anchor.diff:  }
   
   class Rectangle extends RenderNodeWrapper {
  -
  -  Rectangle(this.color, {
  -    Object key
  -  }) : super(
  -    key: key
  -  );
  +  RenderSolidColor root;
  +  RenderSolidColor createNode() =>
  +      new RenderSolidColor(color, desiredSize: new sky.Size(40.0, 130.0));
   
     final int color;
   
  -  RenderSolidColor root;
  -  RenderSolidColor createNode() => new RenderSolidColor(color, desiredSize: new sky.Size(40.0, 130.0));
  -
  -  static final Rectangle _emptyRectangle = new Rectangle(0);
  -  RenderNodeWrapper get emptyNode => _emptyRectangle;
  -
  -}
  +  Rectangle(this.color, { Object key }) : super(key: key);
  +}
  
positive.code:   }) : super(key: key);
  
    RenderNode createNode();
    RenderNodeWrapper get emptyNode;
  
    void insert(RenderNodeWrapper child, dynamic slot);
  
  
negative.code:     Object key,
      List<UINode> children,
      this.direction: FlexDirection.Horizontal
    }) : super(key: key, children: children);
  
    void syncRenderNode(UINode old) {
      super.syncRenderNode(old);
  