anchor.diff:      Source fileSource = _resourceProvider.getFile(path).createSource();
       Uri uri = _sourceFactory.restoreUri(fileSource);
       Source source = _resourceProvider.getFile(path).createSource(uri);
  -    return new _File(this, source);
  +    return new _File.forResolution(this, source);
     }
   
     /**
  
positive.code:       // for missing files. Maybe add this feature to SummaryDataStore?
      }
      // Compute the content hash.
      List<int> textBytes = UTF8.encode(_content);
      List<int> hashBytes = md5.convert(textBytes).bytes;
      _contentHash = hex.encode(hashBytes);
      // Update the current file state.
      driver._fileContentHashMap[path] = _contentHash;
    }
  }
  
  
negative.code:   final _fileContentHashMap = <String, String>{};
  
    /**
     * The API signatures corresponding to [_fileContentHashMap].
     *
     * It maps file paths to the unlinked API signatures.
     */
    final _fileApiSignatureMap = <String, String>{};
  
    /**
     * Mapping from library URIs to the dependency signature of the library.
     */
    final _dependencySignatureMap = <Uri, String>{};
  