anchor.diff:    return {
       'type': mapType(e.runtimeType),
       'widget': mapWidget(e.widget),
  -    'isRenderElement': e is flutter.RenderElement,
  +    'isRenderElement': e is flutter.RenderObjectElement,
       'renderObject': mapRenderObject(e.renderObject)
     };
   }
  
positive.code: 
  import 'dart:async' show Future;
  
  import 'package:widgets/framework.dart' as flutter show Element, RenderElement;
  import 'package:widgets/bindings.dart' as flutterWidgetBindings
      show WidgetBinding;
  
  List<Map<String, dynamic>> stack;
  
  flutter.Element tree =
      flutterWidgetBindings.WidgetBinding.instance.renderViewElement;
  // the root of the element tree
  
  push(Map<String, dynamic> e) {
  
negative.code: }
  
  main() {
    flutterWidgetBindings.WidgetsBinding.instance.registerServiceExtension(
        name: 'returnElementTree', callback: debugReturnElementTree);
    flutterWidgetBindings.WidgetsBinding.instance.registerServiceExtension(
        name: 'returnWidgetTree', callback: debugReturnWidgetTree);
    // to be added to WidgetBinding.initServiceExtensions
  
    flutterWidgetBindings.RendererBinding.instance.registerServiceExtension(
        name: 'returnRenderObjectTree', callback: debugReturnRenderObjectTree);
    // to be added to RenderBinding.initServiceExtensions
  }
  