diff --git a/schala-lang/language/src/ast/mod.rs b/schala-lang/language/src/ast/mod.rs
index 3f54d24..8e22b2a 100644
--- a/schala-lang/language/src/ast/mod.rs
+++ b/schala-lang/language/src/ast/mod.rs
@@ -1,16 +1,14 @@
 #![allow(clippy::upper_case_acronyms)]
 #![allow(clippy::enum_variant_names)]
 
+mod visitor;
+mod operators;
+
+pub use operators::{PrefixOp, BinOp};
+pub use visitor::{walk_ast, ASTVisitor};
+
 use std::rc::Rc;
 use crate::derivative::Derivative;
-
-mod walker;
-mod visitor;
-mod visitor_test;
-mod operators;
-pub use operators::{PrefixOp, BinOp};
-pub use visitor::ASTVisitor;
-pub use walker::walk_ast;
 use crate::tokenizing::Location;
 
 /// An abstract identifier for an AST node. Note that
diff --git a/schala-lang/language/src/ast/visitor.rs b/schala-lang/language/src/ast/visitor.rs
index 3514e98..8d16ed2 100644
--- a/schala-lang/language/src/ast/visitor.rs
+++ b/schala-lang/language/src/ast/visitor.rs
@@ -1,43 +1,212 @@
-use std::rc::Rc;
 use crate::ast::*;
 
-//TODO maybe these functions should take closures that return a KeepRecursing | StopHere type,
-//or a tuple of (T, <that type>)
-
 pub trait ASTVisitor: Sized {
-  fn ast(&mut self, _ast: &AST) {}
-  fn block(&mut self, _statements: &[ Statement ]) {}
-  fn statement(&mut self, _statement: &Statement) {}
-  fn declaration(&mut self, _declaration: &Declaration) {}
-  fn signature(&mut self, _signature: &Signature) {}
-  fn type_declaration(&mut self, _name: &TypeSingletonName, _body: &TypeBody, _mutable: bool) {}
-  fn type_alias(&mut self, _alias: &Rc<String>, _original: &Rc<String>) {}
-  fn binding(&mut self, _name: &Rc<String>, _constant: bool, _type_anno: Option<&TypeIdentifier>, _expr: &Expression) {}
-  fn implemention(&mut self, _type_name: &TypeIdentifier, _interface_name: Option<&TypeSingletonName>, _block: &[ Declaration ]) {}
-  fn interface(&mut self, _name: &Rc<String>, _signatures: &[ Signature ]) {}
-  fn expression(&mut self, _expression: &Expression) {}
-  fn expression_kind(&mut self, _kind: &ExpressionKind) {}
-  fn type_annotation(&mut self, _type_anno: Option<&TypeIdentifier>) {}
-  fn named_struct(&mut self, _name: &QualifiedName, _fields: &[ (Rc<String>, Expression) ]) {}
-  fn call(&mut self, _f: &Expression, _arguments: &[ InvocationArgument ]) {}
-  fn index(&mut self, _indexee: &Expression, _indexers: &[ Expression ]) {}
-  fn if_expression(&mut self, _discrim: Option<&Expression>, _body: &IfExpressionBody) {}
-  fn condition_arm(&mut self, _arm: &ConditionArm) {}
-  #[allow(clippy::ptr_arg)]
-  fn while_expression(&mut self, _condition: Option<&Expression>, _body: &Block) {}
-  fn for_expression(&mut self, _enumerators: &[ Enumerator ], _body: &ForBody) {}
-  #[allow(clippy::ptr_arg)]
-  fn lambda(&mut self, _params: &[ FormalParam ], _type_anno: Option<&TypeIdentifier>, _body: &Block) {}
-  fn invocation_argument(&mut self, _arg: &InvocationArgument) {}
-  fn formal_param(&mut self, _param: &FormalParam) {}
-  fn import(&mut self, _import: &ImportSpecifier) {}
-  fn module(&mut self, _module: &ModuleSpecifier) {}
-  fn qualified_name(&mut self, _name: &QualifiedName) {}
-  fn nat_literal(&mut self, _n: u64) {}
-  fn float_literal(&mut self, _f: f64) {}
-  fn string_literal(&mut self, _s: &Rc<String>) {}
-  fn bool_literal(&mut self, _b: bool) {}
-  fn binexp(&mut self, _op: &BinOp, _lhs: &Expression, _rhs: &Expression) {}
-  fn prefix_exp(&mut self, _op: &PrefixOp, _arg: &Expression) {}
-  fn pattern(&mut self, _pat: &Pattern) {}
