bug#35005: 27.0.50; Fontification unexpectedly works with anonymous faces

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Sat, 09 Nov 2019 16:10:58 -0500
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, 35005@debbugs.gnu.org,
>  emacs-devel@gnu.org
> 
> > Therefore, the description now still does not make clear that anonymous
> > faces can be used here.
> 
> Maybe we should simply better document the general rules about where
> anonymous faces can usually be used and where they usually can't be used
> (AFAICT they can be used where they affect the redisplay (e.g. in the
> `face` and `font-lock-face` properties) but they can't be passed to face
> manipulation functions like `set-face-attributes` and `describe-face`).
> Their usage in font-lock is a natural consequence of those general
> rules and doesn't merit extra discussion in the font-lock-keywords
> doc which is already complex enough IMO.

If someone knows enough to write a documentation patch about this,
please feel free, and TIA.