bug#63323: c-ts-mode does not know about `restrict'

[Eli Zaretskii <eliz@gnu.org>]

> From: Yuan Fu <casouri@gmail.com>
> Date: Sat, 6 May 2023 15:54:32 -0700
> Cc: luangruo@yahoo.com,
>  63323@debbugs.gnu.org
> 
> 
> 
> > Actually, it looks like we recognize the type qualifiers in C as
> > keywords, via a separate list.  So I've just added to that list the
> > two missing qualifiers: 'restrict' and '_Atomic', and that fixes this
> > bug for me.
> > 
> > Yuan, is that the right fix?  I've installed it on the emacs-29
> > branch.
> 
> I check tree-sitter-c’s grammar and it defines type_qualifier [1], so if you move (type_qualifier) @font-lock-type-face out of the check for cpp, if would work. Recognizing them as keywords also works. So both are technically correct. C-mode uses keyword face, so I think your fix is a-ok.
> 
> [1] you probably know this, but for completeness:
> 
>     type_qualifier: $ => choice(
>       'const',
>       'volatile',
>       'restrict',
>       '_Atomic'
>     ),

Right, they just copied from the C Standard.

Whether we want to stay with qualifiers in keywords or not depends on
whether we thing type qualifiers could or should be fontified
differently from keywords.  (What do other IDEs do with C type
qualifiers?)  Something to think for the future, I guess.

For now, I'm closing this bug.