bug#50268: 28.0.50; Assertion warning during native compilation

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Noam Postavsky <npostavs@gmail.com>,  mattiase@acm.org,  larsi@gnus.org,
>   50268@debbugs.gnu.org
> Date: Tue, 21 Sep 2021 15:32:32 -0400
> 
> With my type-systems-guy hat on, I'd say we want to detect those `&rest`
> without a following variable and shame the author of the code.
> 
> But at the same time we could think of `&rest` as something similar to
> `&optional` and decide that it can be handy for generated code to be
> able to generate (x y &optional z &rest).
> 
> The main difference I see is that
> 
>     `(x y &optional ,@args)
> 
> makes a lot of sense and will naturally occasionally lead to `&optional`
> not followed by anything, whereas `&rest` only expects 1 following
> identifier so it seems much less likely that the code will sometimes put
> 0 vars in there.  After all, we do signal an error if there's more than
> 1 var after `&rest`, so I think it makes sense to follow my
> types-systems-guy heart here.

Which basically means we should revert Noam's commit of yore, is that
right?