+    fn expression(&mut self, _expression: &Expression) {}
+    fn expression_post(&mut self, _expression: &Expression) {}
+
+    fn declaration(&mut self, _declaration: &Declaration) {}
+    fn declaration_post(&mut self, _declaration: &Declaration) {}
+
+    fn import(&mut self, _import: &ImportSpecifier) {}
+    fn module(&mut self, _module: &ModuleSpecifier) {}
+    fn module_post(&mut self, _module: &ModuleSpecifier) {}
+
+    fn pattern(&mut self, _pat: &Pattern) {}
+    fn pattern_post(&mut self, _pat: &Pattern) {}
+}
+
+pub fn walk_ast<V: ASTVisitor>(v: &mut V, ast: &AST) {
+    walk_block(v, &ast.statements);
+}
+
+fn walk_block<V: ASTVisitor>(v: &mut V, block: &Block) {
+    use StatementKind::*;
+    for statement in block.iter() {
+        match statement.kind {
+            StatementKind::Expression(ref expr) => {
+                walk_expression(v, expr);
+            }
+            Declaration(ref decl) => {
+                walk_declaration(v, decl);
+            }
+            Import(ref import_spec) => v.import(import_spec),
+            Module(ref module_spec) => {
+                v.module(module_spec);
+                walk_block(v, &module_spec.contents);
+                v.module_post(module_spec);
+            }
+        }
+    }
+}
+
+fn walk_declaration<V: ASTVisitor>(v: &mut V, decl: &Declaration) {
+    use Declaration::*;
+
+    v.declaration(decl);
+
+    match decl {
+        FuncDecl(_sig, block) => {
+            walk_block(v, block);
+        }
+        Binding {
+            name: _,
+            constant: _,
+            type_anno: _,
+            expr,
+        } => {
+            walk_expression(v, expr);
+        }
+        _ => (),
+    };
+    v.declaration_post(decl);
+}
+
+fn walk_expression<V: ASTVisitor>(v: &mut V, expr: &Expression) {
+    use ExpressionKind::*;
+
+    v.expression(expr);
+
+    match &expr.kind {
+        NatLiteral(_) | FloatLiteral(_) | StringLiteral(_) | BoolLiteral(_) | Value(_) => (),
+        BinExp(_, lhs, rhs) => {
+            walk_expression(v, &lhs);
+            walk_expression(v, &rhs);
+        }
+        PrefixExp(_, arg) => {
+            walk_expression(v, &arg);
+        }
+        TupleLiteral(exprs) => {
+            for expr in exprs {
+                walk_expression(v, &expr);
+            }
+        }
+        NamedStruct { name: _, fields } => {
+            for (_, expr) in fields.iter() {
+                walk_expression(v, expr);
+            }
+        }
+        Call { f, arguments } => {
+            walk_expression(v, &f);
+            for arg in arguments.iter() {
+                match arg {
+                    InvocationArgument::Positional(expr) => walk_expression(v, expr),
+                    InvocationArgument::Keyword { expr, .. } => walk_expression(v, expr), //TODO maybe I can combine this pattern
+                    _ => (),
+                }
+            }
+        }
+        Index { indexee, indexers } => {
+            walk_expression(v, &indexee);
+            for indexer in indexers.iter() {
+                walk_expression(v, indexer);
+            }
+        }
+        IfExpression {
+            discriminator,
+            body,
+        } => {
+            if let Some(d) = discriminator.as_ref() {
+                walk_expression(v, &d);
+            }
+            walk_if_expr_body(v, &body.as_ref());
+        }
+        WhileExpression { condition, body } => {
+            if let Some(d) = condition.as_ref() {
+                walk_expression(v, d);
