anchor.diff:              responder.complete([]);
             }
           });
  -        responder.future.then((value) {
  +        await responder.future.then((value) {
             timeoutTimer.cancel();
           });
         }
  
positive.code:     }
    }
  
    Future<void> _dispatch(List<List> calls) async {
      final n = calls.length;
      final results = new List<Future>(n);
      for (var i = 0; i < n; i++) {
  
negative.code:   bool _send(String id, Completer<List<List>> responder) {
      if (_calls.containsKey(id)) {
        final calls = _calls[id];
        if (calls.isEmpty) {
          return false;
        }
        _calls[id] = [];
  