-    //     }
-    // }
-    // impl Resolve for Else {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         let Else { expr } = self;
-    //         expr.resolve(resolver)
-    //     }
-    // }
-
-    // impl Resolve for Continue {
-    //     fn resolve(&mut self, _resolver: &mut Resolver) -> TyResult<Type> {
-    //         // TODO: Finish control flow
-    //         Ok(Type::Never)
-    //     }
-    // }
-    // impl Resolve for Break {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         // TODO: Finish control flow
-    //         let Break { expr } = self;
-    //         expr.resolve(resolver)
-    //     }
-    // }
-    // impl Resolve for Return {
-    //     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-    //         // TODO: Finish control flow
-    //         let Return { expr } = self;
-    //         expr.resolve(resolver)
-    //     }
-    // }
-}
-
-mod ast {
-    #![allow(unused_imports)]
-    use crate::ast::*;
-}
-
-// heakc yea man, generics
-impl<T: Resolve> Resolve for Option<T> {
-    fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-        match self {
-            Some(t) => t.resolve(resolver),
-            None => Ok(Type::Empty),
-        }
-    }
-}
-impl<T: Resolve> Resolve for Box<T> {
-    fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
-        self.as_mut().resolve(resolver)
-    }
-}
-
-use error::{Error, TyResult};
-pub mod error {
-    use super::Type;
-    use std::fmt::Display;
-
-    pub type TyResult<T> = Result<T, Error>;
-
-    impl std::error::Error for Error {}
-    #[derive(Clone, Debug)]
-    pub enum Error {
-        StackUnderflow,
-        // types
-        TypeMismatch { want: Type, got: Type },
-        // modules
-        NonUniqueInModule(String),
-        // lifetimes
-        Uninitialized(String, usize),
-        ImmutableAssign(String, usize),
-        Unbound(String),
-    }
-    impl Display for Error {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            match self {
-                Error::StackUnderflow => "Stack underflow in Resolver".fmt(f),
-                Error::TypeMismatch { want, got } => {
-                    write!(f, "Type error: {want} != {got}")
-                }
-                Error::ImmutableAssign(name, index) => {
-                    write!(f, "Cannot mutate immutable variable {name}(#{index})")
-                }
-                Error::Uninitialized(name, index) => {
-                    write!(f, "{name}(#{index}) was accessed before initialization")
-                }
-                Error::Unbound(name) => write!(f, "{name} not bound before use."),
-                Error::NonUniqueInModule(name) => {
-                    write!(f, "Name {name} not unique at module scope!")
-                }
-            }
-        }
-    }
-}

