private static boolean containsOnlyLiterals(@Nullable GrExpression expression) {
    if (expression instanceof GrLiteral) {
      final String text = expression.getText();
      if ("'".equals(GrStringUtil.getStartQuote(text))) return true;
      if ("\"".equals(GrStringUtil.getStartQuote(text))) return true;
    }
    else if (expression instanceof GrBinaryExpression) {
      final IElementType type = ((GrBinaryExpression)expression).getOperationTokenType();
      if (type != GroovyTokenTypes.mPLUS) return false;

      final GrExpression left = ((GrBinaryExpression)expression).getLeftOperand();
      final GrExpression right = ((GrBinaryExpression)expression).getRightOperand();

      return containsOnlyLiterals(left) && containsOnlyLiterals(right);
    }

    return false;
  }
private static boolean containsOnlyLiterals(@Nullable GrExpression expression)