[BUG] Cache invalidation for queries that contains const of temporary composite type

Hello everyone!

I have found out the problem when try to sequentially call the function
that casts constant to composite type of temporary table that is deleted
ateach transaction termination (i.e. at each function call completion).

For example, we have the following function 'test':

CREATE OR REPLACE FUNCTION test()
 RETURNS void
 LANGUAGE plpgsql
AS $function$
begin
    create temp table tbl (id int) on commit drop;
    perform json_populate_record(null::tbl, '{ "id": 11 }'::json) as tt;
end;
$function$

Оn the second and subsequent calls we'll observe the following error:

ERROR: cache lookup failed for type 16392

I investigated the problem and realized that result type of function
*json_populate_record* (/funcresulttype/ field of /FuncExpr/ struct) as
well as type of the first null argument (/consttype/ field of /Const/
struct) refer to the invalid composite type related with temporary
table'tbl'. Namely they take a value of oid gotten from the first 'tbl'
initialization. The plan of query *'perform
json_populate_record(null::tbl, '{ "id": 11 }'::json) as tt'*is cached
and is not invalidated at each function call. This is because** the
statement of this query doesn't have any dependency from the 'tbl'
relation (/relationOids/ list of /CachedPlanSource/ struct).

Attached patch resolves this problem by adding dependency from relation
upon detection Const expression of composite type of that relation.

--
Regards,
Maksim Milyutin