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

Hello,

when editing .tex files having nil in `flyspell-prog-text-faces' is
useful (even necessary) for flyspell-prog-mode doing its job.

But when using `setopt' (via file variable!) Emacs barfs about the type
not matching.  The type spec of the option is much too restrictive IMO:

#+begin_src emacs-lisp
(defcustom flyspell-prog-text-faces
  '(font-lock-string-face font-lock-comment-face font-lock-doc-face)
  "Faces corresponding to text in programming-mode buffers."
  :type '(set (const font-lock-string-face)
              (const font-lock-comment-face)
              (const font-lock-doc-face))
  :version "28.1")
#+end_src

It limits the value to a subset of three given hardcoded builtin faces.

At least we should allow any valid result of `get-text-property' that is
symbolp, including nil.

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).



Michael.