[libcxx] Add <variant> tests (but not implementation)

[EricWF]

Summary

Although libc++ doesn't yet implement variant we do have tests!

@STL_MSFT @CaseyCarter IIRC you already have a <variant> implementation. Would you mind checking these tests against your implementation?

[CaseyCarter]

I'll take a look at these tomorrow; I don't have easy access to my implementation with the changes from P0510 and P0504 from home (it's waiting on a compiler bugfix to checkin).

test/std/utilities/variant/variant.get/get_type.pass.cpp

19

Space at end-of-line here.

[EricWF]

• Fix a couple extra usages of variant<void> or variant<T&>.
• Fix variant::hash SFINAE tests.

[EricWF]

• Attempt to fix TestTypes::NoCtors actually having constructors.

[CaseyCarter]

test/std/utilities/variant/variant.relops/relops.pass.cpp

61

MSVC with /W4 is, uh, not found of these functions. Adding "return false;" after the assert shuts it up.

190

Bogus test: should be assert(test_less(v1, v2, false, true));. Maybe someone forgot to implement part of P0032?

196

Bogus test again: should be assert(test_less(v1, v2, true, false));.

test/std/utilities/variant/variant.variant/variant.assign/copy.pass.cpp

150

All four of these are non-portable. Implementations are permitted to strengthen noexcept, and these are assignments that can feasibly be implemented to not throw.

test/std/utilities/variant/variant.variant/variant.mod/emplace_index_args.pass.cpp

93

y and z are unused here,

test/std/utilities/variant/variant.variant/variant.mod/emplace_type_args.pass.cpp

94

y and z are unused here.

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

322

Non-portable. Replace with LIBCPP_ASSERT(T::move_called == 1); assert(T::move_called <= 2);

329

Non-portable. Replace with LIBCPP_ASSERT(T::move_called == 2); assert(T::move_called <= 2);

350

Extra space before == here and on 370.

351

Non-portable. Replace with LIBCPP_ASSERT(T2::move_called == 1); assert(T2::move_called <= 1);

353

non-portable. s/b

if (T2::move_called != 0)
    assert(v2.valueless_by_exception());
else
    assert(std::get<1>(v2) == 100);

368

This line is a dup of 369. T1::move_called was probably intended, in which case it is non-portable and should be LIBCPP_ASSERT(T1::move_called == 1); assert(T1::move_called <= 1);

372

Non-portable. S/b:

if (T1::move_called != 0)
    assert(v1.valueless_by_exception());
else
    assert(std::get<0>(v1).value == 42);

376

This test and the next are non-portable and I can't be bothered to fix them.

404

I shouldn't have to point out that a test with the comment "testing libc++ extension" is non-portable ;)

406

guarantee

545

This should be LIBCPP_STATIC_ASSERT (SFINAE isn't mandated for member swap after LWG2749).

test/std/utilities/variant/variant.visit/visit.pass.cpp

43

MSVC complains that all four of these operator() overloads name but do not use args; removing the name shuts up the warning.

[STL_MSFT]

Found some minor issues.

test/std/utilities/variant/variant.get/get_if_index.pass.cpp

93

Technically, addressof() lives in <memory>.

test/std/utilities/variant/variant.get/get_if_type.pass.cpp

53

<memory> for addressof() (although I'll note that the other tests are saying &v).

test/std/utilities/variant/variant.get/get_index.pass.cpp

177

Technically, <utility> for move().

221

<type_traits> for integral_constant.

test/std/utilities/variant/variant.get/get_type.pass.cpp

100

<utility> move()

test/std/utilities/variant/variant.hash/hash.pass.cpp

16

"<class ..._Types>" has really terrible spacing. (Or as I like to say, "Space. The final frontier.")

test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp

34

You aren't directly including <type_traits> (not sure if "variant_test_helpers.hpp" is).

61

The sense of this #if test seems to be flipped.

test/std/utilities/variant/variant.helpers/variant_size.pass.cpp

21

No indentation! :-<

36

Need <type_traits>.

42

Hmm, is this cromulent now that empty variants are forbidden?

test/std/utilities/variant/variant.monostate/monostate.pass.cpp

21

Don't actually need <cassert> since you have no plain asserts and this is C++17.

test/std/utilities/variant/variant.relops/relops.pass.cpp

60

No space after >, but space after < above. Madness!

67

<utility> move()

test/std/utilities/variant/variant.variant/variant.assign/copy.pass.cpp

29

NoCopy doesn't even have a default ctor, how are you supposed to make one? Appears to apply to the classes below.

test/std/utilities/variant/variant.variant/variant.assign/move.pass.cpp

115

"beth". Also, "move and move constructors"?

213

<utility> move()

test/std/utilities/variant/variant.variant/variant.ctor/T.pass.cpp

66

You have like twenty different macros for enabling references.

test/std/utilities/variant/variant.variant/variant.ctor/in_place_index_init_list_Args.pass.cpp

1 ↗

(On Diff #78710)

Should this test filename contain capital A?

test/std/utilities/variant/variant.variant/variant.ctor/in_place_type_Args.pass.cpp

23 ↗

(On Diff #78710)

This file doesn't actually use <string>.

test/std/utilities/variant/variant.variant/variant.ctor/move.pass.cpp

61

Inconsistent indentation.

test/std/utilities/variant/variant.variant/variant.mod/emplace_index_args.pass.cpp

89

Why wrap here?

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

115

Postincrement? You monster!

287

happend

test/std/utilities/variant/variant.visit/visit.pass.cpp

72

Technically, <memory> for addressof().

106

<utility> move()

203

Space. The final frontier. (Occurs below)

test/support/variant_test_helpers.hpp

54

Indentation

64

<type_traits>

[EricWF]

Thanks guys! I'll address all these tomorrow!

[CaseyCarter]

test/std/utilities/variant/variant.hash/hash.pass.cpp

35

This is non-portable. The fact that both your implementation and mine pass this test suggests they both have poor QoI: There's strong opinion in the community that a variant's index should contribute to its hash value, so that e.g. variant<int, int>{in_place_index<0>, 42} and variant<int, int>{in_place_index<1>, 42} have differing hash values.

test/std/utilities/variant/variant.helpers/variant_size.pass.cpp

42

It's not forbidden to *name* variant<>; it is forbidden to *instantiate* it. The pertinent specialization of variant_size:

template <class... Types>
struct variant_size<variant<Types...>>
  : integral_constant<size_t, sizeof...(Types)> { };

is implicitly specified to not instantiate variant<Types...>.

[EricWF]

test/std/utilities/variant/variant.helpers/variant_size.pass.cpp

42

Note that there is no similar requirement that variant<void> or variant<T&> can even be named.

[EricWF]

Address almost all inline comments.

test/std/utilities/variant/variant.get/get_if_index.pass.cpp

93

I'm just changing it to &v.

test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp

34

Fixing this. Does your <variant> somehow not drag in <type_traits>?

test/std/utilities/variant/variant.variant/variant.assign/copy.pass.cpp

29

Don't care about making them. They are only here for testing SFINAE.

150

Ack. Ill rewrite these tests so they check situations the STL is not allowed to strengthen.

test/std/utilities/variant/variant.variant/variant.ctor/T.pass.cpp

66

I thought I regex replaced them all. I guess not :-(

test/std/utilities/variant/variant.variant/variant.ctor/in_place_index_init_list_Args.pass.cpp

1 ↗

(On Diff #78710)

Doesn't really matter. Making them all lower case for consistency.

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

545

Ack.

[EricWF]

Update with fixes.

[STL_MSFT]

test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp

34

Of course <variant> drags in <type_traits>, I'm just being nitpicky :-)

[CaseyCarter]

Other than the note in variant.variant\variant.swap\swap.pass.cpp, all passes now pass and all fails now fail with our implementation.

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

488

This instantiates variant<int, NotSwappable>::swap without meeting the requirements thereof (i.e., our member swap does not SFINAE).

[CaseyCarter]

test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp

34

STL's internal compiler is well-known for being more strict than any shipping compiler.

[EricWF]

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

488

Forgot to wrap that in a LIBCPP_ONLY.

[EricWF]

Wrap explicit instantiation in LIBCPP_ONLY block.

[EricWF]

Checking these into libc++ shortly. (But I'm disabling them for libc++ for obvious reasons).

[EricWF]

r287728.

test/std/utilities/variant/variant.hash/hash.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class... Types> struct hash<variant<Types...>>;
+// template <> struct hash<monostate>;
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+namespace std {
+template <> struct hash<::MakeEmptyT> {
+  size_t operator()(::MakeEmptyT const &) const {
+    assert(false);
+    return 0;
+  }
+};
+}
+#endif
+
+void test_hash_variant() {
+  {
+    using V = std::variant<int, long, int>;
+    using H = std::hash<V>;
+    const V v(std::in_place_index<0>, 42);
+    const V v_copy = v;
+    V v2(std::in_place_index<0>, 100);
+    const V v3(std::in_place_index<2>, 42);
+    const H h{};
+    assert(h(v) == h(v));
+    assert(h(v) != h(v2));
+    assert(h(v) == h(v_copy));
+    {
+      ASSERT_SAME_TYPE(decltype(h(v)), std::size_t);
+      static_assert(std::is_copy_constructible<H>::value, "");
+    }
+  }
+  {
+    using V = std::variant<std::monostate, int, long, const char *>;
+    using H = std::hash<V>;
+    const char *str = "hello";
+    const V v0;
+    const V v0_other;
+    const V v1(42);
+    const V v1_other(100);
+    V v2(100l);
+    V v2_other(999l);
+    V v3(str);
+    V v3_other("not hello");
+    const H h{};
+    assert(h(v0) == h(v0));
+    assert(h(v0) == h(v0_other));
+    assert(h(v1) == h(v1));
+    assert(h(v1) != h(v1_other));
+    assert(h(v2) == h(v2));
+    assert(h(v2) != h(v2_other));
+    assert(h(v3) == h(v3));
+    assert(h(v3) != h(v3_other));
+    assert(h(v0) != h(v1));
+    assert(h(v0) != h(v2));
+    assert(h(v0) != h(v3));
+    assert(h(v1) != h(v2));
+    assert(h(v1) != h(v3));
+    assert(h(v2) != h(v3));
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    using H = std::hash<V>;
+    V v;
+    makeEmpty(v);
+    V v2;
+    makeEmpty(v2);
+    const H h{};
+    assert(h(v) == h(v2));
+  }
+#endif
+}
+
+void test_hash_monostate() {
+  using H = std::hash<std::monostate>;
+  const H h{};
+  std::monostate m1{};
+  const std::monostate m2{};
+  assert(h(m1) == h(m1));
+  assert(h(m2) == h(m2));
+  assert(h(m1) == h(m2));
+  {
+    ASSERT_SAME_TYPE(decltype(h(m1)), std::size_t);
+    static_assert(std::is_copy_constructible<H>::value, "");
+  }
+}
+
+int main() {
+  test_hash_variant();
+  test_hash_monostate();
+}

test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <size_t I, class T> struct variant_alternative; // undefined
+// template <size_t I, class T> struct variant_alternative<I, const T>;
+// template <size_t I, class T> struct variant_alternative<I, volatile T>;
+// template <size_t I, class T> struct variant_alternative<I, const volatile T>;
+// template <size_t I, class T>
+//   using variant_alternative_t = typename variant_alternative<I, T>::type;
+//
+// template <size_t I, class... Types>
+//    struct variant_alternative<I, variant<Types...>>;
+
+#include <memory>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+template <class V, size_t I, class E> void test() {
+  static_assert(
+      std::is_same_v<typename std::variant_alternative<I, V>::type, E>, "");
+  static_assert(
+      std::is_same_v<typename std::variant_alternative<I, const V>::type,
+                     const E>,
+      "");
+  static_assert(
+      std::is_same_v<typename std::variant_alternative<I, volatile V>::type,
+                     volatile E>,
+      "");
+  static_assert(
+      std::is_same_v<
+          typename std::variant_alternative<I, const volatile V>::type,
+          const volatile E>,
+      "");
+  static_assert(std::is_same_v<std::variant_alternative_t<I, V>, E>, "");
+  static_assert(std::is_same_v<std::variant_alternative_t<I, const V>, const E>,
+                "");
+  static_assert(
+      std::is_same_v<std::variant_alternative_t<I, volatile V>, volatile E>,
+      "");
+  static_assert(std::is_same_v<std::variant_alternative_t<I, const volatile V>,
+                               const volatile E>,
+                "");
+}
+
+int main() {
+  {
+    using V = std::variant<int, void *, const void *, long double>;
+    test<V, 0, int>();
+    test<V, 1, void *>();
+    test<V, 2, const void *>();
+    test<V, 3, long double>();
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, int &, int const &, int &&, long double>;
+    test<V, 0, int>();
+    test<V, 1, int &>();
+    test<V, 2, int const &>();
+    test<V, 3, int &&>();
+    test<V, 4, long double>();
+  }
+#endif
+}

test/std/utilities/variant/variant.helpers/variant_size.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class T> struct variant_size; // undefined
+// template <class T> struct variant_size<const T>;
+// template <class T> struct variant_size<volatile T>;
+// template <class T> struct variant_size<const volatile T>;
+// template <class T> constexpr size_t variant_size_v
+//     = variant_size<T>::value;
+
+#include <memory>
+#include <type_traits>
+#include <variant>
+
+template <class V, size_t E> void test() {
+  static_assert(std::variant_size<V>::value == E, "");
+  static_assert(std::variant_size<const V>::value == E, "");
+  static_assert(std::variant_size<volatile V>::value == E, "");
+  static_assert(std::variant_size<const volatile V>::value == E, "");
+  static_assert(std::variant_size_v<V> == E, "");
+  static_assert(std::variant_size_v<const V> == E, "");
+  static_assert(std::variant_size_v<volatile V> == E, "");
+  static_assert(std::variant_size_v<const volatile V> == E, "");
+  static_assert(std::is_base_of<std::integral_constant<std::size_t, E>,
+                                std::variant_size<V>>::value,
+                "");
+};
+
+int main() {
+  test<std::variant<>, 0>();
+  test<std::variant<void *>, 1>();
+  test<std::variant<long, long, void *, double>, 4>();
+}

test/std/utilities/variant/variant.bad_variant_access/bad_variant_access.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+/*
+
+ class bad_variant_access : public exception {
+public:
+  bad_variant_access() noexcept;
+  virtual const char* what() const noexcept;
+};
+
+*/
+
+#include <cassert>
+#include <exception>
+#include <type_traits>
+#include <variant>
+
+int main() {
+  static_assert(std::is_base_of<std::exception, std::bad_variant_access>::value,
+                "");
+  static_assert(noexcept(std::bad_variant_access{}), "must be noexcept");
+  static_assert(noexcept(std::bad_variant_access{}.what()), "must be noexcept");
+  std::bad_variant_access ex;
+  assert(ex.what());
+}

test/std/utilities/variant/variant.general/nothing_to_do.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+int main() {}

test/std/utilities/variant/variant.get/get_if_index.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <size_t I, class... Types>
+//  constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
+//   get_if(variant<Types...>* v) noexcept;
+// template <size_t I, class... Types>
+//  constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
+//   get_if(const variant<Types...>* v) noexcept;
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include <cassert>
+#include <memory>
+#include <variant>
+
+void test_const_get_if() {
+  {
+    using V = std::variant<int>;
+    constexpr const V *v = nullptr;
+    static_assert(std::get_if<0>(v) == nullptr, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42);
+    ASSERT_NOEXCEPT(std::get_if<0>(&v));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int const *);
+    static_assert(*std::get_if<0>(&v) == 42, "");
+    static_assert(std::get_if<1>(&v) == nullptr, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get_if<1>(&v)), long const *);
+    static_assert(*std::get_if<1>(&v) == 42, "");
+    static_assert(std::get_if<0>(&v) == nullptr, "");
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), const int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+#endif
+}
+
+void test_get_if() {
+  {
+    using V = std::variant<int>;
+    V *v = nullptr;
+    assert(std::get_if<0>(v) == nullptr);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42);
+    ASSERT_NOEXCEPT(std::get_if<0>(&v));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int *);
+    assert(*std::get_if<0>(&v) == 42);
+    assert(std::get_if<1>(&v) == nullptr);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get_if<1>(&v)), long *);
+    assert(*std::get_if<1>(&v) == 42);
+    assert(std::get_if<0>(&v) == nullptr);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), const int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<0>(&v)), const int *);
+    assert(std::get_if<0>(&v) == &x);
+  }
+#endif
+}
+
+int main() {
+  test_const_get_if();
+  test_get_if();
+}

