Some work

schala-lang/language/src/ast_visitor.rs

@@ -1,2 +1,64 @@
-
 use ast::*;
+
+pub fn dispatch<T, V: ASTVisitor<T>>(visitor: &mut V, ast: &AST) -> T {
+  visitor.ast(ast);
+  for statement in ast.0.iter() {
+    visitor.statement(statement);
+    match statement {
+      Statement::ExpressionStatement(expr) => visitor.expression(expr),
+      Statement::Declaration(decl) => {
+        visitor.declaration(decl);
+        match decl {
+          Declaration::FuncSig(sig) => visitor.func_signature(sig),
+          Declaration::FuncDecl(sig, block) => visitor.func_declaration(sig, block),
+          Declaration::TypeDecl { .. } => unimplemented!(),
+          Declaration::TypeAlias(..) => unimplemented!(), 
+          Declaration::Binding { .. } => unimplemented!(),
+          Declaration::Impl { .. } => unimplemented!(),
+          Declaration::Interface { .. } => unimplemented!(),
+        };
+        visitor.decl_done();
+      }
+    }
+  }
+  visitor.done()
+}
+
+pub trait ASTVisitor<T> {
+  fn ast(&mut self, ast: &AST) {
+  }
+  fn done(&mut self) -> T;
+
+  fn statement(&mut self, statement: &Statement) {
+  }
+
+  fn declaration(&mut self, statement: &Declaration) {
+  }
+
+  fn decl_done(&mut self) -> T;
+
+  fn func_signature(&mut self, sig: &Signature) {
+  }
+
+  fn func_declaration(&mut self, sig: &Signature, block: &Vec<Statement>) {
+  }
+
+  fn expression(&mut self, statement: &Expression) {
+  }
+
+}
+
+/*----*/
+
+
+struct NullVisitor { }
+impl ASTVisitor<()> for NullVisitor {
+  fn done(&mut self) -> () {
+    ()
+  }
+
+  fn decl_done(&mut self) -> () {
+    ()
+  }
+}
+