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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Preventing private procedure visibility being made public through
 extension
Date: Sun, 21 May 2017 23:20:35 +0200
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Xref: news.eternal-september.org comp.lang.ada:46844
Date: 2017-05-21T23:20:35+02:00
List-Id: <comp.lang.ada>

On 2017-05-21 22:21, Jere wrote:

> The actual use case has
> them in separate packages, but the problem is the same:

No. Robert meant that when you declare a subprogram in a separate 
package [more precisely after the type's freezing point] it will not 
become a primitive operation. A non-primitive operation is simply not 
inherited and if not visible, is gone. Being not inherited is a very 
important point, it will be rejected for derived types even if visible. 
Consider this:

    package Base is
       type Base_Type is tagged null record;
    end Base;

    package Base_Something is
       procedure Something (X : in out Base_Type; Y : Integer) is null;
    end Base_Something;

    package Derived is
       type Derived_Type is new Base_Type with null record;
    end Derived;

    package Derived_Something is
       procedure Something (X : in out Derived_Type; Y : String) is null;
    end Derived_Something;

    use Base, Derived, Base_Something, Derived_Something;
    X : Base_Type;
    Y : Derived_Type;
begin
    Something (X, 1);   -- OK
    Something (Y, 2);   -- Type error!
    Something (Y, "2"); -- OK

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