anchor.diff:      }
       try {
         node.accept(this);
  -    } on NodeLocator_NodeFoundException {} catch (exception, stackTrace) {
  +    } catch (exception, stackTrace) {
         AnalysisEngine.instance.logger.logInformation(
             "Unable to locate element at offset ($_startOffset - $_endOffset)",
             new CaughtException(exception, stackTrace));
  
positive.code:     }
      try {
        node.accept(this);
      } on NodeLocator_NodeFoundException {
        // A node with the right source position was found.
      } catch (exception, stackTrace) {
        AnalysisEngine.instance.logger.logInformation(
            "Unable to locate element at offset ($_startOffset - $_endOffset)",
  
negative.code: 
    @override
    Object visitNode(AstNode node) {
      // Don't visit a new tree if the result has been already found.
      if (_foundNode != null) {
        return null;
      }
      // Check whether the current node covers the selection.
      Token beginToken = node.beginToken;
      Token endToken = node.endToken;
      // Don't include synthetic tokens.
  