libconlang/src/tests.rs

@@ -1,181 +0,0 @@
-mod token {
-    // TODO
-}
-mod ast {
-    // TODO
-}
-mod lexer {
-    #[allow(unused_imports)]
-    use crate::{lexer::Lexer, token::preamble::*};
-
-    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),*) {
-            [$(Data::Identifier($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),*) {
-            [ $(Type::Keyword(Keyword::$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 {
-        use super::*;
-        test_lexer_output_type! {
-            l_curly   { "{ {"   => [ Type::LCurly, Type::LCurly ] }
-            r_curly   { "} }"   => [ Type::RCurly, Type::RCurly ] }
-            l_brack   { "[ ["   => [ Type::LBrack, Type::LBrack ] }
-            r_brack   { "] ]"   => [ Type::RBrack, Type::RBrack ] }
-            l_paren   { "( ("   => [ Type::LParen, Type::LParen ] }
-            r_paren   { ") )"   => [ Type::RParen, Type::RParen ] }
-            amp       { "& &"   => [ Type::Amp, Type::Amp ] }
-            amp_amp   { "&& &&" => [ Type::AmpAmp, Type::AmpAmp ] }
-            amp_eq    { "&= &=" => [ Type::AmpEq, Type::AmpEq ] }
-            arrow     { "-> ->" => [ Type::Arrow, Type::Arrow] }
-            at        { "@ @"   => [ Type::At, Type::At] }
-            backslash { "\\ \\" => [ Type::Backslash, Type::Backslash] }
-            bang      { "! !"   => [ Type::Bang, Type::Bang] }
-            bangbang  { "!! !!" => [ Type::BangBang, Type::BangBang] }
-            bangeq    { "!= !=" => [ Type::BangEq, Type::BangEq] }
-            bar       { "| |"   => [ Type::Bar, Type::Bar] }
-            barbar    { "|| ||" => [ Type::BarBar, Type::BarBar] }
-            bareq     { "|= |=" => [ Type::BarEq, Type::BarEq] }
-            colon     { ": :"   => [ Type::Colon, Type::Colon] }
-            comma     { ", ,"   => [ Type::Comma, Type::Comma] }
-            dot       { ". ."   => [ Type::Dot, Type::Dot] }
-            dotdot    { ".. .." => [ Type::DotDot, Type::DotDot] }
-            dotdoteq  { "..= ..=" => [ Type::DotDotEq, Type::DotDotEq] }
-            eq        { "= ="   => [ Type::Eq, Type::Eq] }
-            eqeq      { "== ==" => [ Type::EqEq, Type::EqEq] }
-            fatarrow  { "=> =>" => [ Type::FatArrow, Type::FatArrow] }
-            grave     { "` `"   => [ Type::Grave, Type::Grave] }
-            gt        { "> >"   => [ Type::Gt, Type::Gt] }
-            gteq      { ">= >=" => [ Type::GtEq, Type::GtEq] }
-            gtgt      { ">> >>" => [ Type::GtGt, Type::GtGt] }
-            gtgteq    { ">>= >>=" => [ Type::GtGtEq, Type::GtGtEq] }
-            hash      { "# #"   => [ Type::Hash, Type::Hash] }
-            lt        { "< <"   => [ Type::Lt, Type::Lt] }
-            lteq      { "<= <=" => [ Type::LtEq, Type::LtEq] }
-            ltlt      { "<< <<" => [ Type::LtLt, Type::LtLt] }
-            ltlteq    { "<<= <<=" => [ Type::LtLtEq, Type::LtLtEq] }
-            minus     { "- -"   => [ Type::Minus, Type::Minus] }
-            minuseq   { "-= -=" => [ Type::MinusEq, Type::MinusEq] }
-            plus      { "+ +"   => [ Type::Plus, Type::Plus] }
-            pluseq    { "+= +=" => [ Type::PlusEq, Type::PlusEq] }
-            question  { "? ?"   => [ Type::Question, Type::Question] }
-            rem       { "% %"   => [ Type::Rem, Type::Rem] }
-            remeq     { "%= %=" => [ Type::RemEq, Type::RemEq] }
-            semi      { "; ;"   => [ Type::Semi, Type::Semi] }
-            slash     { "/ /"   => [ Type::Slash, Type::Slash] }
-            slasheq   { "/= /=" => [ Type::SlashEq, Type::SlashEq] }
-            star      { "* *"   => [ Type::Star, Type::Star] }
-            stareq    { "*= *=" => [ Type::StarEq, Type::StarEq] }
-            tilde     { "~ ~"   => [ Type::Tilde, Type::Tilde] }
-            xor       { "^ ^"   => [ Type::Xor, Type::Xor] }
-            xoreq     { "^= ^=" => [ Type::XorEq, Type::XorEq] }
-            xorxor    { "^^ ^^" => [ Type::XorXor, Type::XorXor] }
-        }
-    }
-}
-mod parser {
-    // TODO
-}
-mod interpreter {
-    // TODO
-}

