BUG #18689: psql : operator "!=" do not behave like "<>"

The following bug has been logged on the website:

Bug reference: 18689
Logged by: Joël HECHT
Email address: jhecht(at)cirilgroup(dot)com
PostgreSQL version: 15.6
Operating system: CentOS Linux release 7.9
Description:

Hello,

according to the documentation, operators != and <> are supposed to be
interchangeable.
But when operator "!=" is followed by a negative number, the request failed
with an error "No operator matches the given name".

Here is how to reproduce the issue directly with psql :

[postgres(at)d04f96727d36 ~]$ psql
psql (15.6)
Type "help" for help.

postgres=# select -1<>-1;
?column?
----------
f
(1 row)

postgres=# select -1!=-1;
ERROR: operator does not exist: integer !=- integer
LINE 1: select -1!=-1;
^
HINT: No operator matches the given name and argument types. You might need
to add explicit type casts.
postgres=#

Regards.