BUG #1517: SQL interval syntax is accepted by the parser, but the interpretation is bogus

The following bug has been logged online:

Bug reference:      1517
Logged by:          Roy Badami
Email address:      roy@gnomon.org.uk
PostgreSQL version: 8.0.1
Operating system:   Solaris 9
Description:        SQL interval syntax is accepted by the parser, but the
interpretation is bogus
Details:

The parser accepts SQL interval syntax, but then silently ignores it,
treating it as a zero interval.

radius=# select date '2005-01-01' + interval '1' month;
      ?column?
---------------------
 2005-01-01 00:00:00
(1 row)

radius=# select timestamp '2005-01-1 00:00:00' + interval '1' minute;
      ?column?
---------------------
 2005-01-01 00:00:00
(1 row)

radius=#