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=ham autolearn_force=no version=3.4.4
X-Google-Thread: 103376,ea5071f634c2ea8b
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII
Received: by 10.68.35.131 with SMTP id h3mr16032630pbj.1.1321861361812;
        Sun, 20 Nov 2011 23:42:41 -0800 (PST)
Path: 
 lh20ni112pbb.0!nntp.google.com!news2.google.com!postnews.google.com!g7g2000vbd.googlegroups.com!not-for-mail
From: AdaMagica <christ-usch.grein@t-online.de>
Newsgroups: comp.lang.ada
Subject: Re: Generic-Package Elaboration Question / Possible GNAT Bug.
Date: Sun, 20 Nov 2011 23:25:39 -0800 (PST)
Organization: http://groups.google.com
Message-ID: <a5d7119f-7bb7-41e4-8d76-ef08f2d958d9@g7g2000vbd.googlegroups.com>
References: 
 <7bf9bc32-850a-40c6-9ae2-5254fe220533@f29g2000yqa.googlegroups.com>
 <wcc4nxzu5gf.fsf@shell01.TheWorld.com>
 <4295dc09-43de-4557-a095-fc108359f27f@y42g2000yqh.googlegroups.com>
 <fe29npj98k5s$.1vzwcva8q22hk.dlg@40tude.net>
NNTP-Posting-Host: 80.156.44.178
Mime-Version: 1.0
X-Trace: posting.google.com 1321861361 18846 127.0.0.1 (21 Nov 2011 07:42:41
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Mon, 21 Nov 2011 07:42:41 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: g7g2000vbd.googlegroups.com; posting-host=80.156.44.178;
 posting-account=rmHyLAoAAADSQmMWJF0a_815Fdd96RDf
User-Agent: G2/1.0
X-Google-Web-Client: true
X-Google-Header-Order: HUALESRCNK
X-HTTP-UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64;
 rv:8.0) Gecko/20100101 Firefox/8.0,gzip(gfe)
Xref: news2.google.com comp.lang.ada:14472
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Date: 2011-11-20T23:25:39-08:00
List-Id: <comp.lang.ada>

On 20 Nov., 10:55, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> > On Nov 19, 4:12=A0pm, Robert A Duff <bobd...@shell01.TheWorld.com>
> > wrote:
> >> In general, the design of Ada is that if a generic body is legal,
> >> then every possible instance is legal (so the compiler need not
> >> check the instances). =A0The design of C++ templates is very different
> >> in this regard!
>
> I don't know if Ada keeps that promise for generic bodies, but it certain=
ly
> does not for the specifications. Generic contracts are too weak for that.
> Example:
>
> generic
> =A0 =A0type T is tagged private;
> package Legal is
> =A0 =A0type S is new T with null record;
> =A0 =A0not overriding procedure Foo (X : in out S);
> end Legal;
>
> This and the body would successfully compile ignoring the fact that there
> might exist tagged types with a primitive operation named Foo.

Note that Bob said this holds true for *bodies*, here you have a
*spec* that might produce an illegal instance.

For bodies, Ada always assumes the worst.