bug#58342: 29.0.50; noverlay branch is O(N) for important calls

[Drew Adams <drew.adams@oracle.com>]

> Does anybody know of an Emacs package that uses a large number of
> overlays that span large amounts of the buffer in complex ways?

Sure.  zones.el does (especially the version
I use, which I haven't yet exposed externally).

The point of zones.el is to manipulate arbitrary
sets of buffer zones, which can be implemented
as overlays (as one possibility).

They can overlap in any way, as the library is
a utility that you can use in any way.  And you
can sort zones, unite/coalesce them, etc.  It's
not at all unusual to deal with many overlapping
zones, e.g., overlays.

Dunno what the "noverlay" branch is.  I haven't
seen any description of it or its purpose,
despite the many, many emails here and in
emacs-devel with "noverlay" in the Subject line.
As a result, those many messages get only an
uninformed glance from me.

But if the "noverlay" branch is supposed to deal
with overlays _in general_ in some way, then I'd
think that the case of many overlapping overlays
wouldn't necessarily be rare.  Why would it be?

You can use an overlay for anything: store any
information on for buffer zone.  An overlay is
just two buffer positions plus a set of
properties - any properties.  _Super_ general.