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

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

diff --git a/lisp/help.el b/lisp/help.el
index e45061536aed584e474aaf6a4738d7a373db8612..c683071ef5b0676c7d83663f0b325337a1fb2743 100644 (file)
--- 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")))))