Re: Should this be legal?

["Mark Lundquist" <mark@rational.com>]

Oliver Kellogg <oliver.kellogg@vs.dasa.de> wrote in message
news:99cjt2$v9g@newsserv.vs.dasa.de...
> Hello Ada experts,
>
> The full declaration of the Derived type looks different than
> the partial view (Base_2 vs. Base(2))
>
> Should this be legal?
> Rational Apex 3.2.0b and GNAT 3.13p both accept it.

Not as you posted it (but I think you cleared this up in another post)

> (However, both compilers tend to have problems with this
> type of construction - especially in more complicated contexts.)

I believe your completion of type Derived is legal, but I'm not a language
lawyer... However, it seems like all the completion rules in 7.3 would
really be unnecessary if the partial and full views were required to "look
the same"...

>
> But then, if Base_2 and Base(2) are supposedly interchangeable,
> how come the function Legal is accepted but function Illegal is
> refused ("constraint not allowed here") ?

Because the construct that follows the "return" must be a subtype_mark, that
is, a name that denotes a (named) subtype (i.e. either the "first subtype"
of a type, or a subtype defined by a subtype declaration).  What you have
there is actually just a syntax error.

Mark Lundquist
Rational Software