The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
template<typename... Types>
Variant<Types...>::Variant(Variant&& source) {
if (!source.empty()) {
std::move(source).visit([&](auto&& value) {
*this = std::move(value);
});
}
}