bug#53885: 28.0.51 [PATCH] Autoload package-installed-p

[Eli Zaretskii]

> From: Corwin Brust <corwin@bru.st>
> Date: Thu, 10 Feb 2022 02:09:34 -0600
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, 53885@debbugs.gnu.org
> 
> On Thu, Feb 10, 2022 at 1:57 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > Now I'm confused: which code calls package-installed-p in the
> > scenarios you have in mind?  I thought it was use-package, but you
> > seem to say that's not the case?
> 
> The user's Emacs configuration, e.g. init.el

Why do users do that without making sure the relevant feature is
loaded?  And what makes package-installed-p special in this case?