anchor.diff:      _parent = parent;
       _slot = newSlot;
       _depth = _parent != null ? _parent.depth + 1 : 1;
  +    if (widget.key is GlobalKey)
  +      widget.key._register(this);
       assert(() { _debugLifecycleState = _ElementLifecycle.mounted; return true; });
     }
   
  
positive.code:   int get hashCode => identityHashCode(value);
  }
  
  typedef void GlobalKeyUpdateListener(GlobalKey key, Element element);
  typedef void GlobalKeyRemoveListener(GlobalKey key);
  
  /// A GlobalKey is one that must be unique across the entire application. It is
  
negative.code:         throw message;
        return true;
      });
      if (_removedKeys.isEmpty)
        return;
      try {
        for (GlobalKey key in _removedKeys) {
          if (!_registry.containsKey(key) && _removeListeners.containsKey(key)) {
            Set<GlobalKeyRemoveListener> localListeners = new Set<GlobalKeyRemoveListener>.from(_removeListeners[key]);
  