David Abrahams wrote:
This is needed if boost::move returns boost::detail::rv<T> instead of T.
But boost::move should return T.
Why? && is a reference, boost::move could return a pseudo-reference.
Returning T from move() avoids the need of explicitly specify movable() when passing arguments by value but makes forwarding really hard.
I don't see how it impacts forwarding.
How can you implement a "forwarding"-like function like this without penalyzing non-movable types? template<class T1, class T2, class T3, ...> emplace(...) if move() returns a pseudo-reference, this almost works easily (non-const references are forwarded as const-references but this might be acceptable for an emulation: template<class T1, class T2, ...> emplace(const T1 &t1, const T1 &t2, ...){ void *ptr = allocate(); new(ptr)(t1, t2, ....) }
On the other hand returning rv<T> makes forwarding easy
I don't see that either. You'll deduce rv<T> in a generic forwarding signature instead of T, which has a lot of potential to screw thinigs up.
See above.
Still lost.
I hope it's more clear now, Ion