For completeness, here's the exact reproducer I should have included:
drop schema if exists cast_repro cascade;
create schema cast_repro;
set search_path = cast_repro, pg_catalog;
create type key_t as (v int);
create function cast_old(key_t) returns int
language sql immutable strict as 'select ($1).v';
create function cast_new(key_t) returns int
language sql immutable strict as 'select ($1).v + 100';
create cast (key_t as int) with function cast_old(key_t) as implicit;
prepare q(key_t) as select $1::int;
execute q(row(1)::key_t);
drop cast (key_t as int);
create cast (key_t as int) with function cast_new(key_t) as implicit;
select row(1)::key_t::int as direct_after;
execute q(row(1)::key_t);
On unpatched master this returns 1, 101, 1. The last value should be 101.
With the patch it returns 1, 101, 101.
Thanks,
Nik
