anchor.diff:            node,
             () => node.elements,
             () => _collectionElements[node] ??=
  -              _transformCollectionElements(node.elements, node.typeArguments));
  +              _transformCollectionElements(node.elements));
   
     @override
     DartType getTypeParameterBound(TypeParameterElementImpl element) {
  
positive.code:   }
  
    List<CollectionElement> _transformCollectionElements(
        NodeList<CollectionElement> elements, TypeArgumentList typeArguments) {
      return elements
          .map(_transformCollectionElement)
          .where((e) => e != null)
  
negative.code:       node,
        () => node.elements,
        () => _collectionElements[node] ??=
            _transformCollectionElements(node.elements));
  
    @override
    List<CollectionElement> getSetOrMapElements(SetOrMapLiteral node) =>
  