gecko-dev/mfbt/tests/TestVariant.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <type_traits>

#include "mozilla/UniquePtr.h"
#include "mozilla/Variant.h"

#include <tuple>

using mozilla::MakeUnique;
using mozilla::UniquePtr;
using mozilla::Variant;

struct Destroyer {
  static int destroyedCount;
  ~Destroyer() { destroyedCount++; }
};

int Destroyer::destroyedCount = 0;

static void testDetails() {
  printf("testDetails\n");

  using mozilla::detail::Nth;

  // Test Nth with a list of 1 item.
  static_assert(std::is_same_v<typename Nth<0, int>::Type, int>,
                "Nth<0, int>::Type should be int");

  // Test Nth with a list of more than 1 item.
  static_assert(std::is_same_v<typename Nth<0, int, char>::Type, int>,
                "Nth<0, int, char>::Type should be int");
  static_assert(std::is_same_v<typename Nth<1, int, char>::Type, char>,
                "Nth<1, int, char>::Type should be char");

  using mozilla::detail::SelectVariantType;

  // SelectVariantType for zero items (shouldn't happen, but `count` should
  // still work ok.)
  static_assert(SelectVariantType<int, char>::count == 0,
                "SelectVariantType<int, char>::count should be 0");

  // SelectVariantType for 1 type, for all combinations from/to T, const T,
  // const T&, T&&
  // - type to type
  static_assert(std::is_same_v<typename SelectVariantType<int, int>::Type, int>,
                "SelectVariantType<int, int>::Type should be int");
  static_assert(SelectVariantType<int, int>::count == 1,
                "SelectVariantType<int, int>::count should be 1");

  // - type to const type
  static_assert(std::is_same_v<typename SelectVariantType<int, const int>::Type,
                               const int>,
                "SelectVariantType<int, const int>::Type should be const int");
  static_assert(SelectVariantType<int, const int>::count == 1,
                "SelectVariantType<int, const int>::count should be 1");

  // - type to const type&
  static_assert(
      std::is_same_v<typename SelectVariantType<int, const int&>::Type,
                     const int&>,
      "SelectVariantType<int, const int&>::Type should be const int&");
  static_assert(SelectVariantType<int, const int&>::count == 1,
                "SelectVariantType<int, const int&>::count should be 1");

  // - type to type&&
  static_assert(
      std::is_same_v<typename SelectVariantType<int, int&&>::Type, int&&>,
      "SelectVariantType<int, int&&>::Type should be int&&");
  static_assert(SelectVariantType<int, int&&>::count == 1,
                "SelectVariantType<int, int&&>::count should be 1");

  // - const type to type
  static_assert(
      std::is_same_v<typename SelectVariantType<const int, int>::Type, int>,
      "SelectVariantType<const int, int>::Type should be int");
  static_assert(SelectVariantType<const int, int>::count == 1,
                "SelectVariantType<const int, int>::count should be 1");

  // - const type to const type
  static_assert(
      std::is_same_v<typename SelectVariantType<const int, const int>::Type,
                     const int>,
      "SelectVariantType<const int, const int>::Type should be const int");
  static_assert(SelectVariantType<const int, const int>::count == 1,
                "SelectVariantType<const int, const int>::count should be 1");

  // - const type to const type&
  static_assert(
      std::is_same_v<typename SelectVariantType<const int, const int&>::Type,
                     const int&>,
      "SelectVariantType<const int, const int&>::Type should be const int&");
  static_assert(SelectVariantType<const int, const int&>::count == 1,
                "SelectVariantType<const int, const int&>::count should be 1");

  // - const type to type&&
  static_assert(
      std::is_same_v<typename SelectVariantType<const int, int&&>::Type, int&&>,
      "SelectVariantType<const int, int&&>::Type should be int&&");
  static_assert(SelectVariantType<const int, int&&>::count == 1,
                "SelectVariantType<const int, int&&>::count should be 1");

  // - const type& to type
  static_assert(
      std::is_same_v<typename SelectVariantType<const int&, int>::Type, int>,
      "SelectVariantType<const int&, int>::Type should be int");
  static_assert(SelectVariantType<const int&, int>::count == 1,
                "SelectVariantType<const int&, int>::count should be 1");

  // - const type& to const type
  static_assert(
      std::is_same_v<typename SelectVariantType<const int&, const int>::Type,
                     const int>,
      "SelectVariantType<const int&, const int>::Type should be const int");
  static_assert(SelectVariantType<const int&, const int>::count == 1,
                "SelectVariantType<const int&, const int>::count should be 1");

