Re: Question about generic formal derived types

[Stephen Leake <Stephen.Leake@gsfc.nasa.gov>]

adam@irvine.com writes:

> In article <uemm6suip.fsf@gsfc.nasa.gov>,
>   Stephen Leake <Stephen.Leake@gsfc.nasa.gov> wrote:
> 
> >
> > After adding a spec for Pack4, running this thru ObjectAda 7.1.2 gives
> > the error:
> >
> > adam.adb: Error: line 32 col 67 LRM:8.3(26), Illegal to override
> >        declaration in same region, Introducing new declaration anyway
> >        (In instance of generic Pack2 at adam.adb: line 13 col 9)
> >
> > I believe that answers all your questions :).
> >
> > -- Stephe
> 
> I hope the smiley means you were kidding.  Certainly, just running it through
> a compiler and seeing what the compiler says doesn't really answer any
> questions, since the Ada language rules are not determined by what a specific
> compiler says they are or aren't.  (This principle might not apply to other
> languages. :-))  Besides, the error message doesn't say what "declaration"
> it considers illegal, and the line number doesn't help because you had to add
> some text to my fragment.

Hmm, I wasn't kidding, although I didn't spend much time on it. I'd
have spent more time if you had posted fully compilable code, and said
what error your compiler gave. Since you didn't, I assumed you had no
compiler, and simply provided the answer a compiler gives. I used
ObjectAda, because it gives LRM references.

I don't intend this as criticism, just as a suggestion on how to
phrase future posts to more likely elicit the response you really
want.

> <snip rummaging thru LRM>
> 
> So after reading everything, it looks like the intent is to make this
> instantiation illegal because of the name conflict, although it seems to be
> the only way I can think of that a generic instantiation can be illegal for
> this reason.  This last makes me skeptical that this was what the language
> designers intended, which is why I'm hoping for an "official" answer from
> someone in the know (i.e. a human someone, not a compiler someone).

Well, I'm not in a position to say anything authoritative. But my
approach to understanding this would be "this would make no sense if
it were legal, so how can I charitably read the LRM to make it
illegal". Depending on why you want to know what the LRM says, this
might be enough (it's enough for me :). If you're writing a compiler,
you need more detail.

-- Stephe