test/std/utilities/variant/variant.get/get_if_type.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+//  template <class T, class... Types>
+//  constexpr add_pointer_t<T> get_if(variant<Types...>* v) noexcept;
+// template <class T, class... Types>
+//  constexpr add_pointer_t<const T> get_if(const variant<Types...>* v)
+//  noexcept;
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include <cassert>
+#include <variant>
+
+void test_const_get_if() {
+  {
+    using V = std::variant<int>;
+    constexpr const V *v = nullptr;
+    static_assert(std::get_if<int>(v) == nullptr, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42);
+    ASSERT_NOEXCEPT(std::get_if<int>(&v));
+    ASSERT_SAME_TYPE(decltype(std::get_if<int>(&v)), int const *);
+    static_assert(*std::get_if<int>(&v) == 42, "");
+    static_assert(std::get_if<long>(&v) == nullptr, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get_if<long>(&v)), long const *);
+    static_assert(*std::get_if<long>(&v) == 42, "");
+    static_assert(std::get_if<int>(&v) == nullptr, "");
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<int &>(&v)), int *);
+    assert(std::get_if<int &>(&v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<int &&>(&v)), int *);
+    assert(std::get_if<int &&>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<const int &&>(&v)), const int *);
+    assert(std::get_if<const int &&>(&v) == &x);
+  }
+#endif
+}
+
+void test_get_if() {
+  {
+    using V = std::variant<int>;
+    V *v = nullptr;
+    assert(std::get_if<int>(v) == nullptr);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42);
+    ASSERT_NOEXCEPT(std::get_if<int>(&v));
+    ASSERT_SAME_TYPE(decltype(std::get_if<int>(&v)), int *);
+    assert(*std::get_if<int>(&v) == 42);
+    assert(std::get_if<long>(&v) == nullptr);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get_if<long>(&v)), long *);
+    assert(*std::get_if<long>(&v) == 42);
+    assert(std::get_if<int>(&v) == nullptr);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<int &>(&v)), int *);
+    assert(std::get_if<int &>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get_if<const int &>(&v)), const int *);
+    assert(std::get_if<const int &>(&v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<int &&>(&v)), int *);
+    assert(std::get_if<int &&>(&v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get_if<const int &&>(&v)), const int *);
+    assert(std::get_if<const int &&>(&v) == &x);
+  }
+#endif
+}
+
+int main() {
+  test_const_get_if();
+  test_get_if();
+}

test/std/utilities/variant/variant.get/get_index.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <size_t I, class... Types>
+//   constexpr variant_alternative_t<I, variant<Types...>>&
+//   get(variant<Types...>& v);
+// template <size_t I, class... Types>
+//   constexpr variant_alternative_t<I, variant<Types...>>&&
+//   get(variant<Types...>&& v);
+// template <size_t I, class... Types>
+//   constexpr variant_alternative_t<I, variant<Types...>> const& get(const
+//   variant<Types...>& v);
+// template <size_t I, class... Types>
+//  constexpr variant_alternative_t<I, variant<Types...>> const&& get(const
+//  variant<Types...>&& v);
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include <cassert>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+void test_const_lvalue_get() {
+  {
+    using V = std::variant<int>;
+    constexpr V v(42);
+    // ASSERT_NOT_NOEXCEPT(std::get<0>(v));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int const &);
+    static_assert(std::get<0>(v) == 42, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<1>(v)), long const &);
+    static_assert(std::get<1>(v) == 42, "");
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int &);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int &);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), const int &);
+    assert(&std::get<0>(v) == &x);
+  }
+#endif
+}
+
+void test_lvalue_get() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<0>(v));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int &);
+    assert(std::get<0>(v) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<1>(v)), long &);
+    assert(std::get<1>(v) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int &);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), const int &);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int &);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), const int &);
+    assert(&std::get<0>(v) == &x);
+  }
+#endif
+}
+
+void test_rvalue_get() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<0>(std::move(v)));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), int &&);
+    assert(std::get<0>(std::move(v)) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<1>(std::move(v))), long &&);
+    assert(std::get<1>(std::move(v)) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), int &);
+    assert(&std::get<0>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), const int &);
+    assert(&std::get<0>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), int &&);
+    int &&xref = std::get<0>(std::move(v));
+    assert(&xref == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), const int &&);
+    const int &&xref = std::get<0>(std::move(v));
+    assert(&xref == &x);
+  }
+#endif
+}
+
+void test_const_rvalue_get() {
+  {
+    using V = std::variant<int>;
+    const V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<0>(std::move(v)));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), const int &&);
+    assert(std::get<0>(std::move(v)) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    const V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<1>(std::move(v))), const long &&);
+    assert(std::get<1>(std::move(v)) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), int &);
+    assert(&std::get<0>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), const int &);
+    assert(&std::get<0>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), int &&);
+    int &&xref = std::get<0>(std::move(v));
+    assert(&xref == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(std::move(v))), const int &&);
+    const int &&xref = std::get<0>(std::move(v));
+    assert(&xref == &x);
+  }
+#endif
+}
+
+template <std::size_t I> using Idx = std::integral_constant<size_t, I>;
+
+void test_throws_for_all_value_categories() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<int, long>;
+  V v0(42);
+  const V &cv0 = v0;
+  assert(v0.index() == 0);
+  V v1(42l);
+  const V &cv1 = v1;
+  assert(v1.index() == 1);
+  std::integral_constant<size_t, 0> zero;
+  std::integral_constant<size_t, 1> one;
+  auto test = [](auto idx, auto &&v) {
+    using Idx = decltype(idx);
+    try {
+      std::get<Idx::value>(std::forward<decltype(v)>(v));
+    } catch (std::bad_variant_access const &) {
+      return true;
+    } catch (...) { /* ... */
+    }
+    return false;
+  };
+  { // lvalue test cases
+    assert(test(one, v0));
+    assert(test(zero, v1));
+  }
+  { // const lvalue test cases
+    assert(test(one, cv0));
+    assert(test(zero, cv1));
+  }
+  { // rvalue test cases
+    assert(test(one, std::move(v0)));
+    assert(test(zero, std::move(v1)));
+  }
+  { // const rvalue test cases
+    assert(test(one, std::move(cv0)));
+    assert(test(zero, std::move(cv1)));
+  }
+#endif
+}
+
+int main() {
+  test_const_lvalue_get();
+  test_lvalue_get();
+  test_rvalue_get();
+  test_const_rvalue_get();
+  test_throws_for_all_value_categories();
+}

test/std/utilities/variant/variant.get/get_type.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class T, class... Types> constexpr T& get(variant<Types...>& v);
+// template <class T, class... Types> constexpr T&& get(variant<Types...>&& v);
+// template <class T, class... Types> constexpr const T& get(const
+// variant<Types...>& v);
+// template <class T, class... Types> constexpr const T&& get(const
+// variant<Types...>&& v);
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include <cassert>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+void test_const_lvalue_get() {
+  {
+    using V = std::variant<int>;
+    constexpr V v(42);
+    // ASSERT_NOT_NOEXCEPT(std::get<int>(v));
+    ASSERT_SAME_TYPE(decltype(std::get<0>(v)), int const &);
+    static_assert(std::get<int>(v) == 42, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<long>(v)), long const &);
+    static_assert(std::get<long>(v) == 42, "");
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<int &>(v)), int &);
+    assert(&std::get<int &>(v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<int &&>(v)), int &);
+    assert(&std::get<int &&>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<const int &&>(v)), const int &);
+    assert(&std::get<const int &&>(v) == &x);
+  }
+#endif
+}
+
+void test_lvalue_get() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<int>(v));
+    ASSERT_SAME_TYPE(decltype(std::get<int>(v)), int &);
+    assert(std::get<int>(v) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<long>(v)), long &);
+    assert(std::get<long>(v) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<int &>(v)), int &);
+    assert(&std::get<int &>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<const int &>(v)), const int &);
+    assert(&std::get<const int &>(v) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<int &&>(v)), int &);
+    assert(&std::get<int &&>(v) == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<const int &&>(v)), const int &);
+    assert(&std::get<const int &&>(v) == &x);
+  }
+#endif
+}
+
+void test_rvalue_get() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<int>(std::move(v)));
+    ASSERT_SAME_TYPE(decltype(std::get<int>(std::move(v))), int &&);
+    assert(std::get<int>(std::move(v)) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<long>(std::move(v))), long &&);
+    assert(std::get<long>(std::move(v)) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<int &>(std::move(v))), int &);
+    assert(&std::get<int &>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<const int &>(std::move(v))),
+                     const int &);
+    assert(&std::get<const int &>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<int &&>(std::move(v))), int &&);
+    int &&xref = std::get<int &&>(std::move(v));
+    assert(&xref == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<const int &&>(std::move(v))),
+                     const int &&);
+    const int &&xref = std::get<const int &&>(std::move(v));
+    assert(&xref == &x);
+  }
+#endif
+}
+
+void test_const_rvalue_get() {
+  {
+    using V = std::variant<int>;
+    const V v(42);
+    ASSERT_NOT_NOEXCEPT(std::get<int>(std::move(v)));
+    ASSERT_SAME_TYPE(decltype(std::get<int>(std::move(v))), const int &&);
+    assert(std::get<int>(std::move(v)) == 42);
+  }
+  {
+    using V = std::variant<int, long>;
+    const V v(42l);
+    ASSERT_SAME_TYPE(decltype(std::get<long>(std::move(v))), const long &&);
+    assert(std::get<long>(std::move(v)) == 42);
+  }
+// FIXME: Remove these once reference support is reinstated
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<int &>(std::move(v))), int &);
+    assert(&std::get<int &>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<const int &>;
+    int x = 42;
+    const V v(x);
+    ASSERT_SAME_TYPE(decltype(std::get<const int &>(std::move(v))),
+                     const int &);
+    assert(&std::get<const int &>(std::move(v)) == &x);
+  }
+  {
+    using V = std::variant<int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<int &&>(std::move(v))), int &&);
+    int &&xref = std::get<int &&>(std::move(v));
+    assert(&xref == &x);
+  }
+  {
+    using V = std::variant<const int &&>;
+    int x = 42;
+    const V v(std::move(x));
+    ASSERT_SAME_TYPE(decltype(std::get<const int &&>(std::move(v))),
+                     const int &&);
+    const int &&xref = std::get<const int &&>(std::move(v));
+    assert(&xref == &x);
+  }
+#endif
+}
+
+template <class Tp> struct identity { using type = Tp; };
+
+void test_throws_for_all_value_categories() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<int, long>;
+  V v0(42);
+  const V &cv0 = v0;
+  assert(v0.index() == 0);
+  V v1(42l);
+  const V &cv1 = v1;
+  assert(v1.index() == 1);
+  identity<int> zero;
+  identity<long> one;
+  auto test = [](auto idx, auto &&v) {
+    using Idx = decltype(idx);
+    try {
+      std::get<typename Idx::type>(std::forward<decltype(v)>(v));
+    } catch (std::bad_variant_access const &) {
+      return true;
+    } catch (...) { /* ... */
+    }
+    return false;
+  };
+  { // lvalue test cases
+    assert(test(one, v0));
+    assert(test(zero, v1));
+  }
+  { // const lvalue test cases
+    assert(test(one, cv0));
+    assert(test(zero, cv1));
+  }
+  { // rvalue test cases
+    assert(test(one, std::move(v0)));
+    assert(test(zero, std::move(v1)));
+  }
+  { // const rvalue test cases
+    assert(test(one, std::move(cv0)));
+    assert(test(zero, std::move(cv1)));
+  }
+#endif
+}
+
+int main() {
+  test_const_lvalue_get();
+  test_lvalue_get();
+  test_rvalue_get();
+  test_const_rvalue_get();
+  test_throws_for_all_value_categories();
+}

test/std/utilities/variant/variant.get/holds_alternative.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class T, class... Types>
+// constexpr bool holds_alternative(const variant<Types...>& v) noexcept;
+
+#include <variant>
+
+int main() {
+  {
+    using V = std::variant<int>;
+    constexpr V v;
+    static_assert(std::holds_alternative<int>(v), "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v;
+    static_assert(std::holds_alternative<int>(v), "");
+    static_assert(!std::holds_alternative<long>(v), "");
+  }
+  { // noexcept test
+    using V = std::variant<int>;
+    const V v;
+    static_assert(noexcept(std::holds_alternative<int>(v)), "must be noexcept");
+  }
+}

test/std/utilities/variant/variant.monostate.relops/relops.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// constexpr bool operator<(monostate, monostate) noexcept { return false; }
+// constexpr bool operator>(monostate, monostate) noexcept { return false; }
+// constexpr bool operator<=(monostate, monostate) noexcept { return true; }
+// constexpr bool operator>=(monostate, monostate) noexcept { return true; }
+// constexpr bool operator==(monostate, monostate) noexcept { return true; }
+// constexpr bool operator!=(monostate, monostate) noexcept { return false; }
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+int main() {
+  using M = std::monostate;
+  constexpr M m1{};
+  constexpr M m2{};
+  {
+    static_assert((m1 < m2) == false, "");
+    static_assert(noexcept(m1 < m2), "");
+  }
+  {
+    static_assert((m1 > m2) == false, "");
+    static_assert(noexcept(m1 > m2), "");
+  }
+  {
+    static_assert((m1 <= m2) == true, "");
+    static_assert(noexcept(m1 <= m2), "");
+  }
+  {
+    static_assert((m1 >= m2) == true, "");
+    static_assert(noexcept(m1 >= m2), "");
+  }
+  {
+    static_assert((m1 == m2) == true, "");
+    static_assert(noexcept(m1 == m2), "");
+  }
+  {
+    static_assert((m1 != m2) == false, "");
+    static_assert(noexcept(m1 != m2), "");
+  }
+}

test/std/utilities/variant/variant.monostate/monostate.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// struct monostate {};
+
+#include <type_traits>
+#include <variant>
+
+int main() {
+  using M = std::monostate;
+  static_assert(std::is_trivially_default_constructible<M>::value, "");
+  static_assert(std::is_trivially_copy_constructible<M>::value, "");
+  static_assert(std::is_trivially_copy_assignable<M>::value, "");
+  static_assert(std::is_trivially_destructible<M>::value, "");
+  constexpr M m{};
+  ((void)m);
+}

