zed-industries/zed · error

checked for type drag state type above

Error message

checked for type drag state type above

What it means

In Div's drop-listener dispatch, the active drag is downcast to the drag state type; the comment says the type was checked above (the listener was only registered for matching drags), so the expect firing means the registration-side type check and the dispatch-side downcast disagree — an internal invariant break.

Source

Thrown at crates/gpui/src/elements/div.rs:2906

            }
        }

        let drag_cursor_style = self.base_style.as_ref().mouse_cursor;

        let mut drag_listener = mem::take(&mut self.drag_listener);
        let drop_listeners = mem::take(&mut self.drop_listeners);
        let click_listeners = mem::take(&mut self.click_listeners);
        let aux_click_listeners = mem::take(&mut self.aux_click_listeners);
        let can_drop_predicate = mem::take(&mut self.can_drop_predicate);

        if !drop_listeners.is_empty() {
            let hitbox = hitbox.clone();
            window.on_mouse_event({
                move |_: &MouseUpEvent, phase, window, cx| {
                    if let Some(drag) = &cx.active_drag
                        && phase == DispatchPhase::Bubble
                        && hitbox.is_hovered(window)
                    {
                        let drag_state_type = drag.value.as_ref().type_id();
                        for (drop_state_type, listener) in &drop_listeners {
                            if *drop_state_type == drag_state_type {
                                let drag = cx
                                    .active_drag
                                    .take()
                                    .expect("checked for type drag state type above");

                                let mut can_drop = true;
                                if let Some(predicate) = &can_drop_predicate {
                                    can_drop = predicate(drag.value.as_ref(), window, cx);
                                }

                                if can_drop {
                                    listener(drag.value.as_ref(), window, cx);
                                    window.refresh();
                                    cx.stop_propagation();
                                }

View on GitHub (pinned to 9d272b0363)

Solutions

1. Compare the type check where the drop listener is registered with the downcast at dispatch
2. Ensure can_drop_predicate/listener registration filters by the same drag type T
3. Treat as a GPUI bug; reproduce with a minimal drag-and-drop of the mismatched state type

When it happens

Trigger: Thrown at crates/gpui/src/elements/div.rs:2788 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@9d272b0363 (2026-08-20). Data as JSON: /api/errors/d4cf502e0c473282. Report an issue: GitHub.