ADA13 — Interface/valuetype forward declarations and Ada2005

Ada2005 features a new language construct, the "limited with" clause,
which brings direct support for forward declarations to the Ada language.
The mapping of interface and valuetype forward declarations (section 4.9
of the Ada mapping version 1.2) could be much simplified by using this
feature.

In order to preserve backward compatibility, I suggest retaining the current
mapping using the CORBA.Foward packages, but marking that mapping as
obsolescent.

I propose adding a new mapping which takes advantage of the Ada2005
"limited with" clause, accompanied by a recommendation that new code
should use this simplified mapping.

The example given in section 4.9.3 of formal/01-10.42,

interface Chicken;
interface Egg

;
interface Chicken

;

could be mapped as follows:

– code mapped from interface Egg
with CORBA.Object;
limited with Chicken;

package Egg is

type Ref is new CORBA.Object.Ref with null record;

procedure hatch (Self : in Ref; Result : out Chicken.Ref'Class);

function To_Ref (The_Ref : in CORBA.Object.Ref'Class)
return Ref;

end Egg;

– code mapped from interface Chicken
with CORBA.Object;
with Egg;

package Chicken is

type Ref is new CORBA.Object.Ref with null record;

procedure lay (Self : in Ref; Result : out Egg.Ref'Class);

function To_Ref (The_Ref : in CORBA.Object.Ref'Class)
return Ref;

end Chicken;

Introduction of Ada 2005 features into the mapping would be beyond the scope of what
an RTF could do; it would require a full RFP to do this.