From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.13.212.12 with SMTP id w12mr8548922ywd.147.1505167208814;
        Mon, 11 Sep 2017 15:00:08 -0700 (PDT)
X-Received: by 10.36.122.208 with SMTP id a199mr660458itc.12.1505167208778;
 Mon, 11 Sep 2017 15:00:08 -0700 (PDT)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!border1.nntp.ams1.giganews.com!nntp.giganews.com!peer02.ams1!peer.ams1.xlned.com!news.xlned.com!peer01.am4!peer.am4.highwinds-media.com!peer01.iad!feed-me.highwinds-media.com!news.highwinds-media.com!q8no2565246qtb.0!news-out.google.com!p6ni28itp.0!nntp.google.com!o200no34777itg.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Mon, 11 Sep 2017 15:00:08 -0700 (PDT)
In-Reply-To: <op6v4m$tmm$1@gioia.aioe.org>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=173.71.208.22;
 posting-account=QF6XPQoAAABce2NyPxxDAaKdAkN6RgAf
NNTP-Posting-Host: 173.71.208.22
References: <op6pfu$h8h$1@gioia.aioe.org>
 <364ff8e0-c7dd-4980-b19f-5d438edd8353@googlegroups.com>
 <op6sr9$oop$1@gioia.aioe.org>
 <7df81b3c-1fde-4395-8b9b-1a945820a7f7@googlegroups.com>
 <op6v4m$tmm$1@gioia.aioe.org>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <ec2642af-9b8e-49a8-a797-f0d56498d786@googlegroups.com>
Subject: Re: Type invariants and private extensions?
From: Jere <jhb.chat@gmail.com>
Injection-Date: Mon, 11 Sep 2017 22:00:08 +0000
Content-Type: text/plain; charset="UTF-8"
X-Received-Body-CRC: 3007193257
X-Received-Bytes: 3090
Xref: news.eternal-september.org comp.lang.ada:48021
Date: 2017-09-11T15:00:08-07:00
List-Id: <comp.lang.ada>

On Monday, September 11, 2017 at 5:27:54 PM UTC-4, Victor Porton wrote:
> Egil H H wrote:
> 
> > On Monday, September 11, 2017 at 10:48:46 PM UTC+2, Victor Porton wrote:
> >> > The Invariant will then be inherited by all derived types
> >> 
> >> It is not what I want. I want different invariants for different derived
> >> types.
> >> 
> > 
> > You can add new invariants in addition to the ones inherited
> 
> I cannot: the compiler gives an error:
> 
> package P is
> 
>   type T is tagged private;
> 
> private
> 
>   type T is tagged null record;
> 
> end P;
> 
> with P; use P;
> 
> package P1 is
> 
>   type T1 is new T with null record
>     with Type_Invariant => True;
> 
> end P1;
> 
> 
> $ gnatgcc -gnatc -c p1.ads 
> p1.ads:6:10: aspect "Type_Invariant" only allowed for private type or 
> corresponding full view
> 
> -- 
> Victor Porton - http://portonvictor.org

You aren't applying it to a private type.  Try:

   package P1 is
      
      type T1 is new T with private
         with Type_Invariant'Class => True;
      
   private

      type T1 is new T with null record;
        

   end P1;

The relevant RM section:

7.3.2

2/3
Type_Invariant

This aspect shall be specified by an expression, called an 
invariant expression. Type_Invariant may be specified on a 
private_type_declaration, on a private_extension_declaration, 
or on a full_type_declaration that declares the completion of 
a private type or private extension.

3/3
Type_Invariant'Class

This aspect shall be specified by an expression, called an 
invariant expression. Type_Invariant'Class may be specified 
on a private_type_declaration or a private_extension_declaration.