bug#60953: The :match predicate with large regexp in tree-sitter font-lock seems inefficient

[Eli Zaretskii]

> Date: Tue, 31 Jan 2023 20:16:01 +0200
> Cc: casouri@gmail.com, 60953@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> > Can you describe what that function should do?  I don't think I have a
> > clear idea of that.
> 
> In Lisp that function could be implemented as
> 
>    (defun buffer-substring-match (regexp &optional start end
>                                   inhibit-modify)
>      (string-match regexp
>                    (buffer-substring (or start (point-min))
>                                      (or end (point-max)))
>                    inhibit-modify))
> 
> Meaning, it matches the regexp against the buffer substring, with the 
> string-start and string-end anchors working.
> 
> But it would be implemented in C, meaning we could avoid the extra 
> consing and funcall overhead.

Now I'm confused, because I thought the C functions we were
considering all fit the above description.

> Anyway, it seems like it might be too late as an addition to Emacs 29. 
> And we can implement the match predicate using narrowing for this 
> release, to be updated later.

Right, this is not a catastrophe, IMO.  The work on TS-based modes is
just beginning.