Re: different empty array syntax requirements

Scott Ribe <scott_ribe(at)elevated-dev(dot)com> writes:
> How is that one pgsql build (both are 9.5.2) has different casting behavior for empty arrays:
> pedcard=# select (ARRAY[])::text[];
> ERROR: cannot determine type of empty array
> LINE 1: select (ARRAY[])::text[];
> ^
> HINT: Explicitly cast to the desired type, for example ARRAY[]::integer[].

... wtf?

[ thinks for awhile ... ]

Oh! I bet this explains it:

regression=# select (ARRAY[])::text[];
array
-------
{}
(1 row)

regression=# set operator_precedence_warning = on;
SET
regression=# select (ARRAY[])::text[];
ERROR: cannot determine type of empty array
LINE 1: select (ARRAY[])::text[];
^
HINT: Explicitly cast to the desired type, for example ARRAY[]::integer[].

The parens turn into an actual parsetree node when
operator_precedence_warning is on, and the cast-of-an-array hack doesn't
know it should look through such a node. That's a bug. Will fix it.

regards, tom lane