bug#27802: 25.2; sh-mode wrongly mismatched ()

[scinart]

emacs -Q a.sh which contains the following line

for ((;;)); do
    echo 123
    break;
done

then mark all buffer and M-x indent-region; the buffer is wrongly
indented due to the fact that '()' are not correctly paired.



In GNU Emacs 25.2.1 (x86_64-suse-linux-gnu, GTK+ Version 3.22.15)
 of 2017-06-17 built on cloud111
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
System Description:     openSUSE Tumbleweed

Configured using:
 'configure --with-pop --without-hesiod --with-kerberos --with-kerberos5
 --with-xim --with-wide-int --with-file-notification=inotify
 --with-modules --enable-autodepend --prefix=/usr
 --mandir=/usr/share/man --infodir=/usr/share/info --datadir=/usr/share
 --localstatedir=/var --sharedstatedir=/var/lib --libexecdir=/usr/lib
 
--enable-locallisppath=/usr/share/emacs/25.2/site-lisp:/usr/share/emacs/site-lisp
 --with-x --with-sound --with-xpm --with-jpeg --with-tiff --with-gif
 --with-png --with-rsvg --with-dbus --with-xft --without-gpm
 --with-x-toolkit=gtk3 --with-xwidgets --with-toolkit-scroll-bars
 --x-includes=/usr/include --x-libraries=/usr/lib64 --with-libotf
 --with-m17n-flt --build=x86_64-suse-linux 'CFLAGS=-fmessage-length=0
 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2
 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables
 -g -D_GNU_SOURCE -DGDK_DISABLE_DEPRECATION_WARNINGS
 -DGLIB_DISABLE_DEPRECATION_WARNINGS -pipe -Wno-pointer-sign
 -Wno-unused-variable -Wno-unused-label -Wno-unprototyped-calls
 -fno-optimize-sibling-calls -fno-PIE -DSYSTEM_PURESIZE_EXTRA=55000
 -DSITELOAD_PURESIZE_EXTRA=10000 ' LDFLAGS=-Wl,-O2'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GCONF GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES XWIDGETS

Important settings:
  value of $LC_NUMERIC: POSIX
  value of $LC_TIME: C
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=fcitx
  locale-coding-system: utf-8-unix

Major mode: Shell-script

Minor modes in effect:
  sh-electric-here-document-mode: t
  tooltip-mode: t
  global-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

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Setting up indent for shell type sh
Indentation variables are now local.
Indentation setup for shell type sh
Mark set [2 times]
Indenting region...done
Making completion list...

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode easymenu
cl-loaddefs pcase cl-lib mail-prsvr mail-utils sh-script smie executable
time-date mule-util delsel lpr tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame 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 charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
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 dbusbind inotify
dynamic-setting system-font-setting font-render-setting xwidget-internal
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 96308 7535)
 (symbols 48 20530 0)
 (miscs 40 54 171)
 (strings 32 17043 4440)
 (string-bytes 1 465198)
 (vectors 16 13232)
 (vector-slots 8 458197 4167)
 (floats 8 169 67)
 (intervals 56 336 0)
 (buffers 976 20))