Re: Is it ok to sort a list of overlays destructively?

[2QdxY4RzWzUUiLuE@potatochowder.com]

On 2021-07-29 at 15:33:23 +0300,
Eli Zaretskii <eliz@gnu.org> wrote:

> > From: John Yates <john@yates-sheets.org>
> > Date: Thu, 29 Jul 2021 07:34:07 -0400
> > Cc: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
> > 
> > On Wed, Jul 28, 2021 at 7:44 AM Eli Zaretskii <eliz@gnu.org> wrote:
> > >
> > > Basically, you should assume that Emacs protects itself where that is
> > > needed, so if it handed you a list or some other data, and nothing in
> > > the doc string warns you against doing something with that data, you
> > > are free to do that, and if that causes unexpected results, there's
> > > either a documentation bug or a code bug that needs to be fixed.
> > 
> > I am not sure if such a statement exists in any of the manuals. Should
> > it not be stated explicitly somewhere?
> 
> I don't think it should be, no.  It's pretty much obvious, IMO.

I'm not disagreeing, but why is it obvious?  Not all software works that
way (it would be great if it did), whether the authors thought about it
at all and/or intended it to work one way or the other, or not.