anchor.diff:    if (FileSystemEntity.isDirectorySync(outputFilePath)) {
       print("'$outputFilePath' is a directory.");
       _printUsage();
  +    exitCode = 1;
       return;
     }
     //
  
positive.code: main(List<String> args) {
    if (args.length < 1 || args.length > 2) {
      _printUsage();
      return;
    }
    //
  
negative.code:     if (!FileSystemEntity.isDirectorySync('$sdkPath/lib')) {
        print("'$sdkPath/lib' does not exist.");
        _printUsage();
        exitCode = 1;
        return;
      }
    } else {
  