Re: abstract sub programs overriding

[evangeli@cnam.fr (Evangelista Sami)]

here is the code :

----------------------------------------------------
package Generator is

   type Element_Record is abstract tagged private;
   type Element is access all Element_Record'Class;

   procedure Generate
     (El : in Element_Record) is abstract;

private

   type Element_Record is abstract tagged record
      null;
   end record;

end Generator;
----------------------------------------------------
package Generator.Declarations is

   type Decl_Record is abstract new Element_Record with private;

   type Type_Decl_Record is abstract new Decl_Record with private;

   type Discrete_Type_Decl_Record is abstract
     new Type_Decl_Record with private;

   type Enumerate_Type_Decl_Record is
     new Discrete_Type_Decl_Record with private;
   type Enumerate_Type_Decl is access all Enumerate_Type_Decl_Record;

   function New_Enumerate_Type_Decl return Element;

private

   type Decl_Record is abstract new Element_Record with record
      null;
   end record;

   type Type_Decl_Record is abstract new Decl_Record with record
      null;
   end record;

   procedure Generate
     (El : in Type_Decl_Record);

   type Discrete_Type_Decl_Record is abstract new Type_Decl_Record with record
      null;
   end record;

   type Enumerate_Type_Decl_Record is new Discrete_Type_Decl_Record with record
      null;
   end record;

end Generator.Declarations;
----------------------------------------------------
package body Generator.Declarations is

   procedure Generate
     (El : in Type_Decl_Record) is
   begin
      null;
   end;

   function New_Enumerate_Type_Decl return Element is
      Result : Enumerate_Type_Decl := new Enumerate_Type_Decl_Record;
   begin
      return Element(Result);
   end;

end Generator.Declarations;
----------------------------------------------------
with Generator; use Generator;
with Generator.Declarations; use Generator.Declarations;

procedure Main is
   El : Element := New_Enumerate_Type_Decl;
begin
   Generate(El.all);
end;
----------------------------------------------------


in fact i have 5 levels :
element -> decl -> type_decl -> discrete_type_decl -> enumerate_type_decl

it crashes on "Generate(El.all);" :
raised CONSTRAINT_ERROR : main.adb:7 access check failed