bug#19079: 24.4; smie mis-highlights unmatchable keywords

[Josh Berdine <josh@berdine.net>]

> On Dec 4, 2020, at 10:26 AM, Lars Ingebrigtsen <larsi@gnus.org> wrote:
> 
> Josh Berdine <josh@berdine.net> writes:
> 
>> emacs -Q
>> M-x load-file
>> ~/.opam/4.02.1/share/tuareg/tuareg.el
>> M-x tuareg-mode
>> M-x show-paren-mode
>> let f () =
>>  let x = 0 in
>>  ()
>> C-u 17 C-b
>> 
>> This starts a fresh emacs, loads the tuareg mode, enables
>> show-paren-mode, enters some ocaml code, and puts the point on a 'let'
>> keyword.  This 'let' is highlighted in 'show-paren-mismatch-face'.  As
>> there is no way for this 'let' to be matched (as far as smie is
>> concerned) this 'let' should not be highlighted.
> 
> (This bug report unfortunately got no response at the time.)
> 
> Stefan M says:
> 
>> And sorry for overlooking the fact that "let" gets highlighted as unmatched; that's  
>> indeed an error. Could you report it via "M-x report-emacs-bug" since it's a bug in  
>> smie.el rather than in Tuareg?  
> 
> This was six years ago.  Is this still an issue in more recent versions
> of Emacs?

Thanks, yes, it still behaves the same way. I have just redone the repro with 27.1:

emacs -nw -Q
M-x load-file
.emacs.d/elpa/tuareg-20200518.1820/tuareg-opam.el
M-x load-file
.emacs.d/elpa/tuareg-20200518.1820/tuareg.el
M-x tuareg-mode
M-x show-paren-mode
let f () =
 let x = 0 in
 ()
C-u 17 C-b


In case it is useful, here is the current output from report-emacs-bug:


In GNU Emacs 27.1 (build 1, x86_64-apple-darwin19.5.0, NS appkit-1894.50 Version 10.15.5 (Build 19F101))
 of 2020-11-14 built on d12frosted.local
System Description:  Mac OS X 10.15.7

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading /Users/jjb/.emacs.d/elpa/tuareg-20200518.1820/tuareg-opam.el (source)...done
Loading /Users/jjb/.emacs.d/elpa/tuareg-20200518.1820/tuareg.el (source)...done
Show-Paren mode enabled
Mark set

Configured using:
 'configure --disable-dependency-tracking --disable-silent-rules
 --enable-locallisppath=/usr/local/share/emacs/site-lisp
 --infodir=/usr/local/Cellar/emacs-plus@27/27.1/share/info/emacs
 --prefix=/usr/local/Cellar/emacs-plus@27/27.1 --with-xml2 --with-gnutls
 --without-dbus --with-imagemagick --with-modules --with-rsvg --with-ns
 --disable-ns-self-contained'

Configured features:
RSVG IMAGEMAGICK GLIB NOTIFY KQUEUE ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS NS MODULES THREADS JSON PDUMPER LCMS2 GMP

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

Major mode: Tuareg

Minor modes in effect:
  show-paren-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
  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
format-spec rfc822 mml mml-sec password-cache epa epg epg-config
gnus-util rmail rmail-loaddefs text-property-search time-date subr-x seq
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils cus-start cus-load paren tuareg speedbar sb-image ezimage
dframe cl-macs pcase find-file tuareg-opam derived skeleton flymake-proc
flymake easymenu compile comint ansi-color ring warnings thingatpt
cl-loaddefs cl-lib smie term/xterm xterm byte-opt gv bytecomp
byte-compile cconv 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 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 loaddefs
button faces cus-face macroexp files 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 86470 4933)
 (symbols 48 9347 1)
 (strings 32 24410 1630)
 (string-bytes 1 762726)
 (vectors 16 10024)
 (vector-slots 8 108386 8922)
 (floats 8 26 495)
 (intervals 56 252 0)
 (buffers 1000 11))