anchor.diff:      Object key,
       List<UINode> children,
       this.direction: FlexDirection.Horizontal
  -  }) : super(
  -    key: key,
  -    children: children
  -  );
  +  }) : super(key: key, children: children);
   
     void syncRenderNode(UINode old) {
       super.syncRenderNode(old);
  
positive.code:       var ancestor = findAncestor(RenderNodeWrapper);
        if (ancestor is RenderNodeWrapper)
          ancestor.insert(this, slot);
        old = emptyNode;
      } else {
        root = old.root;
        assert(root != null);
  
negative.code: }
  
  class BlockContainer extends OneChildListRenderNodeWrapper {
    RenderBlock root;
    RenderBlock createNode() => new RenderBlock();
  
    BlockContainer({ Object key, List<UINode> children })
      : super(key: key, children: children);
  }
  
  class Paragraph extends RenderNodeWrapper {
    RenderParagraph root;
    RenderParagraph createNode() => new RenderParagraph(text);
  
    final String text;
  
    Paragraph({ Object key, this.text }) : super(key: key);
  
    void syncRenderNode(UINode old) {
      super.syncRenderNode(old);
  