anchor.diff:  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;
  
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: }
  
  /**
   * 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.
  