diff --git a/schala-lang/language/src/visitor.rs b/schala-lang/language/src/visitor.rs
index ddda82a..c98a4d1 100644
--- a/schala-lang/language/src/visitor.rs
+++ b/schala-lang/language/src/visitor.rs
@@ -1,5 +1,6 @@
 use std::error::Error;
 use crate::ast::*;
+use crate::builtin::{PrefixOp, BinOp};
 
 pub type VResult = Result<(), Box<dyn Error>>;
 
@@ -7,6 +8,9 @@ pub trait ASTVisitor {
   fn post_ast(&mut self, _: &mut AST) -> VResult {
     Ok(())
   }
+  fn post_statement(&mut self, _: &mut Statement) -> VResult {
+    Ok(())
+  }
   fn post_expression(&mut self, _: &mut Expression) -> VResult {
     Ok(())
   }
@@ -16,6 +20,12 @@ pub trait Visitable {
   fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult;
 }
 
+impl <T: Visitable> Visitable for &mut T {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    self.visit(v)
+  }
+}
+
 impl<T: Visitable> Visitable for Option<T> {
   fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
     match self {
@@ -25,10 +35,31 @@ impl<T: Visitable> Visitable for Option<T> {
   }
 }
 
+impl<T: Visitable> Visitable for Vec<T> {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    for item in self {
+      item.visit(v)?;
+    }
+    Ok(())
+  }
+}
+
+impl <T: Visitable> Visitable for Box<T> {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    self.visit(v)
+  }
+}
+
+impl <T: Visitable> Visitable for Meta<T> {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    self.node_mut().visit(v)
+  }
+}
+
 impl Visitable for AST {
   fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
     for s in self.0.iter_mut() {
-      s.node_mut().visit(v)?
+      s.visit(v)?
     }
     v.post_ast(self)
   }
@@ -37,20 +68,12 @@ impl Visitable for AST {
 impl Visitable for Statement {
   fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
     match self {
-      Statement::ExpressionStatement(meta) => meta.node_mut().visit(v),
+      Statement::ExpressionStatement(meta) => meta.visit(v),
       Statement::Declaration(decl) => decl.visit(v),
     }
   }
 }
 
-impl Visitable for Expression {
-  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
-    let _ = self.kind.visit(v)?;
-    let _ = self.type_anno.visit(v)?;
-    v.post_expression(self)
-  }
-}
-
 impl Visitable for Declaration {
   fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
     use Declaration::*;
@@ -66,8 +89,93 @@ impl Visitable for Declaration {
   }
 }
 
+impl Visitable for Expression {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    let _ = self.kind.visit(v)?;
+    let _ = self.type_anno.visit(v)?;
+    v.post_expression(self)
+  }
+}
+
 impl Visitable for ExpressionKind {
-  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    use ExpressionKind::*;
+    Ok(match self {
+      NatLiteral(_) | FloatLiteral(_) | StringLiteral(_)
+      | BoolLiteral(_) => (),
+      BinExp(op, lhs, rhs) => {
+        let _ = op.visit(v)?;
+        let _ = lhs.visit(v)?;
+        let _ = rhs.visit(v)?;
+        ()
+      },
+      PrefixExp(op, expr) => {
+        let _ = op.visit(v)?;
+        let _ = expr.visit(v)?;
+        ()
+      },
+      TupleLiteral(exprs) => exprs.visit(v)?,
+      Value(_) => (),
+      NamedStruct { fields, .. } => {
+        let mut x: Vec<_> = fields.iter_mut().map(|(_, expr)| expr).collect();
+        x.visit(v)?
+      },
+      Call { f, arguments } => {
+        let _ = f.visit(v)?;
+        arguments.visit(v)?
+      },
+      Index { indexee, indexers } => {
+        let _ = indexee.visit(v)?;
+        indexers.visit(v)?
+      },
+      IfExpression { discriminator, body } => {
+        let _ = discriminator.visit(v)?;
+        body.visit(v)?
+      },
+      WhileExpression { condition, body } => {
+        let _ = condition.visit(v)?;
+        body.visit(v)?
+      },
+      ForExpression { enumerators, body } => {
+        let _ = enumerators.visit(v)?;
+        body.visit(v)?
+      },
+      ListLiteral(expressions) => expressions.visit(v)?,
+      Lambda { params, type_anno, body } => {
+        let _ = params.visit(v)?;
+        let _ = type_anno.visit(v)?;
+        body.visit(v)?
+      },
+    })
+  }
+}
+
+impl Visitable for IfExpressionBody {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for Discriminator {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for InvocationArgument {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for BinOp {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for PrefixOp {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
     Ok(())
   }
 }
@@ -77,3 +185,21 @@ impl Visitable for TypeIdentifier {
     Ok(())
   }
 }
+
+impl Visitable for Enumerator {
+  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for ForBody {
+  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for FormalParam {
+  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}