INSERT with a composite columnt from query

Hi all.

I have two table like these:

create table compo (
t text,
i int
);

create table tab (
x int,
c compo
);

Then I have a function like this:

create or replace function f_compo()
returns setof compo as $body$
...
$body$ language sql stable;

What I'd need to do is to insert the results from f_compo() into
the table TAB along with a value x.

I expected somthing like this to work:

insert into tab
select 42,row( c.* ) from f_compo() c;

But I get
ERROR: cannot cast type record to compo

Any hint?

TALIA

--
Reg me, please!