anchor.diff:        });
         return;
       }
  +
  +    // Compute errors in a part.
  +    if (_errorsRequestedParts.isNotEmpty) {
  +      var path = _errorsRequestedParts.keys.first;
  +      var completers = _errorsRequestedParts.remove(path);
  +      var result = _computeErrors(path: path, asIsIfPartWithoutLibrary: true);
  +      completers.forEach((completer) {
  +        completer.complete(result);
  +      });
  +      return;
  +    }
     }
   
     /// Remove the file with the given [path] from the list of files to analyze.
  
positive.code:       return;
      }
  
      // Process an index request.
      if (_indexRequestedFiles.isNotEmpty) {
        String path = _indexRequestedFiles.keys.first;
  
negative.code:       return null;
      }
  
      var completer = Completer<ErrorsResult>();
      _errorsRequestedFiles
          .putIfAbsent(path, () => <Completer<ErrorsResult>>[])
          .add(completer);
      _scheduler.notify(this);
      return completer.future;
    }
  
    /// Return a [Future] that completes with the list of added files that
  