Casting from interface type

Hello all,

Please consider this small code :
--8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<---
procedure Proc is
type I is interface;
type T is tagged null record;
type DT is new T and I with null record;

var_t: T;
var_tc: T'Class := var_t;

procedure Conv(p: in I'Class) is
begin
if p in T'Class
then
var_t := T(p);
var_tc := T'Class(p);
end if;
end Conv;

var_dt: DT;

begin

Conv(var_dt);

end Proc;
--8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<---

Using the latest GNAT 2006, I receive the following errors:
proc.adb:14:19: invalid tagged conversion, not compatible with
type "I'Class" defined at line 3
proc.adb:15:21: invalid tagged conversion, not compatible with
type "I'Class" defined at line 3

Please, can someone tell me what am I doing wrong ?

Thanks in advance for your time.

Best regards,

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(o< | Yves Bailly : http://kafka-fr.net | -o)
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.