Re: abstract sub programs overriding

[dan@irvine.com (Dan Eilers)]

evangeli@cnam.fr (Evangelista Sami) wrote in message news:<5f59677c.0403050702.5387352b@posting.google.com>...
> here is the code :
>...
> it crashes on "Generate(El.all);" :
> raised CONSTRAINT_ERROR : main.adb:7 access check failed

Here is a slightly modified version.
It still crashes, but commenting out "type unused" makes
it work fine.

procedure Main is
  package Generator is

     type Element_Record is abstract tagged null record;
     type Element is access all Element_Record'Class;

     procedure Generate (El : Element_Record) is abstract;

     type Decl_Record is abstract
        new Element_Record with null record;

     type Type_Decl_Record is new Decl_Record with null record;

     type Discrete_Type_Decl_Record is
        new Type_Decl_Record with private;
     type Discrete_Type_Decl is access all Discrete_Type_Decl_Record;

     procedure Generate (El : Type_Decl_Record);

     type unused is new Discrete_Type_Decl_Record with private;

  private

     type Discrete_Type_Decl_Record is
        new Type_Decl_Record with null record;

     type unused is new Discrete_Type_Decl_Record with null record;

  end Generator;

  package body Generator is
     procedure Generate (El : Type_Decl_Record) is
     begin
        null;
     end;
  end Generator;

  use generator;
  x: Discrete_Type_Decl := new Discrete_Type_Decl_Record;
begin
   Generate(Element(x).all);
end;