anchor.diff:    final Map<String, File> symbolFiles = _listIntlData(dateSymbolsDirectory);
     final Directory datePatternsDirectory = Directory(path.join(pathToIntl, 'src', 'data', 'dates', 'patterns'));
     final Map<String, File> patternFiles = _listIntlData(datePatternsDirectory);
  -  final List<String> materialLocales = _materialLocales().toList();
     final StringBuffer buffer = StringBuffer();
   
     buffer.writeln(
  
positive.code:   throw 'Unsupported JSON type ${json.runtimeType} of value $json.';
  }
  
  Iterable<String> _materialLocales() sync* {
    final RegExp filenameRE = RegExp(r'material_(\w+)\.arb$');
    final Directory materialLocalizationsDirectory = Directory(path.join('packages', 'flutter_localizations', 'lib', 'src', 'l10n'));
    for (FileSystemEntity entity in materialLocalizationsDirectory.listSync()) {
      final String filePath = entity.path;
      if (FileSystemEntity.isFileSync(filePath) && filenameRE.hasMatch(filePath))
        yield filenameRE.firstMatch(filePath)[1];
    }
  }
  
  Map<String, File> _listIntlData(Directory directory) {
  
negative.code: /// supported by flutter_localizations.''');
    buffer.writeln('const Map<String, dynamic> dateSymbols = <String, dynamic> {');
    symbolFiles.forEach((String locale, File data) {
      if (_supportedLocales().contains(locale))
        buffer.writeln(_jsonToMapEntry(locale, json.decode(data.readAsStringSync())));
    });
    buffer.writeln('};');
  