PLS - 00382表达式类型错误

Question

create or replace type demo_type as table (information2 varchar2(4000))

create or replace function demo_func(refnum in risk_headers.reference_num%type)
return varchar2
as 
info_type demo_type;

begin 
  select oth.information2 into info_type  from cnfgtr_otherdtls_grid_tab oth 
 where oth.grpid = 'GRP358' and oth.num_reference_number = refnum 
 and oth.information1 in (select rd.risk1 from risk_details rd where rd.reference_num = refnum);

return info_type;
end;

从函数返回时出错。