anchor.diff:                   of another node, they must have unique keys.''';
         }
       }
  +    return false;
     }
   
     void _ensureClass() {
  
positive.code:   }) : this.children = children == null ? _emptyList : children,
         super(key:key) {
  
      if (_isInCheckedMode) {
        _debugReportDuplicateIds();
      }
    }
  
    void _remove() {
  
negative.code: 
  final sky.Tracing _tracing = sky.window.tracing;
  
  final bool _shouldLogRenderDuration = false;
  final bool _shouldTrace = false;
  
  