anchor.diff:  
     /// The set of all streams forked from this one.
     final _forks = new Set<ScheduledStream<T>>();
  -  final _forkControllers = new Set<StreamController<T>>();
   
     /// The queue of values emitted by [_stream] but not yet emitted through
     /// [next].
  
positive.code:         controller.addError(valueOrError.error, valueOrError.stackTrace);
        }
      }
      if (_isDone) {
        controller.close();
      } else {
        _forkControllers.add(controller);
      }
  
      var fork = new ScheduledStream<T>(controller.stream);
  
negative.code:   /// Handles a "done" event from the underlying stream, as well as [this] being
    /// closed.
    void _onDone() {
      if (_hasNextCompleter != null) {
        _hasNextCompleter.complete(false);
        _hasNextCompleter = null;
  