{"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
    let ty::Coroutine(coroutine_def_id, _) = impl_ty.kind() else {
    let instance = ty::InstanceKind::FutureDropPollShim(def_id, proxy_ty, impl_ty);
        bug!("build_future_drop_poll_shim not for coroutine impl type: ({:?})", instance);