libconlang/src/token.rs

@@ -1,57 +0,0 @@
-//! # Token
-//!
-//! Stores a component of a file as a [Type], some [Data], and a line and column number
-
-pub mod token_data;
-pub mod token_type;
-pub mod preamble {
-    //! Common imports for working with [tokens](super)
-    pub use super::{
-        token_data::Data,
-        token_type::{Keyword, Type},
-        Token,
-    };
-}
-
-use token_data::Data;
-use token_type::Type;
-
-/// Contains a single unit of lexical information,
-/// and an optional bit of [Data]
-#[derive(Clone, Debug, PartialEq)]
-pub struct Token {
-    ty: Type,
-    data: Data,
-    line: u32,
-    col: u32,
-}
-impl Token {
-    /// Creates a new [Token] out of a [Type], [Data], line, and column.
-    pub fn new(ty: Type, data: impl Into<Data>, line: u32, col: u32) -> Self {
-        Self { ty, data: data.into(), line, col }
-    }
-    /// Casts this token to a new [Type]
-    pub fn cast(self, ty: Type) -> Self {
-        Self { ty, ..self }
-    }
-    /// Returns the [Type] of this token
-    pub fn ty(&self) -> Type {
-        self.ty
-    }
-    /// Returns a reference to this token's [Data]
-    pub fn data(&self) -> &Data {
-        &self.data
-    }
-    /// Converts this token into its inner [Data]
-    pub fn into_data(self) -> Data {
-        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
-    }
-}