+            }
+            walk_block(v, &body);
+        }
+        ForExpression { enumerators, body } => {
+            for enumerator in enumerators {
+                walk_expression(v, &enumerator.generator);
+            }
+            match body.as_ref() {
+                ForBody::MonadicReturn(expr) => walk_expression(v, expr),
+                ForBody::StatementBlock(block) => walk_block(v, block),
+            };
+        }
+        Lambda {
+            params: _,
+            type_anno: _,
+            body,
+        } => {
+            walk_block(v, &body);
+        }
+        ListLiteral(exprs) => {
+            for expr in exprs {
+                walk_expression(v, &expr);
+            }
+        }
+    };
+    v.expression_post(expr);
+}
+
+fn walk_if_expr_body<V: ASTVisitor>(v: &mut V, body: &IfExpressionBody) {
+    use IfExpressionBody::*;
+
+    match body {
+        SimpleConditional {
+            then_case,
+            else_case,
+        } => {
+            walk_block(v, then_case);
+            if let Some(block) = else_case.as_ref() {
+                walk_block(v, block)
+            }
+        }
+        SimplePatternMatch {
+            pattern,
+            then_case,
+            else_case,
+        } => {
+            walk_pattern(v, pattern);
+            walk_block(v, &then_case);
+            if let Some(ref block) = else_case.as_ref() {
+                walk_block(v, &block)
+            }
+        }
+        CondList(arms) => {
+            for arm in arms {
+                match arm.condition {
+                    Condition::Pattern(ref pat) => {
+                        walk_pattern(v, pat);
+                    }
+                    Condition::TruncatedOp(ref _binop, ref expr) => {
+                        walk_expression(v, expr);
+                    }
+                    Condition::Expression(ref expr) => {
+                        walk_expression(v, expr);
+                    }
+                    _ => (),
+                }
+            }
+        }
+    }
+}
+
+fn walk_pattern<V: ASTVisitor>(v: &mut V, pat: &Pattern) {
+    use Pattern::*;
+
+    v.pattern(pat);
+
+    match pat {
+        TuplePattern(patterns) => {
+            for pat in patterns {
+                walk_pattern(v, pat);
+            }
+        }
+        TupleStruct(_, patterns) => {
+            for pat in patterns {
+                walk_pattern(v, pat);
+            }
+        }
+        Record(_, name_and_patterns) => {
+            for (_, pat) in name_and_patterns {
+                walk_pattern(v, pat);
+            }
+        }
+        _ => (),
+    };
+
+    v.pattern_post(pat);
 }
diff --git a/schala-lang/language/src/ast/visitor_test.rs b/schala-lang/language/src/ast/visitor_test.rs
deleted file mode 100644
index 7c92a7a..0000000
--- a/schala-lang/language/src/ast/visitor_test.rs
+++ /dev/null
@@ -1,41 +0,0 @@
-#![cfg(test)]
-
-use crate::ast::visitor::ASTVisitor;
-use crate::ast::walker;
-use crate::util::quick_ast;
-
-struct Tester {
-  count: u64,
-  float_count: u64
-}
-
-impl ASTVisitor for Tester {
-  fn nat_literal(&mut self, _n: u64) {
-    self.count += 1;
-  }
-  fn float_literal(&mut self, _f: f64) {
-    self.float_count += 1;
-  }
-}
-
-
-#[test]
-fn foo() {
-  let mut tester = Tester { count: 0, float_count: 0 };
-  let ast = quick_ast(r#"
-import gragh
-
-let a = 20 + 84
-let b = 28 + 1 + 2 + 2.0
-fn heh() {
-  let m = 9
-
-}
-
-"#);
-
-  walker::walk_ast(&mut tester, &ast);
-
