BUG #5799: failed to find conversion function from unknown to text

The following bug has been logged online:

Bug reference: 5799
Logged by: Sandro Santilli
Email address: strk(at)keybit(dot)net
PostgreSQL version: 8.4.3
Operating system: GNU/Linux 64bit
Description: failed to find conversion function from unknown to text
Details:

Function definition:

CREATE OR REPLACE FUNCTION ST_RelateMatch(text, text)
RETURNS bool
AS '$libdir/postgis-2.0', 'ST_RelateMatch'
LANGUAGE 'C' IMMUTABLE STRICT
COST 100;

Function invocation:

SELECT a, b, ST_RelateMatch(a,b) FROM
( SELECT '101202FFF' as a, 'TTTTTTFFF' as b) as f;

Results in:

ERROR: failed to find conversion function from unknown to text