with Ada.Text_IO; use Ada.Text_IO;

procedure Hello is

   package Example is

      type An_Interface is synchronized interface;
      procedure P1 (Self : in out An_Interface) is abstract;

      package Instantiation is

         type Instance is synchronized new An_Interface with private;

         overriding
         procedure P1 (Self : in out Instance);

      private

         protected type Instance is new An_Interface with
            procedure Actual_P1;
         private
         end Instance;

      end Instantiation;

   end Example;

   package body Example is

      package body Instantiation is

         protected body Instance is
            procedure Actual_P1 is
            begin
               Put_Line("Did Something");
            end Actual_P1;
         end Instance;

         procedure P1 (Self : in out Instance) is
         begin
            Self.Actual_P1;
         end P1;

      end Instantiation;

   end Example;

   V : Example.Instantiation.Instance;

begin
   Put_Line("Hello, world!");

   --  dispatching ...
   Example.An_Interface'Class (V).P1;

   --  not dispatching
   V.P1;
end Hello;