test/std/utilities/variant/variant.relops/relops.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types>
+// constexpr bool
+// operator==(variant<Types...> const&, variant<Types...> const&) noexcept;
+//
+// template <class ...Types>
+// constexpr bool
+// operator!=(variant<Types...> const&, variant<Types...> const&) noexcept;
+//
+// template <class ...Types>
+// constexpr bool
+// operator<(variant<Types...> const&, variant<Types...> const&) noexcept;
+//
+// template <class ...Types>
+// constexpr bool
+// operator>(variant<Types...> const&, variant<Types...> const&) noexcept;
+//
+// template <class ...Types>
+// constexpr bool
+// operator<=(variant<Types...> const&, variant<Types...> const&) noexcept;
+//
+// template <class ...Types>
+// constexpr bool
+// operator>=(variant<Types...> const&, variant<Types...> const&) noexcept;
+
+#include <cassert>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+#include "test_macros.h"
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct MakeEmptyT {
+  MakeEmptyT() = default;
+  MakeEmptyT(MakeEmptyT &&) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT &&) { throw 42; }
+};
+inline bool operator==(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+inline bool operator!=(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+inline bool operator<(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+inline bool operator<=(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+inline bool operator>(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+inline bool operator>=(MakeEmptyT const &, MakeEmptyT const &) {
+  assert(false);
+  return false;
+}
+
+template <class Variant> void makeEmpty(Variant &v) {
+  Variant v2(std::in_place_type<MakeEmptyT>);
+  try {
+    v = std::move(v2);
+    assert(false);
+  } catch (...) {
+    assert(v.valueless_by_exception());
+  }
+}
+#endif // TEST_HAS_NO_EXCEPTIONS
+
+void test_equality() {
+  {
+    using V = std::variant<int, long>;
+    constexpr V v1(42);
+    constexpr V v2(42);
+    static_assert(v1 == v2, "");
+    static_assert(v2 == v1, "");
+    static_assert(!(v1 != v2), "");
+    static_assert(!(v2 != v1), "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v1(42);
+    constexpr V v2(43);
+    static_assert(!(v1 == v2), "");
+    static_assert(!(v2 == v1), "");
+    static_assert(v1 != v2, "");
+    static_assert(v2 != v1, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v1(42);
+    constexpr V v2(42l);
+    static_assert(!(v1 == v2), "");
+    static_assert(!(v2 == v1), "");
+    static_assert(v1 != v2, "");
+    static_assert(v2 != v1, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v1(42l);
+    constexpr V v2(42l);
+    static_assert(v1 == v2, "");
+    static_assert(v2 == v1, "");
+    static_assert(!(v1 != v2), "");
+    static_assert(!(v2 != v1), "");
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    V v2;
+    makeEmpty(v2);
+    assert(!(v1 == v2));
+    assert(!(v2 == v1));
+    assert(v1 != v2);
+    assert(v2 != v1);
+  }
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    makeEmpty(v1);
+    V v2;
+    assert(!(v1 == v2));
+    assert(!(v2 == v1));
+    assert(v1 != v2);
+    assert(v2 != v1);
+  }
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    makeEmpty(v1);
+    V v2;
+    makeEmpty(v2);
+    assert(v1 == v2);
+    assert(v2 == v1);
+    assert(!(v1 != v2));
+    assert(!(v2 != v1));
+  }
+#endif
+}
+
+template <class Var>
+constexpr bool test_less(Var const &l, Var const &r, bool expect_less,
+                         bool expect_greater) {
+  return ((l < r) == expect_less) && (!(l >= r) == expect_less) &&
+         ((l > r) == expect_greater) && (!(l <= r) == expect_greater);
+}
+
+void test_relational() {
+  { // same index, same value
+    using V = std::variant<int, long>;
+    constexpr V v1(1);
+    constexpr V v2(1);
+    static_assert(test_less(v1, v2, false, false), "");
+  }
+  { // same index, value < other_value
+    using V = std::variant<int, long>;
+    constexpr V v1(0);
+    constexpr V v2(1);
+    static_assert(test_less(v1, v2, true, false), "");
+  }
+  { // same index, value > other_value
+    using V = std::variant<int, long>;
+    constexpr V v1(1);
+    constexpr V v2(0);
+    static_assert(test_less(v1, v2, false, true), "");
+  }
+  { // LHS.index() < RHS.index()
+    using V = std::variant<int, long>;
+    constexpr V v1(0);
+    constexpr V v2(0l);
+    static_assert(test_less(v1, v2, true, false), "");
+  }
+  { // LHS.index() > RHS.index()
+    using V = std::variant<int, long>;
+    constexpr V v1(0l);
+    constexpr V v2(0);
+    static_assert(test_less(v1, v2, false, true), "");
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  { // LHS.index() < RHS.index(), RHS is empty
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    V v2;
+    makeEmpty(v2);
+    assert(test_less(v1, v2, false, true));
+  }
+  { // LHS.index() > RHS.index(), LHS is empty
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    makeEmpty(v1);
+    V v2;
+    assert(test_less(v1, v2, true, false));
+  }
+  { // LHS.index() == RHS.index(), LHS and RHS are empty
+    using V = std::variant<int, MakeEmptyT>;
+    V v1;
+    makeEmpty(v1);
+    V v2;
+    makeEmpty(v2);
+    assert(test_less(v1, v2, false, false));
+  }
+#endif
+}
+
+int main() {
+  test_equality();
+  test_relational();
+}

test/std/utilities/variant/variant.synopsis/variant_npos.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// constexpr size_t variant_npos = -1;
+
+#include <variant>
+
+int main() {
+  static_assert(std::variant_npos == static_cast<std::size_t>(-1), "");
+}

test/std/utilities/variant/variant.variant/variant.assign/T.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class T>
+// variant& operator=(T&&) noexcept(see below);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+namespace MetaHelpers {
+
+struct Dummy {
+  Dummy() = default;
+};
+
+struct ThrowsCtorT {
+  ThrowsCtorT(int) noexcept(false) {}
+  ThrowsCtorT &operator=(int) noexcept { return *this; }
+};
+
+struct ThrowsAssignT {
+  ThrowsAssignT(int) noexcept {}
+  ThrowsAssignT &operator=(int) noexcept(false) { return *this; }
+};
+
+struct NoThrowT {
+  NoThrowT(int) noexcept {}
+  NoThrowT &operator=(int) noexcept { return *this; }
+};
+
+} // namespace MetaHelpers
+
+namespace RuntimeHelpers {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+
+struct ThrowsCtorT {
+  int value;
+  ThrowsCtorT() : value(0) {}
+  ThrowsCtorT(int) noexcept(false) { throw 42; }
+  ThrowsCtorT &operator=(int v) noexcept {
+    value = v;
+    return *this;
+  }
+};
+
+struct ThrowsAssignT {
+  int value;
+  ThrowsAssignT() : value(0) {}
+  ThrowsAssignT(int v) noexcept : value(v) {}
+  ThrowsAssignT &operator=(int) noexcept(false) { throw 42; }
+};
+
+struct NoThrowT {
+  int value;
+  NoThrowT() : value(0) {}
+  NoThrowT(int v) noexcept : value(v) {}
+  NoThrowT &operator=(int v) noexcept {
+    value = v;
+    return *this;
+  }
+};
+
+#endif // !defined(TEST_HAS_NO_EXCEPTIONS)
+} // namespace RuntimeHelpers
+
+void test_T_assignment_noexcept() {
+  using namespace MetaHelpers;
+  {
+    using V = std::variant<Dummy, NoThrowT>;
+    static_assert(std::is_nothrow_assignable<V, int>::value, "");
+  }
+  {
+    using V = std::variant<Dummy, ThrowsCtorT>;
+    static_assert(!std::is_nothrow_assignable<V, int>::value, "");
+  }
+  {
+    using V = std::variant<Dummy, ThrowsAssignT>;
+    static_assert(!std::is_nothrow_assignable<V, int>::value, "");
+  }
+}
+
+void test_T_assignment_sfinae() {
+  {
+    using V = std::variant<long, unsigned>;
+    static_assert(!std::is_assignable<V, int>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<std::string, std::string>;
+    static_assert(!std::is_assignable<V, const char *>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<std::string, void *>;
+    static_assert(!std::is_assignable<V, int>::value, "no matching operator=");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, int &&>;
+    static_assert(!std::is_assignable<V, int>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<int, int const &>;
+    static_assert(!std::is_assignable<V, int>::value, "ambiguous");
+  }
+#endif
+}
+
+void test_T_assignment_basic() {
+  {
+    std::variant<int> v(43);
+    v = 42;
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == 42);
+  }
+  {
+    std::variant<int, long> v(43l);
+    v = 42;
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == 42);
+    v = 43l;
+    assert(v.index() == 1);
+    assert(std::get<1>(v) == 43);
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &, int &&, long>;
+    int x = 42;
+    V v(43l);
+    v = x;
+    assert(v.index() == 0);
+    assert(&std::get<0>(v) == &x);
+    v = std::move(x);
+    assert(v.index() == 1);
+    assert(&std::get<1>(v) == &x);
+    // 'long' is selected by FUN(int const&) since 'int const&' cannot bind
+    // to 'int&'.
+    int const &cx = x;
+    v = cx;
+    assert(v.index() == 2);
+    assert(std::get<2>(v) == 42);
+  }
+#endif
+}
+
+void test_T_assignment_performs_construction() {
+  using namespace RuntimeHelpers;
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<std::string, ThrowsCtorT>;
+    V v(std::in_place_type<std::string>, "hello");
+    try {
+      v = 42;
+    } catch (...) { /* ... */
+    }
+    assert(v.valueless_by_exception());
+  }
+  {
+    using V = std::variant<ThrowsAssignT, std::string>;
+    V v(std::in_place_type<std::string>, "hello");
+    v = 42;
+    assert(v.index() == 0);
+    assert(std::get<0>(v).value == 42);
+  }
+#endif
+}
+
+void test_T_assignment_performs_assignment() {
+  using namespace RuntimeHelpers;
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<ThrowsCtorT>;
+    V v;
+    v = 42;
+    assert(v.index() == 0);
+    assert(std::get<0>(v).value == 42);
+  }
+  {
+    using V = std::variant<ThrowsCtorT, std::string>;
+    V v;
+    v = 42;
+    assert(v.index() == 0);
+    assert(std::get<0>(v).value == 42);
+  }
+  {
+    using V = std::variant<ThrowsAssignT>;
+    V v(100);
+    try {
+      v = 42;
+      assert(false);
+    } catch (...) { /* ... */
+    }
+    assert(v.index() == 0);
+    assert(std::get<0>(v).value == 100);
+  }
+  {
+    using V = std::variant<std::string, ThrowsAssignT>;
+    V v(100);
+    try {
+      v = 42;
+      assert(false);
+    } catch (...) { /* ... */
+    }
+    assert(v.index() == 1);
+    assert(std::get<1>(v).value == 100);
+  }
+#endif
+}
+
+int main() {
+  test_T_assignment_basic();
+  test_T_assignment_performs_construction();
+  test_T_assignment_performs_assignment();
+  test_T_assignment_noexcept();
+  test_T_assignment_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.assign/copy.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// variant& operator=(variant const&);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+
+struct NoCopy {
+  NoCopy(NoCopy const &) = delete;
+  NoCopy &operator=(NoCopy const &) = default;
+};
+
+struct NothrowCopy {
+  NothrowCopy(NothrowCopy const &) noexcept = default;
+  NothrowCopy &operator=(NothrowCopy const &) noexcept = default;
+};
+
+struct CopyOnly {
+  CopyOnly(CopyOnly const &) = default;
+  CopyOnly(CopyOnly &&) = delete;
+  CopyOnly &operator=(CopyOnly const &) = default;
+  CopyOnly &operator=(CopyOnly &&) = delete;
+};
+
+struct MoveOnly {
+  MoveOnly(MoveOnly const &) = delete;
+  MoveOnly(MoveOnly &&) = default;
+  MoveOnly &operator=(MoveOnly const &) = default;
+};
+
+struct MoveOnlyNT {
+  MoveOnlyNT(MoveOnlyNT const &) = delete;
+  MoveOnlyNT(MoveOnlyNT &&) {}
+  MoveOnlyNT &operator=(MoveOnlyNT const &) = default;
+};
+
+struct CopyAssign {
+  static int alive;
+  static int copy_construct;
+  static int copy_assign;
+  static int move_construct;
+  static int move_assign;
+  static void reset() {
+    copy_construct = copy_assign = move_construct = move_assign = alive = 0;
+  }
+  CopyAssign(int v) : value(v) { ++alive; }
+  CopyAssign(CopyAssign const &o) : value(o.value) {
+    ++alive;
+    ++copy_construct;
+  }
+  CopyAssign(CopyAssign &&o) : value(o.value) {
+    o.value = -1;
+    ++alive;
+    ++move_construct;
+  }
+  CopyAssign &operator=(CopyAssign const &o) {
+    value = o.value;
+    ++copy_assign;
+    return *this;
+  }
+  CopyAssign &operator=(CopyAssign &&o) {
+    value = o.value;
+    o.value = -1;
+    ++move_assign;
+    return *this;
+  }
+  ~CopyAssign() { --alive; }
+  int value;
+};
+
+int CopyAssign::alive = 0;
+int CopyAssign::copy_construct = 0;
+int CopyAssign::copy_assign = 0;
+int CopyAssign::move_construct = 0;
+int CopyAssign::move_assign = 0;
+
+struct CopyMaybeThrows {
+  CopyMaybeThrows(CopyMaybeThrows const &);
+  CopyMaybeThrows &operator=(CopyMaybeThrows const &);
+};
+struct CopyDoesThrow {
+  CopyDoesThrow(CopyDoesThrow const &) noexcept(false);
+  CopyDoesThrow &operator=(CopyDoesThrow const &) noexcept(false);
+};
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct CopyThrows {
+  CopyThrows() = default;
+  CopyThrows(CopyThrows const &) { throw 42; }
+  CopyThrows &operator=(CopyThrows const &) { throw 42; }
+};
+
+struct MoveThrows {
+  static int alive;
+  MoveThrows() { ++alive; }
+  MoveThrows(MoveThrows const &) { ++alive; }
+  MoveThrows(MoveThrows &&) { throw 42; }
+  MoveThrows &operator=(MoveThrows const &) { return *this; }
+  MoveThrows &operator=(MoveThrows &&) { throw 42; }
+  ~MoveThrows() { --alive; }
+};
+
+int MoveThrows::alive = 0;
+
+struct MakeEmptyT {
+  static int alive;
+  MakeEmptyT() { ++alive; }
+  MakeEmptyT(MakeEmptyT const &) {
+    ++alive;
+    // Don't throw from the copy constructor since variant's assignment
+    // operator performs a copy before committing to the assignment.
+  }
+  MakeEmptyT(MakeEmptyT &&) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT const &) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT &&) { throw 42; }
+  ~MakeEmptyT() { --alive; }
+};
+
+int MakeEmptyT::alive = 0;
+
+template <class Variant> void makeEmpty(Variant &v) {
+  Variant v2(std::in_place_type<MakeEmptyT>);
+  try {
+    v = v2;
+    assert(false);
+  } catch (...) {
+    assert(v.valueless_by_exception());
+  }
+}
+#endif // TEST_HAS_NO_EXCEPTIONS
+
+void test_copy_assignment_not_noexcept() {
+  {
+    using V = std::variant<CopyMaybeThrows>;
+    static_assert(!std::is_nothrow_copy_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, CopyDoesThrow>;
+    static_assert(!std::is_nothrow_copy_assignable<V>::value, "");
+  }
+}
+
+void test_copy_assignment_sfinae() {
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_copy_assignable<V>::value, "");
+  }
+  {
+    // variant only provides copy assignment when beth the copy and move
+    // constructors are well formed
+    using V = std::variant<int, CopyOnly>;
+    static_assert(!std::is_copy_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, NoCopy>;
+    static_assert(!std::is_copy_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(!std::is_copy_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnlyNT>;
+    static_assert(!std::is_copy_assignable<V>::value, "");
+  }
+}
+
+void test_copy_assignment_empty_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, long, MET>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+#endif
+}
+
+void test_copy_assignment_non_empty_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET>;
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_index<2>, "hello");
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+#endif
+}
+
+void test_copy_assignment_empty_non_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_index<0>, 42);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 0);
+    assert(std::get<0>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_type<std::string>, "hello");
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+  }
+#endif
+}
+
+void test_copy_assignment_same_index() {
+  {
+    using V = std::variant<int>;
+    V v1(43);
+    V v2(42);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 0);
+    assert(std::get<0>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, long, unsigned>;
+    V v1(43l);
+    V v2(42l);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, CopyAssign, unsigned>;
+    V v1(std::in_place_type<CopyAssign>, 43);
+    V v2(std::in_place_type<CopyAssign>, 42);
+    CopyAssign::reset();
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1).value == 42);
+    assert(CopyAssign::copy_construct == 0);
+    assert(CopyAssign::move_construct == 0);
+    assert(CopyAssign::copy_assign == 1);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_type<MET>);
+    MET &mref = std::get<1>(v1);
+    V v2(std::in_place_type<MET>);
+    try {
+      v1 = v2;
+      assert(false);
+    } catch (...) {
+    }
+    assert(v1.index() == 1);
+    assert(&std::get<1>(v1) == &mref);
+  }
+#endif
+}
+
+void test_copy_assignment_different_index() {
+  {
+    using V = std::variant<int, long, unsigned>;
+    V v1(43);
+    V v2(42l);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, CopyAssign, unsigned>;
+    CopyAssign::reset();
+    V v1(std::in_place_type<unsigned>, 43);
+    V v2(std::in_place_type<CopyAssign>, 42);
+    assert(CopyAssign::copy_construct == 0);
+    assert(CopyAssign::move_construct == 0);
+    assert(CopyAssign::alive == 1);
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1).value == 42);
+    assert(CopyAssign::alive == 2);
+    assert(CopyAssign::copy_construct == 1);
+    assert(CopyAssign::move_construct == 1);
+    assert(CopyAssign::copy_assign == 0);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    // Test that if copy construction throws then original value is
+    // unchanged.
+    using V = std::variant<int, CopyThrows, std::string>;
+    V v1(std::in_place_type<std::string>, "hello");
+    V v2(std::in_place_type<CopyThrows>);
+    try {
+      v1 = v2;
+      assert(false);
+    } catch (...) { /* ... */
+    }
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+  }
+  {
+    // Test that if move construction throws then the variant is left
+    // valueless by exception.
+    using V = std::variant<int, MoveThrows, std::string>;
+    V v1(std::in_place_type<std::string>, "hello");
+    V v2(std::in_place_type<MoveThrows>);
+    assert(MoveThrows::alive == 1);
+    try {
+      v1 = v2;
+      assert(false);
+    } catch (...) { /* ... */
+    }
+    assert(v1.valueless_by_exception());
+    assert(v2.index() == 1);
+    assert(MoveThrows::alive == 1);
+  }
+  {
+    using V = std::variant<int, CopyThrows, std::string>;
+    V v1(std::in_place_type<CopyThrows>);
+    V v2(std::in_place_type<std::string>, "hello");
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+    assert(v2.index() == 2);
+    assert(std::get<2>(v2) == "hello");
+  }
+  {
+    using V = std::variant<int, MoveThrows, std::string>;
+    V v1(std::in_place_type<MoveThrows>);
+    V v2(std::in_place_type<std::string>, "hello");
+    V &vref = (v1 = v2);
+    assert(&vref == &v1);
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+    assert(v2.index() == 2);
+    assert(std::get<2>(v2) == "hello");
+  }
+#endif
+}
+
+int main() {
+  test_copy_assignment_empty_empty();
+  test_copy_assignment_non_empty_empty();
+  test_copy_assignment_empty_non_empty();
+  test_copy_assignment_same_index();
+  test_copy_assignment_different_index();
+  test_copy_assignment_sfinae();
+  test_copy_assignment_not_noexcept();
+}

