Discussion: Rvalue refs and a Move construtor for D

[kinke]

On Friday, 6 September 2019 at 19:25:57 UTC, Manu wrote:
> There's another case where you can attribute a method with 
> `@rvalue` to apply to the `this` reference. This should 
> naturally work in D under the `@rvalue` proposal.
>
> Ie:
>
> struct S
> {
>   Thing member;
>   ref Thing fun() { return member; }
>   Thing fun() @rvalue { return move(member); }
> }
>
> This can be very valuable, and even more so in D where we use a 
> lot of UFCS chains.

Oh wow, this might be able to convince me, as returning an rvalue 
ref from a method invoked on an rvalue instance would allow 
absolutely perfect forwarding of members (no copy/move and 
preserving rvalue-ness):

struct S
{
   Thing member;
   ref Thing fun() { return member; }
   @rvalue ref Thing fun() @rvalue { return member; }
   // maybe we could even represent both at once via something 
like:
   // auto ref Thing fun()() { return member; }
}