//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14

// <variant>

// template <class ...Types> class variant;

// constexpr 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.h"

struct NoCopy {
  NoCopy(const NoCopy&)            = delete;
  NoCopy& operator=(const NoCopy&) = default;
};

struct CopyOnly {
  CopyOnly(const CopyOnly&)            = default;
  CopyOnly(CopyOnly&&)                 = delete;
  CopyOnly& operator=(const CopyOnly&) = default;
  CopyOnly& operator=(CopyOnly&&)      = delete;
};

struct MoveOnly {
  MoveOnly(const MoveOnly&)            = delete;
  MoveOnly(MoveOnly&&)                 = default;
  MoveOnly& operator=(const MoveOnly&) = delete;
  MoveOnly& operator=(MoveOnly&&)      = default;
};

struct MoveOnlyNT {
  MoveOnlyNT(const MoveOnlyNT&) = delete;
  MoveOnlyNT(MoveOnlyNT&&) {}
  MoveOnlyNT& operator=(const MoveOnlyNT&) = delete;
  MoveOnlyNT& operator=(MoveOnlyNT&&)      = default;
};

struct MoveOnlyOddNothrow {
  MoveOnlyOddNothrow(MoveOnlyOddNothrow&&) noexcept(false) {}
  MoveOnlyOddNothrow(const MoveOnlyOddNothrow&)                = delete;
  MoveOnlyOddNothrow& operator=(MoveOnlyOddNothrow&&) noexcept = default;
  MoveOnlyOddNothrow& operator=(const MoveOnlyOddNothrow&)     = delete;
};

struct MoveAssignOnly {
  MoveAssignOnly(MoveAssignOnly&&)            = delete;
  MoveAssignOnly& operator=(MoveAssignOnly&&) = default;
};

struct MoveAssign {
  constexpr MoveAssign(int v, int* move_ctor, int* move_assi)
      : value(v), move_construct(move_ctor), move_assign(move_assi) {}
  constexpr MoveAssign(MoveAssign&& o) : value(o.value), move_construct(o.move_construct), move_assign(o.move_assign) {
    ++*move_construct;
    o.value = -1;
  }
  constexpr MoveAssign& operator=(MoveAssign&& o) {
    value          = o.value;
    move_construct = o.move_construct;
    move_assign    = o.move_assign;
    ++*move_assign;
    o.value = -1;
    return *this;
  }
  int value;
  int* move_construct;
  int* move_assign;
};

struct NTMoveAssign {
  constexpr NTMoveAssign(int v) : value(v) {}
  NTMoveAssign(const NTMoveAssign&)                 = default;
  NTMoveAssign(NTMoveAssign&&)                      = default;
  NTMoveAssign& operator=(const NTMoveAssign& that) = default;
  NTMoveAssign& operator=(NTMoveAssign&& that) {
    value      = that.value;
    that.value = -1;
    return *this;
  };
  int value;
};

static_assert(!std::is_trivially_move_assignable<NTMoveAssign>::value, "");
static_assert(std::is_move_assignable<NTMoveAssign>::value, "");

struct TMoveAssign {
  constexpr TMoveAssign(int v) : value(v) {}
  TMoveAssign(const TMoveAssign&)            = delete;
  TMoveAssign(TMoveAssign&&)                 = default;
  TMoveAssign& operator=(const TMoveAssign&) = delete;
  TMoveAssign& operator=(TMoveAssign&&)      = default;
  int value;
};

static_assert(std::is_trivially_move_assignable<TMoveAssign>::value, "");

struct TMoveAssignNTCopyAssign {
  constexpr TMoveAssignNTCopyAssign(int v) : value(v) {}
  TMoveAssignNTCopyAssign(const TMoveAssignNTCopyAssign&) = default;
  TMoveAssignNTCopyAssign(TMoveAssignNTCopyAssign&&)      = default;
  TMoveAssignNTCopyAssign& operator=(const TMoveAssignNTCopyAssign& that) {
    value = that.value;
    return *this;
  }
  TMoveAssignNTCopyAssign& operator=(TMoveAssignNTCopyAssign&&) = default;
  int value;
};

static_assert(std::is_trivially_move_assignable_v<TMoveAssignNTCopyAssign>, "");

struct TrivialCopyNontrivialMove {
  TrivialCopyNontrivialMove(TrivialCopyNontrivialMove const&) = default;
  TrivialCopyNontrivialMove(TrivialCopyNontrivialMove&&) noexcept {}
  TrivialCopyNontrivialMove& operator=(TrivialCopyNontrivialMove const&) = default;
  TrivialCopyNontrivialMove& operator=(TrivialCopyNontrivialMove&&) noexcept { return *this; }
};

static_assert(std::is_trivially_copy_assignable_v<TrivialCopyNontrivialMove>, "");
static_assert(!std::is_trivially_move_assignable_v<TrivialCopyNontrivialMove>, "");

constexpr 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, "");
  }
}

constexpr void test_move_assignment_sfinae() {
  {
    using V = std::variant<int, long>;
    static_assert(std::is_move_assignable<V>::value, "");
  }
  {
    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, "");
  }