test/std/utilities/variant/variant.variant/variant.assign/move.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// variant& operator=(variant&&) noexcept(see below);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+struct NoCopy {
+  NoCopy(NoCopy const &) = delete;
+  NoCopy &operator=(NoCopy const &) = default;
+};
+
+struct CopyOnly {
+  CopyOnly(CopyOnly const &) = default;
+  CopyOnly(CopyOnly &&) = delete;
+  CopyOnly &operator=(CopyOnly const &) = default;
+  CopyOnly &operator=(CopyOnly &&) = delete;
+};
+
+struct MoveOnly {
+  MoveOnly(MoveOnly const &) = delete;
+  MoveOnly(MoveOnly &&) = default;
+  MoveOnly &operator=(MoveOnly const &) = delete;
+  MoveOnly &operator=(MoveOnly &&) = default;
+};
+
+struct MoveOnlyNT {
+  MoveOnlyNT(MoveOnlyNT const &) = delete;
+  MoveOnlyNT(MoveOnlyNT &&) {}
+  MoveOnlyNT &operator=(MoveOnlyNT const &) = delete;
+  MoveOnlyNT &operator=(MoveOnlyNT &&) = default;
+};
+
+struct MoveOnlyOddNothrow {
+  MoveOnlyOddNothrow(MoveOnlyOddNothrow &&) noexcept(false) {}
+  MoveOnlyOddNothrow(MoveOnlyOddNothrow const &) = delete;
+  MoveOnlyOddNothrow &operator=(MoveOnlyOddNothrow &&) noexcept = default;
+  MoveOnlyOddNothrow &operator=(MoveOnlyOddNothrow const &) = delete;
+};
+
+struct MoveAssignOnly {
+  MoveAssignOnly(MoveAssignOnly &&) = delete;
+  MoveAssignOnly &operator=(MoveAssignOnly &&) = default;
+};
+
+struct MoveAssign {
+  static int move_construct;
+  static int move_assign;
+  static void reset() { move_construct = move_assign = 0; }
+  MoveAssign(int v) : value(v) {}
+  MoveAssign(MoveAssign &&o) : value(o.value) {
+    ++move_construct;
+    o.value = -1;
+  }
+  MoveAssign &operator=(MoveAssign &&o) {
+    value = o.value;
+    ++move_assign;
+    o.value = -1;
+    return *this;
+  }
+  int value;
+};
+
+int MoveAssign::move_construct = 0;
+int MoveAssign::move_assign = 0;
+
+void test_move_assignment_noexcept() {
+  {
+    using V = std::variant<int>;
+    static_assert(std::is_nothrow_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<MoveOnly>;
+    static_assert(std::is_nothrow_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_nothrow_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(std::is_nothrow_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<MoveOnlyNT>;
+    static_assert(!std::is_nothrow_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<MoveOnlyOddNothrow>;
+    static_assert(!std::is_nothrow_move_assignable<V>::value, "");
+  }
+}
+
+void test_move_assignment_sfinae() {
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_move_assignable<V>::value, "");
+  }
+  {
+    // variant only provides move assignment when both the move constructor
+    // and move assignment operator are well formed.
+    using V = std::variant<int, CopyOnly>;
+    static_assert(!std::is_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, NoCopy>;
+    static_assert(!std::is_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(std::is_move_assignable<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnlyNT>;
+    static_assert(std::is_move_assignable<V>::value, "");
+  }
+  {
+    // variant only provides move assignment when the types also provide
+    // a move constructor.
+    using V = std::variant<int, MoveAssignOnly>;
+    static_assert(!std::is_move_assignable<V>::value, "");
+  }
+}
+
+void test_move_assignment_empty_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, long, MET>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+#endif
+}
+
+void test_move_assignment_non_empty_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET>;
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_index<2>, "hello");
+    V v2(std::in_place_index<0>);
+    makeEmpty(v2);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+#endif
+}
+
+void test_move_assignment_empty_non_empty() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_index<0>, 42);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 0);
+    assert(std::get<0>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_index<0>);
+    makeEmpty(v1);
+    V v2(std::in_place_type<std::string>, "hello");
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+  }
+#endif
+}
+
+void test_move_assignment_same_index() {
+  {
+    using V = std::variant<int>;
+    V v1(43);
+    V v2(42);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 0);
+    assert(std::get<0>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, long, unsigned>;
+    V v1(43l);
+    V v2(42l);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, MoveAssign, unsigned>;
+    V v1(std::in_place_type<MoveAssign>, 43);
+    V v2(std::in_place_type<MoveAssign>, 42);
+    MoveAssign::reset();
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1).value == 42);
+    assert(MoveAssign::move_construct == 0);
+    assert(MoveAssign::move_assign == 1);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_type<MET>);
+    MET &mref = std::get<1>(v1);
+    V v2(std::in_place_type<MET>);
+    try {
+      v1 = std::move(v2);
+      assert(false);
+    } catch (...) {
+    }
+    assert(v1.index() == 1);
+    assert(&std::get<1>(v1) == &mref);
+  }
+#endif
+}
+
+void test_move_assignment_different_index() {
+  {
+    using V = std::variant<int, long, unsigned>;
+    V v1(43);
+    V v2(42l);
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1) == 42);
+  }
+  {
+    using V = std::variant<int, MoveAssign, unsigned>;
+    V v1(std::in_place_type<unsigned>, 43);
+    V v2(std::in_place_type<MoveAssign>, 42);
+    MoveAssign::reset();
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 1);
+    assert(std::get<1>(v1).value == 42);
+    assert(MoveAssign::move_construct == 1);
+    assert(MoveAssign::move_assign == 0);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using MET = MakeEmptyT;
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_type<int>);
+    V v2(std::in_place_type<MET>);
+    try {
+      v1 = std::move(v2);
+      assert(false);
+    } catch (...) {
+    }
+    assert(v1.valueless_by_exception());
+    assert(v1.index() == std::variant_npos);
+  }
+  {
+    using V = std::variant<int, MET, std::string>;
+    V v1(std::in_place_type<MET>);
+    V v2(std::in_place_type<std::string>, "hello");
+    V &vref = (v1 = std::move(v2));
+    assert(&vref == &v1);
+    assert(v1.index() == 2);
+    assert(std::get<2>(v1) == "hello");
+  }
+#endif
+}
+
+int main() {
+  test_move_assignment_empty_empty();
+  test_move_assignment_non_empty_empty();
+  test_move_assignment_empty_non_empty();
+  test_move_assignment_same_index();
+  test_move_assignment_different_index();
+  test_move_assignment_sfinae();
+  test_move_assignment_noexcept();
+}

test/std/utilities/variant/variant.variant/variant.ctor/T.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class T> constexpr variant(T&&) noexcept(see below);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+struct Dummy {
+  Dummy() = default;
+};
+
+struct ThrowsT {
+  ThrowsT(int) noexcept(false) {}
+};
+
+struct NoThrowT {
+  NoThrowT(int) noexcept(true) {}
+};
+
+void test_T_ctor_noexcept() {
+  {
+    using V = std::variant<Dummy, NoThrowT>;
+    static_assert(std::is_nothrow_constructible<V, int>::value, "");
+  }
+  {
+    using V = std::variant<Dummy, ThrowsT>;
+    static_assert(!std::is_nothrow_constructible<V, int>::value, "");
+  }
+}
+
+void test_T_ctor_sfinae() {
+  {
+    using V = std::variant<long, unsigned>;
+    static_assert(!std::is_constructible<V, int>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<std::string, std::string>;
+    static_assert(!std::is_constructible<V, const char *>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<std::string, void *>;
+    static_assert(!std::is_constructible<V, int>::value,
+                  "no matching constructor");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, int &&>;
+    static_assert(!std::is_constructible<V, int>::value, "ambiguous");
+  }
+  {
+    using V = std::variant<int, int const &>;
+    static_assert(!std::is_constructible<V, int>::value, "ambiguous");
+  }
+#endif
+}
+
+void test_T_ctor_basic() {
+  {
+    constexpr std::variant<int> v(42);
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v) == 42, "");
+  }
+  {
+    constexpr std::variant<int, long> v(42l);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v) == 42, "");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int const &, int &&, long>;
+    static_assert(std::is_convertible<int &, V>::value, "must be implicit");
+    int x = 42;
+    V v(x);
+    assert(v.index() == 0);
+    assert(&std::get<0>(v) == &x);
+  }
+  {
+    using V = std::variant<int const &, int &&, long>;
+    static_assert(std::is_convertible<int, V>::value, "must be implicit");
+    int x = 42;
+    V v(std::move(x));
+    assert(v.index() == 1);
+    assert(&std::get<1>(v) == &x);
+  }
+#endif
+}
+
+int main() {
+  test_T_ctor_basic();
+  test_T_ctor_noexcept();
+  test_T_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/copy.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// variant(variant const&);
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+
+struct NonT {
+  NonT(int v) : value(v) {}
+  NonT(NonT const &o) : value(o.value) {}
+  int value;
+};
+static_assert(!std::is_trivially_copy_constructible<NonT>::value, "");
+
+struct NoCopy {
+  NoCopy(NoCopy const &) = delete;
+};
+
+struct MoveOnly {
+  MoveOnly(MoveOnly const &) = delete;
+  MoveOnly(MoveOnly &&) = default;
+};
+
+struct MoveOnlyNT {
+  MoveOnlyNT(MoveOnlyNT const &) = delete;
+  MoveOnlyNT(MoveOnlyNT &&) {}
+};
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct MakeEmptyT {
+  static int alive;
+  MakeEmptyT() { ++alive; }
+  MakeEmptyT(MakeEmptyT const &) {
+    ++alive;
+    // Don't throw from the copy constructor since variant's assignment
+    // operator performs a copy before committing to the assignment.
+  }
+  MakeEmptyT(MakeEmptyT &&) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT const &) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT &&) { throw 42; }
+  ~MakeEmptyT() { --alive; }
+};
+
+int MakeEmptyT::alive = 0;
+
+template <class Variant> void makeEmpty(Variant &v) {
+  Variant v2(std::in_place_type<MakeEmptyT>);
+  try {
+    v = v2;
+    assert(false);
+  } catch (...) {
+    assert(v.valueless_by_exception());
+  }
+}
+#endif // TEST_HAS_NO_EXCEPTIONS
+
+void test_copy_ctor_sfinae() {
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_copy_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, NoCopy>;
+    static_assert(!std::is_copy_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(!std::is_copy_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnlyNT>;
+    static_assert(!std::is_copy_constructible<V>::value, "");
+  }
+}
+
+void test_copy_ctor_basic() {
+  {
+    std::variant<int> v(std::in_place_index<0>, 42);
+    std::variant<int> v2 = v;
+    assert(v2.index() == 0);
+    assert(std::get<0>(v2) == 42);
+  }
+  {
+    std::variant<int, long> v(std::in_place_index<1>, 42);
+    std::variant<int, long> v2 = v;
+    assert(v2.index() == 1);
+    assert(std::get<1>(v2) == 42);
+  }
+  {
+    std::variant<NonT> v(std::in_place_index<0>, 42);
+    assert(v.index() == 0);
+    std::variant<NonT> v2(v);
+    assert(v2.index() == 0);
+    assert(std::get<0>(v2).value == 42);
+  }
+  {
+    std::variant<int, NonT> v(std::in_place_index<1>, 42);
+    assert(v.index() == 1);
+    std::variant<int, NonT> v2(v);
+    assert(v2.index() == 1);
+    assert(std::get<1>(v2).value == 42);
+  }
+}
+
+void test_copy_ctor_valueless_by_exception() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<int, MakeEmptyT>;
+  V v1;
+  makeEmpty(v1);
+  V const &cv1 = v1;
+  V v(cv1);
+  assert(v.valueless_by_exception());
+#endif
+}
+
+int main() {
+  test_copy_ctor_basic();
+  test_copy_ctor_valueless_by_exception();
+  test_copy_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/default.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// constexpr variant() noexcept(see below);
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+struct NonDefaultConstructible {
+  NonDefaultConstructible(int) {}
+};
+
+struct NotNoexcept {
+  NotNoexcept() noexcept(false) {}
+};
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct DefaultCtorThrows {
+  DefaultCtorThrows() { throw 42; }
+};
+#endif
+
+void test_default_ctor_sfinae() {
+  {
+    using V = std::variant<std::monostate, int>;
+    static_assert(std::is_default_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<NonDefaultConstructible, int>;
+    static_assert(!std::is_default_constructible<V>::value, "");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int &, int>;
+    static_assert(!std::is_default_constructible<V>::value, "");
+  }
+#endif
+}
+
+void test_default_ctor_noexcept() {
+  {
+    using V = std::variant<int>;
+    static_assert(std::is_nothrow_default_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<NotNoexcept>;
+    static_assert(!std::is_nothrow_default_constructible<V>::value, "");
+  }
+}
+
+void test_default_ctor_throws() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<DefaultCtorThrows, int>;
+  try {
+    V v;
+    assert(false);
+  } catch (int const &ex) {
+    assert(ex == 42);
+  } catch (...) {
+    assert(false);
+  }
+#endif
+}
+
+void test_default_ctor_basic() {
+  {
+    std::variant<int> v;
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == 0);
+  }
+  {
+    std::variant<int, long> v;
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == 0);
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v;
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v) == 0, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v;
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v) == 0, "");
+  }
+}
+
+int main() {
+  test_default_ctor_basic();
+  test_default_ctor_sfinae();
+  test_default_ctor_noexcept();
+  test_default_ctor_throws();
+}

