diff --git a/src/bin/doughlang.rs b/src/bin/doughlang.rs
index f17700e..40503bb 100644
--- a/src/bin/doughlang.rs
+++ b/src/bin/doughlang.rs
@@ -1,13 +1,15 @@
 //! Tests the lexer\
 use doughlang::{
     ast::{
-        Anno, Annotation, Bind, Expr, Pat, Use,
+        Anno, Annotation, Bind, DefaultTypes, Expr, Pat, Use,
         macro_matcher::{Match, Subst},
+        visit::Walk,
     },
     lexer::{EOF, LexError, Lexer},
     parser::{Parse, ParseError, Parser},
     span::Span,
     token::{TKind, Token},
+    typeck::Collector,
 };
 use repline::prebaked::*;
 use std::{
@@ -25,6 +27,7 @@ enum Verbosity {
     #[default]
     Pretty,
     Debug,
+    Frob,
     Quiet,
 }
 impl From<&str> for Verbosity {
@@ -32,6 +35,7 @@ impl From<&str> for Verbosity {
         match value {
             "quiet" | "false" | "0" | "no" => Verbosity::Quiet,
             "debug" | "d" => Verbosity::Debug,
+            "frob" => Verbosity::Frob,
             "pretty" => Verbosity::Pretty,
             _ => Default::default(),
         }
@@ -99,7 +103,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                 println!("Parse mode set to '{parsing:?}'");
                 Ok(Response::Accept)
             }
-            line @ ("quiet" | "debug" | "pretty") => {
+            line @ ("quiet" | "debug" | "frob" | "pretty") => {
                 verbose = Verbosity::from(line);
                 println!("Verbosity set to '{verbose:?}'");
                 Ok(Response::Accept)
@@ -194,7 +198,10 @@ fn tokens<'t, T: Parse<'t> + ?Sized>(document: &'t str, verbose: Verbosity) {
     }
 }
 
-fn parse<'t, T: Parse<'t> + Annotation>(document: &'t str, verbose: Verbosity) {
+fn parse<'t, T: Parse<'t> + Annotation + for<'a> Walk<'a, DefaultTypes>>(
+    document: &'t str,
+    verbose: Verbosity,
+) {
     let mut parser = Parser::new(Lexer::new(document));
     for idx in 0.. {
         match (parser.parse::<Anno<T, _>>(T::Prec::default()), verbose) {
@@ -223,6 +230,10 @@ fn parse<'t, T: Parse<'t> + Annotation>(document: &'t str, verbose: Verbosity) {
             (Ok(Anno(expr, span)), Verbosity::Pretty) => {
                 println!("\x1b[{}m{span}:\n{expr}", (idx + 5) % 6 + 31);
             }
+            (Ok(Anno(expr, span)), Verbosity::Frob) => {
+                println!("\x1b[{}m{span}:\n", (idx + 5) % 6 + 31);
+                let _ = expr.visit_in(&mut Collector::new());
+            }
             (Ok(Anno(expr, span)), Verbosity::Debug) => {
                 println!("\x1b[{}m{span}:\n{expr:#?}", (idx + 5) % 6 + 31);
             }
diff --git a/src/lib.rs b/src/lib.rs
index f24beb9..385f23d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,8 +18,6 @@ pub mod parser;
 
 pub mod typed_ast {
     //! The Typed AST defines an interface between the type checker and code generator
-
-    use crate::span::Span;
     use std::collections::HashMap;
 
     pub struct Table {
@@ -29,16 +27,278 @@ pub mod typed_ast {
         pub local: HashMap<usize, isize>,
     }
 
-    /// `DefID` annotation
-    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-    pub struct Defn {
-        pub span: Span,
-        /// The index of this name in the associated Table
-        pub defid: usize,
+    #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+    pub enum Vis {
+        #[default]
+        Private,
+        Public,
+    }
+
+    #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+    pub enum Mut {
+        #[default]
+        Not,
+        Mut,
+    }
+
+    #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+    pub enum Binding {
+        #[default]
+        Const,
+        Static,
+        Local,
     }
 }
 
