bug#62412: 29.0.60; strange c++ indentation behavior with tree sitter

[Herman, Geza]

Copy this half-written program to a c++-ts-mode buffer:

----- 8< -----------------------

void foo() {
  for (int i=0
}

int main(int argc, char *argv[]) {
}

----- 8< -----------------------

Move the point to the end of the line of the for loop, and press ";" (as 
if you continued to write the loop). Notice that the line will lose its 
indentation ("for" will be moved to column 1). If you continue writing 
the for loop, it will be correctly re-indented after the closing 
parenthesis (for example, continue the line with "; i<10; i++)", and 
notice that after pressing ")", the line will be re-indented).

This doesn't happen if the main function is deleted. I'm not sure 
whether this is a tree-sitter or emacs problem, but I reported here 
because I think it's more likely that this is some emacs problem.


In GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.36, cairo version 1.16.0) of 2023-03-23 built on okoska
Repository revision: d93a439846f03dfb2be28d6b5c2e963ef6be0c22
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12101006
System Description: Debian GNU/Linux bookworm/sid

Configured using:
 'configure --with-native-compilation=aot --without-compress-install
 --with-json --with-xinput2 --with-xwidgets --with-tree-sitter
 --with-cairo'

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

Important settings:
  value of $LC_ALL: C.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: C++//

Minor modes in effect:
  tooltip-mode: t
  global-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 sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils c-ts-mode
c-ts-common treesit comp comp-cstr warnings icons subr-x rx cl-seq
cl-macs gv cl-extra help-mode bytecomp byte-compile cc-mode cc-fonts
cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode 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 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
theme-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 dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit xinput2 x multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 109621 7046)
 (symbols 48 9139 0)
 (strings 32 26509 2321)
 (string-bytes 1 916195)
 (vectors 16 18595)
 (vector-slots 8 371251 16029)
 (floats 8 33 41)
 (intervals 56 351 0)
 (buffers 984 12))