anchor.diff:    final Queue<_EventRequest> _requestQueue = new Queue();
   
     /// Create a `StreamQueue` of the events of [source].
  -  StreamQueue(Stream source)
  -      : _sourceStream = source;
  +  factory StreamQueue(Stream source) = _StreamQueue<T>;
  +
  +  StreamQueue._();
   
     /// Asks if the stream has any more events.
     ///
  
positive.code: abstract class _EventRequest {
    /// Handle available events.
    ///
    /// The available events are provided as a queue. The `addEvents` function
    /// should only remove events from the front of the event queue, e.g.,
    /// using [removeFirst].
    ///
  
negative.code:       for (var event in events) {
          event.addTo(controller);
        }
        controller.addStream(_streamQueue._extractStream(), cancelOnError: false)
                  .whenComplete(controller.close);
        _completer.setSourceStream(controller.stream);
      }
      return true;
    }
  }
  
  