-pub mod typeck {}
+pub mod typeck {
+    use crate::{
+        ast::{
+            types::Symbol,
+            visit::{Visit, Walk},
+            *,
+        },
+        typed_ast::{Binding, Mut, Vis},
+    };
+
+    /*
+    TODO:
+    - Make Expr polymorphic over the Path type
+    - Construct disjoint set forest of names
+    - Replace names with their resolved module identifiers
+
+
+    Pattern matching
+
+    A ::=           Decision trees
+        Leaf(k)     success (k is an action, an integer)
+        Fail        failure
+        Switch(L)  multi-way test (o is an occurrence)
+        Swap(A)    stack swap (i is an integer)
+
+
+
+    What information do I need to collect before type inference can be run?
+    1. Where all the items are
+    2. Where all the imports link to
+
+    How do I represent that information?
+
+    - Directed graph?
+
+    How do I represent a *lazy* back edge?
+    */
+
+    #[derive(Clone, Copy, Debug, Default)]
+    pub enum List<'parent, T> {
+        Cons(&'parent List<'parent, T>, T),
+        #[default]
+        Nil,
+    }
+
+    impl<'parent, T> List<'parent, T> {
+        pub fn new(value: T) -> List<'static, T> {
+            List::Cons(&List::Nil, value)
+        }
+
+        pub fn enter<'a>(&'a self, value: T) -> List<'a, T>
+        where T: 'a {
+            List::Cons(self, value)
+        }
+
+        pub fn parent(&self) -> Option<&List<'parent, T>> {
+            match self {
+                Self::Cons(parent, _) => Some(parent),
+                Self::Nil => None,
+            }
+        }
+    }
+
+    type Path<'parent> = List<'parent, Symbol>;
+
+    impl From<Path<'_>> for crate::ast::types::Path {
+        fn from(value: Path<'_>) -> Self {
+            fn inner(path: &Path<'_>, vec: &mut Vec<Symbol>) {
+                match path {
+                    List::Nil => {}
+                    &List::Cons(nested, name) => {
+                        inner(nested, vec);
+                        vec.push(name);
+                    }
+                }
+            }
+
+            let mut parts = vec![];
+            inner(&value, &mut parts);
+            Self { parts }
+        }
+    }
+
+    impl std::fmt::Display for Path<'_> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            match self {
+                Self::Cons(Self::Nil, name) => name.fmt(f),
+                Self::Cons(parent, name) => write!(f, "{parent}::{name}"),
+                Self::Nil => Ok(()),
+            }
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct Collector<'parent, 'source, A: AstTypes> {
+        pub path: List<'parent, &'parent A::Symbol>,
+        pub meta: List<'parent, &'source Expr<A>>,
+        pub visible: Vis,
+        pub mutable: Mut,
+        pub binding: Binding,
+    }
+
+    impl<'parent, 'source, A: AstTypes> Default for Collector<'parent, 'source, A> {
+        fn default() -> Self {
+            Self {
+                path: Default::default(),
+                meta: Default::default(),
+                visible: Default::default(),
+                mutable: Default::default(),
+                binding: Default::default(),
+            }
+        }
+    }
+
+    impl<'a, 'source, A: AstTypes> Collector<'a, 'source, A> {
+        pub fn new() -> Collector<'static, 'static, A> {
+            Collector::default()
+        }
+
+        pub fn scope<'b>(&'b self, name: &'b A::Symbol) -> Collector<'b, 'source, A> {
+            Collector { path: self.path.enter(name), ..*self }
+        }
+
+        pub fn module<'b>(&'b self, part: &'b A::Symbol) -> Collector<'b, 'source, A> {
+            let Collector { path, .. } = self;
+            Collector { path: path.enter(part), binding: Binding::Const, ..Default::default() }
+        }
+
+        pub fn function<'b>(&'b self, part: &'b A::Symbol) -> Collector<'b, 'source, A> {
+            let Collector { path, .. } = self;
+            Collector { path: path.enter(part), binding: Binding::Local, ..Default::default() }
+        }
+
+        pub fn meta<'e>(&self, expr: &'e Expr<A>) -> Collector<'_, 'e, A>
+        where 'source: 'e {
+            let &Self { path, ref meta, .. } = self;
