Create a variant object holding the same alternative (if any) held by the specified original. If this variant is allocator-aware, the allocator of original is used to supply memory. If original is not valueless by exception, the contained value is move-constructed from the contained value of original. This constructor participates in overload resolution only if all alternatives are move constructible. For simplicity of implementation, this method differs from the standard in the following ways: * conditional triviality is not implemented * constexpr is not implemented * noexcept specification is not implemented