bug#65797: `buffer-match-p` should not use `func-arity`

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>>> FWIW The intention here was to be able and specify simpler conditions
>>> that don't have to handle the alist.
>> You mean for `display-buffer-alist`?
>> Do you have examples that rely on this?
> From the core?  No, I cannot think of an example, but any user
> configuration may make use of this feature.

From the core would have been good, but from elsewhere (including
random .emacs config you may find on the web) would be helpful to gauge
how important that could be.

> I am not sure if I just missed it, but is there no technical solution
> around the advice issue?  Couldn't `func-arity' check if the actual
> function and the advice function have the same arity, and return the
> right value in that case?  My impression is that in 99% of the cases,
> advice isn't used to increase or decrease the arity of a function.

There are various 99% solutions, yes.
There is no 100% solution, OTOH :-(
So the documented behavior is inherently unreliable.


        Stefan