bug#63253: 29.0.90; with-delayed-message fails in combination with inhibit-message

[Stefan Monnier]

> There seems to exist an interaction issue of `with-delayed-message' with
> `inhibit-message'. In order to reproduce the issue, start emacs -Q and
> evaluate the following function:
>
> (defun delayed-message-bug ()
>   (interactive)
>   (setq inhibit-message-regexps (list "\\`something"))
>   (add-to-list 'set-message-functions #'inhibit-message)
>   (while t
>     (with-delayed-message (0.5 "Fontifying...")
>       (font-lock-flush (point-min) (point-max))
>       (font-lock-ensure (point-min) (point-max)))
>     (message "Done")))
>
> Then open a large file like emacs/src/xterm.c and run `M-x
> delayed-message-bug'. The error may not occur on the first try since it
> is timing dependent. Retry a few times if no error is observed. I
> observe the internal error

After several unsuccessful attempts, I just managed to reproduce the
problem here.  Not sure yet what was the magic incantation, but at least
I should now be able to look into the source of the problem.


        Stefan