Function move

include/pybind11/cast.h:1754–1771

template <typename T>
detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
    if (obj.ref_count() > 1) {
#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
        throw cast_error(
            "Unable to cast Python " + str(type::handle_of(obj)).cast<std::string>()
            + " instance to C++ rvalue: instance has multiple references"
              " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
#else
        throw cast_error("Unable to move from Python "
                         + str(type::handle_of(obj)).cast<std::string>() + " instance to C++ "
                         + type_id<T>() + " instance: instance has multiple references");
#endif
    }

    // Move into a temporary and return that, because the reference may be a local value of `conv`
    T ret = std::move(detail::load_type<T>(obj).operator T &());
    return ret;
}

// Calling cast() on an rvalue calls pybind11::cast with the object rvalue, which does:
// - If we have to move (because T has no copy constructor), do it.  This will fail if the moved