bug#58158: 29.0.50; [overlay] Interval tree iteration considered harmful

[Eli Zaretskii]

> Date: Tue, 11 Oct 2022 05:12:11 +0300
> Cc: gerd.moellmann@gmail.com, 58158@debbugs.gnu.org, monnier@iro.umontreal.ca
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> What is a "subset of matches"?

Feel free to suggest a less vague description.  The idea is that the
list in Xref buffer doesn't show all the references to the identifier,
making renaming infeasible.

> Perhaps we should make the error very specific, like "you can't replace 
> inside xref-find-definitions results". Since that is going to be the 
> exception in like 99.9% of the cases.

That'd be my preference, but what are those 0.1% of cases where the
Xref buffer produced by other commands could fit?

More generally, what exactly does xref.el test to produce the error
message, and how to describe that in user-level terms?

> It's possible for other backend commands (such as find-references) to 
> return unsuitable xref values in third-party backends, or for other code 
> to use xref-show-xrefs with such, but those will be really very rare, if 
> happen at all.

You are saying that 'r' is only useful after M-?, is that right?  The
manual says so, but the manual doesn't have to say "the whole truth".
The doc string should.