anchor.diff:    /// Pointer to the owner Element object
     StatefulComponentElement _element;
   
  +  /// The context in which this object will be built
  +  BuildContext get context => _element;
  +
     /// Called when this object is inserted into the tree. Override this function
     /// to perform initialization that depends on the location at which this
     /// object was inserted into the tree or on the widget configuration object.
  
positive.code: 
  abstract class BuildContext {
    InheritedWidget inheritedWidgetOfType(Type targetType);
  }
  
  /// Elements are the instantiations of Widget configurations.
  
negative.code:       ancestor = ancestor._parent;
      return ancestor?.widget;
    }
  
    RenderObject findRenderObject() => renderObject;
  
    void dependenciesChanged() {
      assert(false);
  