anchor.diff:          // the non-existent file 'username@hostname.pid'. To avoid these dummy
           // links causing the analyzer to thrash, just ignore links to
           // non-existent files.
  -        return file.exists;
  +        return !mustExist || file.exists;
         }
       }
       return false;
  
positive.code:           }
          }
  
          callbacks.applyFileRemoved(info.analysisDriver, path);
          break;
        case ChangeType.MODIFY:
          Resource resource = resourceProvider.getResource(path);
  
negative.code:   /**
     * Return `true` if the given [file] should be analyzed.
     */
    bool _shouldFileBeAnalyzed(File file, {bool mustExist = true}) {
      for (Glob glob in analyzedFilesGlobs) {
        if (glob.matches(file.path)) {
          // Emacs creates dummy links to track the fact that a file is open for
  