BUG #14919: Invalid column in sub select is still a valid select

The following bug has been logged on the website:

Bug reference:      14919
Logged by:          Tanes Sriviroolchai
Email address:      tanes@siamscan.net
PostgreSQL version: 9.3.18
Operating system:   Ubuntu 14.04
Description:

Not sure if this is a bug or feature but when I query with sub select while
sub select has invalid column the query is still valid and running. For
example:

create temp table a ( id integer, descr text);
create temp table b ( b_id integer, descr text);

# select * from a where id=(select id from b where descr='A');

 id | descr 
----+-------
(0 rows)

# select id from b where descr='A';

ERROR:  column "id" does not exist
LINE 1: select id from b where descr='A';
               ^