anchor.diff:          help:
               'Whether to generate a stand-alone executable or an AOT snapshot.')
       ..addOption('packages',
  -        valueHelp: 'path', help: 'Where to find a package spec file.');
  +        valueHelp: 'path', help: 'Where to find a package spec file.')
  +    ..addFlag('verbose',
  +        abbr: 'v', negatable: false, help: 'Enables more verbose output.');
   
  -  final ArgResults parsedArgs = parser.parse(args);
  +  ArgResults parsedArgs;
  +  try {
  +    parsedArgs = parser.parse(args);
  +  } on FormatException catch (e) {
  +    stderr.writeln('Error: ${e.message}');
  +    await stderr.flush();
  +    printUsage(parser);
  +    exit(1);
  +  }
   
     if (parsedArgs['help']) {
       printUsage(parser);
  
positive.code:     }
  
      if (kind == Kind.exe) {
        print('Generating executable.');
        await writeAppendedExecutable(dartaotruntime, snapshotFile, outputFile);
  
        if (Platform.isLinux || Platform.isMacOS) {
          print('Marking binary executable.');
          await markExecutable(outputFile);
        }
      }
  
negative.code: final String platformDill =
      path.join(sdkDir, 'lib', '_internal', 'vm_platform_strong.dill');
  
  Future<void> generateNative(
      Kind kind,
      String sourceFile,
      String outputFile,
      String packages,
      List<String> defines,
      bool enableAsserts,
      bool verbose) async {
    final Directory tempDir = Directory.systemTemp.createTempSync();
    try {
      final String kernelFile = path.join(tempDir.path, 'kernel.dill');
  