bug#48585: 28.0.50; Missing Edebug instrumentation for some 'if-let' variants

[Philipp]

Instrument the following definition using C-u C-M-x:
(defun f (x) (if-let* (x) 1))

Then, evaluate this form:
(f 2)

Edebug will step into 'f', but won't stop at 'x'.

The problem lies in this part of the Edebug specification for 'if-let*':

[&or symbolp (symbolp form) (form)]

The 'symbolp' specification element causes Edebug to not instrument the
'x' symbol.  However, the 'symbolp' specification is also necessary
here; we couldn't just replace it with 'form' because that would make
the branches overlap.  What we'd need here is something like
[&and symbolp form], i.e. match only in case of a symbol, but also
instrument as a form.  IIUC Edebug doesn't support such constructs yet.


In GNU Emacs 28.0.50 (build 125, aarch64-apple-darwin20.4.0, NS appkit-2022.44 
Version 11.3.1 (Build 20E241))
 of 2021-05-22
Repository revision: 91fa95bde0619b4f3bc7d93d06c7c75998b1588d
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2022
System Description:  macOS 11.3.1

Configured using:
 'configure --with-modules --without-xml2 --without-pop --with-mailutils
 --enable-gcc-warnings=warn-only --enable-checking=all
 --enable-check-lisp-object-type 'CFLAGS=-ggdb3 -O0''

Configured features:
ACL GNUTLS JSON LCMS2 MODULES NOTIFY KQUEUE NS PDUMPER PNG THREADS
TOOLKIT_SCROLL_BARS ZLIB

Important settings:
  value of $LANG: de_DE.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
  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 mml-sec epa epg epg-config gnus-util rmail rmail-loaddefs 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 rx
gnutls puny dbus xml subr-x seq byte-opt gv bytecomp byte-compile cconv
compile text-property-search comint ansi-color ring cl-loaddefs cl-lib
iso-transl tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type 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 elisp-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 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 button
loaddefs faces cus-face macroexp files window text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads kqueue cocoa ns lcms2
multi-tty make-network-process emacs)

Memory information:
((conses 16 70783 6422)
 (symbols 48 8363 1)
 (strings 32 24254 2096)
 (string-bytes 1 793113)
 (vectors 16 16076)
 (vector-slots 8 212949 7797)
 (floats 8 26 28)
 (intervals 56 219 0)
 (buffers 992 10))