gcc/testsuite/gnat.dg/generic_call_iface.adb

   1 --  { dg-do compile }
   2
   3 procedure Generic_Call_Iface is
   4
   5    generic
   6      type Subscriber_Type is interface;
   7      with procedure On_Changed (Subscriber : in out Subscriber_Type)
   8        is abstract;
   9    package My_Generic is
  10       type Subscriber_Ptr is access all Subscriber_Type'Class;
  11       procedure Update;
  12       Subscriber : Subscriber_Ptr := null;
  13    end;
  14
  15    package body My_Generic is
  16       procedure Update is
  17       begin
  18          if Subscriber /= null then
  19             Subscriber.On_Changed;
  20          end if;
  21       end;
  22    end;
  23
  24    package User is
  25       type Integer_Subscriber is interface;
  26       procedure On_Changed_Int (I : in out Integer_Subscriber) is abstract;
  27
  28       package P is new My_Generic
  29         (Subscriber_Type => Integer_Subscriber,
  30          On_Changed      => On_Changed_Int);
  31    end;
  32 begin
  33    null;
  34 end;