diff --git a/schala-lang/language/src/reduced_ast.rs b/schala-lang/language/src/reduced_ast.rs
index 5737587..2531c74 100644
--- a/schala-lang/language/src/reduced_ast.rs
+++ b/schala-lang/language/src/reduced_ast.rs
@@ -115,7 +115,7 @@ impl ASTVisitor for Reducer {
 
 pub fn perform_reduction(mut input: AST, _symbol_table: &SymbolTable) -> Result<ReducedAST, String> {
   let mut reducer = Reducer::new();
-  input.visit(&mut reducer);
+  let _ = input.visit(&mut reducer).map_err(|e| e.to_string())?;
   reducer.output()
 }
 
diff --git a/schala-lang/language/src/visitor.rs b/schala-lang/language/src/visitor.rs
index 4f93143..ddda82a 100644
--- a/schala-lang/language/src/visitor.rs
+++ b/schala-lang/language/src/visitor.rs
@@ -4,7 +4,10 @@ use crate::ast::*;
 pub type VResult = Result<(), Box<dyn Error>>;
 
 pub trait ASTVisitor {
-  fn visit_expression(&mut self, _: &mut Expression) -> VResult {
+  fn post_ast(&mut self, _: &mut AST) -> VResult {
+    Ok(())
+  }
+  fn post_expression(&mut self, _: &mut Expression) -> VResult {
     Ok(())
   }
 }
@@ -13,16 +16,63 @@ pub trait Visitable {
   fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult;
 }
 
+impl<T: Visitable> Visitable for Option<T> {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    match self {
+      Some(t) => t.visit(v),
+      None => Ok(())
+    }
+  }
+}
+
 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)?
     }
-    Ok(())
+    v.post_ast(self)
   }
 }
 
 impl Visitable for Statement {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult {
+    match self {
+      Statement::ExpressionStatement(meta) => meta.node_mut().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::*;
+    Ok(match self {
+      FuncSig(sig) => (),
+      FuncDecl(sig, block) => (),
+      TypeDecl { .. } => (),
+      TypeAlias(_, _) => (),
+      Binding { .. } => (),
+      Impl { .. } => (),
+      Interface { .. } => (),
+    })
+  }
+}
+
+impl Visitable for ExpressionKind {
+  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
+}
+
+impl Visitable for TypeIdentifier {
   fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
     Ok(())
   }