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From: okellogg@users.sourceforge.net
Newsgroups: comp.lang.ada
Subject: Re: What would you like in Ada202X?
Date: Sun, 29 Apr 2012 14:37:40 -0700 (PDT)
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Date: 2012-04-29T14:37:40-07:00
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On Sunday, April 29, 2012 9:04:34 PM UTC+2, Robert A Duff wrote:
> 
> package P is
>     package Q is
>     private
>     end Q;
> private
> end P;
> 
> package body P is
>     package body Q is
>     end Q;
> end P;
> 
> In the above nested case:
> P spec can see things in Q spec (imagine all sorts of declarations
>  at various places above).

Right. This appears natural to me because of the physical nesting: The full source text of Q spec is known to P spec once we're past the "end Q;".

> Private part of Q cannot see things in private part of P.

Again due to the physical nesting: At the point of Q's declaration the source text of P private part has not yet been seen.
Thinking ahead, P.Q.R would differ in this respect as child R could see the private parts of its parent packages - IIUC a consequence of R's physical separation of the source text.

> Nobody can say "with P.Q;".
> If you say "with P;" you can automatically see Q.
> Q cannot have its own with clauses.

I'll admit, the fact that "with P.Q;" is illegal but "with P.Q.R;" would be legal seems a bit non-intuitive at first.

> The one you mentioned: you can't have a child "package P.Q.R is".
> Q spec is elaborated in the middle of elaborating P spec,
>  and similarly for the bodies.

This does not change when Q is extended by child R: P and P.Q are elaborated before child R.

> If we transform that structure into child packages:
> [...]
> 
> Now every statement I made above about the nested case
> is no longer true.  I don't like that.  I think the semantics
> of the two above structures should be identical. [...]

If I play parser I can see why they are semantically different - but not in any way that would present an obstacle to my proposal, unless I'm overlooking something.

Thanks,

  Oliver