ORA-06575: Package or function … is in an invalid state

create table tq84_tab (num number);
insert into tq84_tab values(42);

create or replace function tq84_fnc return number as
   ret number;
begin
   select max(num) into ret from tq84_tab;
   return ret;
end tq84_fnc;
/

drop table tq84_tab;

select * from user_errors where name = 'TQ84_FNC';

select tq84_fnc from dual;

select text from user_errors where name = 'TQ84_FNC';
--
-- PL/SQL: ORA-00942: table or view does not exist
-- PL/SQL: SQL Statement ignored
--

drop table tq84_tab;
drop function tq84_fnc;