libconlang/src/token/token_type.rs

@@ -1,239 +0,0 @@
-//! 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 Type {
-    // Invalid syntax
-    Invalid,
-    // Any kind of comment
-    Comment,
-    // Any identifier
-    Identifier,
-    Keyword(Keyword),
-    // Literals
-    Integer,
-    Float,
-    String,
-    Character,
-    // Delimiters and 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,     // ^^
-}
-
-/// Represents a reserved word.
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
-pub enum Keyword {
-    Break,
-    Cl,
-    Const,
-    Continue,
-    Else,
-    Enum,
-    False,
-    For,
-    Fn,
-    If,
-    Impl,
-    In,
-    Let,
-    Mod,
-    Mut,
-    Pub,
-    Return,
-    SelfKw,
-    SelfTy,
-    Static,
-    Struct,
-    Super,
-    True,
-    Type,
-    While,
-}
-
-impl Display for Type {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Type::Invalid => "invalid".fmt(f),
-            Type::Comment => "comment".fmt(f),
-            Type::Identifier => "identifier".fmt(f),
-            Type::Keyword(k) => k.fmt(f),
-            Type::Integer => "integer literal".fmt(f),
-            Type::Float => "float literal".fmt(f),
-            Type::String => "string literal".fmt(f),
-            Type::Character => "char literal".fmt(f),
-            Type::LCurly => "left curly".fmt(f),
-            Type::RCurly => "right curly".fmt(f),
-            Type::LBrack => "left brack".fmt(f),
-            Type::RBrack => "right brack".fmt(f),
-            Type::LParen => "left paren".fmt(f),
-            Type::RParen => "right paren".fmt(f),
-            Type::Amp => "and".fmt(f),
-            Type::AmpAmp => "and-and".fmt(f),
-            Type::AmpEq => "and-assign".fmt(f),
-            Type::Arrow => "arrow".fmt(f),
-            Type::At => "at".fmt(f),
-            Type::Backslash => "backslash".fmt(f),
-            Type::Bang => "bang".fmt(f),
-            Type::BangBang => "not-not".fmt(f),
-            Type::BangEq => "not equal to".fmt(f),
-            Type::Bar => "or".fmt(f),
-            Type::BarBar => "or-or".fmt(f),
-            Type::BarEq => "or-assign".fmt(f),
-            Type::Colon => "colon".fmt(f),
-            Type::ColonColon => "path separator".fmt(f),
-            Type::Comma => "comma".fmt(f),
-            Type::Dot => "dot".fmt(f),
-            Type::DotDot => "exclusive range".fmt(f),
-            Type::DotDotEq => "inclusive range".fmt(f),
-            Type::Eq => "assign".fmt(f),
-            Type::EqEq => "equal to".fmt(f),
-            Type::FatArrow => "fat arrow".fmt(f),
-            Type::Grave => "grave".fmt(f),
-            Type::Gt => "greater than".fmt(f),
-            Type::GtEq => "greater than or equal to".fmt(f),
-            Type::GtGt => "shift right".fmt(f),
-            Type::GtGtEq => "shift right-assign".fmt(f),
-            Type::Hash => "hash".fmt(f),
-            Type::HashBang => "shebang".fmt(f),
-            Type::Lt => "less than".fmt(f),
-            Type::LtEq => "less than or equal to".fmt(f),
-            Type::LtLt => "shift left".fmt(f),
-            Type::LtLtEq => "shift left-assign".fmt(f),
-            Type::Minus => "sub".fmt(f),
-            Type::MinusEq => "sub-assign".fmt(f),
-            Type::Plus => "add".fmt(f),
-            Type::PlusEq => "add-assign".fmt(f),
-            Type::Question => "huh?".fmt(f),
-            Type::Rem => "rem".fmt(f),
-            Type::RemEq => "rem-assign".fmt(f),
-            Type::Semi => "ignore".fmt(f),
-            Type::Slash => "div".fmt(f),
-            Type::SlashEq => "div-assign".fmt(f),
-            Type::Star => "star".fmt(f),
-            Type::StarEq => "star-assign".fmt(f),
-            Type::Tilde => "tilde".fmt(f),
-            Type::Xor => "xor".fmt(f),
-            Type::XorEq => "xor-assign".fmt(f),
-            Type::XorXor => "cat-ears".fmt(f),
-        }
-    }
-}
-
-impl Display for Keyword {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Self::Break => "break".fmt(f),
-            Self::Cl => "cl".fmt(f),
-            Self::Const => "const".fmt(f),
-            Self::Continue => "continue".fmt(f),
-            Self::Else => "else".fmt(f),
-            Self::Enum => "enum".fmt(f),
-            Self::False => "false".fmt(f),
-            Self::For => "for".fmt(f),
-            Self::Fn => "fn".fmt(f),
-            Self::If => "if".fmt(f),
-            Self::Impl => "impl".fmt(f),
-            Self::In => "in".fmt(f),
-            Self::Let => "let".fmt(f),
-            Self::Mod => "mod".fmt(f),
-            Self::Mut => "mut".fmt(f),
-            Self::Pub => "pub".fmt(f),
-            Self::Return => "return".fmt(f),
-            Self::SelfKw => "self".fmt(f),
-            Self::SelfTy => "Self".fmt(f),
-            Self::Static => "static".fmt(f),
-            Self::Struct => "struct".fmt(f),
-            Self::Super => "super".fmt(f),
-            Self::True => "true".fmt(f),
-            Self::Type => "type".fmt(f),
-            Self::While => "while".fmt(f),
-        }
-    }
-}
-impl FromStr for Keyword {
-    /// [FromStr] can only fail when an identifier isn't a keyword
-    type Err = ();
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        Ok(match s {
-            "break" => Self::Break,
-            "cl" => Self::Cl,
-            "const" => Self::Const,
-            "continue" => Self::Continue,
-            "else" => Self::Else,
-            "enum" => Self::Enum,
-            "false" => Self::False,
-            "for" => Self::For,
-            "fn" => Self::Fn,
-            "if" => Self::If,
-            "impl" => Self::Impl,
-            "in" => Self::In,
-            "let" => Self::Let,
-            "mod" => Self::Mod,
-            "mut" => Self::Mut,
-            "pub" => Self::Pub,
-            "return" => Self::Return,
-            "self" => Self::SelfKw,
-            "Self" => Self::SelfTy,
-            "static" => Self::Static,
-            "struct" => Self::Struct,
-            "super" => Self::Super,
-            "true" => Self::True,
-            "type" => Self::Type,
-            "while" => Self::While,
-            _ => Err(())?,
-        })
-    }
-}

readme.md

@@ -1,8 +1,7 @@
 # Conlang: Expression-Oriented Programming Language
 This project began out of a desire to merge Rust-style control flow expressions 
 with Python's fun for-else/while-else syntax. I fully intend to devote my spare time
-to conlang for the forseeable future, and I livestream development on Twitch for one 
-Friday each month.
+to conlang for the forseeable future.
 
