anchor.diff:    /// Additional CSS classes to be attached to the root menu item element.
     final BuiltList<String> cssClasses;
   
  -  void _noop() {}
  -  Function get nullAwareActionHandler => action != null ? action : _noop;
  -
     @virtual
     bool enabled;
  -  bool get hasIcon => icon != null;
  -
  -  bool get hasSubMenu => subMenu != null;
  -  bool get showTooltip => isNotEmpty(tooltip);
  -  @override
  -  String get uiDisplayName => label;
  -  bool get hasSecondaryLabel => secondaryLabel != null;
   
     /// The constructor for a [MenuItem] which displays [label].
     ///
  
positive.code:       }.toString();
  }
  
  /// Type that can be specified to mark that there can be no subMenus for
  /// a given [MenuItem].
  abstract class NullMenuItem extends MenuItem<NullMenuItem> {
  
negative.code:   Function action;
  
    final Icon icon;
  
    /// List of rendered suffixes for this menu item.
    final ObservableList<MenuItemAffix> itemSuffixes;
  