anchor.diff:    }
   
     void _recordChange(ListChangeRecord record) {
  -    if (!_hasListObservers) return;
  +    if (!hasListObservers) return;
   
       if (_listRecords == null) {
         _listRecords = [];
  
positive.code:     var records = projectListSplices(this, _listRecords);
      _listRecords = null;
  
      if (_hasListObservers && !records.isEmpty) {
        _listChanges.add(new UnmodifiableListView<ListChangeRecord>(records));
        return true;
      }
  
negative.code:     return _listChanges.stream;
    }
  
    bool get hasListObservers =>
        _listChanges != null && _listChanges.hasListener;
  
    @reflectable int get length => _list.length;
  