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.pl@gmail.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 ?