bug#64818: 30.0.50; c++-ts-mode highlight does not work

[Eli Zaretskii]

> From: Wang Diancheng <dianchengwang@gmail.com>
> Date: Mon, 24 Jul 2023 12:49:06 +0800
> 
> I use the latest tree-sitter and tree-sitter modules.
> Only preprocessor instructions and comments are highlighted, please see 
> attached
> screenshot. BTW c-ts-mode highlight is OK.
> 
> Following are values of treesit-font-lock-feature-list and
> treesit-font-lock-level:
> 
> treesit-font-lock-feature-list is a variable defined in ‘treesit.el’.
> 
> Its value is
> ((comment definition) (keyword preprocessor string type)
>  (assignment constant escape-sequence label literal)
>  (bracket delimiter error function operator property variable))
> Local in buffer sql_select.cc; global value is nil
> 
> treesit-font-lock-level is a variable defined in ‘treesit.el’.
> 
> Its value is 3

Thanks.

Yuan, Theo: can you please look into this?  I can confirm the above
behavior, and I also see it in the very first pretest 29.0.90.  So
either some change broke c++-ts-mode before April, or maybe the latest
changes in the C++ grammar library did that.  treesit-explore-mode
seems to show that the code is parsed correctly, so why aren't
fontifications working?