easy_variant is an extension of variant, which includes generic handling for throwing moves in user-defined types.

Synopsis

Defined in file <strict_variant/variant.hpp>:

template <typename... Ts>
using easy_variant = variant<wrap_if_throwing_move_t<Ts>...>;

where wrap_if_throwing_move_t is defined:

struct <typename T, typename = std::enable_if_t<std::is_nothrow_destructible<T>::value && !std::is_reference<T>::value>>
struct wrap_if_throwing_move {
  using type = typename std::conditional<std::is_nothrow_move_constructible<T>::value,
                                         T,
                                         recursive_wrapper<T>>::type;
};

template <typename T>
using wrap_if_throwing_move_t = typename wrap_if_throwing_move<T>::type;

That is, if T is no-throw move constructible, we use T, otherwise, we use recursive_wrapper<T>.

Description

easy_variant is meant to easily replace uses of boost::variant and other common variant types.

Since recursive_wrapper is no-throw move constructible, and is transparently pierced at all parts of the variant interface, easy_variant is always able to generate assignment operators and such regardless of the noexcept status of the user-defined types which are passed to it. It is thus a general-purpose variant type.