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From: Jacob Sparre Andersen <sparre@nbi.dk>
Newsgroups: comp.lang.ada
Subject: Re: Is this a bug in my code or the compiler?
Date: Sat, 13 Jun 2015 15:33:07 +0200
Organization: Jacob Sparre Andersen Research & Innovation
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Xref: number.nntp.giganews.com comp.lang.ada:193610
Date: 2015-06-13T15:33:07+02:00
List-Id: <comp.lang.ada>

David Botton wrote:

>    function Token_Start (Source : in out Awesome.Source.Source_Type'Class)
>                          return Character;
>    function Token_End (Source : in out Awesome.Source.Source_Type'Class)
>                        return String;

>    return Token_Start (Source) & Token_End (Source);

Doesn't your compiler warn you about modifying Source in two places
(roughly) at the same time?

GNAT 4.9 complains loudly about the roughly similar case:

   procedure P (A, B : in out T);

   P (C, C);

But I can't get it to complain about a simplified variation of your
case.

Maybe there is an AdaControl rule to detect this kind of problem.  But
it is an obviously faulty expression, so it would make most sense if it
was forbidden in the language.

Greetings,

Jacob
-- 
"It is very easy to get ridiculously confused about the
 tenses of time travel, but most things can be resolved
 by a sufficiently large ego."