Discriminant within discriminants

["stuart clark" <stuart.clark@baesystems.com>]

I have a the following

package message_types

  type id_type is range 1..8;

 type dispense_ack (size:id_type:=id_Type'first) is
   record
     dispense_acks:array(1..size) of acks;
   end record;

  type message_types(dispense_acknowledgement, dispense_request);

  type in_messages(kind :msg_types:=msg_types'first) is
   record
    case type is
      when dispense_acknowledgement =>
         acknowledgements:dispense_ack;
      when dispense_request
         request:integer;
    end case
  end record;

end message_types;

i want to declare a message that is of dispense_acknowledgment type
with a size of 8

i can do

msg:message_types.in_messages(kind=>message_types.dispense_acknowledgment);

this gives me the correct message type but as the dispense_ack is
defaulted to size=1
i get a message of size 1.

the only way i can get my code to compile with a message size of 8 is
to use

declare
  msg:message_types.in_messages;
  dispense_ack_msg:message_types.dispense_ack(size=>8);
begin
  msg:=(kind=>message_types.dispense_acknowledgement,
            acknowledgements=>dispense_ack_msg);

end;

QUESTION : can i declare a message with a type and size in the one
statement without using the intermediate message.