anchor.diff:  
     @override
     InheritedWidget inheritFromWidgetOfExactType(Type targetType) {
  -    assert(_debugCheckStateIsActiveForAncestorLoopkup());
  +    assert(_debugCheckStateIsActiveForAncestorLookup());
       final InheritedElement ancestor = _inheritedWidgets == null ? null : _inheritedWidgets[targetType];
       if (ancestor != null) {
         assert(ancestor is InheritedElement);
  
positive.code: 
    @override
    RenderObject ancestorRenderObjectOfType(TypeMatcher matcher) {
      assert(_debugCheckStateIsActiveForAncestorLoopkup());
      Element ancestor = _parent;
      while (ancestor != null) {
        if (ancestor is RenderObjectElement && matcher.check(ancestor.renderObject))
  
negative.code: 
    @override
    Widget ancestorWidgetOfExactType(Type targetType) {
      assert(_debugCheckStateIsActiveForAncestorLookup());
      Element ancestor = _parent;
      while (ancestor != null && ancestor.widget.runtimeType != targetType)
        ancestor = ancestor._parent;
  