anchor.diff:    /// Ensures that we are listening on events from [_sourceStream].
     ///
     /// Resumes subscription on [_sourceStream], or creates it if necessary.
  -  StreamSubscription _ensureListening() {
  +  void _ensureListening() {
       assert(!_isDone);
       if (_subscription == null) {
         _subscription =
  
positive.code: ///
  /// The [close] method is also called immediately when the source stream
  /// is done.
  abstract class _EventRequest implements EventSink {
    /// Handle available events.
    ///
    /// The available events are provided as a queue. The `addEvents` function
  
negative.code:   /// The future completed when the correct number of events have been captured.
    Future get future => _completer.future;
  
    bool addEvents(Queue<Result> events) {
      while (_list.length < _eventsToTake) {
        if (events.isEmpty) return false;
        var result = events.removeFirst();
  