anchor.diff:    /// be deferred due to the `inference-update-1` feature, a list of them is
     /// returned.
     List<_DeferredClosure>? _visitArguments(
  -      {required FunctionType? rawType,
  -      List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo,
  +      {List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo,
         Substitution? substitution,
         GenericInferrer? inferrer}) {
       assert(whyNotPromotedList.isEmpty);
  
positive.code:     List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo =
          _isIdentical ? [] : null;
      var deferredClosures = _visitArguments(
          rawType: rawType,
          identicalInfo: identicalInfo,
          substitution: substitution,
          inferrer: inferrer);
  
negative.code:               rawType!.typeFormals, inferrer.partialInfer());
          }
          _resolveDeferredClosures(
              deferredClosures: stage,
              identicalInfo: identicalInfo,
              substitution: substitution,
  