bug#73725: Master: Wrong position for byte compiler warning message.

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> I haven't, no.  It might well work.  But I think the `push' form should
> go outside of the loop,

Really?  I thought it made more sense to put it inside the loop, so
a macro X1 that expands to macro X2 ... will get all of the
corresponding locations pushed, thus preserving more of the info about
where things are coming from.

> I'm also a little wary about pushing an item onto stack when it
> doesn't get popped again after the form(s) it is "guarding".

The patch seemed like an easier way to describe the intent than trying
to phrase it in prose, but it's definitely not meant to be used as-is.
I agree that we need to make sure things get popped as needed (tho I got
the impression that it should indeed already occur (at least in the
call-path I looked at)).

>> If it doesn't work, do you happen to know why?
> I'm not sure whether it would work for the (similar) bug, bug#73746,
> where the symbols with position were getting lost in byte-opt.el.

Oh, indeed my patch won't work at all when the warning/error message is
emitted later on: we need to preserve the info in the macro-expanded
code itself rather than in the locations-info stack.


        Stefan