bug#72328: [PATCH] Nested backquote in pcase

[Eli Zaretskii <eliz@gnu.org>]

Ping!  Stefan, should I install this in your name?

> Cc: michael_heerdegen@web.de, thuna.cing@gmail.com, 72328@debbugs.gnu.org
> Date: Fri, 23 Aug 2024 22:29:10 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > From: Stefan Monnier <monnier@iro.umontreal.ca>
> > Cc: michael_heerdegen@web.de,  thuna.cing@gmail.com,  72328@debbugs.gnu.org
> > Date: Fri, 23 Aug 2024 15:11:04 -0400
> > 
> > >> > Would be good to hear from Stefan
> > >> The first step is to declare nested backquotes unsupported and add
> > >> a warning when we encounter them.
> > > Where and how would you suggest to do that?
> > 
> > Somethink like...
> > 
> > 
> >         Stefan
> > 
> > 
> > diff --git a/lisp/emacs-lisp/pcase.el b/lisp/emacs-lisp/pcase.el
> > index fd6b0c8db5c..fe62820f0cb 100644
> > --- a/lisp/emacs-lisp/pcase.el
> > +++ b/lisp/emacs-lisp/pcase.el
> > @@ -1172,7 +1172,10 @@ pcase--expand-\`
> >            (upatd (pcase--expand-\` (cdr qpat))))
> >        (if (and (eq (car-safe upata) 'quote) (eq (car-safe upatd) 'quote))
> >            `'(,(cadr upata) . ,(cadr upatd))
> > -        `(and (pred consp)
> > +        `(and ,@(when (eq (car qpat) '\`)
> > +                  `((guard ,(macroexp-warn-and-return
> > +                             "Nested ` are not supported" t nil nil qpat))))
> > +              (pred consp)
> >                (app car-safe ,upata)
> >                (app cdr-safe ,upatd)))))
> >     ((or (stringp qpat) (numberp qpat) (symbolp qpat)) `',qpat)
> 
> Feel free to install on master, and thanks.
> 
> 
> 
>