anchor.diff:    ///
     /// See the [RenderObjectElement] documentation for more information on slots.
     @protected
  +  @pragma('vm:prefer-inline')
     Element? updateChild(Element? child, Widget? newWidget, Object? newSlot) {
       if (newWidget == null) {
         if (child != null)
  
positive.code:   /// Called by the [BuildOwner] when [BuildOwner.scheduleBuildFor] has been
    /// called to mark this element dirty, by [mount] when the element is first
    /// built, and by [update] when the widget has changed.
    void rebuild() {
      assert(_lifecycleState != _ElementLifecycle.initial);
      if (_lifecycleState != _ElementLifecycle.active || !_dirty)
  
negative.code:   /// The element returned by this function will already have been mounted and
    /// will be in the "active" lifecycle state.
    @protected
    @pragma('vm:prefer-inline')
    Element inflateWidget(Widget newWidget, Object? newSlot) {
      assert(newWidget != null);
      final Key? key = newWidget.key;
  