anchor.diff:    void scheduleBuildFor(BuildableElement element) {
       assert(element != null);
       assert(element.owner == this);
  -    assert(element._inDirtyList == _dirtyElements.contains(element));
       assert(() {
         if (debugPrintScheduleBuildForStacks)
           debugPrintStack(label: 'scheduleBuildFor() called for $element${_dirtyElements.contains(element) ? " (ALREADY IN LIST)" : ""}');
  
positive.code:   /// This function is called only during the "active" lifecycle state.
    @mustCallSuper
    void update(@checked Widget newWidget) {
      assert(_debugLifecycleState == _ElementLifecycle.active);
      assert(widget != null);
      assert(newWidget != null);
      assert(newWidget != widget);
      assert(depth != null);
      assert(_active);
      assert(Widget.canUpdate(widget, newWidget));
      _widget = newWidget;
    }
  
  
negative.code: 
    @override
    void _reassemble() {
      markNeedsBuild();
      super._reassemble();
    }
  