Subject: Re: bug#25678: 25.1; defcustom type `(file :must-match t)' seems not to work

From: Tim Landscheidt <[email-masked]>
Date: Sun, 14 Jan 2018 23:07:12 +0000

AFAICT, this setting is only obeyed when executing M-x
customize-set-value RET foo-file RET.