Merge pull request #5477 from youknowone/better-downcast-error

youknowone · web-flow · commit db283a66e8a2 · 2025-01-21T13:54:45.000+09:00
Add better panic for abnormal downcast error
diff --git a/vm/src/vm/vm_new.rs b/vm/src/vm/vm_new.rs
@@ -365,7 +365,15 @@ impl VirtualMachine {
         let actual_class = obj.class();
         let actual_type = &*actual_class.name();
         let expected_type = &*class.name();
-        let msg = format!("Expected {msg} '{expected_type}' but '{actual_type}' found");
+        let msg = format!("Expected {msg} '{expected_type}' but '{actual_type}' found.");
+        #[cfg(debug_assertions)]
+        let msg = if class.get_id() == actual_class.get_id() {
+            let mut msg = msg;
+            msg += " Did you forget to add `#[pyclass(with(Constructor))]`?";
+            msg
+        } else {
+            msg
+        };
         self.new_exception_msg(error_type.to_owned(), msg)
     }
 
