describe-function bad def value ("nil") when not near a function name

[Drew Adams]

emacs -q

go to the empty *scratch* buffer, and do `C-h f', then do M-n at the
prompt. The default value you see is "nil". The default value should be
nil, not "nil".

Here's the code:

(defun describe-function (function)
  "Display the full documentation of FUNCTION (a symbol)."
  (interactive
   (let ((fn (function-called-at-point))
         (enable-recursive-minibuffers t)
         val)
     (setq val (completing-read
                (if fn
                    (format "Describe function (default %s): " fn)
                  "Describe function: ")
                obarray 'fboundp t nil nil (symbol-name fn)))
  ...

In this case, fn is nil, so (symbol-name fn) is "nil" - a bad default
value. Just use (and fn (symbol-name fn)).



In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2005-06-26 on NONIQPC
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc
(3.3) --cflags -I../../jpeg-6b-3/include -I../../libpng-1.2.8/include -I../.
./tiff-3.6.1-2/include -I../../xpm-nox-4.2.0/include -I../../zlib-1.2.2/incl
ude'