Re: Why does `Unchecked_Deallocation` need the access type?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Tue, 28 Jul 2015 16:25:19 -0500, Randy Brukardt wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
> news:170ajsv4tazu3.mgrs0or8en9w$.dlg@40tude.net...
>> 3. Tagged hierarchies
>>
>> type S is new T with private;
>>
>> S'Parent (T'Class) = T (in a public context)
>>
>> The argument indicates the hierarchy where to search for the ancestor (due
>> to MI).
> 
> We tried such an attribute sometime during the Ada 2005 work and eventually 
> gave up. The problem being that the parent (in a language sense - it's the 
> subtype after "new") depends on the visibility on the type, and that is very 
> unconfortable (besides causing problems):
> 
>   package P is
>       type S is new T with private;
>       procedure Bar (Obj : in out S'Parent); -- S'Parent is T here.
>   private
>       type S in new U with private; -- U is descended from T, of course.
>   end P;
> 
>   package body P is
>       procedure Bar (Obj : in out S'Parent) is -- !! - S'Parent is U here.

I see. Perhaps:

   procedure Bar (Obj : in out S'Public_Parent) is
      -- S'Parent is U here
      -- S'Public_Parent is still T

------------------------
Of course nobody should ever declare non-primitive operations defined on
the parent type. And doing that in the public scope is almost a criminal
offense.

If we designed Ada from a fresh start I would try to eliminate all
non-primitive operations. Any operations would be either primitive or
class-wide. And a class-wide operation would be still primitive of T'Class
and thus dispatch on T'Class'Class etc.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de