anchor.diff:      _updateEntry();
       // resolve references in the comment
       incrementalResolver._resolveReferences(newComment);
  +    // OK
  +    return true;
     }
   
     Token _scan(String code) {
  
positive.code:           _updateDelta = newUnit.length - oldUnit.length;
            // A Dart documentation comment change.
            if (firstPair.kind == _TokenDifferenceKind.COMMENT_DOC) {
              _resolveComment(oldUnit, newUnit, firstPair);
              logger.log('Success.');
              return true;
            }
            // A pure whitespace change.
            if (firstPair.kind == _TokenDifferenceKind.OFFSET) {
  
negative.code:     }
    }
  
    /**
     * Attempts to resolve a documentation comment change.
     * Returns `true` if success.
     */
    bool _resolveComment(CompilationUnit oldUnit, CompilationUnit newUnit,
        _TokenPair firstPair) {
      Token oldToken = firstPair.oldToken;
      Token newToken = firstPair.newToken;
      CommentToken oldComments = oldToken.precedingComments;
      CommentToken newComments = newToken.precedingComments;
      if (oldComments == null || newComments == null) {
        return false;
      }
      // find nodes
      int offset = oldComments.offset;
      logger.log('offset: $offset');
      Comment oldComment = _findNodeCovering(oldUnit, offset, offset);
      Comment newComment = _findNodeCovering(newUnit, offset, offset);
  