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Require valueless to be first, add test

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This commit is contained in:
Peter Dimov
2017-06-14 01:04:36 +03:00
parent 44d2ead565
commit 4de9f80487
3 changed files with 249 additions and 11 deletions
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include/boost/variant2/variant.hpp
+13 -11
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@@ -407,7 +407,7 @@ template<class T1, class... T> union variant_storage_impl<mp_true, T1, T...>
rest_.emplace( mp_size_t<I-1>(), std::forward<A>(a)... );
}
template<std::size_t I, class... A> constexpr void emplace_impl( mp_true, mp_size_t<I>, A&&... a ) noexcept
template<std::size_t I, class... A> constexpr void emplace_impl( mp_true, mp_size_t<I>, A&&... a )
{
*this = variant_storage_impl( mp_size_t<I>(), std::forward<A>(a)... );
}
@@ -459,8 +459,10 @@ 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<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>...>, std::is_same<T, valueless>...>::value, T...>;
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...>;
struct none {};
@@ -517,10 +519,10 @@ 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 )
{
std::size_t const K = mp_find<mp_list<T...>, valueless>::value;
if( K < sizeof...(T) ) // have valueless
if( can_be_valueless<T...>::value ) // T0 == valueless
{
std::size_t const K = 0;
try
{
st1_.emplace( mp_size_t<J>(), std::forward<A>(a)... );
@@ -550,7 +552,7 @@ template<class... T> struct variant_base_impl<true, true, T...>
std::size_t const J = I+1;
using U = mp_at_c<variant<T...>, I>;
this->emplace_impl<J, U>( std::is_nothrow_constructible<U, A...>(), mp_all<variant2::detail::is_trivially_move_constructible<U>, variant2::detail::is_trivially_move_assignable<T>...>(), std::forward<A>(a)... );
this->emplace_impl<J, U>( std::is_nothrow_constructible<U, A&&...>(), mp_all<variant2::detail::is_trivially_move_constructible<U>, variant2::detail::is_trivially_move_assignable<T>...>(), std::forward<A>(a)... );
}
};
@@ -670,8 +672,6 @@ template<class... T> struct variant_base_impl<false, true, T...>
{
size_t const J = I+1;
std::size_t const K = mp_find<mp_list<T...>, valueless>::value;
using U = mp_at_c<variant<T...>, I>;
if( std::is_nothrow_constructible<U, A...>::value )
@@ -681,8 +681,10 @@ template<class... T> struct variant_base_impl<false, true, T...>
st1_.emplace( mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
else if( K < sizeof...(T) ) // have valueless
else if( can_be_valueless<T...>::value ) // T0 == valueless
{
std::size_t const K = 0;
_destroy();
try
@@ -692,8 +694,8 @@ template<class... T> struct variant_base_impl<false, true, T...>
}
catch( ... )
{
st1_.emplace( mp_size_t<K>() );
ix_ = K;
st1_.emplace( mp_size_t<K+1>() );
ix_ = K+1;
throw;
}