anchor.diff:  }
   
   /**
  + * And implementation of [DartFixContext].
  + */
  +class _DartFixContextImpl implements DartFixContext {
  +  @override
  +  final ResourceProvider resourceProvider;
  +
  +  @override
  +  final engine.AnalysisContext analysisContext;
  +
  +  @override
  +  final CompilationUnit unit;
  +
  +  @override
  +  final engine.AnalysisError error;
  +
  +  _DartFixContextImpl(
  +      this.resourceProvider, this.analysisContext, this.unit, this.error);
  +}
  +
  +/**
    * An object managing a single [Refactoring] instance.
    *
    * The instance is identified by its kind, file, offset and length.
  
positive.code: import 'package:analysis_server/src/services/correction/assist.dart';
  import 'package:analysis_server/src/services/correction/assist_internal.dart';
  import 'package:analysis_server/src/services/correction/fix.dart';
  import 'package:analysis_server/src/services/correction/organize_directives.dart';
  import 'package:analysis_server/src/services/correction/sort_members.dart';
  import 'package:analysis_server/src/services/correction/status.dart';
  
negative.code: import 'package:analyzer/dart/ast/ast.dart';
  import 'package:analyzer/dart/element/element.dart';
  import 'package:analyzer/error/error.dart' as engine;
  import 'package:analyzer/file_system/file_system.dart';
  import 'package:analyzer/src/dart/analysis/driver.dart';
  import 'package:analyzer/src/dart/scanner/scanner.dart' as engine;
  import 'package:analyzer/src/error/codes.dart' as engine;
  