Fix lisp-comment-indent for single-semicolon case

* lisp/emacs-lisp/lisp-mode.el (lisp-comment-indent): Only check for
open paren if we're looking at multiple comment characters.
* test/lisp/emacs-lisp/lisp-mode-tests.el (lisp-comment-indent-1)
(lisp-comment-indent-2): New tests.

1 files changed, 8 insertions, 6 deletions

diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index 985b7513a3b..fa25a0c3975 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -738,12 +738,14 @@ or to switch back to an existing one."
 
 (defun lisp-comment-indent ()
   "Like `comment-indent-default', but don't put space after open paren."
-  (let ((pt (point)))
-    (skip-syntax-backward " ")
-    (if (eq (preceding-char) ?\()
-        (cons (current-column) (current-column))
-      (goto-char pt)
-      (comment-indent-default))))
+  (or (when (looking-at "\\s<\\s<")
+        (let ((pt (point)))
+          (skip-syntax-backward " ")
+          (if (eq (preceding-char) ?\()
+              (cons (current-column) (current-column))
+            (goto-char pt)
+            nil)))
+      (comment-indent-default)))
 
 (define-obsolete-function-alias 'lisp-mode-auto-fill 'do-auto-fill "23.1")