anchor.diff:  
     static final Container _emptyContainer = new Container();
   
  -  Node get _emptyNode => _emptyContainer;
  +  RenderNode get _emptyNode => _emptyContainer;
   
     Container({
       Object key,
  
positive.code:         break;
        }
  
        // print('> syncing matched at: $endIndex : $oldEndIndex');
        endIndex--;
        oldEndIndex--;
        sync(endIndex);
  
negative.code:   }
  }
  
  EventMap _emptyEventMap = new EventMap();
  
  abstract class Component extends Node {
    bool get _isBuilding => _currentlyBuilding == this;
    bool _dirty = true;
  
    Node _built;
    final int _order;
    static int _currentOrder = 0;
    bool _stateful;
    static Component _currentlyBuilding;
  
    Component({ Object key, bool stateful })
        : _stateful = stateful != null ? stateful : false,
  