bug#68213: 30.0.50; completion-preview-tests failure in --without-x build

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: john muhl <jm@pub.pink>,  68213@debbugs.gnu.org
> Date: Sun, 07 Jan 2024 12:03:45 -0500
> 
> > I don't understand how that can happen when completion-preview.el has
> > these symbols defvar'ed.  Stefan, what am I missing here?
> 
> (defvar VAR) does not define the variable, it only tells the byte
> compiler that the var is probably defined elsewhere, and that it should
> be considered as dynamically scoped rather than statically scoped.
> 
> IOW, it just silenced the warnings.

So in that case we need something like

  (or (boundp 'mouse-wheel-up-event)
      (defvar mouse-wheel-up-event nil))

?

But I guess I will wait until Po Lu explains why these are defined as
they are before doing something about this test failure.