Problem creating trigger-function with arguments (8.0rc4)

Hi

I want to create a simple trigger that denies inserts into a particular
table - but, since I want meaningfull error-messages, but don't
want to create a function for each table, I figured I could pass
the error-message to the trigger-function.
This is what I tried:

CREATE OR REPLACE FUNCTION functions.t_insert_deny(v_message text)
RETURNS "trigger" AS $$
begin
    raise exception '%', v_message ;
end ;
$$ LANGUAGE 'plpgsql' VOLATILE STRICT;

This results in a parse error at "v_message" (in the 4th line).

If I replace RETURNS "trigger" with e.g. RETURNS "int8" it works...
Is this is a bug, or has something regarding triggerfunctions and
parameters changed in 8.0 (I also try omiting the parameter name
in the function declartion, and using "$1" directly, but then
the error-message says "Unknown parameter $1").

greetings, Florian Pflug