anchor.diff:    @protected
     void didUpdateWidget(covariant T oldWidget) { }
   
  -  /// Called whenever the application is reassembled during debugging, for
  -  /// example during hot reload.
  -  ///
  -  /// This method should rerun any initialization logic that depends on global
  -  /// state, for example, image loading from asset bundles (since the asset
  -  /// bundle may have changed).
  +  /// {@macro flutter.widgets.reassemble}
     ///
     /// In addition to this method being invoked, it is guaranteed that the
     /// [build] method will be invoked when a reassemble is signaled. Most
     /// widgets therefore do not need to do anything in the [reassemble] method.
     ///
  -  /// This function will only be called during development. In release builds,
  -  /// the `ext.flutter.reassemble` hook is not available, and so this code will
  -  /// never execute.
  -  ///
     /// See also:
     ///
  +  ///  * [Element.reassemble]
     ///  * [BindingBase.reassembleApplication]
     ///  * [Image], which uses this to reload images.
     @protected
  
positive.code:     try {
        assert(root._parent == null);
        assert(root.owner == this);
        root._reassemble();
      } finally {
        Timeline.finishSync();
      }
  
negative.code:   protected,
    required,
    visibleForTesting;
  export 'package:flutter/foundation.dart' show FlutterError, debugPrint, debugPrintStack;
  export 'package:flutter/foundation.dart' show VoidCallback, ValueChanged, ValueGetter, ValueSetter;
  export 'package:flutter/foundation.dart' show DiagnosticLevel;
  