test/std/utilities/variant/variant.variant/variant.ctor/in_place_index_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <size_t I, class ...Args>
+// constexpr explicit variant(in_place_index_t<I>, Args&&...);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+void test_ctor_sfinae() {
+  {
+    using V = std::variant<int>;
+    static_assert(
+        std::is_constructible<V, std::in_place_index_t<0>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<0>, int>(), "");
+  }
+  {
+    using V = std::variant<int, long, long long>;
+    static_assert(
+        std::is_constructible<V, std::in_place_index_t<1>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<1>, int>(), "");
+  }
+  {
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        std::is_constructible<V, std::in_place_index_t<2>, int *>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<2>, int *>(), "");
+  }
+  { // args not convertible to type
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_index_t<0>, int *>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<0>, int *>(), "");
+  }
+  { // index not in variant
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_index_t<3>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<3>, int>(), "");
+  }
+}
+
+void test_ctor_basic() {
+  {
+    constexpr std::variant<int> v(std::in_place_index<0>, 42);
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v) == 42, "");
+  }
+  {
+    constexpr std::variant<int, long, long> v(std::in_place_index<1>, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v) == 42, "");
+  }
+  {
+    constexpr std::variant<int, const int, long> v(std::in_place_index<1>, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v) == 42, "");
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_index<0>, x);
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == x);
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_index<1>, x);
+    assert(v.index() == 1);
+    assert(std::get<1>(v) == x);
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_index<2>, x);
+    assert(v.index() == 2);
+    assert(std::get<2>(v) == x);
+  }
+}
+
+int main() {
+  test_ctor_basic();
+  test_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/in_place_index_init_list_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <size_t I, class Up, class ...Args>
+// constexpr explicit
+// variant(in_place_index_t<I>, initializer_list<Up>, Args&&...);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+struct InitList {
+  std::size_t size;
+  constexpr InitList(std::initializer_list<int> il) : size(il.size()) {}
+};
+
+struct InitListArg {
+  std::size_t size;
+  int value;
+  constexpr InitListArg(std::initializer_list<int> il, int v)
+      : size(il.size()), value(v) {}
+};
+
+void test_ctor_sfinae() {
+  using IL = std::initializer_list<int>;
+  { // just init list
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(std::is_constructible<V, std::in_place_index_t<0>, IL>::value,
+                  "");
+    static_assert(!test_convertible<V, std::in_place_index_t<0>, IL>(), "");
+  }
+  { // too many arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_index_t<0>, IL, int>::value,
+        "");
+    static_assert(!test_convertible<V, std::in_place_index_t<0>, IL, int>(),
+                  "");
+  }
+  { // too few arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_index_t<1>, IL>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<1>, IL>(), "");
+  }
+  { // init list and arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        std::is_constructible<V, std::in_place_index_t<1>, IL, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<1>, IL, int>(),
+                  "");
+  }
+  { // not constructible from arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_index_t<2>, IL>::value, "");
+    static_assert(!test_convertible<V, std::in_place_index_t<2>, IL>(), "");
+  }
+}
+
+void test_ctor_basic() {
+  {
+    constexpr std::variant<InitList, InitListArg, InitList> v(
+        std::in_place_index<0>, {1, 2, 3});
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v).size == 3, "");
+  }
+  {
+    constexpr std::variant<InitList, InitListArg, InitList> v(
+        std::in_place_index<2>, {1, 2, 3});
+    static_assert(v.index() == 2, "");
+    static_assert(std::get<2>(v).size == 3, "");
+  }
+  {
+    constexpr std::variant<InitList, InitListArg, InitListArg> v(
+        std::in_place_index<1>, {1, 2, 3, 4}, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v).size == 4, "");
+    static_assert(std::get<1>(v).value == 42, "");
+  }
+}
+
+int main() {
+  test_ctor_basic();
+  test_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/in_place_type_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class Tp, class ...Args>
+// constexpr explicit variant(in_place_type_t<Tp>, Args&&...);
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+void test_ctor_sfinae() {
+  {
+    using V = std::variant<int>;
+    static_assert(
+        std::is_constructible<V, std::in_place_type_t<int>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_type_t<int>, int>(), "");
+  }
+  {
+    using V = std::variant<int, long, long long>;
+    static_assert(
+        std::is_constructible<V, std::in_place_type_t<long>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_type_t<long>, int>(), "");
+  }
+  {
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        std::is_constructible<V, std::in_place_type_t<int *>, int *>::value,
+        "");
+    static_assert(!test_convertible<V, std::in_place_type_t<int *>, int *>(),
+                  "");
+  }
+  { // duplicate type
+    using V = std::variant<int, long, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_type_t<int>, int>::value, "");
+    static_assert(!test_convertible<V, std::in_place_type_t<int>, int>(), "");
+  }
+  { // args not convertible to type
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_type_t<int>, int *>::value, "");
+    static_assert(!test_convertible<V, std::in_place_type_t<int>, int *>(), "");
+  }
+  { // type not in variant
+    using V = std::variant<int, long, int *>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_type_t<long long>, int>::value,
+        "");
+    static_assert(!test_convertible<V, std::in_place_type_t<long long>, int>(),
+                  "");
+  }
+}
+
+void test_ctor_basic() {
+  {
+    constexpr std::variant<int> v(std::in_place_type<int>, 42);
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v) == 42, "");
+  }
+  {
+    constexpr std::variant<int, long> v(std::in_place_type<long>, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v) == 42, "");
+  }
+  {
+    constexpr std::variant<int, const int, long> v(
+        std::in_place_type<const int>, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v) == 42, "");
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_type<const int>, x);
+    assert(v.index() == 0);
+    assert(std::get<0>(v) == x);
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_type<volatile int>, x);
+    assert(v.index() == 1);
+    assert(std::get<1>(v) == x);
+  }
+  {
+    using V = std::variant<const int, volatile int, int>;
+    int x = 42;
+    V v(std::in_place_type<int>, x);
+    assert(v.index() == 2);
+    assert(std::get<2>(v) == x);
+  }
+}
+
+int main() {
+  test_ctor_basic();
+  test_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/in_place_type_init_list_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class Tp, class Up, class ...Args>
+// constexpr explicit
+// variant(in_place_type_t<Tp>, initializer_list<Up>, Args&&...);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+struct InitList {
+  std::size_t size;
+  constexpr InitList(std::initializer_list<int> il) : size(il.size()) {}
+};
+
+struct InitListArg {
+  std::size_t size;
+  int value;
+  constexpr InitListArg(std::initializer_list<int> il, int v)
+      : size(il.size()), value(v) {}
+};
+
+void test_ctor_sfinae() {
+  using IL = std::initializer_list<int>;
+  { // just init list
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        std::is_constructible<V, std::in_place_type_t<InitList>, IL>::value,
+        "");
+    static_assert(!test_convertible<V, std::in_place_type_t<InitList>, IL>(),
+                  "");
+  }
+  { // too many arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(!std::is_constructible<V, std::in_place_type_t<InitList>, IL,
+                                         int>::value,
+                  "");
+    static_assert(
+        !test_convertible<V, std::in_place_type_t<InitList>, IL, int>(), "");
+  }
+  { // too few arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_type_t<InitListArg>, IL>::value,
+        "");
+    static_assert(!test_convertible<V, std::in_place_type_t<InitListArg>, IL>(),
+                  "");
+  }
+  { // init list and arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(std::is_constructible<V, std::in_place_type_t<InitListArg>,
+                                        IL, int>::value,
+                  "");
+    static_assert(
+        !test_convertible<V, std::in_place_type_t<InitListArg>, IL, int>(), "");
+  }
+  { // not constructible from arguments
+    using V = std::variant<InitList, InitListArg, int>;
+    static_assert(
+        !std::is_constructible<V, std::in_place_type_t<int>, IL>::value, "");
+    static_assert(!test_convertible<V, std::in_place_type_t<int>, IL>(), "");
+  }
+  { // duplicate types in variant
+    using V = std::variant<InitListArg, InitListArg, int>;
+    static_assert(!std::is_constructible<V, std::in_place_type_t<InitListArg>,
+                                         IL, int>::value,
+                  "");
+    static_assert(
+        !test_convertible<V, std::in_place_type_t<InitListArg>, IL, int>(), "");
+  }
+}
+
+void test_ctor_basic() {
+  {
+    constexpr std::variant<InitList, InitListArg> v(
+        std::in_place_type<InitList>, {1, 2, 3});
+    static_assert(v.index() == 0, "");
+    static_assert(std::get<0>(v).size == 3, "");
+  }
+  {
+    constexpr std::variant<InitList, InitListArg> v(
+        std::in_place_type<InitListArg>, {1, 2, 3, 4}, 42);
+    static_assert(v.index() == 1, "");
+    static_assert(std::get<1>(v).size == 4, "");
+    static_assert(std::get<1>(v).value == 42, "");
+  }
+}
+
+int main() {
+  test_ctor_basic();
+  test_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.ctor/move.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// variant(variant&&) noexcept(see below);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+
+struct ThrowsMove {
+  ThrowsMove(ThrowsMove &&) noexcept(false) {}
+};
+
+struct NoCopy {
+  NoCopy(NoCopy const &) = delete;
+};
+
+struct MoveOnly {
+  int value;
+  MoveOnly(int v) : value(v) {}
+  MoveOnly(MoveOnly const &) = delete;
+  MoveOnly(MoveOnly &&) = default;
+};
+
+struct MoveOnlyNT {
+  int value;
+  MoveOnlyNT(int v) : value(v) {}
+  MoveOnlyNT(MoveOnlyNT const &) = delete;
+  MoveOnlyNT(MoveOnlyNT &&other) : value(other.value) { other.value = -1; }
+};
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct MakeEmptyT {
+  static int alive;
+  MakeEmptyT() { ++alive; }
+  MakeEmptyT(MakeEmptyT const &) {
+    ++alive;
+    // Don't throw from the copy constructor since variant's assignment
+    // operator performs a copy before committing to the assignment.
+  }
+  MakeEmptyT(MakeEmptyT &&) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT const &) { throw 42; }
+  MakeEmptyT &operator=(MakeEmptyT &&) { throw 42; }
+  ~MakeEmptyT() { --alive; }
+};
+
+int MakeEmptyT::alive = 0;
+
+template <class Variant> void makeEmpty(Variant &v) {
+  Variant v2(std::in_place_type<MakeEmptyT>);
+  try {
+    v = v2;
+    assert(false);
+  } catch (...) {
+    assert(v.valueless_by_exception());
+  }
+}
+#endif // TEST_HAS_NO_EXCEPTIONS
+
+void test_move_noexcept() {
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_nothrow_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(std::is_nothrow_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnlyNT>;
+    static_assert(!std::is_nothrow_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, ThrowsMove>;
+    static_assert(!std::is_nothrow_move_constructible<V>::value, "");
+  }
+}
+
+void test_move_ctor_sfinae() {
+  {
+    using V = std::variant<int, long>;
+    static_assert(std::is_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnly>;
+    static_assert(std::is_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, MoveOnlyNT>;
+    static_assert(std::is_move_constructible<V>::value, "");
+  }
+  {
+    using V = std::variant<int, NoCopy>;
+    static_assert(!std::is_move_constructible<V>::value, "");
+  }
+}
+
+void test_move_ctor_basic() {
+  {
+    std::variant<int> v(std::in_place_index<0>, 42);
+    std::variant<int> v2 = std::move(v);
+    assert(v2.index() == 0);
+    assert(std::get<0>(v2) == 42);
+  }
+  {
+    std::variant<int, long> v(std::in_place_index<1>, 42);
+    std::variant<int, long> v2 = std::move(v);
+    assert(v2.index() == 1);
+    assert(std::get<1>(v2) == 42);
+  }
+  {
+    std::variant<MoveOnly> v(std::in_place_index<0>, 42);
+    assert(v.index() == 0);
+    std::variant<MoveOnly> v2(std::move(v));
+    assert(v2.index() == 0);
+    assert(std::get<0>(v2).value == 42);
+  }
+  {
+    std::variant<int, MoveOnly> v(std::in_place_index<1>, 42);
+    assert(v.index() == 1);
+    std::variant<int, MoveOnly> v2(std::move(v));
+    assert(v2.index() == 1);
+    assert(std::get<1>(v2).value == 42);
+  }
+  {
+    std::variant<MoveOnlyNT> v(std::in_place_index<0>, 42);
+    assert(v.index() == 0);
+    std::variant<MoveOnlyNT> v2(std::move(v));
+    assert(v2.index() == 0);
+    assert(std::get<0>(v).value == -1);
+    assert(std::get<0>(v2).value == 42);
+  }
+  {
+    std::variant<int, MoveOnlyNT> v(std::in_place_index<1>, 42);
+    assert(v.index() == 1);
+    std::variant<int, MoveOnlyNT> v2(std::move(v));
+    assert(v2.index() == 1);
+    assert(std::get<1>(v).value == -1);
+    assert(std::get<1>(v2).value == 42);
+  }
+}
+
+void test_move_ctor_valueless_by_exception() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<int, MakeEmptyT>;
+  V v1;
+  makeEmpty(v1);
+  V v(std::move(v1));
+  assert(v.valueless_by_exception());
+#endif
+}
+
+int main() {
+  test_move_ctor_basic();
+  test_move_ctor_valueless_by_exception();
+  test_move_noexcept();
+  test_move_ctor_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.dtor/dtor.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// ~variant();
+
+#include <cassert>
+#include <type_traits>
+#include <variant>
+
+#include "test_macros.h"
+
+struct NonTDtor {
+  static int count;
+  NonTDtor() = default;
+  ~NonTDtor() { ++count; }
+};
+int NonTDtor::count = 0;
+static_assert(!std::is_trivially_destructible<NonTDtor>::value, "");
+
+struct NonTDtor1 {
+  static int count;
+  NonTDtor1() = default;
+  ~NonTDtor1() { ++count; }
+};
+int NonTDtor1::count = 0;
+static_assert(!std::is_trivially_destructible<NonTDtor1>::value, "");
+
+struct TDtor {
+  TDtor(TDtor const &) {} // non-trivial copy
+  ~TDtor() = default;
+};
+static_assert(!std::is_trivially_copy_constructible<TDtor>::value, "");
+static_assert(std::is_trivially_destructible<TDtor>::value, "");
+
+int main() {
+  {
+    using V = std::variant<int, long, TDtor>;
+    static_assert(std::is_trivially_destructible<V>::value, "");
+  }
+  {
+    using V = std::variant<NonTDtor, int, NonTDtor1>;
+    static_assert(!std::is_trivially_destructible<V>::value, "");
+    {
+      V v(std::in_place_index<0>);
+      assert(NonTDtor::count == 0);
+      assert(NonTDtor1::count == 0);
+    }
+    assert(NonTDtor::count == 1);
+    assert(NonTDtor1::count == 0);
+    NonTDtor::count = 0;
+    { V v(std::in_place_index<1>); }
+    assert(NonTDtor::count == 0);
+    assert(NonTDtor1::count == 0);
+    {
+      V v(std::in_place_index<2>);
+      assert(NonTDtor::count == 0);
+      assert(NonTDtor1::count == 0);
+    }
+    assert(NonTDtor::count == 0);
+    assert(NonTDtor1::count == 1);
+  }
+}

