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Add a missing SFINAE condition to the variant's converting constructor.

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Remarks: This function shall not participate in overload resolution unless
         `is_same_v<decay_t<T>, variant>` is false, unless `decay_t<T>` is
         neither a specialization of `in_place_type_t` nor a specialization of
         `in_place_index_t`, unless `is_constructible_v<Tj, T>` is true, and
         unless the expression `FUN(std::forward<T>(t))` (with `FUN` being the
         above-mentioned set of imaginary functions) is well formed.

Depends on D34111.

Reviewers: EricWF, K-ballo

Reviewed By: EricWF

Subscribers: fhahn

Differential Revision: https://reviews.llvm.org/D34112

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@305668 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Park
2017-06-19 08:25:57 +00:00
parent 7db4f7b426
commit b47a9bc6c4
2 changed files with 16 additions and 0 deletions
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2
include/variant
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@@ -1116,6 +1116,8 @@ public:
template < template <
class _Arg, class _Arg,
enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0, enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
enable_if_t<!__is_inplace_type<decay_t<_Arg>>::value, int> = 0,
enable_if_t<!__is_inplace_index<decay_t<_Arg>>::value, int> = 0,
class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>, class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
size_t _Ip = size_t _Ip =
__find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,

14
test/std/utilities/variant/variant.variant/variant.ctor/T.pass.cpp
View File

@@ -37,6 +37,9 @@ struct NoThrowT {
NoThrowT(int) noexcept(true) {} NoThrowT(int) noexcept(true) {}
}; };
struct AnyConstructible { template <typename T> AnyConstructible(T&&) {} };
struct NoConstructible { NoConstructible() = delete; };
void test_T_ctor_noexcept() { void test_T_ctor_noexcept() {
{ {
using V = std::variant<Dummy, NoThrowT>; using V = std::variant<Dummy, NoThrowT>;
@@ -62,6 +65,17 @@ void test_T_ctor_sfinae() {
static_assert(!std::is_constructible<V, int>::value, static_assert(!std::is_constructible<V, int>::value,
"no matching constructor"); "no matching constructor");
} }
{
using V = std::variant<AnyConstructible, NoConstructible>;
static_assert(
!std::is_constructible<V, std::in_place_type_t<NoConstructible>>::value,
"no matching constructor");
static_assert(!std::is_constructible<V, std::in_place_index_t<1>>::value,
"no matching constructor");
}
#if !defined(TEST_VARIANT_HAS_NO_REFERENCES) #if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
{ {
using V = std::variant<int, int &&>; using V = std::variant<int, int &&>;