anchor.diff:  import 'dart:io' as io;
   
   import 'package:analyzer/dart/ast/ast.dart';
  +import 'package:analyzer/dart/ast/visitor.dart';
   import 'package:front_end/src/testing/package_root.dart' as package_root;
   import 'package:path/path.dart' as path;
   import 'package:test/test.dart';
  
positive.code:     return codes.toList();
    }
  
    List<String> getTranslatedCodes(String astBuilderPath) {
      String content = new io.File(astBuilderPath).readAsStringSync();
      CompilationUnit unit = parseCompilationUnit(content);
  
negative.code: 
  @reflectiveTest
  class AbstractRecoveryTest extends FastaParserTestCase {
    /**
     * Given the path to the file containing the declaration of the fasta Parser,
     * return a set containing the names of all the messages and templates that
     * are referenced (presumably because they are being generated) within that
     * file.
     */
    Set<String> getGeneratedNames(String parserPath) {
      String content = new io.File(parserPath).readAsStringSync();
      CompilationUnit unit = parseCompilationUnit(content);
      expect(unit, isNotNull);
      GeneratedCodesVisitor visitor = new GeneratedCodesVisitor();
      unit.accept(visitor);
      return visitor.generatedNames;
    }
  
    /**
     * Given the path to the file 'message.yaml', return a list of the top-level
     * keys defined in that file that define an 'analyzerCode'.
     */
    List<String> getMappedCodes(String messagesPath) {
      String content = new io.File(messagesPath).readAsStringSync();
      YamlDocument document = loadYamlDocument(content);
      expect(document, isNotNull);
      Set<String> codes = new Set<String>();
      YamlNode contents = document.contents;
      if (contents is YamlMap) {
        for (String name in contents.keys) {
          Object value = contents[name];
          if (value is YamlMap) {
            if (value['analyzerCode'] != null) {
              codes.add(name);
            }
          }
        }
      }
      return codes.toList();
    }
  
    /**
     * Given the path to the file 'message.yaml', return a list of the analyzer
     * codes defined in that file.
     */
    List<String> getReferencedCodes(String messagesPath) {
      String content = new io.File(messagesPath).readAsStringSync();
      YamlDocument document = loadYamlDocument(content);
  