bug#65270: 30.0.50; `describe-function' issue with some methods

[David Ponce <da_vid@orange.fr>]

Hello,

It seems there is an issue with `describe-function' of a method that
calls `cl-call-next-method'.  For a such method `describe-function' says
that the method is "Undocumented" even if a doc string is present.

Also the mentioned signature is weird.  See an illustration below using
a simple recipe, running 'emacs -Q'.

Thanks!

<1> In scratch buffer eval:
===========================
*scratch*
------------------------------------------------------------------
(cl-defgeneric foo (arg)
   "Generic foo receiving any ARG."
   (format "%S" arg))
foo

(cl-defmethod foo ((arg atom))
   "Specialized foo receiving any atoms."
   (format "atom %s" (cl-call-next-method)))
foo

(cl-defmethod foo ((arg string))
   "Specialized foo receiving strings."
   (format "string %S" arg))
foo

;; Check results are correct
(foo 1)
"atom 1"
(foo '(1))
"(1)"
(foo "1")
"string \"1\""
------------------------------------------------------------------

<2> M-x describe-function RET foo RET
=====================================
*Help* (is not correct for the method using `cl-call-next-method')
------------------------------------------------------------------
foo is a byte-compiled Lisp function.

(foo ARG)

Generic foo receiving any ARG.

   Probably introduced at or before Emacs version 1.2.


This is a generic function.

Implementations:

(foo (ARG string))
Specialized foo receiving strings.

(foo (ARG0 atom) &rest CL--ARGS) <<<<<<<<<<<<< Incorrect
Undocumented

(foo ARG)
Undocumented
------------------------------------------------------------------


<3> In scratch buffer eval:
===========================
*scratch*
------------------------------------------------------------------
;; Redefine method without calling `cl-call-next-method'
(cl-defmethod foo ((arg atom))
   "Specialized foo receiving any atoms."
   (format "atom %S" arg))
foo

;; Check results are correct
(foo 1)
"atom 1"
(foo '(1))
"(1)"
(foo "1")
"string \"1\""
------------------------------------------------------------------

<4> M-x describe-function RET foo RET
=====================================
*Help* (is correct)
------------------------------------------------------------------
foo is a byte-compiled Lisp function.

(foo ARG)

Generic foo receiving any ARG.

   Probably introduced at or before Emacs version 1.2.


This is a generic function.

Implementations:

(foo (ARG string))
Specialized foo receiving strings.

(foo (ARG atom)) <<<<<<<<<<<<< Correct
Specialized foo receiving any atoms.

(foo ARG)
Undocumented
------------------------------------------------------------------

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
  3.24.38, cairo version 1.17.8) of 2023-08-13
Repository revision: de6c1c4d5c92b92d5b280e157c2a5bc3228749f2
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 38 (KDE Plasma)

Configured using:
  'configure --with-x-toolkit=gtk3
  --with-native-compilation=no'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
   value of $LC_TIME: fr_FR.utf8
   value of $LANG: fr_FR.UTF-8
   locale-coding-system: utf-8-unix