anchor.diff:  }
   
   class _ConstInstantiation {
  -  static const String tag = '_ConstInstantiation';
  -
     final ir.Class cls;
     final List<ir.DartType> typeArguments;
     final ir.LibraryDependency import;
   
     _ConstInstantiation(this.cls, this.typeArguments, this.import);
  -
  -  factory _ConstInstantiation.fromDataSource(DataSource source) {
  -    source.begin(tag);
  -    ir.Class cls = source.readClassNode();
  -    List<ir.DartType> typeArguments = source.readDartTypeNodes();
  -    ir.LibraryDependency import = source.readLibraryDependencyNodeOrNull();
  -    source.end(tag);
  -    return new _ConstInstantiation(cls, typeArguments, import);
  -  }
  -
  -  void toDataSink(DataSink sink) {
  -    sink.begin(tag);
  -    sink.writeClassNode(cls);
  -    sink.writeDartTypeNodes(typeArguments);
  -    sink.writeLibraryDependencyNodeOrNull(import);
  -    sink.end(tag);
  -  }
   }
   
   enum _Feature {
  
positive.code: 
    _ForInData(this.iterableType, this.iteratorType, this.iteratorClassRelation,
        {this.isAsync});
  
    factory _ForInData.fromDataSource(DataSource source) {
      source.begin(tag);
      ir.DartType iterableType = source.readDartTypeNode();
      ir.DartType iteratorType = source.readDartTypeNode(allowNull: true);
      ClassRelation iteratorClassRelation = source.readEnum(ClassRelation.values);
      bool isAsync = source.readBool();
      return new _ForInData(iterableType, iteratorType, iteratorClassRelation,
          isAsync: isAsync);
    }
  
    void toDataSink(DataSink sink) {
      sink.begin(tag);
      sink.writeDartTypeNode(iterableType);
      sink.writeDartTypeNode(iteratorType);
      sink.writeEnum(iteratorClassRelation);
      sink.writeBool(isAsync);
      sink.end(tag);
    }
  }
  
negative.code: }
  
  class _ForInData {
    final ir.DartType iterableType;
    final ir.DartType iteratorType;
    final ClassRelation iteratorClassRelation;
  