bug#56679: 28.1; [PATCH] whitespace-style cannot be configured for diff-mode via hook

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Cc: YE <yet@ego.team>,  56679@debbugs.gnu.org
> Date: Mon, 25 Jul 2022 04:38:18 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Can we delay loading whitespace.el until the user actually wants to
> > turn on whitespace-mode, or until he/she customizes this option?
> > AFAIU, whitespace-mode is not turned on unconditionally by diff-mode,
> > so this 'require' is not needed for users who don't turn that minor
> > mode in Diff buffers.
> 
> Principally correct - but how do we do this correctly for the
> (get 'whitespace-style 'custom-type) :type definition?

What are the problems with this that require us to load whitespace.el
up front?