bug#46794: 28.0.50; octave-mode: parse error in debug mode

[Juang Dse]

Suppose the file
-------------------
# hoo.m
function hoo ()
   for j = 1 : 10
      y(j) = j ;
   endfor
endfunction
-------------------
is in the search path (e.g. same directory). Then execute
dbstop hoo
hoo() ;

from within emacs (octave-send-line twice), and in the file hoo.m mark
the region of the for-loop, followed by octave-send-region. The
following error is thrown:

debug> debug> debug>    for j = 1 : 10
      y(j) = j ;
   endfor

> > debug> error: parse error:

  syntax error

>>>    endfor
            ^


------------------------------------------------------------------------------
In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, cairo version 1.17.4)
Repository revision: 90ac40570280f4f423b55a2d9eea5a44317a66e3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Manjaro Linux

Configured using:
 'configure --prefix=/opt/emacs --without-docs --with-x-toolkit=no'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
OLDXMENU PDUMPER PNG RSVG SOUND THREADS TIFF X11 XDBE XIM XPM ZLIB


Major mode: Octave

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 puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map time-date subr-x seq byte-opt gv
bytecomp byte-compile cconv mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils compile text-property-search
cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine
cc-vars cc-defs cl-loaddefs cl-lib octave smie easymenu comint
ansi-color ring iso-transl 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 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 dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo x multi-tty
make-network-process emacs)