Question about tagged types and functions

[dhunter@interserf.net (David Hunter)]

Given:

  package Test is

    type BaseType is tagged record
      null;
    end BaseType;

    function Create return BaseType;

    type DerivedType is new BaseType with record
      null;
    end DerivedType;

  end Test;

Why does Ada-95 (GNAT 3.01a) tell me that I also
*must* have:

    function Create return DerivedType;

There is something going on with tagged types
and functions that I don't understand because
if I use

    procedure Create(a : out BaseType);

it (Ada-95) does not object.

===============================================
David Hunter (hunter@mwc.edu)
CPSC Department
Mary Washington College
Fredericksburg, VA 22401