BUG #3518: ERROR: IN types character varying and integer cannot be matched

The following bug has been logged online:

Bug reference: 3518
Logged by: Tomasz Kawczynski
Email address: sober(dot)pl(at)gmail(dot)com
PostgreSQL version: 8.2.4
Operating system: Linux Gentoo
Description: ERROR: IN types character varying and integer cannot be
matched
Details:

Hello everyone,

After

SELECT * FROM s_skladnik WHERE kod IN (902,902)

kod character(3)

i get error message

ERROR: IN types character varying and integer cannot be matched

whitch is ok (ive read about this restriction in 8.2.x)

but why after

SELECT * FROM s_skladnik WHERE kod IN (902)
or
SELECT * FROM s_skladnik WHERE kod = 902

I dont get error but query gives me correct result ?