anchor.diff:      assert(renderObject is RenderBox);
       return (renderObject as RenderBox).localToGlobal(point);
     }
  +}
  +
  +bool _canSync(Widget a, Widget b) {
  +  return a.runtimeType == b.runtimeType && a.key == b.key;
   }
   
   
  
positive.code: export 'package:sky/rendering/flex.dart' show FlexDirection;
  export 'package:sky/rendering/object.dart' show Point, Offset, Size, Rect, Color, Paint, Path;
  
  final bool _shouldLogRenderDuration = false;
  
  typedef Widget Builder();
  typedef void WidgetTreeWalker(Widget);
  
negative.code:   bool retainStatefulNodeIfPossible(StatefulComponent newNode) {
      assert(!_disqualifiedFromEverAppearingAgain);
      assert(newNode != null);
      assert(_canSync(this, newNode);
      assert(_child != null);
      newNode._disqualifiedFromEverAppearingAgain = true;
  
  