bug#58557: 29.0.50; elisp-completion-at-point don't complete local variables when using setq

[Disroot]

elisp-completion-at-point will not complete local variables when using setq.

Tested with emacs -Q, latest Emacs master

Steps to Reproduce:

Snippet a:
(let (foo foo-foo bar bar-bar)
  (setq foo))
               ^

^ marked cursor position.

When pressing C-M-i (completion-at-point), no local variable completion will be 
provided.

And I found out it was related with elisp--local-variables and macroexpand-all:


Debug snippet:

Snippet b:

(let ((macroexpand-advice (lambda (expander form &rest args)
                            (condition-case nil
                                (apply expander form args)
                              (error form)
                              ))))
  (unwind-protect
      (progn
        (advice-add 'macroexpand :around macroexpand-advice)
        (macroexpand-all
         '(setq elisp--witness--lisp)))
    (advice-remove 'macroexpand macroexpand-advice)))

Return value in Emacs 29.0.50: 

(signal 'wrong-number-of-arguments
        '(setq 1))


I also tested those two steps on Emacs 28.2, released version 
with emacs -Q,

and with following system-configuration-features:
"ACL GMP GNUTLS JSON LIBXML2 MODULES NOTIFY 
KQUEUE NS PDUMPER THREADS TOOLKIT_SCROLL_BARS ZLIB”

completion-at-point worked normally in Snippet a.

Return value of Snippet b is:

(setq elisp--witness--lisp)
——————————————————————————————————————————— 
In GNU Emacs 29.0.50 (build 1, x86_64-apple-darwin21.6.0, NS
appkit-2113.60 Version 12.6 (Build 21G115)) of 2022-10-15 built on
MacBook-Pro-4.local
Repository revision: 9fcd59a97820e5154e678be8b98fe0cac4e4546e
Repository branch: HEAD
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.6

Configured using:
'configure --prefix=/opt/local --disable-silent-rules --without-dbus
--without-gconf --without-libotf --without-m17n-flt --with-libgmp
--with-gnutls --with-json --with-xml2 --with-modules --infodir
/opt/local/share/info/my-emacs --with-sqlite3 --with-webp --with-ns
--with-lcms2 --without-harfbuzz --without-imagemagick --without-xaw3d
--with-rsvg --with-xwidgets --with-native-compilation 'CFLAGS=-pipe -Os
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk -arch
x86_64' 'CPPFLAGS=-I/opt/local/include
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk'
'LDFLAGS=-L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-rpath
/opt/local/lib/gcc12 -Wl,-no_pie
-Wl,-syslibroot,/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
-arch x86_64''

Configured features:
ACL GIF GLIB GMP GNUTLS JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY KQUEUE NS PDUMPER PNG RSVG SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XIM XWIDGETS ZLIB

Important settings:
  value of $LC_ALL: en_US.UTF-8
  value of $LC_CTYPE: UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-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
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv cl-extra
help-mode bytecomp byte-compile cconv cl-lib sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils rmc iso-transl tooltip eldoc
paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode
mwheel term/ns-win ns-win ucs-normalize mule-util term/common-win
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq
simple cl-generic indonesian philippine 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 emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button
loaddefs faces cus-face macroexp files window text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads xwidget-internal kqueue cocoa
ns lcms2 multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 78018 5659)
(symbols 48 7047 0)
(strings 32 19585 2332)
(string-bytes 1 603284)
(vectors 16 16757)
(vector-slots 8 335119 11861)
(floats 8 27 30)
(intervals 56 268 0)
(buffers 1000 11))