test/std/utilities/variant/variant.variant/variant.mod/emplace_index_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <size_t I, class ...Args> void emplace(Args&&... args);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_convertible.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+template <class Var, size_t I, class... Args>
+constexpr auto test_emplace_exists_imp(int) -> decltype(
+    std::declval<Var>().template emplace<I>(std::declval<Args>()...), true) {
+  return true;
+}
+
+template <class, size_t, class...>
+constexpr auto test_emplace_exists_imp(long) -> bool {
+  return false;
+}
+
+template <class Var, size_t I, class... Args> constexpr bool emplace_exists() {
+  return test_emplace_exists_imp<Var, I, Args...>(0);
+}
+
+void test_emplace_sfinae() {
+  {
+    using V = std::variant<int, void *, const void *, TestTypes::NoCtors>;
+    static_assert(emplace_exists<V, 0>(), "");
+    static_assert(emplace_exists<V, 0, int>(), "");
+    static_assert(!emplace_exists<V, 0, decltype(nullptr)>(),
+                  "cannot construct");
+    static_assert(emplace_exists<V, 1, decltype(nullptr)>(), "");
+    static_assert(emplace_exists<V, 1, int *>(), "");
+    static_assert(!emplace_exists<V, 1, const int *>(), "");
+    static_assert(!emplace_exists<V, 1, int>(), "cannot construct");
+    static_assert(emplace_exists<V, 2, const int *>(), "");
+    static_assert(emplace_exists<V, 2, int *>(), "");
+    static_assert(!emplace_exists<V, 3>(), "cannot construct");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, int &, int const &, int &&, TestTypes::NoCtors>;
+    static_assert(emplace_exists<V, 0>(), "");
+    static_assert(emplace_exists<V, 0, int>(), "");
+    static_assert(emplace_exists<V, 0, long long>(), "");
+    static_assert(!emplace_exists<V, 0, int, int>(), "too many args");
+    static_assert(emplace_exists<V, 1, int &>(), "");
+    static_assert(!emplace_exists<V, 1>(), "cannot default construct ref");
+    static_assert(!emplace_exists<V, 1, int const &>(), "cannot bind ref");
+    static_assert(!emplace_exists<V, 1, int &&>(), "cannot bind ref");
+    static_assert(emplace_exists<V, 2, int &>(), "");
+    static_assert(emplace_exists<V, 2, const int &>(), "");
+    static_assert(emplace_exists<V, 2, int &&>(), "");
+    static_assert(!emplace_exists<V, 2, void *>(),
+                  "not constructible from void*");
+    static_assert(emplace_exists<V, 3, int>(), "");
+    static_assert(!emplace_exists<V, 3, int &>(), "cannot bind ref");
+    static_assert(!emplace_exists<V, 3, int const &>(), "cannot bind ref");
+    static_assert(!emplace_exists<V, 3, int const &&>(), "cannot bind ref");
+    static_assert(!emplace_exists<V, 4>(), "no ctors");
+  }
+#endif
+}
+
+void test_basic() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    v.emplace<0>();
+    assert(std::get<0>(v) == 0);
+    v.emplace<0>(42);
+    assert(std::get<0>(v) == 42);
+  }
+  {
+    using V =
+        std::variant<int, long, const void *, TestTypes::NoCtors, std::string>;
+    const int x = 100;
+    V v(std::in_place_index<0>, -1);
+    // default emplace a value
+    v.emplace<1>();
+    assert(std::get<1>(v) == 0);
+    v.emplace<2>(&x);
+    assert(std::get<2>(v) == &x);
+    // emplace with multiple args
+    v.emplace<4>(3, 'a');
+    assert(std::get<4>(v) == "aaa");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, long, int const &, int &&, TestTypes::NoCtors,
+                           std::string>;
+    const int x = 100;
+    int y = 42;
+    int z = 43;
+    V v(std::in_place_index<0>, -1);
+    // default emplace a value
+    v.emplace<1>();
+    assert(std::get<1>(v) == 0);
+    // emplace a reference
+    v.emplace<2>(x);
+    assert(&std::get<2>(v) == &x);
+    // emplace an rvalue reference
+    v.emplace<3>(std::move(y));
+    assert(&std::get<3>(v) == &y);
+    // re-emplace a new reference over the active member
+    v.emplace<3>(std::move(z));
+    assert(&std::get<3>(v) == &z);
+    // emplace with multiple args
+    v.emplace<5>(3, 'a');
+    assert(std::get<5>(v) == "aaa");
+  }
+#endif
+}
+
+int main() {
+  test_basic();
+  test_emplace_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.mod/emplace_index_init_list_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <size_t I, class U, class ...Args>
+// void emplace(initializer_list<U> il,Args&&... args);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+struct InitList {
+  std::size_t size;
+  constexpr InitList(std::initializer_list<int> il) : size(il.size()) {}
+};
+
+struct InitListArg {
+  std::size_t size;
+  int value;
+  constexpr InitListArg(std::initializer_list<int> il, int v)
+      : size(il.size()), value(v) {}
+};
+
+template <class Var, size_t I, class... Args>
+constexpr auto test_emplace_exists_imp(int) -> decltype(
+    std::declval<Var>().template emplace<I>(std::declval<Args>()...), true) {
+  return true;
+}
+
+template <class, size_t, class...>
+constexpr auto test_emplace_exists_imp(long) -> bool {
+  return false;
+}
+
+template <class Var, size_t I, class... Args> constexpr bool emplace_exists() {
+  return test_emplace_exists_imp<Var, I, Args...>(0);
+}
+
+void test_emplace_sfinae() {
+  using V =
+      std::variant<int, TestTypes::NoCtors, InitList, InitListArg, long, long>;
+  using IL = std::initializer_list<int>;
+  static_assert(!emplace_exists<V, 1, IL>(), "no such constructor");
+  static_assert(emplace_exists<V, 2, IL>(), "");
+  static_assert(!emplace_exists<V, 2, int>(), "args don't match");
+  static_assert(!emplace_exists<V, 2, IL, int>(), "too many args");
+  static_assert(emplace_exists<V, 3, IL, int>(), "");
+  static_assert(!emplace_exists<V, 3, int>(), "args don't match");
+  static_assert(!emplace_exists<V, 3, IL>(), "too few args");
+  static_assert(!emplace_exists<V, 3, IL, int, int>(), "too many args");
+}
+
+void test_basic() {
+  using V = std::variant<int, InitList, InitListArg, TestTypes::NoCtors>;
+  V v;
+  v.emplace<1>({1, 2, 3});
+  assert(std::get<1>(v).size == 3);
+  v.emplace<2>({1, 2, 3, 4}, 42);
+  assert(std::get<2>(v).size == 4);
+  assert(std::get<2>(v).value == 42);
+  v.emplace<1>({1});
+  assert(std::get<1>(v).size == 1);
+}
+
+int main() {
+  test_basic();
+  test_emplace_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.mod/emplace_type_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class T, class ...Args> void emplace(Args&&... args);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_convertible.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+template <class Var, class T, class... Args>
+constexpr auto test_emplace_exists_imp(int) -> decltype(
+    std::declval<Var>().template emplace<T>(std::declval<Args>()...), true) {
+  return true;
+}
+
+template <class, class, class...>
+constexpr auto test_emplace_exists_imp(long) -> bool {
+  return false;
+}
+
+template <class... Args> constexpr bool emplace_exists() {
+  return test_emplace_exists_imp<Args...>(0);
+}
+
+void test_emplace_sfinae() {
+  {
+    using V = std::variant<int, void *, const void *, TestTypes::NoCtors>;
+    static_assert(emplace_exists<V, int>(), "");
+    static_assert(emplace_exists<V, int, int>(), "");
+    static_assert(!emplace_exists<V, int, decltype(nullptr)>(),
+                  "cannot construct");
+    static_assert(emplace_exists<V, void *, decltype(nullptr)>(), "");
+    static_assert(!emplace_exists<V, void *, int>(), "cannot construct");
+    static_assert(emplace_exists<V, void *, int *>(), "");
+    static_assert(!emplace_exists<V, void *, const int *>(), "");
+    static_assert(emplace_exists<V, void const *, const int *>(), "");
+    static_assert(emplace_exists<V, void const *, int *>(), "");
+    static_assert(!emplace_exists<V, TestTypes::NoCtors>(), "cannot construct");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  using V = std::variant<int, int &, int const &, int &&, long, long,
+                         TestTypes::NoCtors>;
+  static_assert(emplace_exists<V, int>(), "");
+  static_assert(emplace_exists<V, int, int>(), "");
+  static_assert(emplace_exists<V, int, long long>(), "");
+  static_assert(!emplace_exists<V, int, int, int>(), "too many args");
+  static_assert(emplace_exists<V, int &, int &>(), "");
+  static_assert(!emplace_exists<V, int &>(), "cannot default construct ref");
+  static_assert(!emplace_exists<V, int &, int const &>(), "cannot bind ref");
+  static_assert(!emplace_exists<V, int &, int &&>(), "cannot bind ref");
+  static_assert(emplace_exists<V, int const &, int &>(), "");
+  static_assert(emplace_exists<V, int const &, const int &>(), "");
+  static_assert(emplace_exists<V, int const &, int &&>(), "");
+  static_assert(!emplace_exists<V, int const &, void *>(),
+                "not constructible from void*");
+  static_assert(emplace_exists<V, int &&, int>(), "");
+  static_assert(!emplace_exists<V, int &&, int &>(), "cannot bind ref");
+  static_assert(!emplace_exists<V, int &&, int const &>(), "cannot bind ref");
+  static_assert(!emplace_exists<V, int &&, int const &&>(), "cannot bind ref");
+  static_assert(!emplace_exists<V, long, long>(), "ambiguous");
+  static_assert(!emplace_exists<V, TestTypes::NoCtors>(),
+                "cannot construct void");
+#endif
+}
+
+void test_basic() {
+  {
+    using V = std::variant<int>;
+    V v(42);
+    v.emplace<int>();
+    assert(std::get<0>(v) == 0);
+    v.emplace<int>(42);
+    assert(std::get<0>(v) == 42);
+  }
+  {
+    using V =
+        std::variant<int, long, const void *, TestTypes::NoCtors, std::string>;
+    const int x = 100;
+    V v(std::in_place_type<int>, -1);
+    // default emplace a value
+    v.emplace<long>();
+    assert(std::get<1>(v) == 0);
+    v.emplace<const void *>(&x);
+    assert(std::get<2>(v) == &x);
+    // emplace with multiple args
+    v.emplace<std::string>(3, 'a');
+    assert(std::get<4>(v) == "aaa");
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  {
+    using V = std::variant<int, long, int const &, int &&, TestTypes::NoCtors,
+                           std::string>;
+    const int x = 100;
+    int y = 42;
+    int z = 43;
+    V v(std::in_place_index<0>, -1);
+    // default emplace a value
+    v.emplace<long>();
+    assert(std::get<long>(v) == 0);
+    // emplace a reference
+    v.emplace<int const &>(x);
+    assert(&std::get<int const &>(v) == &x);
+    // emplace an rvalue reference
+    v.emplace<int &&>(std::move(y));
+    assert(&std::get<int &&>(v) == &y);
+    // re-emplace a new reference over the active member
+    v.emplace<int &&>(std::move(z));
+    assert(&std::get<int &&>(v) == &z);
+    // emplace with multiple args
+    v.emplace<std::string>(3, 'a');
+    assert(std::get<std::string>(v) == "aaa");
+  }
+#endif
+}
+
+int main() {
+  test_basic();
+  test_emplace_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.mod/emplace_type_init_list_args.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// template <class T, class U, class ...Args>
+// void emplace(initializer_list<U> il,Args&&... args);
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_convertible.hpp"
+#include "test_macros.h"
+
+struct InitList {
+  std::size_t size;
+  constexpr InitList(std::initializer_list<int> il) : size(il.size()) {}
+};
+
+struct InitListArg {
+  std::size_t size;
+  int value;
+  constexpr InitListArg(std::initializer_list<int> il, int v)
+      : size(il.size()), value(v) {}
+};
+
+template <class Var, class T, class... Args>
+constexpr auto test_emplace_exists_imp(int) -> decltype(
+    std::declval<Var>().template emplace<T>(std::declval<Args>()...), true) {
+  return true;
+}
+
+template <class, class, class...>
+constexpr auto test_emplace_exists_imp(long) -> bool {
+  return false;
+}
+
+template <class... Args> constexpr bool emplace_exists() {
+  return test_emplace_exists_imp<Args...>(0);
+}
+
+void test_emplace_sfinae() {
+  using V =
+      std::variant<int, TestTypes::NoCtors, InitList, InitListArg, long, long>;
+  using IL = std::initializer_list<int>;
+  static_assert(emplace_exists<V, InitList, IL>(), "");
+  static_assert(!emplace_exists<V, InitList, int>(), "args don't match");
+  static_assert(!emplace_exists<V, InitList, IL, int>(), "too many args");
+  static_assert(emplace_exists<V, InitListArg, IL, int>(), "");
+  static_assert(!emplace_exists<V, InitListArg, int>(), "args don't match");
+  static_assert(!emplace_exists<V, InitListArg, IL>(), "too few args");
+  static_assert(!emplace_exists<V, InitListArg, IL, int, int>(),
+                "too many args");
+}
+
+void test_basic() {
+  using V = std::variant<int, InitList, InitListArg, TestTypes::NoCtors>;
+  V v;
+  v.emplace<InitList>({1, 2, 3});
+  assert(std::get<InitList>(v).size == 3);
+  v.emplace<InitListArg>({1, 2, 3, 4}, 42);
+  assert(std::get<InitListArg>(v).size == 4);
+  assert(std::get<InitListArg>(v).value == 42);
+  v.emplace<InitList>({1});
+  assert(std::get<InitList>(v).size == 1);
+}
+
+int main() {
+  test_basic();
+  test_emplace_sfinae();
+}

test/std/utilities/variant/variant.variant/variant.status/index.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// constexpr size_t index() const noexcept;
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+int main() {
+  {
+    using V = std::variant<int, ConstexprTestTypes::NoCtors>;
+    constexpr V v;
+    static_assert(v.index() == 0, "");
+  }
+  {
+    using V = std::variant<int, long>;
+    constexpr V v(std::in_place_index<1>);
+    static_assert(v.index() == 1, "");
+  }
+  {
+    using V = std::variant<int, std::string>;
+    V v("abc");
+    assert(v.index() == 1);
+    v = 42;
+    assert(v.index() == 0);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v;
+    assert(v.index() == 0);
+    makeEmpty(v);
+    assert(v.index() == std::variant_npos);
+  }
+#endif
+}

test/std/utilities/variant/variant.variant/variant.status/valueless_by_exception.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// constexpr bool valueless_by_exception() const noexcept;
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "archetypes.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+int main() {
+  {
+    using V = std::variant<int, ConstexprTestTypes::NoCtors>;
+    constexpr V v;
+    static_assert(!v.valueless_by_exception(), "");
+  }
+  {
+    using V = std::variant<int, long, std::string>;
+    const V v("abc");
+    assert(!v.valueless_by_exception());
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v;
+    assert(!v.valueless_by_exception());
+    makeEmpty(v);
+    assert(v.valueless_by_exception());
+  }
+#endif
+}