  // - const type& to const type&
  static_assert(
      std::is_same_v<typename SelectVariantType<const int&, const int&>::Type,
                     const int&>,
      "SelectVariantType<const int&, const int&>::Type should be const int&");
  static_assert(SelectVariantType<const int&, const int&>::count == 1,
                "SelectVariantType<const int&, const int&>::count should be 1");

  // - const type& to type&&
  static_assert(
      std::is_same_v<typename SelectVariantType<const int&, int&&>::Type,
                     int&&>,
      "SelectVariantType<const int&, int&&>::Type should be int&&");
  static_assert(SelectVariantType<const int&, int&&>::count == 1,
                "SelectVariantType<const int&, int&&>::count should be 1");

  // - type&& to type
  static_assert(
      std::is_same_v<typename SelectVariantType<int&&, int>::Type, int>,
      "SelectVariantType<int&&, int>::Type should be int");
  static_assert(SelectVariantType<int&&, int>::count == 1,
                "SelectVariantType<int&&, int>::count should be 1");

  // - type&& to const type
  static_assert(
      std::is_same_v<typename SelectVariantType<int&&, const int>::Type,
                     const int>,
      "SelectVariantType<int&&, const int>::Type should be const int");
  static_assert(SelectVariantType<int&&, const int>::count == 1,
                "SelectVariantType<int&&, const int>::count should be 1");

  // - type&& to const type&
  static_assert(
      std::is_same_v<typename SelectVariantType<int&&, const int&>::Type,
                     const int&>,
      "SelectVariantType<int&&, const int&>::Type should be const int&");
  static_assert(SelectVariantType<int&&, const int&>::count == 1,
                "SelectVariantType<int&&, const int&>::count should be 1");

  // - type&& to type&&
  static_assert(
      std::is_same_v<typename SelectVariantType<int&&, int&&>::Type, int&&>,
      "SelectVariantType<int&&, int&&>::Type should be int&&");
  static_assert(SelectVariantType<int&&, int&&>::count == 1,
                "SelectVariantType<int&&, int&&>::count should be 1");

  // SelectVariantType for two different types.
  // (Don't test all combinations, trust that the above tests are sufficient.)
  static_assert(
      std::is_same_v<typename SelectVariantType<int, int, char>::Type, int>,
      "SelectVariantType<int, int, char>::Type should be int");
  static_assert(SelectVariantType<int, int, char>::count == 1,
                "SelectVariantType<int, int, char>::count should be 1");
  static_assert(
      std::is_same_v<typename SelectVariantType<char, int, char>::Type, char>,
      "SelectVariantType<char, int, char>::Type should be char");
  static_assert(SelectVariantType<char, int, char>::count == 1,
                "SelectVariantType<char, int, char>::count should be 1");

  // SelectVariantType for two identical types.
  static_assert(
      std::is_same_v<typename SelectVariantType<int, int, int>::Type, int>,
      "SelectVariantType<int, int, int>::Type should be int");
  static_assert(SelectVariantType<int, int, int>::count == 2,
                "SelectVariantType<int, int, int>::count should be 2");

  // SelectVariantType for two identical types, with others around.
  static_assert(
      std::is_same_v<typename SelectVariantType<int, char, int, int>::Type,
                     int>,
      "SelectVariantType<int, char, int, int>::Type should be int");
  static_assert(SelectVariantType<int, char, int, int>::count == 2,
                "SelectVariantType<int, char, int, int>::count should be 2");

  static_assert(
      std::is_same_v<typename SelectVariantType<int, int, char, int>::Type,
                     int>,
      "SelectVariantType<int, int, char, int>::Type should be int");
  static_assert(SelectVariantType<int, int, char, int>::count == 2,
                "SelectVariantType<int, int, char, int>::count should be 2");

  static_assert(
      std::is_same_v<typename SelectVariantType<int, int, int, char>::Type,
                     int>,
      "SelectVariantType<int, int, int, char>::Type should be int");
  static_assert(SelectVariantType<int, int, int, char>::count == 2,
                "SelectVariantType<int, int, int, char>::count should be 2");

  static_assert(
      std::is_same_v<
          typename SelectVariantType<int, char, int, char, int, char>::Type,
          int>,
      "SelectVariantType<int, char, int, char, int, char>::Type should be int");
  static_assert(
      SelectVariantType<int, char, int, char, int, char>::count == 2,
      "SelectVariantType<int, char, int, char, int, char>::count should be 2");

