(hs-grok-mode-type) Handle nil `comment-start' and `comment-end'.

diff --git a/lisp/progmodes/hideshow.el b/lisp/progmodes/hideshow.el
index a94672ac7bc36fd423516a3d34f707eacaab1f9f..d811e7d50b859325147c1f0a95649fcf400b2c3e 100644 (file)
--- a/lisp/progmodes/hideshow.el
+++ b/lisp/progmodes/hideshow.el
@@ -5,7 +5,7 @@
 ;; Author: Thien-Thi Nguyen <ttn@netcom.com>
 ;;     Dan Nicolaescu <done@ece.arizona.edu>
 ;; Keywords: C C++ java lisp tools editing comments blocks hiding outlines
-;; Maintainer-Version: 4.20
+;; Maintainer-Version: 4.21
 ;; Time-of-Day-Author-Most-Likely-to-be-Recalcitrant: early morning
 
 ;; This file is part of GNU Emacs.
@@ -497,19 +497,21 @@ If `hs-special-modes-alist' has information associated with the
 current buffer's major mode, use that.
 Otherwise, guess start, end and comment-start regexps; forward-sexp
 function; and adjust-block-beginning function."
-  (when (and (boundp 'comment-start)
-            (boundp 'comment-end))
-    (let ((lookup (assoc major-mode hs-special-modes-alist)))
-      (setq hs-block-start-regexp (or (nth 1 lookup) "\\s\(")
-           hs-block-end-regexp (or (nth 2 lookup) "\\s\)")
-           hs-c-start-regexp (or (nth 3 lookup)
-                                 (let ((c-start-regexp
-                                        (regexp-quote comment-start)))
-                                   (if (string-match " +$" c-start-regexp)
-                                        (substring c-start-regexp 0 (1- (match-end 0)))
-                                     c-start-regexp)))
-           hs-forward-sexp-func (or (nth 4 lookup) 'forward-sexp)
-           hs-adjust-block-beginning (nth 5 lookup)))))
+  (if (and (boundp 'comment-start)
+          (boundp 'comment-end)
+          comment-start comment-end)
+      (let ((lookup (assoc major-mode hs-special-modes-alist)))
+       (setq hs-block-start-regexp (or (nth 1 lookup) "\\s\(")
+             hs-block-end-regexp (or (nth 2 lookup) "\\s\)")
+             hs-c-start-regexp (or (nth 3 lookup)
+                                   (let ((c-start-regexp
+                                          (regexp-quote comment-start)))
+                                     (if (string-match " +$" c-start-regexp)
+                                         (substring c-start-regexp 0 (1- (match-end 0)))
+                                       c-start-regexp)))
+             hs-forward-sexp-func (or (nth 4 lookup) 'forward-sexp)
+             hs-adjust-block-beginning (nth 5 lookup)))
+    (error "% Mode doesn't support Hideshow Mode" mode-name)))
 
 (defun hs-find-block-beginning ()
   "Reposition point at block-start.