-  assert_eq!(tester.count, 6);
-  assert_eq!(tester.float_count, 1);
-}
diff --git a/schala-lang/language/src/ast/walker.rs b/schala-lang/language/src/ast/walker.rs
deleted file mode 100644
index 4fc63b8..0000000
--- a/schala-lang/language/src/ast/walker.rs
+++ /dev/null
@@ -1,273 +0,0 @@
-#![allow(dead_code)]
-use std::rc::Rc;
-use crate::ast::*;
-use crate::ast::visitor::ASTVisitor;
-use crate::util::deref_optional_box;
-
-pub fn walk_ast<V: ASTVisitor>(v: &mut V, ast: &AST) {
-  v.ast(ast);
-  walk_block(v, &ast.statements);
-}
-
-#[allow(clippy::ptr_arg)]
-fn walk_block<V: ASTVisitor>(v: &mut V, block: &Vec<Statement>) {
-  for s in block {
-    v.statement(s);
-    statement(v, s);
-  }
-}
-
-fn statement<V: ASTVisitor>(v: &mut V, statement: &Statement) {
-  use StatementKind::*;
-  match statement.kind {
-    Expression(ref expr) => {
-      v.expression(expr);
-      expression(v, expr);
-    },
-    Declaration(ref decl) => {
-      v.declaration(decl);
-      declaration(v, decl);
-    },
-    Import(ref import_spec) => v.import(import_spec),
-    Module(ref module_spec) => {
-      v.module(module_spec);
-      walk_block(v, &module_spec.contents);
-    }
-  }
-}
-
-fn declaration<V: ASTVisitor>(v: &mut V, decl: &Declaration) {
-  use Declaration::*;
-  match decl {
-    FuncSig(sig) => {
-      v.signature(sig);
-      signature(v, sig);
-    },
-    FuncDecl(sig, block) => {
-      v.signature(sig);
-      v.block(block);
-      walk_block(v, block);
-    },
-    TypeDecl { name, body, mutable  } => v.type_declaration(name, body, *mutable),
-    TypeAlias { alias, original} => v.type_alias(alias, original), 
-    Binding { name, constant, type_anno, expr } => {
-      v.binding(name, *constant, type_anno.as_ref(), expr);
-      v.type_annotation(type_anno.as_ref());
-      v.expression(expr);
-      expression(v, expr);
-    },
-    Impl { type_name, interface_name, block } => {
-      v.implemention(type_name, interface_name.as_ref(), block);
-    }
-    Interface { name, signatures } => v.interface(name, signatures),
-    //TODO fill this in
-    Annotation { .. } => ()
-  }
-}
-
-fn signature<V: ASTVisitor>(v: &mut V, signature: &Signature) {
-  for p in signature.params.iter() {
-    v.formal_param(p);
-  }
-  v.type_annotation(signature.type_anno.as_ref());
-  for p in signature.params.iter() {
-    formal_param(v, p);
-  }
-}
-
-fn expression<V: ASTVisitor>(v: &mut V, expression: &Expression) {
-  v.expression_kind(&expression.kind);
-  v.type_annotation(expression.type_anno.as_ref());
-  expression_kind(v, &expression.kind);
-}
-
-
-fn call<V: ASTVisitor>(v: &mut V, f: &Expression, args: &[ InvocationArgument ]) {
-  v.expression(f);
-  expression(v, f);
-  for arg in args.iter() {
-    v.invocation_argument(arg);
-    invocation_argument(v, arg);
-  }
-}
-
-fn invocation_argument<V: ASTVisitor>(v: &mut V, arg: &InvocationArgument) {
-  use InvocationArgument::*;
-  match arg {
-    Positional(expr) => {
-      v.expression(expr);
-      expression(v, expr);
-    },
-    Keyword { expr, .. } => {
-      v.expression(expr);
-      expression(v, expr);
-    },
-    Ignored => (),
-  }
-}
-
-fn index<V: ASTVisitor>(v: &mut V, indexee: &Expression, indexers: &[ Expression ]) {
-  v.expression(indexee);
-  for i in indexers.iter() {
-    v.expression(i);
-  }
-}
-
-fn named_struct<V: ASTVisitor>(v: &mut V, n: &QualifiedName, fields: &[ (Rc<String>, Expression) ]) {
-  v.qualified_name(n);
-  for (_, expr) in fields.iter() {
-    v.expression(expr);
