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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Which compiler is correct?
Date: 1997/06/18
Message-ID: <EBz083.9EB@world.std.com>#1/1
X-Deja-AN: 249440768
References: <33A77C54.5484@bix.com>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-06-18T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <33A77C54.5484@bix.com>, Tom Moran  <tmoran@bix.com> wrote:
>Compilers G and J accept this code.  Compiler O gives the error message
>indicted in the comment, on said line.  Which is correct Ada?

Compiler O is correct.  The inherited i component of type y is
implicitly declared within the private part of a.b.  Since a.c cannot
see this implicit declaration, the i component of z is never implicitly
declared (although it still exists at run time, and you can get at it by
doing "x(two).i").

The rules for this stuff are somewhat arcane.  See 3.4 and 7.3.1.

>package a is
>    type x is tagged private;
>private
>    type x is tagged record
>        i:integer;
>    end record;
>end a;
>package a.b is
>    type y is new x with private;
>private
>    type y is new x with record 
>        j:integer;
>    end record;
>end a.b;
>with a.b;
>package a.c is
>    type z is new a.b.y with private;
>    procedure p;
>private
>    type z is new a.b.y with record
>        k:integer;
>    end record;
>end a.c;
>package body a.c is
>    procedure p is
>       one:x;
>       two:z;
>    begin
>        one.i:=1;
>        two.k:=2;
>        two.i:=3;   -- test_vis.ada: Error: line 31 col 13 LRM:4.1.3(5),
>No possible interpretation for selected component i, Ignoring future
>references 
>
>    end p;
>end a.c;

- Bob