 ## Immediate Goals:
 - [x] Decide on a minimal set of keywords and operators to support
@@ -20,10 +19,11 @@ Friday each month.
 ## Short Goals:
 - [x] `for` loops and `while` loops can be used on the trailing side of an assignment
 - [x] Tree-walk interpreter for prototyping and debugging
-- [ ] Data structures and sum-type enums
+- [x] Data structures and sum-type enums
 - [ ] Expression type-checker
-- [ ] Trait/Interface system
+- [ ] Pattern destructuring, to take advantage of sum-type enums
 - [ ] Three-address bytecode VM for standard library development
+- [ ] Trait/Interface system
 
 ## Long Goals:
 - [ ] Minimize the number of kinds of statements

repline/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "repline"
+repository.workspace = true
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]
+crossterm = { version = "0.27.0", default-features = false }

repline/src/editor.rs

@@ -0,0 +1,324 @@
+//! The [Editor] is a multi-line buffer of [`char`]s which operates on an ANSI-compatible terminal.
+
+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(())
+}
+
+/// A multi-line editor which operates on an un-cleared ANSI terminal.
+#[derive(Clone, 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> {
+    /// Constructs a new Editor with the provided prompt color, begin prompt, and again prompt.
+    pub fn new(color: &'a str, begin: &'a str, again: &'a str) -> Self {
+        Self { head: Default::default(), tail: Default::default(), color, begin, again }
+    }
+
+    /// Returns an iterator over characters in the editor.
+    pub fn iter(&self) -> impl Iterator<Item = &char> {
+        let Self { head, tail, .. } = self;
+        head.iter().chain(tail.iter())
+    }
+
+    /// Moves up to the first line of the editor, and clears the screen.
+    ///
+    /// This assumes the screen hasn't moved since the last draw.
+    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(())
+    }
+
+    /// Redraws the entire editor
+    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(())
+    }
+
+    /// Prints a context-sensitive prompt (either `begin` if this is the first line,
+    /// or `again` for subsequent lines)
+    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(())
+    }
+
+    /// Prints the characters before the cursor on the current line.
+    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(())
+    }
+
+    /// Prints the characters after the cursor on the current line.
+    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(())
+    }
+
+    /// Writes a character at the cursor, shifting the text around as necessary.
+    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(())
+    }
+
+    /// Erases a character at the cursor, shifting the text around as necessary.
+    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)
+    }
+
+    /// Writes characters into the editor at the location of the cursor.
+    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(())
+    }
+
+    /// Sets the editor to the contents of a string, placing the cursor at the end.
+    pub fn restore(&mut self, s: &str) {
+        self.clear();
+        self.head.extend(s.chars())
+    }
+
+    /// Clears the editor, removing all characters.
+    pub fn clear(&mut self) {
+        self.head.clear();
+        self.tail.clear();
+    }
+
+    /// Pops the character after the cursor, redrawing if necessary
+    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)
+    }
+
+    /// Erases a word from the buffer, where a word is any non-whitespace characters
+    /// preceded by a single whitespace character
+    pub fn erase_word<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
+        while self.pop(w)?.filter(|c| !c.is_whitespace()).is_some() {}
+        Ok(())
+    }
+
+    /// Returns the number of characters in the buffer
+    pub fn len(&self) -> usize {
+        self.head.len() + self.tail.len()
+    }
+
+    /// Returns true if the buffer is empty.
+    pub fn is_empty(&self) -> bool {
+        self.head.is_empty() && self.tail.is_empty()
+    }
+
+    /// Returns true if the buffer ends with a given pattern
+    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(())
+    }
+
+    /// Moves the cursor 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)?,
+            }
+        }
+    }
+
+    /// Moves the cursor 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;
+        for c in self.iter() {
+            f.write_char(*c)?;
+        }
+        Ok(())
+    }
+}

repline/src/error.rs

@@ -0,0 +1,42 @@
+use crate::iter::chars::BadUnicode;
+
+/// 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, "\\u{{{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)
+    }
+}
+impl From<BadUnicode> for Error {
+    fn from(value: BadUnicode) -> Self {
+        let BadUnicode(code) = value;
+        Self::BadUnicode(code)
+    }
+}

