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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: a new language, designed for safety !
Date: Fri, 06 Jun 2014 15:43:37 -0400
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Date: 2014-06-06T15:43:37-04:00
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Niklas Holsti <niklas.holsti@tidorum.invalid> writes:

> The error, as I understand it, is trying to convert X, which is of a
> classwide type covering Pak.P2.T, to a classwide type (Pak.P3.TA'Class)
> which does not cover Pak.P2.T. (Apologies if I'm not using the correct
> ARM terms for this.) The dispatching call is not the problem.

Right.

> This error is more similar to a subtype or type conversion error, where
> the source value violates the constraints of the target type.

It is EXACTLY a type conversion error.  The Tag is wrong, so the type
conversion raises Constraint_Error.  It never gets to the dispatching
call.  There is no dangling dispatching in Ada!  It is impossible for
a call to (try to) call the nonexistent body of an abstract operation.

> Yes, Ada has run-time errors, but they are not the result of
> "unimplemented methods".

Right.

- Bob