bug#81638: 32.0.50; flyspell-prog-text-faces type and semantics

> And if all of the above is not enough, and you still insist, I could
> agree to adding nil to the valid values (but then please suggest a
> suitable :tag),

BTW, there can be other good reasons to use a value not covered by the
current `:type`, e.g. it can make a lot of sense to put `sh-heredoc` or
`perl-heredoc` in there.  I'd rather not have such a closed set of
values in this `:type` (which, in turn, precludes the use of Custom's
`set` type).

> but allowing any symbol is IMO too dangerous, especially as we use
> cl-flet there.  Next we will hear from someone reporting
> a vulnerability in Emacs.

`cl-flet` just lets you define a lexically-local function.  It's no
more dangerous than (let ((f (lambda ...))) ...).
It doesn't touch any global definition.

You're probably confusing it with  `cl-letf` or the old cl.el's `flet`.

We could (should?) mark `flyspell-prog-text-faces` as a safe
file-local variable.

>> But I wonder if we should, in addition, generalize
>> `flyspell-generic-progmode-verify' so that members of
>> `flyspell-prog-text-faces' are allowed to be functions (test
>> predicates).
> If you want to do that, it is better (and easier) to override
> flyspell-generic-progmode-verify with your own function.

You mean set `flyspell-generic-check-word-predicate`?
Agreed.


=== Stefan