-  }
-}
-
-#[allow(clippy::ptr_arg)]
-fn lambda<V: ASTVisitor>(v: &mut V, params: &Vec<FormalParam>, type_anno: Option<&TypeIdentifier>, body: &Block) {
-  for param in params {
-    v.formal_param(param);
-    formal_param(v, param);
-  }
-  v.type_annotation(type_anno);
-  v.block(body);
-  walk_block(v, body);
-}
-
-fn formal_param<V: ASTVisitor>(v: &mut V, param: &FormalParam) {
-    if let Some(p) = param.default.as_ref() {
-        v.expression(p);
-        expression(v, p);
-    };
-    v.type_annotation(param.anno.as_ref());
-}
-
-fn expression_kind<V: ASTVisitor>(v: &mut V, expression_kind: &ExpressionKind) {
-  use ExpressionKind::*;
-  match expression_kind {
-    NatLiteral(n) => v.nat_literal(*n),
-    FloatLiteral(f) => v.float_literal(*f),
-    StringLiteral(s) => v.string_literal(s),
-    BoolLiteral(b) => v.bool_literal(*b),
-    BinExp(op, lhs, rhs) => {
-      v.binexp(op, lhs, rhs);
-      expression(v, lhs);
-      expression(v, rhs);
-    },
-    PrefixExp(op, arg) => {
-      v.prefix_exp(op, arg);
-      expression(v, arg);
-    }
-    TupleLiteral(exprs) => {
-      for expr in exprs {
-        v.expression(expr);
-        expression(v, expr);
-      }
-    },
-    Value(name) => v.qualified_name(name),
-    NamedStruct { name, fields } => {
-      v.named_struct(name, fields);
-      named_struct(v, name, fields);
-    }
-    Call { f, arguments } => {
-      v.call(f, arguments);
-      call(v, f, arguments);
-    },
-    Index { indexee, indexers } => {
-      v.index(indexee, indexers);
-      index(v, indexee, indexers);
-    },
-    IfExpression { discriminator, body } => {
-      v.if_expression(deref_optional_box(discriminator), body);
-      if let Some(d) = discriminator.as_ref() { expression(v, d) }
-      if_expression_body(v, body);
-    },
-    WhileExpression { condition, body } => v.while_expression(deref_optional_box(condition), body),
-    ForExpression { enumerators, body } => v.for_expression(enumerators, body),
-    Lambda { params , type_anno, body } => {
-      v.lambda(params, type_anno.as_ref(), body);
-      lambda(v, params, type_anno.as_ref(), body);
-    },
-    ListLiteral(exprs) => {
-      for expr in exprs {
-        v.expression(expr);
-        expression(v, expr);
-      }
-    },
-  }
-}
-
-fn if_expression_body<V: ASTVisitor>(v: &mut V, body: &IfExpressionBody) {
-  use IfExpressionBody::*;
-  match body {
-    SimpleConditional { then_case, else_case } => {
-      walk_block(v, then_case);
-      if let Some(block) = else_case.as_ref() { walk_block(v, block) }
-    },
-    SimplePatternMatch { pattern, then_case, else_case } => {
-      v.pattern(pattern);
-      walk_pattern(v, pattern);
-      walk_block(v, then_case);
-      if let Some(block) = else_case.as_ref() { walk_block(v, block) }
-    },
-    CondList(arms) => {
-      for arm in arms {
-        v.condition_arm(arm);
-        condition_arm(v, arm);
-      }
-    }
-  }
-}
-
-fn condition_arm<V: ASTVisitor>(v: &mut V, arm: &ConditionArm) {
-  use Condition::*;
-  v.condition_arm(arm);
-  match arm.condition {
-    Pattern(ref pat) => {
-      v.pattern(pat);
-      walk_pattern(v, pat);
-    },
-    TruncatedOp(ref _binop, ref expr) => {
-      v.expression(expr);
-      expression(v, expr);
-    },
-    Expression(ref expr) => {
-      v.expression(expr);
-      expression(v, expr);
-    },
-    _ => ()
-  }
-  if let Some(guard) = arm.guard.as_ref() {
-      v.expression(guard);
-      expression(v, guard);
-  };
