Workaround GCC bug PR78489 - SFINAE order is not respected.

This patch works around variant test failures which are new to
GCC 8. GCC 8 either doesn't perform SFINAE in lexical order, or
it doesn't halt after encountering the first failure. This
causes hard error to occur instead of substitution failure.

See gcc.gnu.org/PR78489

llvm-svn: 328261
This commit is contained in:
Eric Fiselier 2018-03-22 22:32:55 +00:00
parent adb173314d
commit a595456731
2 changed files with 18 additions and 17 deletions

View File

@ -1156,29 +1156,24 @@ public:
: __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {}
template <size_t _Ip, class... _Args,
class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
enable_if_t<(_Ip < sizeof...(_Types)), size_t> _Ip2 = _Ip,
class _Tp = variant_alternative_t<_Ip2, variant<_Types...>>,
enable_if_t<is_constructible<_Tp, _Args...>::value, int> = 0>
inline _LIBCPP_INLINE_VISIBILITY
explicit constexpr variant(
in_place_index_t<_Ip>,
_Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
explicit constexpr variant(in_place_index_t<_Ip>,
_Args&&... __args)
noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
: __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
template <
size_t _Ip,
class _Up,
class... _Args,
enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
template <size_t _Ip, class _Up, class... _Args,
enable_if_t<(_Ip < sizeof...(_Types)), size_t> _Ip2 = _Ip,
class _Tp = variant_alternative_t<_Ip2, variant<_Types...>>,
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
int> = 0>
inline _LIBCPP_INLINE_VISIBILITY
explicit constexpr variant(
in_place_index_t<_Ip>,
initializer_list<_Up> __il,
_Args&&... __args) noexcept(
is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
explicit constexpr variant(in_place_index_t<_Ip>, initializer_list<_Up> __il,
_Args&&... __args)
noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
: __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
template <

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@ -73,6 +73,12 @@ void test_ctor_sfinae() {
!std::is_constructible<V, std::in_place_index_t<2>, IL>::value, "");
static_assert(!test_convertible<V, std::in_place_index_t<2>, IL>(), "");
}
{ // index not in variant
using V = std::variant<InitList, InitListArg, int>;
static_assert(
!std::is_constructible<V, std::in_place_index_t<3>, IL>::value, "");
static_assert(!test_convertible<V, std::in_place_index_t<3>, IL>(), "");
}
}
void test_ctor_basic() {