DIP 36: Rvalue References

[Timon Gehr]

On 04/21/2013 02:51 AM, Manu wrote:
> On 21 April 2013 06:51, Timon Gehr <timon.gehr at gmx.ch
> <mailto:timon.gehr at gmx.ch>> wrote:
>
>     On 04/20/2013 05:56 PM, Dicebot wrote:
>
>         You miss quite an important point - DIP36 does not add new
>         feature. It
>         partially defines existing feature (scope) to replace an
>         existing but
>         broken solution (auto ref). Nothing new is really added to the
>         language,
>         only existing stuff better defined.
>
>
>     _New meaning_ is assigned to existing grammar whose original purpose
>     is at most loosely related to the _new_ features.
>
>     I do not think that making 'scope' indicate an rvalue reference is
>     particularly future proof.
>
>
> That's not what scope does. Scope promises that the variables will not
> escape the scope.

That is the intention, but this formulation is awfully imprecise. Hence 
nothing has been implemented.

void foo(scope ref int x){ ... }
void foo(scope int* x){ ... }
void foo(scope ref int* x){ ... }

// ???

struct S{
     scope S* x; // ???
}

> And as such, just happens to make passing a temporary
> by ref safe.
> ...

But this is not about safety! Passing an rvalue by ref is disallowed 
even in @system code. Hence 'scope' is assigned a meaning different from 
its intention. The DIP also aims to add more special behaviour to 
built-in literals.