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Remove valueless; monostate is enough

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Peter Dimov committed 2018-10-18 03:32:57 +03:00
1 parent 19d48d9d8b
commit 46ee0af110
2 files changed
+174 -162
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include/boost/variant2/variant.hpp
+10 -18
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@@ -58,19 +58,6 @@ constexpr bool operator>=(monostate, monostate) noexcept { return true; }
constexpr bool operator==(monostate, monostate) noexcept { return true; }
constexpr bool operator!=(monostate, monostate) noexcept { return false; }
// valueless
struct valueless
{
};
constexpr bool operator<(valueless, valueless) noexcept { return false; }
constexpr bool operator>(valueless, valueless) noexcept { return false; }
constexpr bool operator<=(valueless, valueless) noexcept { return true; }
constexpr bool operator>=(valueless, valueless) noexcept { return true; }
constexpr bool operator==(valueless, valueless) noexcept { return true; }
constexpr bool operator!=(valueless, valueless) noexcept { return false; }
// variant forward declaration
template<class... T> class variant;
@@ -459,7 +446,8 @@ template<class U, class... T> using resolve_overload_index = mp_find<mp_list<T..
// variant_base
template<class... T> using can_be_valueless = std::is_same<mp_first<mp_list<T...>>, valueless>;
template<class... T> using can_be_valueless = mp_any<std::is_same<T, monostate>..., std::is_nothrow_default_constructible<T>...>;
template<class... T> using valueless_index = mp_if<mp_contains<mp_list<T...>, monostate>, mp_find<mp_list<T...>, monostate>, mp_find_if<mp_list<T...>, std::is_nothrow_default_constructible>>;
template<bool is_trivially_destructible, bool is_single_buffered, class... T> struct variant_base_impl; // trivially destructible, single buffered
template<class... T> using variant_base = variant_base_impl<mp_all<std::is_trivially_destructible<T>...>::value, mp_any<mp_all<std::is_nothrow_move_constructible<T>...>, can_be_valueless<T...>>::value, T...>;
@@ -519,9 +507,11 @@ template<class... T> struct variant_base_impl<true, true, T...>
template<std::size_t J, class U, class... A> void emplace_impl( mp_false, mp_false, A&&... a )
{
if( can_be_valueless<T...>::value ) // T0 == valueless
if( can_be_valueless<T...>::value )
{
std::size_t const K = 0;
std::size_t const K = valueless_index<T...>::value;
assert( K < sizeof...(T) );
try
{
@@ -681,9 +671,11 @@ template<class... T> struct variant_base_impl<false, true, T...>
st1_.emplace( mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
else if( can_be_valueless<T...>::value ) // T0 == valueless
else if( can_be_valueless<T...>::value )
{
std::size_t const K = 0;
std::size_t const K = valueless_index<T...>::value;
assert( K < sizeof...(T) );
_destroy();