  // Make sure we properly propagate triviality (see P0602R4).
  {
    using V = std::variant<int, long>;
    static_assert(std::is_trivially_move_assignable<V>::value, "");
  }
  {
    using V = std::variant<int, NTMoveAssign>;
    static_assert(!std::is_trivially_move_assignable<V>::value, "");
    static_assert(std::is_move_assignable<V>::value, "");
  }
  {
    using V = std::variant<int, TMoveAssign>;
    static_assert(std::is_trivially_move_assignable<V>::value, "");
  }
  {
    using V = std::variant<int, TMoveAssignNTCopyAssign>;
    static_assert(std::is_trivially_move_assignable<V>::value, "");
  }
  {
    using V = std::variant<int, TrivialCopyNontrivialMove>;
    static_assert(!std::is_trivially_move_assignable<V>::value, "");
  }
  {
    using V = std::variant<int, CopyOnly>;
    static_assert(std::is_trivially_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 // TEST_HAS_NO_EXCEPTIONS
}

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 // TEST_HAS_NO_EXCEPTIONS
}

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 // TEST_HAS_NO_EXCEPTIONS
}

template <typename T>
struct Result {
  std::size_t index;
  T value;
};

TEST_CONSTEXPR_CXX20 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>;
    int move_construct = 0;
    int move_assign    = 0;
    V v1(std::in_place_type<MoveAssign>, 43, &move_construct, &move_assign);
    V v2(std::in_place_type<MoveAssign>, 42, &move_construct, &move_assign);
    V& vref = (v1 = std::move(v2));
    assert(&vref == &v1);
    assert(v1.index() == 1);
    assert(std::get<1>(v1).value == 42);
    assert(move_construct == 0);
    assert(move_assign == 1);
  }

  // Make sure we properly propagate triviality, which implies constexpr-ness (see P0602R4).
  {
    struct {
      constexpr Result<int> operator()() const {
        using V = std::variant<int>;
        V v(43);
        V v2(42);
        v = std::move(v2);
        return {v.index(), std::get<0>(v)};
      }
    } test;
    constexpr auto result = test();
    static_assert(result.index == 0, "");
    static_assert(result.value == 42, "");
  }
  {
    struct {
      constexpr Result<long> operator()() const {
        using V = std::variant<int, long, unsigned>;
        V v(43l);
        V v2(42l);
        v = std::move(v2);
        return {v.index(), std::get<1>(v)};
      }
    } test;
    constexpr auto result = test();
    static_assert(result.index == 1, "");
    static_assert(result.value == 42l, "");
  }
  {
    struct {
      constexpr Result<int> operator()() const {
        using V = std::variant<int, TMoveAssign, unsigned>;
        V v(std::in_place_type<TMoveAssign>, 43);
        V v2(std::in_place_type<TMoveAssign>, 42);
        v = std::move(v2);
        return {v.index(), std::get<1>(v).value};
      }
    } test;
    constexpr auto result = test();
    static_assert(result.index == 1, "");
    static_assert(result.value == 42, "");
  }
}

TEST_CONSTEXPR_CXX20 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>;
    int move_construct = 0;
    int move_assign    = 0;
    V v1(std::in_place_type<unsigned>, 43u);
    V v2(std::in_place_type<MoveAssign>, 42, &move_construct, &move_assign);
    V& vref = (v1 = std::move(v2));
    assert(&vref == &v1);
    assert(v1.index() == 1);
    assert(std::get<1>(v1).value == 42);
    assert(move_construct == 1);
    assert(move_assign == 0);
  }

