Same reason why std::move exists
Why do we have std::move? Why not just use static_cast<T&&>(value)?

Tymi.

On Wed, 4 Jun 2025, 12:19 Jonathan Wakely, <cxx_at_[hidden]> wrote:

>
>
> On Wed, 4 Jun 2025, 10:14 Tymi, <tymi.cpp_at_[hidden]> wrote:
>
>> "moving" meaning "using std::move" meaning casting to an rvalue
>> reference, let's not point such things out when we know what we are talking
>> about :/
>>
>>
>> > I don't think your std:: expected example works, it didn't have a
>> conversion operator. What you want is just std:: move(*exp) or
>> *std::move(exp).
>>
>> My std::expected example does not currently work, but std::move_as opens
>> a possibility for std::expected to implement such a conversion.
>> std::move(*myExpected) works, but std::move_as<Value>(myExpected) seems
>> cleaner to me.
>>
>
> It seems more verbose and completely unnecessary when you can already
> achieve the same thing.
>
> Not being convertible to its result is an intentional design choice for
> expected (and for optional) so changing that to enable your new feature
> seems like a bad trade off.
>
> > And your string example works with just static_cast<std::string&&>(obj).
>>
>> And no, static_cast<std::string&&>(obj) does not work.
>>
>
> Oh right, your conversion is && qualified. So
> static_cast<string&&>(std::move(obj))
>
> I still see no need to introduce a new feature to do this.
>
>
>
> On 04.06.2025 11:08, Jonathan Wakely wrote:
>>
>>
>>
>> On Wed, 4 Jun 2025, 09:03 Tymi via Std-Proposals, <
>> std-proposals_at_[hidden]> wrote:
>>
>>> I find the move_as example more intuitive and generally "safer". Also my
>>> first thought was that std::string(std::move(c)) copied c._value and
>>> created a new object out of it, instead of just moving c._value.
>>>
>>
>> You seem to be saying "moving" when you mean "casting to rvalue
>> reference", which is not moving.
>>
>>
>> I don't think your std:: expected example works, it didn't have a
>> conversion operator. What you want is just std:: move(*exp) or
>> *std::move(exp).
>>
>> And your string example works with just static_cast<std::string&&>(obj).
>>
>> So I think the existing solutions are fine.
>>
>>
>>