Subject: Re: bug#62951: 29.0.90; c-ts-mode: Incorrect fontification due to FOR_EACH_TAIL_SAFE

From: Yuan Fu <[email-masked]>
Date: Fri, 21 Apr 2023 13:37:08 -0700

Eli Zaretskii <[email-masked]> writes:

> To reproduce:
>
>   emacs -Q
>   C-x C-f src/fns.c RET
>   C-u 3365 M-g g
>
> Observe that "if" and "STRINGP" in the body of FOR_EACH_TAIL_SAFE are
> fontified in font-lock-function-name-face.  This is because the
> FOR_EACH_TAIL_SAFE macro is misparsed by tree-sitter as a declaration.
>
> Can we teach c-ts-mode to recognize FOR_EACH_TAIL_SAFE and
> FOR_EACH_TAIL for what they are, perhaps conditioned on
> c-ts-mode-emacs-sources-support being non-nil?

I’m aware of this issue, but the truth is there isn’t a good solution to
it. We need to recognize FOR_EACH_TAIL_SAFE (not hard) and fix arbitrary
code after it (hard). In this case it’s a if statement, with macro calls
and AND operation in it’s condition, it’s already three things we need
to recognize and somehow handle. It can also be a for loop, a switch
case, a function call, a while loop. If we want to fix FOR_EACH_TAIL we
would need to handle every possible thing, at that point we might as
well have wrote a parser :-)

We can probably fix this very particular case, but it’s still work and
overhead, and doesn’t mean much.

Yuan