bug#27229: eldoc wrong highlighting for "when"

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: andrewjmoreton@gmail.com,  27229@debbugs.gnu.org
> Date: Tue, 03 May 2022 13:09:38 +0200
> 
> If we want *Help* to display &rest body in a different way, then we
> should fix that in help-mode, not mess up the calling convention string.
> 
> > IOW, the removed (fn ..." stuff was there for a reason.  The original
> > bug report here wasn't about how we display the doc string, it was
> > about what eldoc does.  So IMO the fix should have been in eldoc,
> > which would also avoid this negative effect.
> 
> As the bug report explains, there is no fix possible, since the "..."
> syntax is ambiguous: We use it both for "and then there's more" and
> "there are alternating pairs of arguments".

So you are saying that we cannot use "(fn ..." because eldoc doesn't
like that?  Doesn't sound reasonable to me.  eldoc is a minor, albeit
important, mode; it isn't right for a minor mode to dictate our
documentation formats.