test/std/utilities/variant/variant.variant/variant.swap/swap.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+// void swap(variant& rhs) noexcept(see below)
+
+#include <cassert>
+#include <string>
+#include <type_traits>
+#include <variant>
+
+#include "test_convertible.hpp"
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+struct NotSwappable {};
+void swap(NotSwappable &, NotSwappable &) = delete;
+
+struct NotCopyable {
+  NotCopyable() = default;
+  NotCopyable(NotCopyable const &) = delete;
+  NotCopyable &operator=(NotCopyable const &) = delete;
+};
+
+struct NotCopyableWithSwap {
+  NotCopyableWithSwap() = default;
+  NotCopyableWithSwap(NotCopyableWithSwap const &) = delete;
+  NotCopyableWithSwap &operator=(NotCopyableWithSwap const &) = delete;
+};
+void swap(NotCopyableWithSwap &, NotCopyableWithSwap) {}
+
+struct NotMoveAssignable {
+  NotMoveAssignable() = default;
+  NotMoveAssignable(NotMoveAssignable &&) = default;
+  NotMoveAssignable &operator=(NotMoveAssignable &&) = delete;
+};
+
+struct NotMoveAssignableWithSwap {
+  NotMoveAssignableWithSwap() = default;
+  NotMoveAssignableWithSwap(NotMoveAssignableWithSwap &&) = default;
+  NotMoveAssignableWithSwap &operator=(NotMoveAssignableWithSwap &&) = delete;
+};
+void swap(NotMoveAssignableWithSwap &, NotMoveAssignableWithSwap &) noexcept {}
+
+template <bool Throws> void do_throw() {}
+
+template <> void do_throw<true>() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  throw 42;
+#else
+  std::abort();
+#endif
+}
+
+template <bool NT_Copy, bool NT_Move, bool NT_CopyAssign, bool NT_MoveAssign,
+          bool NT_Swap, bool EnableSwap = true>
+struct NothrowTypeImp {
+  static int move_called;
+  static int move_assign_called;
+  static int swap_called;
+  static void reset() { move_called = move_assign_called = swap_called = 0; }
+  NothrowTypeImp() = default;
+  explicit NothrowTypeImp(int v) : value(v) {}
+  NothrowTypeImp(NothrowTypeImp const &o) noexcept(NT_Copy) : value(o.value) {
+    assert(false);
+  } // never called by test
+  NothrowTypeImp(NothrowTypeImp &&o) noexcept(NT_Move) : value(o.value) {
+    ++move_called;
+    do_throw<!NT_Move>();
+    o.value = -1;
+  }
+  NothrowTypeImp &operator=(NothrowTypeImp const &) noexcept(NT_CopyAssign) {
+    assert(false);
+    return *this;
+  } // never called by the tests
+  NothrowTypeImp &operator=(NothrowTypeImp &&o) noexcept(NT_MoveAssign) {
+    ++move_assign_called;
+    do_throw<!NT_MoveAssign>();
+    value = o.value;
+    o.value = -1;
+    return *this;
+  }
+  int value;
+};
+template <bool NT_Copy, bool NT_Move, bool NT_CopyAssign, bool NT_MoveAssign,
+          bool NT_Swap, bool EnableSwap>
+int NothrowTypeImp<NT_Copy, NT_Move, NT_CopyAssign, NT_MoveAssign, NT_Swap,
+                   EnableSwap>::move_called = 0;
+template <bool NT_Copy, bool NT_Move, bool NT_CopyAssign, bool NT_MoveAssign,
+          bool NT_Swap, bool EnableSwap>
+int NothrowTypeImp<NT_Copy, NT_Move, NT_CopyAssign, NT_MoveAssign, NT_Swap,
+                   EnableSwap>::move_assign_called = 0;
+template <bool NT_Copy, bool NT_Move, bool NT_CopyAssign, bool NT_MoveAssign,
+          bool NT_Swap, bool EnableSwap>
+int NothrowTypeImp<NT_Copy, NT_Move, NT_CopyAssign, NT_MoveAssign, NT_Swap,
+                   EnableSwap>::swap_called = 0;
+
+template <bool NT_Copy, bool NT_Move, bool NT_CopyAssign, bool NT_MoveAssign,
+          bool NT_Swap>
+void swap(NothrowTypeImp<NT_Copy, NT_Move, NT_CopyAssign, NT_MoveAssign,
+                         NT_Swap, true> &lhs,
+          NothrowTypeImp<NT_Copy, NT_Move, NT_CopyAssign, NT_MoveAssign,
+                         NT_Swap, true> &rhs) noexcept(NT_Swap) {
+  lhs.swap_called++;
+  do_throw<!NT_Swap>();
+  int tmp = lhs.value;
+  lhs.value = rhs.value;
+  rhs.value = tmp;
+}
+
+// throwing copy, nothrow move ctor/assign, no swap provided
+using NothrowMoveable = NothrowTypeImp<false, true, false, true, false, false>;
+// throwing copy and move assign, nothrow move ctor, no swap provided
+using NothrowMoveCtor = NothrowTypeImp<false, true, false, false, false, false>;
+// nothrow move ctor, throwing move assignment, swap provided
+using NothrowMoveCtorWithThrowingSwap =
+    NothrowTypeImp<false, true, false, false, false, true>;
+// throwing move ctor, nothrow move assignment, no swap provided
+using ThrowingMoveCtor =
+    NothrowTypeImp<false, false, false, true, false, false>;
+// throwing special members, nothrowing swap
+using ThrowingTypeWithNothrowSwap =
+    NothrowTypeImp<false, false, false, false, true, true>;
+using NothrowTypeWithThrowingSwap =
+    NothrowTypeImp<true, true, true, true, false, true>;
+// throwing move assign with nothrow move and nothrow swap
+using ThrowingMoveAssignNothrowMoveCtorWithSwap =
+    NothrowTypeImp<false, true, false, false, true, true>;
+// throwing move assign with nothrow move but no swap.
+using ThrowingMoveAssignNothrowMoveCtor =
+    NothrowTypeImp<false, true, false, false, false, false>;
+
+struct NonThrowingNonNoexceptType {
+  static int move_called;
+  static void reset() { move_called = 0; }
+  NonThrowingNonNoexceptType() = default;
+  NonThrowingNonNoexceptType(int v) : value(v) {}
+  NonThrowingNonNoexceptType(NonThrowingNonNoexceptType &&o) noexcept(false)
+      : value(o.value) {
+    ++move_called;
+    o.value = -1;
+  }
+  NonThrowingNonNoexceptType &
+  operator=(NonThrowingNonNoexceptType &&) noexcept(false) {
+    assert(false); // never called by the tests.
+    return *this;
+  }
+  int value;
+};
+int NonThrowingNonNoexceptType::move_called = 0;
+
+struct ThrowsOnSecondMove {
+  int value;
+  int move_count;
+  ThrowsOnSecondMove(int v) : value(v), move_count(0) {}
+  ThrowsOnSecondMove(ThrowsOnSecondMove &&o) noexcept(false)
+      : value(o.value), move_count(o.move_count + 1) {
+    if (move_count == 2)
+      do_throw<true>();
+    o.value = -1;
+  }
+  ThrowsOnSecondMove &operator=(ThrowsOnSecondMove &&) {
+    assert(false); // not called by test
+    return *this;
+  }
+};
+
+void test_swap_valueless_by_exception() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  using V = std::variant<int, MakeEmptyT>;
+  { // both empty
+    V v1;
+    makeEmpty(v1);
+    V v2;
+    makeEmpty(v2);
+    assert(MakeEmptyT::alive == 0);
+    { // member swap
+      v1.swap(v2);
+      assert(v1.valueless_by_exception());
+      assert(v2.valueless_by_exception());
+      assert(MakeEmptyT::alive == 0);
+    }
+    { // non-member swap
+      swap(v1, v2);
+      assert(v1.valueless_by_exception());
+      assert(v2.valueless_by_exception());
+      assert(MakeEmptyT::alive == 0);
+    }
+  }
+  { // only one empty
+    V v1(42);
+    V v2;
+    makeEmpty(v2);
+    { // member swap
+      v1.swap(v2);
+      assert(v1.valueless_by_exception());
+      assert(std::get<0>(v2) == 42);
+      // swap again
+      v2.swap(v1);
+      assert(v2.valueless_by_exception());
+      assert(std::get<0>(v1) == 42);
+    }
+    { // non-member swap
+      swap(v1, v2);
+      assert(v1.valueless_by_exception());
+      assert(std::get<0>(v2) == 42);
+      // swap again
+      swap(v1, v2);
+      assert(v2.valueless_by_exception());
+      assert(std::get<0>(v1) == 42);
+    }
+  }
+#endif
+}
+
+void test_swap_same_alternative() {
+  {
+    using T = ThrowingTypeWithNothrowSwap;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>, 100);
+    v1.swap(v2);
+    assert(T::swap_called == 1);
+    assert(std::get<0>(v1).value == 100);
+    assert(std::get<0>(v2).value == 42);
+    swap(v1, v2);
+    assert(T::swap_called == 2);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<0>(v2).value == 100);
+  }
+  {
+    using T = NothrowMoveable;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>, 100);
+    v1.swap(v2);
+    assert(T::swap_called == 0);
+    assert(T::move_called == 1);
+    assert(T::move_assign_called == 2);
+    assert(std::get<0>(v1).value == 100);
+    assert(std::get<0>(v2).value == 42);
+    T::reset();
+    swap(v1, v2);
+    assert(T::swap_called == 0);
+    assert(T::move_called == 1);
+    assert(T::move_assign_called == 2);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<0>(v2).value == 100);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using T = NothrowTypeWithThrowingSwap;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T::swap_called == 1);
+    assert(T::move_called == 0);
+    assert(T::move_assign_called == 0);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<0>(v2).value == 100);
+  }
+  {
+    using T = ThrowingMoveCtor;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T::move_called == 1); // call threw
+    assert(T::move_assign_called == 0);
+    assert(std::get<0>(v1).value ==
+           42); // throw happened before v1 was moved from
+    assert(std::get<0>(v2).value == 100);
+  }
+  {
+    using T = ThrowingMoveAssignNothrowMoveCtor;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<0>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T::move_called == 1);
+    assert(T::move_assign_called == 1);  // call threw and didn't complete
+    assert(std::get<0>(v1).value == -1); // v1 was moved from
+    assert(std::get<0>(v2).value == 100);
+  }
+#endif
+}
+
+void test_swap_different_alternatives() {
+  {
+    using T = NothrowMoveCtorWithThrowingSwap;
+    using V = std::variant<T, int>;
+    T::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    v1.swap(v2);
+    assert(T::swap_called == 0);
+    // The libc++ implementation double copies the argument, and not
+    // the variant swap is called on.
+    LIBCPP_ASSERT(T::move_called == 1);
+    assert(T::move_called <= 2);
+    assert(T::move_assign_called == 0);
+    assert(std::get<1>(v1) == 100);
+    assert(std::get<0>(v2).value == 42);
+    T::reset();
+    swap(v1, v2);
+    assert(T::swap_called == 0);
+    LIBCPP_ASSERT(T::move_called == 2);
+    assert(T::move_called <= 2);
+    assert(T::move_assign_called == 0);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<1>(v2) == 100);
+  }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  {
+    using T1 = ThrowingTypeWithNothrowSwap;
+    using T2 = NonThrowingNonNoexceptType;
+    using V = std::variant<T1, T2>;
+    T1::reset();
+    T2::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T1::swap_called == 0);
+    assert(T1::move_called == 1); // throws
+    assert(T1::move_assign_called == 0);
+    // FIXME: libc++ shouldn't move from T2 here.
+    LIBCPP_ASSERT(T2::move_called == 1);
+    assert(T2::move_called <= 1);
+    assert(std::get<0>(v1).value == 42);
+    if (T2::move_called != 0)
+      assert(v2.valueless_by_exception());
+    else
+      assert(std::get<1>(v2).value == 100);
+  }
+  {
+    using T1 = NonThrowingNonNoexceptType;
+    using T2 = ThrowingTypeWithNothrowSwap;
+    using V = std::variant<T1, T2>;
+    T1::reset();
+    T2::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    LIBCPP_ASSERT(T1::move_called == 0);
+    assert(T1::move_called <= 1);
+    assert(T2::swap_called == 0);
+    assert(T2::move_called == 1); // throws
+    assert(T2::move_assign_called == 0);
+    if (T1::move_called != 0)
+      assert(v1.valueless_by_exception());
+    else
+      assert(std::get<0>(v1).value == 42);
+    assert(std::get<1>(v2).value == 100);
+  }
+// FIXME: The tests below are just very libc++ specific
+#ifdef _LIBCPP_VERSION
+  {
+    using T1 = ThrowsOnSecondMove;
+    using T2 = NonThrowingNonNoexceptType;
+    using V = std::variant<T1, T2>;
+    T2::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    v1.swap(v2);
+    assert(T2::move_called == 2);
+    assert(std::get<1>(v1).value == 100);
+    assert(std::get<0>(v2).value == 42);
+    assert(std::get<0>(v2).move_count == 1);
+  }
+  {
+    using T1 = NonThrowingNonNoexceptType;
+    using T2 = ThrowsOnSecondMove;
+    using V = std::variant<T1, T2>;
+    T1::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T1::move_called == 1);
+    assert(v1.valueless_by_exception());
+    assert(std::get<0>(v2).value == 42);
+  }
+#endif
+// testing libc++ extension. If either variant stores a nothrow move
+// constructible type v1.swap(v2) provides the strong exception safety
+// guarantee.
+#ifdef _LIBCPP_VERSION
+  {
+
+    using T1 = ThrowingTypeWithNothrowSwap;
+    using T2 = NothrowMoveable;
+    using V = std::variant<T1, T2>;
+    T1::reset();
+    T2::reset();
+    V v1(std::in_place_index<0>, 42);
+    V v2(std::in_place_index<1>, 100);
+    try {
+      v1.swap(v2);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T1::swap_called == 0);
+    assert(T1::move_called == 1);
+    assert(T1::move_assign_called == 0);
+    assert(T2::swap_called == 0);
+    assert(T2::move_called == 2);
+    assert(T2::move_assign_called == 0);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<1>(v2).value == 100);
+    // swap again, but call v2's swap.
+    T1::reset();
+    T2::reset();
+    try {
+      v2.swap(v1);
+      assert(false);
+    } catch (int) {
+    }
+    assert(T1::swap_called == 0);
+    assert(T1::move_called == 1);
+    assert(T1::move_assign_called == 0);
+    assert(T2::swap_called == 0);
+    assert(T2::move_called == 2);
+    assert(T2::move_assign_called == 0);
+    assert(std::get<0>(v1).value == 42);
+    assert(std::get<1>(v2).value == 100);
+  }
+#endif // _LIBCPP_VERSION
+#endif
+}
+
+template <class Var>
+constexpr auto has_swap_member_imp(int)
+    -> decltype(std::declval<Var &>().swap(std::declval<Var &>()), true) {
+  return true;
+}
+
+template <class Var> constexpr auto has_swap_member_imp(long) -> bool {
+  return false;
+}
+
+template <class Var> constexpr bool has_swap_member() {
+  return has_swap_member_imp<Var>(0);
+}
+
+void test_swap_sfinae() {
+  {
+    // This variant type does not provide either a member or non-member swap
+    // but is still swappable via the generic swap algorithm, since the
+    // variant is move constructible and move assignable.
+    using V = std::variant<int, NotSwappable>;
+    LIBCPP_STATIC_ASSERT(!has_swap_member<V>());
+    static_assert(std::is_swappable_v<V>, "");
+  }
+  {
+    using V = std::variant<int, NotCopyable>;
+    LIBCPP_STATIC_ASSERT(!has_swap_member<V>(), "");
+    static_assert(!std::is_swappable_v<V>, "");
+  }
+  {
+    using V = std::variant<int, NotCopyableWithSwap>;
+    LIBCPP_STATIC_ASSERT(!has_swap_member<V>(), "");
+    static_assert(!std::is_swappable_v<V>, "");
+  }
+  {
+    using V = std::variant<int, NotMoveAssignable>;
+    LIBCPP_STATIC_ASSERT(!has_swap_member<V>(), "");
+    static_assert(!std::is_swappable_v<V>, "");
+  }
+}
+
+void test_swap_noexcept() {
+  {
+    using V = std::variant<int, NothrowMoveable>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    using V = std::variant<int, NothrowMoveCtor>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(!std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    using V = std::variant<int, ThrowingTypeWithNothrowSwap>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(!std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    using V = std::variant<int, ThrowingMoveAssignNothrowMoveCtor>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(!std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    using V = std::variant<int, ThrowingMoveAssignNothrowMoveCtorWithSwap>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    using V = std::variant<int, NotMoveAssignableWithSwap>;
+    static_assert(std::is_swappable_v<V> && has_swap_member<V>(), "");
+    static_assert(std::is_nothrow_swappable_v<V>, "");
+    // instantiate swap
+    V v1, v2;
+    v1.swap(v2);
+    swap(v1, v2);
+  }
+  {
+    // This variant type does not provide either a member or non-member swap
+    // but is still swappable via the generic swap algorithm, since the
+    // variant is move constructible and move assignable.
+    using V = std::variant<int, NotSwappable>;
+    LIBCPP_STATIC_ASSERT(!has_swap_member<V>());
+    static_assert(std::is_swappable_v<V>, "");
+    static_assert(std::is_nothrow_swappable_v<V>, "");
+    V v1, v2;
+    swap(v1, v2);
+  }
+}
+
+
+// This is why variant should SFINAE member swap. :-)
+LIBCPP_ONLY(template class std::variant<int, NotSwappable>;)
+
+
+int main() {
+  test_swap_valueless_by_exception();
+  test_swap_same_alternative();
+  test_swap_different_alternatives();
+  test_swap_sfinae();
+  test_swap_noexcept();
+}

