GNU bug report logs - #55205
28.1.50; completion--replace illegally mutates completion candidates

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: mail <at> daniel-mendler.de, larsi <at> gnus.org, 55205 <at> debbugs.gnu.org
Subject: bug#55205: 28.1.50; completion--replace illegally mutates completion candidates
Date: Mon, 02 May 2022 12:34:28 -0400

> I have no idea.  The way you present this is waaay above my level of
> understanding.
>
> Completion takes text typed by the user and produces strings that the
> user could possibly mean by typing what he/she typed.  Some part(s) of
> the candidates can legitimately come from what the user typed, some
> other part(s) could be invented by the completion machinery more or
> less out of thin air.  Why should anyone expect this meat-grinder to
> refrain from destructively modifying any of the involved strings?

Because the overwhelming majority of strings are never modified.
It's very unusual to modify a string by side effect (as opposed to
creating a new string object via `concat`, `substring`, ...).
This is true in most languages, AFAICT, but it's definitely true in
ELisp.


        Stefan

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