  // Make sure we properly propagate triviality, which implies constexpr-ness (see P0602R4).
  {
    struct {
      constexpr Result<long> operator()() const {
        using V = std::variant<int, long, unsigned>;
        V v(43);
        V v2(42l);
        v = std::move(v2);
        return {v.index(), std::get<1>(v)};
      }
    } test;
    constexpr auto result = test();
    static_assert(result.index == 1, "");
    static_assert(result.value == 42l, "");
  }
  {
    struct {
      constexpr Result<long> operator()() const {
        using V = std::variant<int, TMoveAssign, unsigned>;
        V v(std::in_place_type<unsigned>, 43u);
        V v2(std::in_place_type<TMoveAssign>, 42);
        v = std::move(v2);
        return {v.index(), std::get<1>(v).value};
      }
    } test;
    constexpr auto result = test();
    static_assert(result.index == 1, "");
    static_assert(result.value == 42, "");
  }
}

void test_assignment_throw() {
#ifndef TEST_HAS_NO_EXCEPTIONS
  using MET = MakeEmptyT;
  // same index
  {
    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);
  }

  // different indices
  {
    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 // TEST_HAS_NO_EXCEPTIONS
}

template <std::size_t NewIdx, class T, class ValueType>
constexpr void test_constexpr_assign_imp(T&& v, ValueType&& new_value) {
  using Variant = std::decay_t<T>;
  Variant v2(std::forward<ValueType>(new_value));
  const auto cp = v2;
  v             = std::move(v2);
  assert(v.index() == NewIdx);
  assert(std::get<NewIdx>(v) == std::get<NewIdx>(cp));
}

constexpr void test_constexpr_move_assignment_trivial() {
  // Make sure we properly propagate triviality, which implies constexpr-ness (see P0602R4).
  using V = std::variant<long, void*, int>;
  static_assert(std::is_trivially_copyable<V>::value, "");
  static_assert(std::is_trivially_move_assignable<V>::value, "");
  test_constexpr_assign_imp<0>(V(42l), 101l);
  test_constexpr_assign_imp<0>(V(nullptr), 101l);
  test_constexpr_assign_imp<1>(V(42l), nullptr);
  test_constexpr_assign_imp<2>(V(42l), 101);
}

struct NonTrivialMoveAssign {
  int i = 0;
  constexpr NonTrivialMoveAssign(int ii) : i(ii) {}
  constexpr NonTrivialMoveAssign(const NonTrivialMoveAssign& other) = default;
  constexpr NonTrivialMoveAssign(NonTrivialMoveAssign&& other) : i(other.i) {}
  constexpr NonTrivialMoveAssign& operator=(const NonTrivialMoveAssign&) = default;
  constexpr NonTrivialMoveAssign& operator=(NonTrivialMoveAssign&& o) {
    i = o.i;
    return *this;
  }
  TEST_CONSTEXPR_CXX20 ~NonTrivialMoveAssign() = default;
  friend constexpr bool operator==(const NonTrivialMoveAssign& x, const NonTrivialMoveAssign& y) { return x.i == y.i; }
};

TEST_CONSTEXPR_CXX20 void test_constexpr_move_assignment_non_trivial() {
  using V = std::variant<long, void*, NonTrivialMoveAssign>;
  static_assert(!std::is_trivially_copyable<V>::value);
  static_assert(!std::is_trivially_move_assignable<V>::value);
  test_constexpr_assign_imp<0>(V(42l), 101l);
  test_constexpr_assign_imp<0>(V(nullptr), 101l);
  test_constexpr_assign_imp<1>(V(42l), nullptr);
  test_constexpr_assign_imp<2>(V(42l), NonTrivialMoveAssign(5));
  test_constexpr_assign_imp<2>(V(NonTrivialMoveAssign(3)), NonTrivialMoveAssign(5));
}

void non_constexpr_test() {
  test_move_assignment_empty_empty();
  test_move_assignment_non_empty_empty();
  test_move_assignment_empty_non_empty();
  test_assignment_throw();
}

constexpr bool cxx17_constexpr_test() {
  test_move_assignment_sfinae();
  test_move_assignment_noexcept();
  test_constexpr_move_assignment_trivial();

  return true;
}

TEST_CONSTEXPR_CXX20 bool cxx20_constexpr_test() {
  test_move_assignment_same_index();
  test_move_assignment_different_index();
  test_constexpr_move_assignment_non_trivial();

  return true;
}

int main(int, char**) {
  non_constexpr_test();
  cxx17_constexpr_test();
  cxx20_constexpr_test();

  static_assert(cxx17_constexpr_test());
#if TEST_STD_VER >= 20
  static_assert(cxx20_constexpr_test());
#endif
  return 0;
}