I have just come across a weird thing. It works for any table and seems
to be not documented.
SELECT c.name FROM (VALUES(1, 'A', true)) c;
SELECT c.name FROM pg_class c;
And it does not work in these cases:
SELECT name FROM (VALUES(1, 'A', true));
SELECT name FROM pg_class;
PostgreSQL 8.4.2 on x86_64-redhat-linux-gnu, compiled by GCC gcc (GCC)
4.1.2 20071124 (Red Hat 4.1.2-42), 64-bit