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Add reference specializations to variant_alternative

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This commit is contained in:
Peter Dimov
2019-02-21 22:22:07 +02:00
parent 87a2e88edb
commit d8cd270268
2 changed files with 89 additions and 0 deletions
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24
include/boost/variant2/variant.hpp
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@ -133,6 +133,14 @@ template<std::size_t I, class... T> struct variant_alternative_impl<I, variant<T
{
};
template<std::size_t I, class... T> struct variant_alternative_impl<I, variant<T...>&, true>: std::add_lvalue_reference< mp11::mp_at_c<variant<T...>, I> >
{
};
template<std::size_t I, class... T> struct variant_alternative_impl<I, variant<T...>&&, true>: std::add_rvalue_reference< mp11::mp_at_c<variant<T...>, I> >
{
};
} // namespace detail
template<std::size_t I, class T> struct variant_alternative
@ -155,6 +163,14 @@ template<std::size_t I, class... T> struct variant_alternative<I, variant<T...>
{
};
template<std::size_t I, class... T> struct variant_alternative<I, variant<T...>&>: public detail::variant_alternative_impl<I, variant<T...>&, (I < sizeof...(T))>
{
};
template<std::size_t I, class... T> struct variant_alternative<I, variant<T...>&&>: public detail::variant_alternative_impl<I, variant<T...>&&, (I < sizeof...(T))>
{
};
#else
namespace detail
@ -180,6 +196,14 @@ template<std::size_t I, class T> struct variant_alternative<I, T const volatile>
{
};
template<std::size_t I, class T> struct variant_alternative<I, T&>: mp11::mp_defer<detail::var_alt_impl, mp11::mp_size_t<I>, T, mp11::mp_quote_trait<std::add_lvalue_reference>>
{
};
template<std::size_t I, class T> struct variant_alternative<I, T&&>: mp11::mp_defer<detail::var_alt_impl, mp11::mp_size_t<I>, T, mp11::mp_quote_trait<std::add_rvalue_reference>>
{
};
template<std::size_t I, class... T> struct variant_alternative<I, variant<T...>>: mp11::mp_defer<mp11::mp_at, variant<T...>, mp11::mp_size_t<I>>
{
};

65
test/variant_alternative.cpp
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@ -25,65 +25,130 @@ int main()
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void> volatile>, void volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void> const volatile>, void const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char>&>, char&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char> const&>, char const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char>&&>, char&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char> const&&>, char const&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int>>, void>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int> const>, void const>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int> volatile>, void volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int> const volatile>, void const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int>&>, char&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int> const&>, char const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int>&&>, char&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int> const&&>, char const&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int>>, int>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int> const>, int const>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int> volatile>, int volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int> const volatile>, int const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int>&>, int&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int> const&>, int const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int>&&>, int&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int> const&&>, int const&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int, float>>, void>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int, float> const>, void const>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int, float> volatile>, void volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<void, int, float> const volatile>, void const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int, float>&>, char&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int, float> const&>, char const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int, float>&&>, char&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<0, variant<char, int, float> const&&>, char const&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float>>, int>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float> const>, int const>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float> volatile>, int volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float> const volatile>, int const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float>&>, int&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float> const&>, int const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float>&&>, int&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<1, variant<void, int, float> const&&>, int const&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float>>, float>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float> const>, float const>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float> volatile>, float volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float> const volatile>, float const volatile>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float>&>, float&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float> const&>, float const&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float>&&>, float&&>));
BOOST_TEST_TRAIT_TRUE((std::is_same<variant_alternative_t<2, variant<void, int, float> const&&>, float const&&>));
variant_alternative<0, void>();
variant_alternative<0, void const>();
variant_alternative<0, void volatile>();
variant_alternative<0, void const volatile>();
variant_alternative<0, int&>();
variant_alternative<0, int const&>();
variant_alternative<0, int&&>();
variant_alternative<0, int const&&>();
variant_alternative<0, variant<>>();
variant_alternative<0, variant<> const>();
variant_alternative<0, variant<> volatile>();
variant_alternative<0, variant<> const volatile>();
variant_alternative<0, variant<>&>();
variant_alternative<0, variant<> const&>();
variant_alternative<0, variant<>&&>();
variant_alternative<0, variant<> const&&>();
variant_alternative<1, variant<int>>();
variant_alternative<1, variant<int> const>();
variant_alternative<1, variant<int> volatile>();
variant_alternative<1, variant<int> const volatile>();
variant_alternative<1, variant<int>&>();
variant_alternative<1, variant<int> const&>();
variant_alternative<1, variant<int>&&>();
variant_alternative<1, variant<int> const&&>();
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, void>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, void const>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, void volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, void const volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, int&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, int const&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, int&&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, int const&&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<>>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<> const>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<> volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<> const volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<>&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<> const&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<>&&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<0>, variant<> const&&>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int>>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int> const>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int> volatile>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int> const volatile>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int>&>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int> const&>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int>&&>));
BOOST_TEST_TRAIT_TRUE((mp_valid<var_alt_t, mp_size_t<0>, variant<int> const&&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int>>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int> const>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int> volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int> const volatile>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int>&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int> const&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int>&&>));
BOOST_TEST_TRAIT_FALSE((mp_valid<var_alt_t, mp_size_t<1>, variant<int> const&&>));
return boost::report_errors();
}