rvalues -> ref (yup... again!)

[Manu]

On 26 March 2018 at 07:40, Atila Neves via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Friday, 23 March 2018 at 22:01:44 UTC, Manu wrote:
>>
>> Forked from the x^^y thread...
>> <snip>
>
>
> There are too many replies on this thread, addressing all the comments would
> take forever and pollute the thread itself. So forgive me if I say something
> that was covered already by someone else.
>
> AFAIK being able to bind rvalues to `ref const(T)`, only makes sense when
> calling C++ functions that take `const T&` (especially since that is
> common). I have not yet heard any other use for them. I'd be in favour of
> allowing it _only_ for `extern(C++)` functions. Otherwise use `auto ref` or
> have overloads for pass-by-value and pass-by-ref.
> I too, once a recent immigrant from the lands of C++, used to keep writing
> `ref const(T)`. I just pass by value now.
>
> C++ T&& (forwarding reference) -> D auto ref T
> C++ T&& (Rvalue reference) -> D T
> C++ const T& -> D T

Yeah, no... T may be big. Copying a large thing sucks. Memory copying
is the slowest thing computers can do.
As an API author, exactly as in C++, you will make a judgement on a
case-by-case basis on this matter. It may be by-value, it may be by
const-ref. It depends on a bunch of things, and they are points for
consideration by the API author, not the user.

> C++ T& -> D ref T

I agree the other 3 cases are correct.