bug#55205: 28.1.50; completion--replace illegally mutates completion candidates

[Eli Zaretskii]

> Date: Mon, 2 May 2022 12:46:00 +0300
> Cc: mail@daniel-mendler.de, larsi@gnus.org, monnier@iro.umontreal.ca,
>  55205@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> On 02.05.2022 05:23, Eli Zaretskii wrote:
> > Collection can include functions, and how do you copy that?
> 
> Collection can be a function, not "include functions". You fetch the 
> list of strings using that function (for the given input) and then make 
> a deep copy of that.

So I need to call that function twice, is that it?  It is normally
called by the completion machinery out of my control.