repline/src/iter.rs

@@ -0,0 +1,68 @@
+//! Shmancy iterator adapters
+
+pub use chars::Chars;
+pub use flatten::Flatten;
+
+pub mod chars {
+    //! Converts an <code>[Iterator]<Item = [u8]></code> into an
+    //! <code>[Iterator]<Item = [Result]<[char], [BadUnicode]>></code>
+
+    /// Invalid unicode codepoint found when iterating over [Chars]
+    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+    pub struct BadUnicode(pub u32);
+    impl std::error::Error for BadUnicode {}
+    impl std::fmt::Display for BadUnicode {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self(code) = self;
+            write!(f, "Bad unicode: {code}")
+        }
+    }
+
+    /// 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>> Iterator for Chars<I> {
+        type Item = Result<char, BadUnicode>;
+        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(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`
+    #[derive(Clone, Debug)]
+    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()?
+        }
+    }
+}

repline/src/lib.rs

@@ -0,0 +1,13 @@
+//! A small pseudo-multiline editing library
+
+mod editor;
+mod iter;
+mod raw;
+
+pub mod error;
+pub mod prebaked;
+pub mod repline;
+
+pub use error::Error;
+pub use prebaked::{read_and, Response};
+pub use repline::Repline;

repline/src/prebaked.rs

@@ -0,0 +1,56 @@
+//! Here's a menu I prepared earlier!
+//!
+//! Constructs a [Repline] and repeatedly runs the provided closure on the input strings,
+//! obeying the closure's [Response].
+
+use std::error::Error;
+
+use crate::{error::Error as RlError, repline::Repline};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+/// Control codes for the [prebaked menu](read_and)
+pub enum Response {
+    /// Accept the line, and save it to history
+    Accept,
+    /// Reject the line, and clear the buffer
+    Deny,
+    /// End the loop
+    Break,
+    /// Gather more input and try again
+    Continue,
+}
+
+/// Implements a basic menu loop using an embedded [Repline].
+///
+/// Repeatedly runs the provided closure on the input strings,
+/// obeying the closure's [Response].
+///
+/// Captures and displays all user [Error]s.
+///
+/// # Keybinds
+/// - `Ctrl+C` exits the loop
+/// - `Ctrl+D` clears the input, but *runs the closure* with the old input
+pub fn read_and<F>(color: &str, begin: &str, again: &str, mut f: F) -> Result<(), RlError>
+where F: FnMut(&str) -> Result<Response, Box<dyn Error>> {
+    let mut rl = Repline::new(color, begin, again);
+    loop {
+        let line = match rl.read() {
+            Err(RlError::CtrlC(_)) => break,
+            Err(RlError::CtrlD(line)) => {
+                rl.deny();
+                line
+            }
+            Ok(line) => line,
+            Err(e) => Err(e)?,
+        };
+        print!("\x1b[G\x1b[J");
+        match f(&line) {
+            Ok(Response::Accept) => rl.accept(),
+            Ok(Response::Deny) => rl.deny(),
+            Ok(Response::Break) => break,
+            Ok(Response::Continue) => continue,
+            Err(e) => print!("\x1b[40G\x1b[A\x1bJ\x1b[91m{e}\x1b[0m\x1b[B"),
+        }
+    }
+    Ok(())
+}

repline/src/raw.rs

@@ -0,0 +1,21 @@
+//! 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");
+    }
+}

