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:         _emitter.constructorAccess(constant.type.element);
      List<jsAst.Expression> fields = [];
      _elementEnvironment.forEachInstanceField(element, (_, FieldEntity field) {
        FieldAnalysisData fieldData = _fieldAnalysis.getFieldData(field);
        if (fieldData.isElided) return;
        if (!fieldData.isInitializedInAllocator) {
          fields.add(_constantReferenceGenerator(constant.fields[field]));
        }
      });
      if (_rtiNeed.classNeedsTypeArguments(constant.type.element)) {
  
negative.code:     jsAst.Expression jsMap() {
        List<jsAst.Property> properties = [];
        for (int i = 0; i < constant.length; i++) {
          final key = constant.keys[i] as StringConstantValue;
          if (key.stringValue ==
              constant_system.JavaScriptMapConstant.PROTO_PROPERTY) {
            continue;
  