BUG #17853: COLLATE does not work with numeric column references in ORDER BY

The following bug has been logged on the website:

Bug reference:      17853
Logged by:          Branko Radovanovic
Email address:      branko.radovanovic.zg@gmail.com
PostgreSQL version: 13.4
Operating system:   Debian
Description:

The following SQL:

values ('a')
order by 1 collate "C";

...returns an error: SQL Error [42804]: ERROR: collations are not supported
by type integer

In the above query, "1" is not an integer but a column reference, so it
should be treated as well-formed and work the same as with the actual column
label:

values ('a')
order by column1 collate "C";

Best regards,
Branko