GNU bug report logs - #15718
24.3.50; `C-M-x' does not work, with `defcustom' inside `when'

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From: Drew Adams <drew.adams <at> oracle.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 15718 <at> debbugs.gnu.org
Subject: bug#15718: 24.3.50; `C-M-x' does not work, with `defcustom' inside `when'
Date: Wed, 14 Aug 2019 21:41:37 -0700 (PDT)

> > emacs -Q
> >
> > (when t
> >   (defcustom foo nil
> >    "..."
> >    :type boolean))
> >
> > M-x set-variable foo t
> >
> > Put point on foo in the defcustom sexp, and do `C-M-x'.  `foo' is
> echoed
> > in the echo area, giving you the impression that the defcustom was
> > reevaluated, reinitializing `foo'.
> >
> > C-h v foo ;; => t, not nil.
> >
> > Without the `when', i.e., with the `defcustom' at top level, the
> value
> > is nil, as a user would expect.
> 
> I think this works as documented:
> 
> --
> Evaluate the top-level form containing point, or after point.
           ^^^^^^^^^^^^^^^^^^
> 
> If the current defun is actually a call to ‘defvar’ or ‘defcustom’,
> evaluating it this way resets the variable using its initial value
> expression (using the defcustom’s :set function if there is one), even
> if the variable already has some other value.  (Normally ‘defvar’ and
> ‘defcustom’ do not alter the value if there already is one.)
> --
> 
> So only if the def* is top-level does the magic DWIM value-setting
> thing happen.

Yes.  That's the problem.

This is an enhancement request - a request that it
instead work not just at the top level.

What's the reason why it should not "work" when
inside, say, `when'?  AFAIK, that feature just
hasn't been implemented yet.  Hence this request.
 
> Closing.

Unfortunate.

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