anchor.diff:  
     _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);
  -  }
  -}
  +}
  
positive.code: }
  
  class _ForInData {
    static const String tag = '_ForInData';
  
    final ir.DartType iterableType;
    final ir.DartType iteratorType;
    final ClassRelation iteratorClassRelation;
  
negative.code: }
  
  class _ConstInstantiation {
    final ir.Class cls;
    final List<ir.DartType> typeArguments;
    final ir.LibraryDependency import;
  
    _ConstInstantiation(this.cls, this.typeArguments, this.import);
  }
  
  enum _Feature {
  