BUG #3259: Problem with automatic string cast

The following bug has been logged online:

Bug reference: 3259
Logged by: Thomas
Email address: thbley(at)gmail(dot)com
PostgreSQL version: 8.2.1
Operating system: WinXP SP2
Description: Problem with automatic string cast
Details:

I have this SQL:

select * from (select 'years' as recurrence) p where recurrence = 'years'

it gives:

ERROR: failed to find conversion function from "unknown" to text SQL state:
XX000

but this one is ok:

select * from (select 'years' as recurrence union select 'years' as
recurrence) p where recurrence='years'

it gives:

recurrence text
'years'

this is a default installation with the binaries from postgresql.org with no
changes in the configs:
PostgreSQL 8.2.1 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 3.4.2
(mingw-special)