Starting to implement ASTVisitor

schala-lang/language/src/ast.rs

@@ -19,6 +19,10 @@ impl<T> Meta<T> {
   pub fn node(&self) -> &T {
     &self.n
   }
+
+  pub fn node_mut(&mut self) -> &mut T {
+    &mut self.n
+  }
 }
 
 //TODO this PartialEq is here to make tests work - find a way to make it not necessary

schala-lang/language/src/visitor.rs

@@ -1,7 +1,29 @@
 use std::error::Error;
+use crate::ast::*;
 
-pub type VResult<T> = Result<T, Box<dyn Error>>;
-
-pub trait Visitor {
+pub type VResult = Result<(), Box<dyn Error>>;
 
+pub trait ASTVisitor {
+  fn visit_expression(&mut self, _: &mut Expression) -> VResult {
+    Ok(())
+  }
+}
+
+pub trait Visitable {
+  fn visit(&mut self, v: &mut dyn ASTVisitor) -> VResult;
+}
+
+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(())
+  }
+}
+
+impl Visitable for Statement {
+  fn visit(&mut self, _v: &mut dyn ASTVisitor) -> VResult {
+    Ok(())
+  }
 }