Plan cache and name space behavior in 9.2

I came across a new behavior in 9.2 with nested plpgsql functions and
temporary table.

create or replace function chck(tname text) returns void as $$
declare
cnt int;
begin
select count(*) from pg_attribute where attrelid = tname::regclass::oid
into cnt;
end;
$$ language plpgsql;

create or replace function train(tname text) returns text as $$
declare
begin
perform chck(tname);
return 'OK';
end;
$$ language plpgsql;

create or replace function test(tname text) returns text as $$
declare
result text;
begin
result = train(tname);
return result;
end;
$$ language plpgsql;

drop table if exists tbl;
create table tbl(a int);
select test('tbl'); -- call 1
drop table if exists tbl;

create temp table tbl(a int);
select test('tbl'); -- call 2
drop table tbl;

I expected success in tname::regclass in the function chck(), but it
actually fails for your first run in the session. The second run of
this script will succeed. I assume it's the cause is the new plan
cache behavior. On the first run of the script, the temporary
namespace was not created when the chck() is called at call 1 , and it
saves namespace, then it searches the old saved namespace for 'tbl' at
call 2, fails to find 'tbl'. Removing the call 1 call it runs
successfully. The second run of this script in the same session
succeeds because the temporary namespace has been created in the first
run. I confirmed it runs fine in 9.1 Is this a bug in 9.2 or an
expected behavior in the new plan cache?

Thanks,
--
Hitoshi Harada