> In my case, m_new_data is actually a table row type rather than plain
> "record". The row is passed on to another function which calculates the
> altered columns and logs the changes.
In my experience, to specify composite-typed receiver as one element
of INTO list, it need to be column of composite variable.
CREATE TABLE t (a int, b int, c int);
CREATE TYPE wrap AS (v t);
DO $DO$
DECLARE
s text;
w wrap;
BEGIN
INSERT INTO t VALUES (1, 2, 3)
RETURNING 'text', t
INTO s, w.v;
RAISE '%, %', s, w.v;
END;
$DO$;
https://dbfiddle.uk/e5Q4Fj6l
