Subject: Re: bug#19734: 25.0.50; nested backquotes: recent changes not backward compatible
From: Stefan Monnier <[email-masked]>
To: Michael Heerdegen <[email-masked]>
Cc: [email-masked]
Date: Fri, 30 Jan 2015 16:01:55 -0500
List-Id: <debbugs-submit.debbugs.gnu.org>

>     * lisp/emacs-lisp/backquote.el (backquote-process): Optimize away
>       the ,' case.
> were not backwards compatible.  If this was intended (?), it should be
> mentioned in the news I think.

As the commit message indicates, this was supposed to be an
optimization, i.e. no change in observable behavior.

> In trunk, the backquote expression evals to something different now, and
>     ,,'(my-make-feh-cmd)
> from above must now be
>       ,(my-make-feh-cmd)

Yes, your rewrite is correct and desirable, but indeed we had a bug
which I've just fixed in master.  Thanks.

        Stefan