(describe-function-1): Distinguish special form from

builtin function.  Sanity-check presence of arglist for builtins.

1 files changed, 21 insertions, 14 deletions

diff --git a/lisp/help.el b/lisp/help.el
index e45061536ae..c683071ef5b 100644
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -621,7 +621,9 @@ It can also be nil, if the definition is not associated with any file."
                      (vectorp def))
                  "a keyboard macro")
                 ((subrp def)
-                 (concat beg "built-in function"))
+                 (if (eq 'unevalled (cdr (subr-arity def)))
+                     (concat beg "special form")
+                   (concat beg "built-in function")))
                 ((byte-code-function-p def)
                  (concat beg "compiled Lisp function"))
                 ((symbolp def)
@@ -716,19 +718,24 @@ It can also be nil, if the definition is not associated with any file."
       (if doc
           (progn (terpri)
                  (princ doc)
-                 (with-current-buffer standard-output
-                   (beginning-of-line)
-                   ;; Builtins get the calling sequence at the end of
-                   ;; the doc string.  Move it to the same place as
-                   ;; for other functions.
-                   (when (looking-at (format "(%S[ )]" function))
-                     (let ((start (point-marker)))
-                       (goto-char (point-min))
-                       (forward-paragraph)
-                       (insert-buffer-substring (current-buffer) start)
-                       (insert ?\n)
-                       (delete-region (1- start) (point-max))
-                       (goto-char (point-max)))))
+                 (if (subrp (symbol-function function))
+                     (with-current-buffer standard-output
+                       (beginning-of-line)
+                       ;; Builtins get the calling sequence at the end of
+                       ;; the doc string.  Move it to the same place as
+                       ;; for other functions.
+                       (if (looking-at (format "(%S[ )]" function))
+                           (let ((start (point-marker)))
+                             (goto-char (point-min))
+                             (forward-paragraph)
+                             (insert-buffer-substring (current-buffer) start)
+                             (insert ?\n)
+                             (delete-region (1- start) (point-max)))
+                         (goto-char (point-min))
+                         (forward-paragraph)
+                         (insert
+                          "[Missing arglist.  Please make a bug report.]\n"))
+                       (goto-char (point-max))))
                  (help-setup-xref (list #'describe-function function)
                                   interactive-p))
         (princ "not documented")))))