unnest array of row type

Hi!

CREATE TYPE my_row_type AS (c1 SMALLINT,c2 TEXT);

CREATE FUNCTION tmp_get_c1(my_row_type) RETURNS SMALLINT AS 'SELECT $1.c1' LANGUAGE SQL;

CREATE FUNCTION tmp_get_c2(my_row_type) RETURNS TEXT AS 'SELECT $1.c2' LANGUAGE SQL;

CREATE TABLE test (c1 SMALLINT,c2 TEXT,c3 TEXT);

INSERT INTO test
SELECT tmp_get_c1(r),tmp_get_c2(r),'x'
FROM (
    SELECT UNNEST(ARRAY[ROW(1::SMALLINT,'a'::TEXT),ROW(2::SMALLINT,'b'::TEXT)]) AS r
) s;

I get error "record type has not been registered" from the previous INSERT.

I have tested version 9.1 and have confirmed that PL/PGSQL "FOREACH ... IN ARRAY ... LOOP ... END LOOP;" does the job.
BecauseI wonder "INSERT INTO ... SELECT ... FROM" being faster than "LOOP ... END LOOP;", I raise this question. 

Thank you in advance!
CN