Function accepting array of complex type

This works:

CREATE TYPE c AS (r float, i float);
CREATE FUNCTION mag(c c) RETURNS float LANGUAGE sql AS $$
SELECT sqrt(c.r^2 + c.i^2)
$$;
SELECT mag( (2.2, 2.2) );
mag
------------------
3.11126983722081

But this doesn't:
CREATE FUNCTION magsum( c c[] ) RETURNS float LANGUAGE sql AS $$
SELECT sum(sqrt(c.r^2 + c.i^2)) FROM unnest(c) c
$$;
SELECT magsum( array[row(2.1, 2.1), row(2.2,2.2)] );
ERROR: function magsum(record[]) does not exist at character 8

Presumably we're playing some games with resolving (...) into a complex
type instead of a raw record; what would be involved with making that
work for an array of a complex type? I don't see anything array-specific
in parse_func.c, so I'm not sure what the path for this is...
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com