Find unused definitions in Emacs Lisp

find-unused-def.el

(defun check-next-def ()
  (push-mark nil t)
  (when (re-search-forward
         (concat "(def\\(?:un\\|macro\\|subst\\|var\\|const\\) "
                 "\\(\\(?:\\sw\\|\\s_\\)+\\)")
         nil 'move)
    (save-excursion
      (let ((name (match-string 1)))
        (goto-char (point-min))
        (unless (re-search-forward (concat "\\_<" name "\\_>") nil t 2)
          name)))))

(defun find-unused-def ()
  (interactive)
  (let (name)
    (while (and (not (eobp))
                (not (setq name (check-next-def)))))
    (message "Found! %s" name)))

(global-set-key [f7] 'find-unused-def)