return query/composite types

create table foo(a int, b int);
postgres=# create function rfoo() returns setof foo as $$ begin return
query select foo from foo; end; $$ language plpgsql;
CREATE FUNCTION
Time: 25.606 ms
postgres=#
postgres=#
postgres=# select rfoo();
ERROR: structure of query does not match function result type
DETAIL: Number of returned columns (1) does not match expected column
count (2).

Any reason why the above shouldn't work? Why does 'return query'
assume that returned composite types are expanded?

merlin