bug#42672: 28.0.50; cl-defgeneric with :method generates incorrect Edebug symbols

[Philipp Stephani <p.stephani2@gmail.com>]

Create a file /tmp/defmethod.el:

$ cat /tmp/defmethod.el 
(cl-defgeneric foo (_)
  (:method ((_ number)) 1))

Visit the file in Emacs:

$ emacs -Q /tmp/defmethod.el

Instrument the `cl-defgeneric' form using C-u C-M-x.  The *Messages*
buffer now contains

Edebug: nil ((_ number))
Edebug: foo

The second line is for the generic function itself.  The first line,
however, is for the method defined by the `:method' form.  But its name
should be `foo ((_ number))', not `nil ((_ number))'.  This becomes a
problem if there are multiple such generic functions with different
names but identical signatures, because Edebug will then generate
duplicate symbols.  This breaks e.g. coverage instrumentation because
the instrumented frequencies will be attached to the wrong symbol.

Implementation-wise, I guess this is a problem with
`edebug-match-cl-generic-method-args'.  That function contains the
snippet

    ;; Append the arguments to edebug-def-name.
    (setq edebug-def-name
          (intern (format "%s %s" edebug-def-name args)))

However, `edebug-def-name' is only non-nil when using `cl-defmethod',
not when using `cl-defgeneric' with `:method'.


In GNU Emacs 28.0.50 (build 60, x86_64-pc-linux-gnu, GTK+ Version 3.24.18, cairo version 1.16.0)
 of 2020-08-02
Repository revision: 929e7e141c5780e51173fda7d7fc5b73411e4465
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux rodete

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --enable-gcc-warnings=warn-only
 --enable-gtk-deprecation-warnings --without-pop --with-mailutils
 --enable-checking=all --enable-check-lisp-object-type --with-modules
 'CFLAGS=-O1 -ggdb3 -fno-omit-frame-pointer -fsanitize=address
 -fsanitize=undefined -fsanitize=pointer-compare
 -fsanitize=pointer-subtract''

Configured features:
XPM JPEG TIFF GIF PNG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS FREETYPE HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS GTK3 X11
XDBE XIM MODULES THREADS LIBSYSTEMD JSON PDUMPER

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc dired dired-loaddefs rfc822
mml easymenu mml-sec epa epg epg-config gnus-util rmail rmail-loaddefs
text-property-search time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils phst skeleton derived edmacro
kmacro pcase ffap thingatpt url url-proxy url-privacy url-expand
url-methods url-history url-cookie url-domsuf url-util url-parse
auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json map url-vars mailcap subr-x rx gnutls puny seq
byte-opt gv bytecomp byte-compile cconv dbus xml compile comint
ansi-color ring cl-loaddefs cl-lib tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify dynamic-setting system-font-setting
font-render-setting cairo move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 68799 8226)
 (symbols 48 8629 1)
 (strings 32 23745 2016)
 (string-bytes 1 764226)
 (vectors 16 13112)
 (vector-slots 8 166374 4864)
 (floats 8 25 30)
 (intervals 56 221 0)
 (buffers 992 11))

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