bug#59498: 29.0.50; c++-ts-mode get wrong-type-argument error when enabled

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Yuan Fu <casouri@gmail.com>,  dev@rjt.dev,  aqua0210@foxmail.com,
>   59498@debbugs.gnu.org,  mardani29@yahoo.es
> Date: Sun, 27 Nov 2022 02:18:06 -0500
> 
> >> I added treesit-comment-start/end to help indenting comments. So this is
> >> the correct way to use them. The following comment explains why I created
> >> new variables:
> >> 
> >> ;; `comment-start' and `comment-end' assume there is only one type of
> >> ;; comment, and that the comment spans only one line.  So they are not
> >> ;; sufficient for our purpose.
> >
> > ??? This is surprisingly unclean, IMO.  For starters, the names of the
> > variables are confusing.  The need to define two sets of comment-start and
> > comment-end regexps is also a nuisance and a source of errors.
> >
> > How do non-treesit modes handle this issue?  Why do the treesit-based modes
> > need something special here?
> >
> > Stefan, any ideas?
> 
> `comment-start` and `comment-end` do not describe the set of possible
> comment delimiters.  They describe the comment delimiters that should be
> *inserted* when we do things like `comment-dwim`.
> 
> To find/match comment delimiters we have `comment-start-skip` and
> `comment-end-skip`.  They're not ideal, but they've been good enough so far.
> They don't say which comment starter matches which comment-ender (that
> was done by the syntax-tables), but tree-sitter should be able to tell
> us that when we need it.
> 
> It would be nice if we could avoid the need to set/use
> `comment-start-skip` and `comment-end-skip` when using tree-sitter.
> Maybe we can compute their values from the tree-sitter grammar.
> But getting rid of uses of those vars will take a fair bit more work,
> I think.

OK, but do you agree that adding yet another pair of variables,
treesit-comment-start/end, is the opposite of what we want?