program.adb

With Ada.Text_IO; Use Ada.Text_IO;  
 
procedure Program is
 
  package Classes is
	  type Class1 is tagged
	    record
	      i: integer;
	    end record;
 
	  procedure Foo(self: in out Class1);
	  
	  type Class2 is new Class1 with null record;
	  
	  procedure Foo(self: in out Class2);	  
  end;
  
  package body Classes is
	  procedure Foo(self: in out Class1) is
	  begin
	    Put_Line("foo");
	  end;
	  
	  procedure Foo(self: in out Class2) is
	  begin
	    Put_Line("foobar");
	  end;
  end;
 
  object_storage: Classes.Class2;
  object: Classes.Class1'class := object_storage;
begin
  object.Foo;
end Program;