anchor.diff:  class ExternalLibrary {
     final Uri uri;
   
  -  ExternalLibrary(this.uri);
  +  ExternalLibrary._(this.uri);
   }
   
   /// [FileContentOverlay] is used to temporary override content of files.
  
positive.code:   Either2<FileState?, ExternalLibrary> getFileForUri(Uri uri) {
      // If the external store has this URI, create a stub file for it.
      // We are given all required unlinked and linked summaries for it.
      if (externalSummaries != null) {
        String uriStr = uri.toString();
        if (externalSummaries!.hasLinkedLibrary(uriStr)) {
          return Either2.t2(ExternalLibrary(uri));
        }
      }
  
  
negative.code: 
    LibraryCycle? get internal_libraryCycle => _libraryCycle;
  
    /// Return `true` if the file does not have a `library` directive, and has a
    /// `part of` directive, so is probably a part.
    bool get isPart {
      return !_unlinked2!.hasLibraryDirective && _unlinked2!.hasPartOfDirective;
    }
  
  