-  v.block(&arm.body);
-  walk_block(v, &arm.body);
-}
-
-fn walk_pattern<V: ASTVisitor>(v: &mut V, pat: &Pattern) {
-  use Pattern::*;
-  match pat {
-    TuplePattern(patterns) => {
-      for pat in patterns {
-        v.pattern(pat);
-        walk_pattern(v, pat);
-      }
-    },
-    TupleStruct(qualified_name, patterns) => {
-      v.qualified_name(qualified_name);
-      for pat in patterns {
-        v.pattern(pat);
-        walk_pattern(v, pat);
-      }
-    },
-    Record(qualified_name, name_and_patterns) => {
-      v.qualified_name(qualified_name);
-      for (_, pat) in name_and_patterns {
-        v.pattern(pat);
-        walk_pattern(v, pat);
-      }
-    },
-    VarOrName(qualified_name) => {
-      v.qualified_name(qualified_name);
-    },
-    _ => ()
-  }
-}
diff --git a/schala-lang/language/src/symbol_table/resolver.rs b/schala-lang/language/src/symbol_table/resolver.rs
index 00111e0..ae27f35 100644
--- a/schala-lang/language/src/symbol_table/resolver.rs
+++ b/schala-lang/language/src/symbol_table/resolver.rs
@@ -46,12 +46,11 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    // This might be a variable or a pattern, depending on whether this symbol
-    // already exists in the table.
-    fn qualified_name_in_pattern(&mut self, qualified_name: &QualifiedName) {
-        let maybe_sym = self.symbol_table.id_to_symbol.get(&qualified_name.id).cloned();
-        if let Some(symbol) = maybe_sym {
-            self.symbol_table.id_to_symbol.insert(qualified_name.id.clone(), symbol);
+    fn qualified_name(&mut self, name: &QualifiedName) {
+        let fqsn = self.lookup_name_in_scope(name);
+        let symbol = self.symbol_table.fqsn_to_symbol.get(&fqsn);
+        if let Some(symbol) = symbol {
+            self.symbol_table.id_to_symbol.insert(name.id.clone(), symbol.clone());
         }
     }
 }
@@ -100,35 +99,28 @@ impl<'a> ASTVisitor for Resolver<'a> {
         };
     }
 
-    fn qualified_name(&mut self, qualified_name: &QualifiedName) {
-        let fqsn = self.lookup_name_in_scope(qualified_name);
-        let symbol = self.symbol_table.fqsn_to_symbol.get(&fqsn);
-        if let Some(symbol) = symbol {
-            self.symbol_table.id_to_symbol.insert(qualified_name.id.clone(), symbol.clone());
-        }
-    }
-
-    fn named_struct(
-        &mut self,
-        qualified_name: &QualifiedName,
-        _fields: &[(Rc<String>, Expression)],
-    ) {
-        let fqsn = self.lookup_name_in_scope(qualified_name);
-
-        let symbol = self.symbol_table.fqsn_to_symbol.get(&fqsn);
-        if let Some(symbol) = symbol {
-            self.symbol_table.id_to_symbol.insert(qualified_name.id.clone(), symbol.clone());
+    fn expression(&mut self, expression: &Expression) {
+        use ExpressionKind::*;
+        match &expression.kind {
+            Value(name) => {
+                self.qualified_name(name);
+            },
+            NamedStruct { name, fields: _ } => {
+                self.qualified_name(name);
+            },
+            _ => (),
         }
     }
 
     fn pattern(&mut self, pat: &Pattern) {
         use Pattern::*;
+
         match pat {
             //TODO I think not handling TuplePattern is an oversight
             TuplePattern(_) => (),
             Literal(_) | Ignored => (),
             TupleStruct(name, _) | Record(name, _) | VarOrName(name) => {
-                self.qualified_name_in_pattern(name)
+                self.qualified_name(name);
             }
         };
     }