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

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

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Standard C accepts a keyword `restrict', which is used to declare
pointers whose referenced object must only be accessed by lvalues based
upon one such pointer within the block where they are declared.

Like so:

  argb *restrict src, *restrict dest;

c-ts-mode does not understand this keyword.  It is not fontified within
such declarations.

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

[Eli Zaretskii]

> Date: Sat, 06 May 2023 16:19:32 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Standard C accepts a keyword `restrict', which is used to declare
> pointers whose referenced object must only be accessed by lvalues based
> upon one such pointer within the block where they are declared.
> 
> Like so:
> 
>   argb *restrict src, *restrict dest;
> 
> c-ts-mode does not understand this keyword.  It is not fontified within
> such declarations.

It looks like c-ts-mode thinks type qualifiers are possible only in
C++?

   :feature 'type
   `((primitive_type) @font-lock-type-face
     (type_identifier) @font-lock-type-face
     (sized_type_specifier) @font-lock-type-face
     ,@(when (eq mode 'cpp) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
         '((type_qualifier) @font-lock-type-face

           (qualified_identifier
            scope: (namespace_identifier) @font-lock-type-face)

           (operator_cast) type: (type_identifier) @font-lock-type-face))
     [,@c-ts-mode--type-keywords] @font-lock-type-face)

The tree-sitter library returns a type_qualifier node for 'restrict':

       (parameter_declaration type: (type_identifier)
	declarator: 
	 (pointer_declarator *
	  (type_qualifier restrict)
	  declarator: (identifier)))

Yuan, can you look into fixing this, please?

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

[Eli Zaretskii]

> Cc: 63323@debbugs.gnu.org
> Date: Sat, 06 May 2023 13:31:03 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> It looks like c-ts-mode thinks type qualifiers are possible only in
> C++?
> 
>    :feature 'type
>    `((primitive_type) @font-lock-type-face
>      (type_identifier) @font-lock-type-face
>      (sized_type_specifier) @font-lock-type-face
>      ,@(when (eq mode 'cpp) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>          '((type_qualifier) @font-lock-type-face
> 
>            (qualified_identifier
>             scope: (namespace_identifier) @font-lock-type-face)
> 
>            (operator_cast) type: (type_identifier) @font-lock-type-face))
>      [,@c-ts-mode--type-keywords] @font-lock-type-face)
> 
> The tree-sitter library returns a type_qualifier node for 'restrict':
> 
>        (parameter_declaration type: (type_identifier)
> 	declarator: 
> 	 (pointer_declarator *
> 	  (type_qualifier restrict)
> 	  declarator: (identifier)))
> 
> Yuan, can you look into fixing this, please?

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.

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

[Yuan Fu]

> On May 6, 2023, at 5:19 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> Cc: 63323@debbugs.gnu.org
>> Date: Sat, 06 May 2023 13:31:03 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> 
>> It looks like c-ts-mode thinks type qualifiers are possible only in
>> C++?
>> 
>>   :feature 'type
>>   `((primitive_type) @font-lock-type-face
>>     (type_identifier) @font-lock-type-face
>>     (sized_type_specifier) @font-lock-type-face
>>     ,@(when (eq mode 'cpp) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>>         '((type_qualifier) @font-lock-type-face
>> 
>>           (qualified_identifier
>>            scope: (namespace_identifier) @font-lock-type-face)
>> 
>>           (operator_cast) type: (type_identifier) @font-lock-type-face))
>>     [,@c-ts-mode--type-keywords] @font-lock-type-face)
>> 
>> The tree-sitter library returns a type_qualifier node for 'restrict':
>> 
>>       (parameter_declaration type: (type_identifier)
>> declarator: 
>>  (pointer_declarator *
>>   (type_qualifier restrict)
>>   declarator: (identifier)))
>> 
>> Yuan, can you look into fixing this, please?
> 
> 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'
    ),


Yuan

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

[Eli Zaretskii]

> 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.