(j3.2006) About extending abstract types with deferred bindings

[Cohen Malcolm]

Right, and instantiating it is not allowed.

There is no conjecture here.
It is actively prohibited.

You are not allowed to instantiate it ever, whether that is in the context 
of a tbp invocation or not!!!   Instantiating it *ever* would allow the 
deferred tbp to be eventually invoked.  That's why we do not allow that.

Any constraint on invocation would be completely and utterly ineffective. 
Or at best redundant.

-----Original Message----- 
From: Van Snyder
Sent: Friday, September 9, 2016 3:26 AM
To: j3 at mailman.j3-fortran.org
Subject: Re: (j3.2006) About extending abstract types with deferred bindings

On Thu, 2016-09-08 at 17:28 +0900, Cohen Malcolm wrote:
> Your ancestor component *IS* an object of abstract type.

Right, but it *IS* instantiated.  We can't rely on the conjecture that
it's impossible to instantiate an object of abstract type to prevent
invoking deferred procedures bound to their types.  We need actively to
prohibit using them.  Is there a constraint that does this?  I haven't
found it yet.

>
> -----Original Message----- 
> From: Van Snyder
> Sent: Thursday, September 8, 2016 5:22 PM
> To: j3 at mailman.j3-fortran.org
> Subject: Re: (j3.2006) About extending abstract types with deferred 
> bindings
>
> On Thu, 2016-09-08 at 17:15 +0900, Cohen Malcolm wrote:
> > <<<
> > Is there a prohibition against invoking an accessible deferred
> > procedure
> > binding using an abstract ancestor component of a non-abstract object?
> > >>>
> >
> > In effect.  The rules prevent instantiating an object of abstract type
> > in
> > the first place.
>
> You don't need an object of abstract type to do this.  An ancestor
> component of abstract type, of an object of concrete type, is of
> abstract type.  The object of concrete type can be instantiated.
>
> type, abstract :: T1
> ...
> contains
>   procedure(...), deferred :: P1
> end type T1
>
> type, extends(t1) :: T2
> ...
> contains
>   procedure(...) :: P1
> end type T2
>
> type(t2) :: X
>
>   call x%t1%p1
>
>
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-- 
........................Malcolm Cohen, Nihon NAG, Tokyo.