bug#56459: 29.0.50; Edebug disables Eldoc

[Eli Zaretskii]

> From: João Távora <joaotavora@gmail.com>
> Date: Wed, 1 Mar 2023 18:25:04 +0000
> Cc: Dmitry Gutov <dgutov@yandex.ru>, Max Brieiev <max.brieiev@gmail.com>, 
>       Lars Ingebrigtsen <larsi@gnus.org>, 56459@debbugs.gnu.org, 
> friedman@splode.com
> 
> I think there's a decent place in eldoc.el to do this check, though we should 
> take care not to require
> edebug.el in eldoc.el.
> 
> I'll look at it later, but I think if one searches for the phrase "check if 
> we have permission to mess with the
> echo area at all", or something to that effect, one would see it.

The condition which was misfiring is in
eldoc-display-message-no-interference-p, which is called by that
place.  So the problem is not _where_ to make the test, the problem is
what should the test be to avoid overwriting Edebug evaluation results
with ElDoc stuff.  I couldn't find an indication we could depend on to
distinguish stepping through Lisp from typing in the buffer popped by
'E', for example.  Every test I tried either succeeded in both cases
or failed in both cases.

Of course, I'm nowhere near being an expert on Edebug's internals, so
I might be missing something.