Bug#642981: smaller example

[Nicolas Boulenguez <nicolas@debian.org>]

Here is a short source triggering the bug.
# gcc-4.6 -c -O1 -gnatn pack.adb

package Pack is
   type T is tagged null record;
   type A is access T'Class;
   type V (Discriminant : Boolean := True) is record
      case Discriminant is
         when False => I_Field : Integer;
         when True  => A_Field : A;
      end case;
   end record;
   procedure Proc;
end Pack;

with Ada.Strings.Hash;
with Ada.Unchecked_Deallocation;
with Ada.Containers.Indefinite_Hashed_Maps;
package body Pack is
   package Maps is new Ada.Containers.Indefinite_Hashed_Maps
      (String, V, Ada.Strings.Hash, "=", "=");
   M : Maps.Map;
   procedure Free is new Ada.Unchecked_Deallocation (T'Class, A);
   procedure Proc is
      V_Variable : V := Maps.Element (Maps.First (M));
   begin
      Free (V_Variable.A_Field);
   end Proc;
end Pack;