Bug in 7.1.3 and 7.2?

there seems to be a problem in 7.1.3 and 7.2:

test=# select * from a;id
---- 1 2 3
(3 rows)

test=# select * from b;id
---- 3 4
(2 rows)

test=# select a.*, d.* from a as c, b as d where a.id=b.id;
NOTICE:  Adding missing FROM-clause entry for table "a"
NOTICE:  Adding missing FROM-clause entry for table "b"id | id
----+---- 3 |  3 3 |  3 3 |  3 3 |  4 3 |  4 3 |  4
(6 rows)

Althoug c and d are aliases for a and b, the two tables are added to the

list in the from clause. Is this the desired behaviour or is it a bug?
   Hans