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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: making a son benefit access ton an instanciation of a generic
 package required as a formal parameter to his father and instanciated by him
Date: Mon, 22 Jan 2018 15:52:04 +0000
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Xref: reader02.eternal-september.org comp.lang.ada:50056
Date: 2018-01-22T15:52:04+00:00
List-Id: <comp.lang.ada>

"J-P. Rosen" <rosen@adalog.fr> writes:

> Right, and there is a good reason.
> Assuming exception E is declared in generic package GP1:
>
> Imagine this:
> generic
>    package P1 is new GP1 (<>);
>    package P2 is new GP1 (<>);
> package GP2 is... end GP2;
>
> package body GP2 is
>    ...
> begin
>    exception
>       when P1.E =>  -- not allowed by Ada
>          ...
>       when P2.E =>  -- not allowed by Ada
>          ...
> end GP2;
>
> So far, so good. But then, if you instantiate:
> package Inst1 is new GP1;
>
> package Inst2 is new GP2 (Inst1, Inst1);
>
> then you would end up with two different handlers for the same
> exception (since formals P1 and P2 are actually the same package
> Inst1). And

This doesn't seem a million miles away from having name clashes caused
by use-visibility.

Agreed, the _instantiation_ must fail.