didAdoptChild method
Copied from SliverMultiBoxAdaptorElement.didAdoptChild. An assertion has been removed to allow adoption of off-list elements.
Implementation
@override
void didAdoptChild(final RenderBox child) {
if (_creatingDisposableElement) return;
assert(_currentlyUpdatingChildIndex != null);
final childParentData =
child.parentData! as MultiSliverMultiBoxAdaptorParentData;
childParentData.index = _currentlyUpdatingChildIndex;
childParentData.key = _currentlyUpdatingPopUpList;
}