Access type scope

[Lin@post.com (Lin)]

When I compile the main program below, the error message is "type
extension at deeper accessibility level than parent". How can I deal
with it if I need the extension? Any clues about it? Many Thanks.

--Lin

--------------------------------
with System.RPC; use System.RPC;
with test;
procedure main is 
   procedure Fred(Y: access Params_Stream_Type) is
      type APS is access all System.RPC.Params_Stream_Type;
      type msg_type is new test.Msg_Type with
      record
         params : APS;
      end record;
      X : APS;
      Msg : msg_type;
   begin
      Msg := (
        test.Msg_Type with
        params => APS (Y));
      X := APS(Y);
   end Fred;
   PS : aliased Params_Stream_Type(0);
begin
   Fred(PS'access);
end main;

with System.RPC;
package test is
  type Msg_Type is tagged
   record
     From_Par_Id : System.RPC.Partition_ID;
   end record;
end test;