feature request: IN clause optimized through append nodes with UNION ALL

In the script below, the presence of an IN clause forces the internal
components of the UNION ALL clause to fully compute even though they are
fully optimizable. = ANY doesn't have this issue, so I wonder if there is
any opportunity to convert the 'slow' variant (see below) to the 'fast'
variant. thank you!

merlin

drop table a cascade;
drop table b cascade;
drop table c cascade;

create table a (a_id int primary key);
create table b (b_id int primary key, a_id int references a);
create table c (c_id int primary key, b_id int references b);

insert into a select s from generate_series(1, 50000) s;
insert into b select s, (s % 50000 ) + 1 from generate_series(1, 100000) s;
insert into c select s, (s % 100000 ) + 1 from generate_series(1, 1000000)
s;

create index on b (a_id, b_id);
create index on c (b_id, c_id);

analyze a;
analyze b;
analyze c;

create temp table d (a_id int);
insert into d values (99);
insert into d values (999);
insert into d values (9999);
analyze d;

create or replace view v as
select * from a join b using(a_id) join c using(b_id)
union all select * from a join b using(a_id) join c using(b_id);

explain analyze select * from v where a_id in (select a_id from d); --
this is slow
explain analyze select * from v where a_id = any(array(select a_id from
d)); -- this is fast