font-lock-keywords: matcher function not working

[Raffaele Ricciardi]

Hello everybody,

I'm trying to highlight the first parenthesis of each line in Lisp code.

After having read the documentation of `font-lock-keywords', I've
written a matcher function which behaves as required (I've tested it
with `eval-expression').  However, first parentheses are not
highlighted.


Here is my code, tested on GNU Emacs 24.3

;; Tested in the *scratch* buffer after "emacs -Q".

(require 'cl)

(defun* rr-first-non-blank? (&optional (point (point)))
  "Return non-NIL if POINT is on the first non-blank character of the
current line."
  (= point
     (save-excursion
       (back-to-indentation)
       (point))))

(defun rr-match-indented-paren (^end)
  "Matcher for `font-lock-keywords' that matches a parenthesis made
 redundant by indentation."
  (if (and (eql (char-after) ?\()
           (rr-first-non-blank?))
      (re-search-forward "(" ^end)
      nil))

(font-lock-add-keywords 'lisp-interaction-mode
                        '(
                          (rr-match-indented-paren . 
'font-lock-warning-face)
                          ))

(font-lock-fontify-buffer)