Re: Ada design bug or GNAT bug?

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

On Mon, 22 Jun 2015 12:39:16 -0500, Randy Brukardt wrote:

> We don't have a choice about allowing hidden controlling results and 
> controlling access results (unless, of course, we want to abandon real 
> privacy, which we're not going to do).

If function is invisible it is, and its result is as well.

> The only way to avoid that problem is 

Which problem is? The operation is not visible, it cannot be called.

> to not have the feature at all (which is where I would stand).

I don't see connection to anonymous access types, the rule applies to
tagged results as well:

package P1 is
   type T1 is tagged null record;
   type T2 is new T1 with null record;
   function Foo return T2;
end P1;

with P1; use P1;
package P2 is
   type T3 is new T1 with private;
private
   type T3 is new T2 with null record; -- Legal!
end P2;

with P1; use P1;
package P2 is
   type T3 is new T1 with private;
private
   type T3 is new T2 with null record;
   overriding function Foo return T3; -- ILLEGAL!
end P2;

As such the rule does not make any sense. You shall under no circumstance
prohibit overriding of inherited operations.

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