anchor.diff:  /// Visitor that creates [jsAst.Expression]s for constants that are inlined
   /// and therefore can be created during modular code generation.
   class ModularConstantEmitter
  -    implements ConstantValueVisitor<jsAst.Expression, Null> {
  +    implements ConstantValueVisitor<jsAst.Expression?, Null> {
     final CompilerOptions _options;
     final ModularNamer _namer;
   
  
positive.code:   }
  
    @override
    jsAst.Expression visitInstantiation(InstantiationConstantValue constant,
            [_]) =>
        null;
  
    @override
    jsAst.Expression visitDeferredGlobal(DeferredGlobalConstantValue constant,
            [_]) =>
        null;
  
    @override
    jsAst.Expression visitInterceptor(InterceptorConstantValue constant, [_]) =>
        null;
  
    @override
    jsAst.Expression visitType(TypeConstantValue constant, [_]) => null;
  
    @override
    jsAst.Expression visitConstructed(ConstructedConstantValue constant, [_]) =>
        null;
  
    @override
    jsAst.Expression visitMap(MapConstantValue constant, [_]) => null;
  
    @override
    jsAst.Expression visitSet(SetConstantValue constant, [_]) => null;
  
    @override
    jsAst.Expression visitList(ListConstantValue constant, [_]) => null;
  }
  
  /// Generates the JavaScript expressions for constants.
  
negative.code:         _emitter.constructorAccess(constant.type.element);
      List<jsAst.Expression> fields = [];
      _elementEnvironment.forEachInstanceField(element, (_, FieldEntity field) {
        FieldAnalysisData fieldData =
            _fieldAnalysis.getFieldData(field as JField);
        if (fieldData.isElided) return;
        if (!fieldData.isInitializedInAllocator) {
          fields.add(_constantReferenceGenerator(constant.fields[field]!));
        }
      });
      if (_rtiNeed.classNeedsTypeArguments(constant.type.element)) {
  