@@ -17,2 +18,4 @@
     pass
 
+# place the `virtual` class infront of the construct of NAC3 object to ensure the
+# virtual class is known during the initializing of NAC3 object

@@ -114,0 +111,4 @@
+            // do not handle type var param and concrete check here
+            Ok(Ok((unifier.add_ty(TypeEnum::TTuple { ty: vec![] }), false)))
+        } else if let Some(def_id) = self.pyid_to_def.read().get(&ty_id).cloned() {
+            // println!("getting def");

@@ -114,1 +113,4 @@
+        } else if let Some(def_id) = self.pyid_to_def.read().get(&ty_id).cloned() {
+            // println!("getting def");
             let def = defs[def_id.0].read();
+            // println!("got def");

@@ -69,0 +71,4 @@
+            assert_eq!(targets.len(), 1, "only support single assignment for now, at {}", targets[0].location);
+            if let ExprKind::Call { func, args, .. } = &value.node {
+                if matches!(&func.node, ExprKind::Name { id, .. } if id == &"TypeVar".into()) {
+                    print!("registering typevar {:?}", targets[0].node);

@@ -69,0 +87,4 @@
+                        })
+                        .collect::<Vec<_>>();
+                    let res_ty = composer.unifier.get_fresh_var_with_range(&constraints).0;
+                    println!(

@@ -68,1 +68,4 @@
     for stmt in parser_result.into_iter() {
+        // handle type vars in toplevel
+        if let StmtKind::Assign { value, targets, .. } = &stmt.node {
+            assert_eq!(targets.len(), 1, "only support single assignment for now, at {}", targets[0].location);

@@ -69,0 +88,4 @@
+                    let res_ty = composer.unifier.get_fresh_var_with_range(&constraints).0;
+                    internal_resolver.add_id_type(
+                        if let ExprKind::Name { id, .. } = &targets[0].node { *id } else {
+                            panic!("must assign simple name variable as type variable")