An idea and a question

[Bonita Montero]

Does anyone know some library that does a move-construction or move
-assigment on a foreign type, i.e. not on its own type ? I'm wondering
if this makes sense sometimes.

[Daniel]

std::optional<T> has a converting move constructor,

template < class U >
constexpr optional( optional<U>&& other );

with the requirements that T is not constructible from std::optional<U>,
and std::optional<U> is not convertible to T.

See https://en.cppreference.com/w/cpp/utility/optional/optional.

Daniel

[Bonita Montero]

Cool, thanks.
I think an r-value reference also makes sense if the moved of forwared
object is later a part of the constructed object; but I never had such
code so far.