repline/src/repline.rs

@@ -0,0 +1,175 @@
+//! Prompts the user, reads the lines. Not much more to it than that.
+//!
+//! This module is in charge of parsing keyboard input and interpreting it for the line editor.
+
+use crate::{editor::Editor, error::*, iter::*, raw::raw};
+use std::{
+    collections::VecDeque,
+    io::{stdout, Bytes, Read, Result, Write},
+};
+
+/// Prompts the user, reads the lines. Not much more to it than that.
+#[derive(Debug)]
+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> 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)
+    }
+}
+
+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
+    }
+    /// Append line to history and clear it
+    pub fn accept(&mut self) {
+        self.history_append(self.ed.to_string());
+        self.ed.clear();
+        self.hindex = self.history.len();
+    }
+    /// Clear the line
+    pub fn deny(&mut self) {
+        self.ed.clear()
+    }
+    /// 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.
+                '\x03' => {
+                    drop(_make_raw);
+                    writeln!(stdout)?;
+                    return Err(Error::CtrlC(self.ed.to_string()));
+                }
+                // Ctrl+D: End of Transmission. Ends the current line.
+                '\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());
+                }
+                // Ctrl+Backspace in my terminal
+                '\x17' => {
+                    self.ed.erase_word(stdout)?;
+                }
+                // 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) {
+                        self.ed.extend(c.escape_debug(), stdout)?;
+                    }
+                }
+                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(other.escape_debug(), 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());
+                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)?? {
+                    let _ = self.ed.delete(w);
+                }
+            }
+            other => {
+                if cfg!(debug_assertions) {
+                    self.ed.extend(other.escape_debug(), w)?;
+                }
+            }
+        }
+        Ok(())
+    }
+    /// Restores the currently selected history
+    fn restore_history<W: Write>(&mut self, w: &mut W) -> ReplResult<()> {
+        let Self { history, hindex, ed, .. } = self;
+        ed.undraw(w)?;
+        ed.clear();
+        ed.print_head(w)?;
+        if let Some(history) = history.get(*hindex) {
+            ed.extend(history.chars(), w)?
+        }
+        Ok(())
+    }
+
+    /// Append line to history
+    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();
+        }
+    }
+}

sample-code/fib.cl

@@ -0,0 +1,29 @@
+// Calculate Fibonacci numbers
+
+fn main() {
+    for num in 0..=30 {
+        print("fib(", num, ") = ", fib_iterative(num))
+    }
+    for num in 0..=30 {
+        print("fib(", num, ") = ", fib(num))
+    }
+}
+
+/// The classic recursive definition of fib()
+fn fib(a: i64) -> i64 {
+    if a > 1 {
+        fib(a - 1) + fib(a - 2)
+    } else a
+}
+
+/// The classic iterative algorithm for fib()
+fn fib_iterative(n: i64) -> i64 {
+    let mut a = 0;
+    let mut b = 1;
+    let mut c = 1;
+    for _ in 0..n {
+        a = b;
+        b = c;
+        c = a + b;
+    } else a
+}

sample-code/fizzbuzz.cl

@@ -1,11 +1,11 @@
 // FizzBuzz, using the unstable variadic-`print` builtin
 
 fn main() {
-    fizz_buzz(10, 20)
+    fizzbuzz(10, 20)
 }
 
 // Outputs FizzBuzz for numbers between `start` and `end`, inclusive
-fn fizz_buzz(start: i128, end: i128) {
+fn fizzbuzz(start: i128, end: i128) {
     for x in start..=end {
         print(if x % 15 == 0 {
             "FizzBuzz"

sample-code/hello.cl

@@ -0,0 +1,3 @@
+fn main() {
+    print("Hello, world!")
+}

sample-code/hex.cl

@@ -0,0 +1,31 @@
+//! Formats numbers in hexadecimal, octal, or binary
+mod math;
+
+// TODO: casting and/or conversion
+const HEX_LUT: Array = [
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
+];
+
+pub fn hex(n: u64) {
+    let out = "0x";
+    for xd in min(count_leading_zeroes(n) / 4, 15)..16 {
+        out += HEX_LUT[(n >> (15 - xd) * 4) & 0xf]
+    }
+    out
+}
+
+pub fn oct(n: u64) {
+    let out = "0o";
+    for xd in min((count_leading_zeroes(n) + 2) / 3, 21)..22 {
+        out += HEX_LUT[(n >> max(63 - (3 * xd), 0)) & 7]
+    }
+    out
+}
+
+pub fn bin(n: u64) {
+    let out = "0b";
+    for xd in min(count_leading_zeroes(n), 63)..64 {
+        out += HEX_LUT[(n >> 63 - xd) & 1]
+    }
+    out
+}