anchor.diff:              'use --engine-src-path to specify the path to the root of your flutter/engine repository.');
           throw new ProcessExit(2);
         }
  +    }
  +
  +    if (engineSourcePath != null && _tryEnginePath(engineSourcePath) == null) {
  +      stderr.writeln('Unable to detect a Flutter engine build directory in $engineSourcePath.\n'
  +          'Please ensure that $engineSourcePath is a Flutter engine \'src\' directory and that\n'
  +          'you have compiled the engine in that directory, which should produce an \'out\' directory');
  +      throw new ProcessExit(2);
       }
   
       return engineSourcePath;
  
positive.code:             engineSourcePath = null;
          } on FileSystemException { }
        }
        if (engineSourcePath == null) {
          String tryEnginePath(String enginePath) {
            if (FileSystemEntity.isDirectorySync(path.join(enginePath, 'out')))
              return enginePath;
            return null;
          }
          engineSourcePath = tryEnginePath(path.join(ArtifactStore.flutterRoot, '../engine/src'));
        }
        if (engineSourcePath == null) {
          stderr.writeln('Unable to detect local Flutter engine build directory.\n'
              'Either specify a dependency_override for the $kFlutterEnginePackageName package in your pubspec.yaml and\n'
  
negative.code:     return 0;
    }
  
    String _tryEnginePath(String enginePath) {
      if (FileSystemEntity.isDirectorySync(path.join(enginePath, 'out')))
        return enginePath;
      return null;
    }
  
    String _findEnginePath(ArgResults globalResults) {
      String engineSourcePath = globalResults['engine-src-path'] ?? Platform.environment[kFlutterEngineEnvironmentVariableName];
      bool isDebug = globalResults['debug'];
  