+            Collector { path, meta: meta.enter(expr), ..*self }
+        }
+
+        pub fn visible(&self, visible: Vis) -> Self {
+            Self { visible, ..*self }
+        }
+        pub fn mutable(&self, mutable: Mut) -> Self {
+            Self { mutable, ..*self }
+        }
+        pub fn bindmode(&self, binding: Binding) -> Self {
+            Self { binding, ..*self }
+        }
+    }
+
+    impl<A: AstTypes> std::fmt::Display for Collector<'_, '_, A> {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { path, meta, visible, mutable, binding } = self;
+
+            fn walk_meta<A: AstTypes>(
+                f: &mut std::fmt::Formatter<'_>,
+                meta: &List<'_, &Expr<A>>,
+            ) -> std::fmt::Result {
+                match meta {
+                    List::Cons(nested, expr) => {
+                        walk_meta(f, nested)?;
+                        writeln!(f, "{expr}")
+                    }
+                    List::Nil => Ok(()),
+                }
+            }
+            fn walk_path<D: std::fmt::Display>(
+                f: &mut std::fmt::Formatter<'_>,
+                meta: &List<'_, &D>,
+            ) -> std::fmt::Result {
+                match meta {
+                    List::Cons(nested, expr) => {
+                        walk_path(f, nested)?;
+                        write!(f, "::{expr}")
+                    }
+                    List::Nil => Ok(()),
+                }
+            }
+
+            walk_meta(f, meta)?;
+            match binding {
+                Binding::Const => "const ",
+                Binding::Static => "static ",
+                Binding::Local => "local ",
+            }
+            .fmt(f)?;
+
+            match visible {
+                Vis::Private => "",
+                Vis::Public => "pub ",
+            }
+            .fmt(f)?;
+
+            match mutable {
+                Mut::Not => "",
+                Mut::Mut => "mut ",
+            }
+            .fmt(f)?;
+
+            walk_path(f, path)
+        }
+    }
+
+    impl<'b> Visit<'b, DefaultTypes> for Collector<'_, '_, DefaultTypes> {
+        type Error = ();
+
+        fn visit_expr(&mut self, expr: &'b Expr) -> Result<(), Self::Error> {
+            match expr {
+                Expr::Op(Op::Pub, exprs) => self.visible(Vis::Public).visit(exprs),
+                Expr::Op(Op::Const, exprs) => self.bindmode(Binding::Const).visit(exprs),
+                Expr::Op(Op::Static, exprs) => self.bindmode(Binding::Static).visit(exprs),
+                Expr::Op(Op::Meta, exprs) => match exprs.as_slice() {
+                    [Anno(meta, _), exprs @ ..] => self.meta(meta).visit(exprs),
+                    [] => Ok(()),
+                },
+                _ => expr.children(self),
+            }
+        }
+
+        fn visit_bind(&mut self, item: &'b Bind) -> Result<(), Self::Error> {
+            if let Bind(BindOp::Match | BindOp::Impl, _, pat, ..) = item {
+                // TODO: convert patterns into concrete type annotations
+                return item.children(&mut self.scope(&pat.to_string().as_str().into()));
+            }
+            println!("{self}::{}", item.2);
+
+            match item {
+                Bind(BindOp::Fn, _, Pat::Op(PatOp::TypePrefixed, pats), exprs) => {
+                    match pats.as_slice() {
+                        [Pat::Name(name), ..] => self.function(name).visit(exprs),
+                        [other, ..] => {
+                            println!("Warning: unhandled fn pattern: {other}");
+                            Ok(())
+                        }
+                        [] => Ok(()),
+                    }
+                }
+                Bind(BindOp::Mod, _, Pat::Name(name), exprs) => self.module(name).visit(exprs),
+                _ => item.children(
+                    &mut self
+                        .visible(Vis::Private)
+                        .scope(&Symbol::from(format!("{:?}", item.0).as_str())),
+                ),
+            }?;
+
+            Ok(())
+        }
+    }
+}
 
 pub mod ir {
     //! The IR defines an interface between the code generator and interpreter(?)