Scalar Subqueries in Select List fail with a "Column does not exist" error

[zoe-j-m]

Describe the bug

Scalar subqueries are subqueries usually in the select list, which select a single column and should return at most 1 row.
This bug causes kysely's migrations to fail.

Error: column "a.id" does not exist

🐜 This seems to be an execution error, which means that your request syntax seems okay,
    but the resulting statement cannot be executed → Probably not a pg-mem error.

To Reproduce

(The inserts aren't really needed to produce the error, but mean that the pg version returns nice results)

create table test(id text); 
create table test2(id text);
insert into test values ('value');    
insert into test2 values ('value');
insert into test2 values ('value2');
select a.id,
  (
    select
      true as "something"
    from
      "test"
    where
      "id" = a.id 
  ) as "something"
from
  test2 as a;

Expected result:

id	something
value	true
value2	null

pg-mem version

3.0.4