Subject: bug#63410: 30.0.50; [FR] Optionally allow defcustom to check type for standard value

From: Eli Zaretskii <[email-masked]>
Date: Wed, 10 May 2023 18:40:19 +0300

> Cc: "[email-masked]" <[email-masked]>
> Date: Wed, 10 May 2023 22:51:14 +0800
> From:  Ruijie Yu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <[email-masked]>
> 
> My request is that Emacs should (optionally, maybe behind a defcustom,
> or configure, or cli flag, etc.) warn you warn a defcustom's standard
> value does not match its declared type.

Warn you at what time?  When defcustom is byte-compiled? when it is
evaluated at run time? when the user says "M-x set-variable"?
something else?

> Since a similar warning is already in place for `setopt', I don't
> think it is farfetched to request `defcustom' to follow suit.

setopt says it when you invoke it.  But setopt is designed to be
called as a function at run time, whereas defcustom isn't.