BUG #2811: Error determining param type in prepared statement of unused variable

The following bug has been logged online:

Bug reference:      2811
Logged by:          Ross Cohen
Email address:      rcohen@snurgle.org
PostgreSQL version: 8.2
Operating system:   linux (fedora core 4, released RPMS)
Description:        Error determining param type in prepared statement of
unused variable
Details:

Got this error:
ERROR:  could not determine data type of parameter $1

However, $1 is never used in the query so this shouldn't be a problem. The
following query demonstrates the problem.

PREPARE demo (unknown) AS SELECT 1;