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Sender: sjw@galadriel.frlngtn.gecm.com
Newsgroups: comp.lang.ada
Subject: Re: Legality: formal packages with controlled types
References: <x7vg0742hlp.fsf@smaug.pushface.org>
From: Simon Wright <simon.j.wright@amsjv.com>
Date: 28 Nov 2001 11:29:59 +0000
Message-ID: <x7v667v16bs.fsf@galadriel.frlngtn.gecm.com>
Organization: Alenia Marconi Systems, ISD, Farlington
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Date: 2001-11-28T11:29:59+00:00
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Simon Wright <simon@pushface.org> writes:

> The code below fails on OA 7.2 with
> 
> bug.ada: Error: line 21 col 42 LRM:3.9.1(3), The accessibility level
>        of a record extension shall not exceed that of its parent; this
>        also applies in a generic instantiation (In instance of generic
>        base at bug.ada: line 7 col 7)
> 
> and similar code fails similarly on OA 7.2.1 and AdaMULTI v3.1 I'm
> told.  Presumably they all share a front end.
> 
> The code compiles OK if Base.Container isn't derived from Controlled.
> 
> Is it really the case that it's legal to instantiate a generic package
> with a package that contains a controlled type but illegal to
> instantiate a generic subprogram?
> 
> ========================================================
> with ada.finalization;
> generic
> 	type item is private;
> package base is
> 	type container is tagged private;
> private
> 	type container is new ada.finalization.controlled with record
> 		the_item : item;
> 	end record;
> end base;
> 
> with base;
> generic
> 	type item is private;
> 	with package New_Base is new base (item);  -- <==== ok
> package Generic_package is end Generic_package;
> 
> with base;
> generic
> 	type item is private;
> 	with package new_base is new base (item);  -- <==== failure
> procedure Generic_Procedure;
> 
> procedure generic_procedure is
> begin
> 	null;
> end generic_procedure;

I'm informed by ACT that this code is legal and that the compilers
that reject it (which, BTW, include Apex) are wrong to do so.