bug#67991: 30.0.50; boundp always returns nil in format-mode-line with let* after 0fde935

[Eli Zaretskii <eliz@gnu.org>]

> Cc: monnier@iro.umontreal.ca, 67991@debbugs.gnu.org
> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Sat, 23 Dec 2023 10:52:22 -0500
> 
> On Sat, Dec 23, 2023 at 10:21 AM Gerd Möllmann <gerd.moellmann@gmail.com> wrote:
> >
> > Aaron Jensen <aaronjensen@gmail.com> writes:
> >
> > > After commits:
> > >
> > > 0fde935b66e43e4d7ec137ba6195de993168587a
> > > a63b206fbde2ead91f1053d80a275f8850e5ffce
> > >
> > > boundp returns nil here, rather than t, like it used to:
> > >
> > > (format-mode-line
> > >  '(:eval (let* ((some-var "some-value")
> > >                 (_ (message "Bound: %S" (boundp 'some-var))))
> > >            (message "Var: %S, Bound: %S" some-var (boundp 'some-var)))))
> > >
> > > This has an impact on a particular package I use for my modeline, which
> > > can be worked around if this behavior is expected. It seemed a
> > > significant chagne, so I wanted to report it, in case it was not expected.
> >
> > I don't know why that would have changed things with Stefan's commit,
> > but are your sure that some-var is declared special (has a defvar, for
> > instance)? When it is, boundp returns t here.
> 
> It's not in the package in question. But even if I defvar w/o giving
> it a value, it does not return t:
> 
> (defvar some-var)
> 
> (let* ((some-var "some-value")
>                 (_ (message "Bound: %S" (boundp 'some-var))))
>            (message "Var: %S, Bound: %S" some-var (boundp 'some-var)))
> 
> (format-mode-line
>  '(:eval (let* ((some-var "some-value")
>                 (_ (message "Bound: %S" (boundp 'some-var))))
>            (message "Var: %S, Bound: %S" some-var (boundp 'some-var)))))
> 
> The first returns t, the second does not.

This one will return t:

  (format-mode-line
   '(:eval (progn
	     (defvar some-var)
	     (let* ((some-var "some-value")
		    (_ (message "Bound: %S" (boundp 'some-var))))
	       (message "Var: %S, Bound: %S" some-var (boundp 'some-var))))))

> As to your question, Eli, I don't know. If it shouldn't return nil
> then I can report that downstream and they can fix it there.

Let's wait for Stefan to chime in, he made the change you blamed.