{"ast_node_type":"other","tokens":[{"end":46,"kind":"keyword","start":0,"text":"//"}]}
        // Safe due to `#[repr(transparent)]`.
    fn index_mut(&mut self, _key: Key<P::K, P::V, P>) -> &mut Self::Output {
        unsafe { std::mem::transmute::<&mut DynMap, &mut KeyMap<Key<P::K, P::V, P>>>(self) }