plpgsql + named parameters

I followed the past discussions regarding the syntax for named
parameters and I am currently using Pavel Stehule's patch for named
and mixed notation on top of the 8.4 beta.

It seems the way plpgsql substitutes $1, $2, etc for the parameters is
going to reduce the usefulness of this feature. Consider these two
functions:

CREATE FUNCTION fun1(a INT DEFAULT 1) RETURNS INT AS 'SELECT $1'
LANGUAGE SQL;
CREATE FUNCTION fun2(a INT) RETURNS INT AS $$
DECLARE
t INT;
BEGIN
t := fun1(1 as a); -- syntax error: "SELECT fun1(1 as $1 )"
t := fun1(a as a); -- syntax error: "SELECT fun1( $1 as $1 )"
RETURN 0;
END;
$$ LANGUAGE plpgsql;

I would think this would be a very common scenario where one function
calls another similar function that has similar parameter names.

Am I missing something or are there any obvious solutions to this?

Pavel's patch:
http://archives.postgresql.org/message-id/162867790903042341o477b115dtb6b351dd8ff758cc@mail.gmail.com

Thanks,
-Steve