{"ast_node_type":"other","tokens":[{"end":94,"kind":"keyword","start":0,"text":"CoroutineKind::Async"}]}
            CoroutineKind::Async { return_impl_trait_id, .. } => (return_impl_trait_id, None),
        let (opaque_ty_node_id, allowed_features) = match coro {
            CoroutineKind::Gen { return_impl_trait_id, .. } => (return_impl_trait_id, None),