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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: generic formal object of class-wide type
Date: 1999/04/29
Message-ID: <m3d80nsu54.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 472218538
NNTP-Posting-Date: Thu, 29 Apr 1999 01:28:57 PDT
Newsgroups: comp.lang.ada
Date: 1999-04-29T00:00:00+00:00
List-Id: <comp.lang.ada>

When I try to compile package Q (see below), I get this error:

q.ads:3:25: type of actual does not match type of "O"

Why?  

Generic formal object O (in GQ) is of type P.T'Class.  

Actual object O is of specific type NT, yes, but that type is in
T'Class.  So why isn't object O allowed as the actual for formal GC.O?




package P is
   type T is abstract tagged limited null record;
end;


package P.C is
   type NT is new T with null record;
   O : NT;
end;


with P;
generic
  O : in out P.T'Class;
package GQ is
end;


with GQ, P.C;
package Q is new GQ (P.C.O);