On Fri, 4 Oct 2024 at 06:56, Timon Gehr via Digitalmars-d <digitalmars-d@puremagic.com> wrote:

On 10/3/24 17:47, Walter Bright wrote:
>
> __rvalue() is not a move, it just guides the overload resolution to the
> move constructor/assignment. It's a hint.

It has to be a move though. An rvalue is owned, an lvalue is not.
Whenever an lvalue goes into an rvalue, it is either copy or move.

If `__rvalue` is just some sort of ad-hoc type-punning operation
exclusively for overload resolution, it will often copy the argument,
unless your intention is to force it to be consumed by a function that
is implicitly `@move` (such as a move constructor or a move assignment).

Yes, exactly... __rvalue() must be SOME KIND of move; it is explicitly taking ownership away from the owner, and handing it to some new owner.

The thing about __rvalue() is that you will hide it inside some function, like `T move(ref T t) => __rvalue(t)`

That encapsulates the ownership transfer, and separates the visibility of the ownership transfer from the calling scope where that information is needed.

Maybe you should reserve the name `move` and make it an error for a user to produce any declaration with that name? That might avoid your surprise overload issue?