anchor.diff:  
     @override
     void onQueueOpen(
  -      Enqueuer enqueuer, FunctionEntity mainMethod, Iterable<Uri> libraries) {
  +      Enqueuer enqueuer, FunctionEntity? mainMethod, Iterable<Uri> libraries) {
       enqueuer.applyImpact(_nativeEnqueuer.processNativeClasses(libraries));
       if (mainMethod != null) {
         enqueuer.applyImpact(_computeMainImpact(mainMethod));
  
positive.code:     _customElementsAnalysis.registerStaticUse(member);
  
      if (member.isFunction && member.isInstanceMember) {
        ClassEntity cls = member.enclosingClass;
        if (member.name == Identifiers.call &&
            _elementEnvironment.isGenericClass(cls) &&
            _rtiNeed.methodNeedsSignature(member)) {
          worldImpact.addImpact(_registerComputeSignature());
        }
      }
  
negative.code:           .registerTypeUse(TypeUse.instantiation(_commonElements.typeType));
        // If the type is a web component, we need to ensure the constructors are
        // available to 'upgrade' the native object.
        final representedType = constant.representedType;
        if (representedType is InterfaceType) {
          _customElementsAnalysis.registerTypeConstant(representedType.element);
        }
      } else if (constant is InstantiationConstantValue) {
  