DIP1000: Scoped Pointers

[Mike via Digitalmars-d-announce]

On Wednesday, 17 August 2016 at 06:44:41 UTC, Mike wrote:
> On Wednesday, 17 August 2016 at 04:28:33 UTC, Rory McGuire 
> wrote:
>
>> Basically DIP1000 makes it so that:
>>> void main()
>>> {
>>>     A obj;
>>>     {
>>>         scope A a = new A(1);
>>>         obj = a;
>>>     }
>>>     assert(obj.x == 1);  // fails, 'a' has been destroyed
>>> }
>>
>> Will not compile.
>
> Ok, that makes sense. But then the feature illustrated on the 
> deprecations page is wrong.  I think what has been deprecated 
> is `scope` as a type modifier, not `scope` as a storage class, 
> but the example on the deprecations page illustrates the 
> `scope` storage class, not the type modifier.
>
> I believe what the deprecations page intended to say was that 
> this has been deprecated:
> scope class A
> {
>     this(int x) { }
> }
>
> And DIP1000 finally implements the `scope` storage class 
> properly:
> void main()
> {
>     A obj;
>     {
>         scope A a = new A(1);
>         obj = a;              // compile-time error.  Good!
>     }
>     assert(obj.x == 1);       // or is it usage that triggers 
> the compile-time error?
> }
>
> Mike

Or perhaps DIP1000 changes the current behavior of the `scope` 
storage class.

My understanding is that the `scope` storage class currently 
allocates a class on the stack (though its usage for this purpose 
is deprecated in favor of std.typecons.scoped).  If DIP1000 is 
implemented, it will change that behavior, so the allocation will 
instead be on the GC heap, but the compiler will do some 
flow-control analysis to prevent escaping references.  Is that 
right?

Mike