test/std/utilities/variant/variant.variant/variant_array.fail.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+
+#include <variant>
+#include <type_traits>
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include "test_convertible.hpp"
+
+int main()
+{
+    // expected-error@variant:* 3 {{static_assert failed}}
+    std::variant<int, int[]> v; // expected-note {{requested here}}
+    std::variant<int, int[42]> v2; // expected-note {{requested here}}
+    std::variant<int, int[][42]> v3; // expected-note {{requested here}}
+}

test/std/utilities/variant/variant.variant/variant_empty.fail.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+int main()
+{
+    // expected-error@variant:* 1 {{static_assert failed}}
+    std::variant<> v; // expected-note {{requested here}}
+}

test/std/utilities/variant/variant.variant/variant_reference.fail.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+#include <variant>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+
+int main()
+{
+    // expected-error@variant:* 3 {{static_assert failed}}
+    std::variant<int, int&> v; // expected-note {{requested here}}
+    std::variant<int, int const&> v2; // expected-note {{requested here}}
+    std::variant<int, int&&> v3; // expected-note {{requested here}}
+}

test/std/utilities/variant/variant.variant/variant_void.fail.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+
+// template <class ...Types> class variant;
+
+
+#include <variant>
+#include <type_traits>
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+#include "variant_test_helpers.hpp"
+#include "test_convertible.hpp"
+
+int main()
+{
+    // expected-error@variant:* 3 {{static_assert failed}}
+    std::variant<int, void> v; // expected-note {{requested here}}
+    std::variant<int, const void> v2; // expected-note {{requested here}}
+    std::variant<const volatile void, int> v3; // expected-note {{requested here}}
+}

test/std/utilities/variant/variant.visit/visit.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <variant>
+// template <class Visitor, class... Variants>
+// constexpr see below visit(Visitor&& vis, Variants&&... vars);
+
+#include <cassert>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+#include "test_macros.h"
+#include "type_id.h"
+#include "variant_test_helpers.hpp"
+
+enum CallType : unsigned {
+  CT_None,
+  CT_NonConst = 1,
+  CT_Const = 2,
+  CT_LValue = 4,
+  CT_RValue = 8
+};
+
+inline constexpr CallType operator|(CallType LHS, CallType RHS) {
+  return static_cast<CallType>(static_cast<unsigned>(LHS) |
+                               static_cast<unsigned>(RHS));
+}
+
+struct ForwardingCallObject {
+
+  template <class... Args> bool operator()(Args &&...) & {
+    set_call<Args &&...>(CT_NonConst | CT_LValue);
+    return true;
+  }
+
+  template <class... Args> bool operator()(Args &&...) const & {
+    set_call<Args &&...>(CT_Const | CT_LValue);
+    return true;
+  }
+
+  // Don't allow the call operator to be invoked as an rvalue.
+  template <class... Args> bool operator()(Args &&...) && {
+    set_call<Args &&...>(CT_NonConst | CT_RValue);
+    return true;
+  }
+
+  template <class... Args> bool operator()(Args &&...) const && {
+    set_call<Args &&...>(CT_Const | CT_RValue);
+    return true;
+  }
+
+  template <class... Args> static void set_call(CallType type) {
+    assert(last_call_type == CT_None);
+    assert(last_call_args == nullptr);
+    last_call_type = type;
+    last_call_args = std::addressof(makeArgumentID<Args...>());
+  }
+
+  template <class... Args> static bool check_call(CallType type) {
+    bool result = last_call_type == type && last_call_args &&
+                  *last_call_args == makeArgumentID<Args...>();
+    last_call_type = CT_None;
+    last_call_args = nullptr;
+    return result;
+  }
+
+  static CallType last_call_type;
+  static TypeID const *last_call_args;
+};
+
+CallType ForwardingCallObject::last_call_type = CT_None;
+TypeID const *ForwardingCallObject::last_call_args = nullptr;
+
+void test_call_operator_forwarding() {
+  using Fn = ForwardingCallObject;
+  Fn obj{};
+  Fn const &cobj = obj;
+  { // test call operator forwarding - single variant, single arg
+    using V = std::variant<int>;
+    V v(42);
+    std::visit(obj, v);
+    assert(Fn::check_call<int &>(CT_NonConst | CT_LValue));
+    std::visit(cobj, v);
+    assert(Fn::check_call<int &>(CT_Const | CT_LValue));
+    std::visit(std::move(obj), v);
+    assert(Fn::check_call<int &>(CT_NonConst | CT_RValue));
+    std::visit(std::move(cobj), v);
+    assert(Fn::check_call<int &>(CT_Const | CT_RValue));
+  }
+  { // test call operator forwarding - single variant, multi arg
+    using V = std::variant<int, long, double>;
+    V v(42l);
+    std::visit(obj, v);
+    assert(Fn::check_call<long &>(CT_NonConst | CT_LValue));
+    std::visit(cobj, v);
+    assert(Fn::check_call<long &>(CT_Const | CT_LValue));
+    std::visit(std::move(obj), v);
+    assert(Fn::check_call<long &>(CT_NonConst | CT_RValue));
+    std::visit(std::move(cobj), v);
+    assert(Fn::check_call<long &>(CT_Const | CT_RValue));
+  }
+  { // test call operator forwarding - multi variant, multi arg
+    using V = std::variant<int, long, double>;
+    using V2 = std::variant<int *, std::string>;
+    V v(42l);
+    V2 v2("hello");
+    std::visit(obj, v, v2);
+    assert((Fn::check_call<long &, std::string &>(CT_NonConst | CT_LValue)));
+    std::visit(cobj, v, v2);
+    assert((Fn::check_call<long &, std::string &>(CT_Const | CT_LValue)));
+    std::visit(std::move(obj), v, v2);
+    assert((Fn::check_call<long &, std::string &>(CT_NonConst | CT_RValue)));
+    std::visit(std::move(cobj), v, v2);
+    assert((Fn::check_call<long &, std::string &>(CT_Const | CT_RValue)));
+  }
+}
+
+void test_argument_forwarding() {
+  using Fn = ForwardingCallObject;
+  Fn obj{};
+  const auto Val = CT_LValue | CT_NonConst;
+  { // single argument - value type
+    using V = std::variant<int>;
+    V v(42);
+    V const &cv = v;
+    std::visit(obj, v);
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, cv);
+    assert(Fn::check_call<int const &>(Val));
+    std::visit(obj, std::move(v));
+    assert(Fn::check_call<int &&>(Val));
+    std::visit(obj, std::move(cv));
+    assert(Fn::check_call<const int &&>(Val));
+  }
+#if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
+  { // single argument - lvalue reference
+    using V = std::variant<int &>;
+    int x = 42;
+    V v(x);
+    V const &cv = v;
+    std::visit(obj, v);
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, cv);
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, std::move(v));
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, std::move(cv));
+    assert(Fn::check_call<int &>(Val));
+  }
+  { // single argument - rvalue reference
+    using V = std::variant<int &&>;
+    int x = 42;
+    V v(std::move(x));
+    V const &cv = v;
+    std::visit(obj, v);
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, cv);
+    assert(Fn::check_call<int &>(Val));
+    std::visit(obj, std::move(v));
+    assert(Fn::check_call<int &&>(Val));
+    std::visit(obj, std::move(cv));
+    assert(Fn::check_call<int &&>(Val));
+  }
+  { // multi argument - multi variant
+    using S = std::string const &;
+    using V = std::variant<int, S, long &&>;
+    std::string const str = "hello";
+    long l = 43;
+    V v1(42);
+    V const &cv1 = v1;
+    V v2(str);
+    V const &cv2 = v2;
+    V v3(std::move(l));
+    V const &cv3 = v3;
+    std::visit(obj, v1, v2, v3);
+    assert((Fn::check_call<int &, S, long &>(Val)));
+    std::visit(obj, cv1, cv2, std::move(v3));
+    assert((Fn::check_call<const int &, S, long &&>(Val)));
+  }
+#endif
+}
+
+struct ReturnFirst {
+  template <class... Args> constexpr int operator()(int f, Args &&...) const {
+    return f;
+  }
+};
+
+struct ReturnArity {
+  template <class... Args> constexpr int operator()(Args &&...) const {
+    return sizeof...(Args);
+  }
+};
+
+void test_constexpr() {
+  constexpr ReturnFirst obj{};
+  constexpr ReturnArity aobj{};
+  {
+    using V = std::variant<int>;
+    constexpr V v(42);
+    static_assert(std::visit(obj, v) == 42, "");
+  }
+  {
+    using V = std::variant<short, long, char>;
+    constexpr V v(42l);
+    static_assert(std::visit(obj, v) == 42, "");
+  }
+  {
+    using V1 = std::variant<int>;
+    using V2 = std::variant<int, char *, long long>;
+    using V3 = std::variant<bool, int, int>;
+    constexpr V1 v1;
+    constexpr V2 v2(nullptr);
+    constexpr V3 v3;
+    static_assert(std::visit(aobj, v1, v2, v3) == 3, "");
+  }
+  {
+    using V1 = std::variant<int>;
+    using V2 = std::variant<int, char *, long long>;
+    using V3 = std::variant<void *, int, int>;
+    constexpr V1 v1;
+    constexpr V2 v2(nullptr);
+    constexpr V3 v3;
+    static_assert(std::visit(aobj, v1, v2, v3) == 3, "");
+  }
+}
+
+void test_exceptions() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  ReturnArity obj{};
+  auto test = [&](auto &&... args) {
+    try {
+      std::visit(obj, args...);
+    } catch (std::bad_variant_access const &) {
+      return true;
+    } catch (...) {
+    }
+    return false;
+  };
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    V v;
+    makeEmpty(v);
+    assert(test(v));
+  }
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    using V2 = std::variant<long, std::string, void *>;
+    V v;
+    makeEmpty(v);
+    V2 v2("hello");
+    assert(test(v, v2));
+  }
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    using V2 = std::variant<long, std::string, void *>;
+    V v;
+    makeEmpty(v);
+    V2 v2("hello");
+    assert(test(v2, v));
+  }
+  {
+    using V = std::variant<int, MakeEmptyT>;
+    using V2 = std::variant<long, std::string, void *, MakeEmptyT>;
+    V v;
+    makeEmpty(v);
+    V2 v2;
+    makeEmpty(v2);
+    assert(test(v, v2));
+  }
+#endif
+}
+
+int main() {
+  test_call_operator_forwarding();
+  test_argument_forwarding();
+  test_constexpr();
+  test_exceptions();
+}

test/support/archetypes.ipp

struct AllCtors : DEFINE_BASE(AllCtors) {
   DEFINE_EXPLICIT DEFINE_CONSTEXPR AllCtors(AllCtors &&) DEFINE_CTOR;
   DEFINE_ASSIGN_CONSTEXPR AllCtors& operator=(AllCtors const&) DEFINE_ASSIGN;
   DEFINE_ASSIGN_CONSTEXPR AllCtors& operator=(AllCtors &&) DEFINE_ASSIGN;
   DEFINE_DTOR(AllCtors)
 };
 
 struct NoCtors : DEFINE_BASE(NoCtors) {
   using Base = DEFINE_BASE(NoCtors);
-  using Base::Base;
   DEFINE_EXPLICIT NoCtors() = delete;
   DEFINE_EXPLICIT NoCtors(NoCtors const&) = delete;
   NoCtors& operator=(NoCtors const&) = delete;
   DEFINE_DTOR(NoCtors)
 };
 
 struct NoDefault : DEFINE_BASE(NoDefault) {
   using Base = DEFINE_BASE(NoDefault);

test/support/variant_test_helpers.hpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SUPPORT_VARIANT_TEST_HELPERS_HPP
+#define SUPPORT_VARIANT_TEST_HELPERS_HPP
+
+#include <type_traits>
+#include <utility>
+#include <cassert>
+
+#include "test_macros.h"
+
+#if TEST_STD_VER <= 14
+#error This file requires C++17
+#endif
+
+// FIXME: Currently the variant<T&> tests are disabled using this macro.
+#define TEST_VARIANT_HAS_NO_REFERENCES
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct CopyThrows {
+  CopyThrows() = default;
+  CopyThrows(CopyThrows const&) { throw 42; }
+  CopyThrows& operator=(CopyThrows const&) { throw 42; }
+};
+
+struct MoveThrows {
+  static int alive;
+  MoveThrows() { ++alive; }
+  MoveThrows(MoveThrows const&) {++alive;}
+  MoveThrows(MoveThrows&&) {  throw 42; }
+  MoveThrows& operator=(MoveThrows const&) { return *this; }
+  MoveThrows& operator=(MoveThrows&&) { throw 42; }
+  ~MoveThrows() { --alive; }
+};
+
+int MoveThrows::alive = 0;
+
+struct MakeEmptyT {
+  static int alive;
+  MakeEmptyT() { ++alive; }
+  MakeEmptyT(MakeEmptyT const&) {
+      ++alive;
+      // Don't throw from the copy constructor since variant's assignment
+      // operator performs a copy before committing to the assignment.
+  }
+  MakeEmptyT(MakeEmptyT &&) {
+      throw 42;
+  }
+  MakeEmptyT& operator=(MakeEmptyT const&) {
+      throw 42;
+  }
+  MakeEmptyT& operator=(MakeEmptyT&&) {
+      throw 42;
+  }
+   ~MakeEmptyT() { --alive; }
+};
+static_assert(std::is_swappable_v<MakeEmptyT>, ""); // required for test
+
+int MakeEmptyT::alive = 0;
+
+template <class Variant>
+void makeEmpty(Variant& v) {
+    Variant v2(std::in_place_type<MakeEmptyT>);
+    try {
+        v = v2;
+        assert(false);
+    }  catch (...) {
+        assert(v.valueless_by_exception());
+    }
+}
+#endif // TEST_HAS_NO_EXCEPTIONS
+
+
+#endif // SUPPORT_VARIANT_TEST_HELPERS_HPP