isRvalue trait

[Marc Schütz via Digitalmars-d-learn]

On Monday, 10 October 2016 at 11:46:01 UTC, Nordlöw wrote:
> At
>
> https://github.com/nordlow/phobos-next/blob/master/src/moval.d
>
> I've implemented a helper function for creating r-value out of 
> l-values defined as
>
> E movedToRvalue(E)(ref E e)
> {
>     import std.algorithm.mutation : move;
>     E value;
>     move(e, value);             // this can be optimized
>     return value;
> }
>

Doesn't the second overload of `move()` already do what you want?

https://dlang.org/phobos/std_algorithm_mutation.html#.move

Note that in your implementation, you needlessly initialize 
`value`, which then needs to be properly destroyed by `move()`, 
which the Phobos implementation avoids:

https://github.com/dlang/phobos/blob/master/std/algorithm/mutation.d#L1083-L1088

> For the case when movedToRvalue is called with an r-value, such 
> as in,
>
>     static assert(__traits(compiles, { consume(S(14)); }));
>
> I would like to overload to an identity op.

If the compiler is smart enough to understand what 
`moveEmplace()` does, it could already do this automatically.