  // SelectVariantType for two identically-selectable types (first one wins!).
  static_assert(
      std::is_same_v<typename SelectVariantType<int, int, const int>::Type,
                     int>,
      "SelectVariantType<int, int, const int>::Type should be int");
  static_assert(SelectVariantType<int, int, const int>::count == 2,
                "SelectVariantType<int, int, const int>::count should be 2");
  static_assert(
      std::is_same_v<typename SelectVariantType<int, const int, int>::Type,
                     const int>,
      "SelectVariantType<int, const int, int>::Type should be const int");
  static_assert(SelectVariantType<int, const int, int>::count == 2,
                "SelectVariantType<int, const int, int>::count should be 2");
  static_assert(
      std::is_same_v<typename SelectVariantType<int, const int, int&&>::Type,
                     const int>,
      "SelectVariantType<int, const int, int&&>::Type should be const int");
  static_assert(SelectVariantType<int, const int, int&&>::count == 2,
                "SelectVariantType<int, const int, int&&>::count should be 2");
}

static void testSimple() {
  printf("testSimple\n");
  using V = Variant<uint32_t, uint64_t>;

  // Non-const lvalue.
  V v(uint64_t(1));
  MOZ_RELEASE_ASSERT(v.is<uint64_t>());
  MOZ_RELEASE_ASSERT(!v.is<uint32_t>());
  MOZ_RELEASE_ASSERT(v.as<uint64_t>() == 1);

  MOZ_RELEASE_ASSERT(v.is<1>());
  MOZ_RELEASE_ASSERT(!v.is<0>());
  static_assert(std::is_same_v<decltype(v.as<1>()), uint64_t&>,
                "v.as<1>() should return a uint64_t&");
  MOZ_RELEASE_ASSERT(v.as<1>() == 1);

  // Const lvalue.
  const V& cv = v;
  MOZ_RELEASE_ASSERT(cv.is<uint64_t>());
  MOZ_RELEASE_ASSERT(!cv.is<uint32_t>());
  MOZ_RELEASE_ASSERT(cv.as<uint64_t>() == 1);

  MOZ_RELEASE_ASSERT(cv.is<1>());
  MOZ_RELEASE_ASSERT(!cv.is<0>());
  static_assert(std::is_same_v<decltype(cv.as<1>()), const uint64_t&>,
                "cv.as<1>() should return a const uint64_t&");
  MOZ_RELEASE_ASSERT(cv.as<1>() == 1);

  // Non-const rvalue, using a function to create a temporary.
  auto MakeV = []() { return V(uint64_t(1)); };
  MOZ_RELEASE_ASSERT(MakeV().is<uint64_t>());
  MOZ_RELEASE_ASSERT(!MakeV().is<uint32_t>());
  MOZ_RELEASE_ASSERT(MakeV().as<uint64_t>() == 1);

  MOZ_RELEASE_ASSERT(MakeV().is<1>());
  MOZ_RELEASE_ASSERT(!MakeV().is<0>());
  static_assert(std::is_same_v<decltype(MakeV().as<1>()), uint64_t&&>,
                "MakeV().as<1>() should return a uint64_t&&");
  MOZ_RELEASE_ASSERT(MakeV().as<1>() == 1);

  // Const rvalue, using a function to create a temporary.
  auto MakeCV = []() -> const V { return V(uint64_t(1)); };
  MOZ_RELEASE_ASSERT(MakeCV().is<uint64_t>());
  MOZ_RELEASE_ASSERT(!MakeCV().is<uint32_t>());
  MOZ_RELEASE_ASSERT(MakeCV().as<uint64_t>() == 1);

  MOZ_RELEASE_ASSERT(MakeCV().is<1>());
  MOZ_RELEASE_ASSERT(!MakeCV().is<0>());
  static_assert(std::is_same_v<decltype(MakeCV().as<1>()), const uint64_t&&>,
                "MakeCV().as<1>() should return a const uint64_t&&");
  MOZ_RELEASE_ASSERT(MakeCV().as<1>() == 1);
}

static void testDuplicate() {
  printf("testDuplicate\n");
  Variant<uint32_t, uint64_t, uint32_t> v(uint64_t(1));
  MOZ_RELEASE_ASSERT(v.is<uint64_t>());
  MOZ_RELEASE_ASSERT(v.as<uint64_t>() == 1);
  // Note: uint32_t is not unique, so `v.is<uint32_t>()` is not allowed.

  MOZ_RELEASE_ASSERT(v.is<1>());
  MOZ_RELEASE_ASSERT(!v.is<0>());
  MOZ_RELEASE_ASSERT(!v.is<2>());
  static_assert(std::is_same_v<decltype(v.as<0>()), uint32_t&>,
                "as<0>() should return a uint64_t");
  static_assert(std::is_same_v<decltype(v.as<1>()), uint64_t&>,
                "as<1>() should return a uint64_t");
  static_assert(std::is_same_v<decltype(v.as<2>()), uint32_t&>,
                "as<2>() should return a uint64_t");
  MOZ_RELEASE_ASSERT(v.as<1>() == 1);
  MOZ_RELEASE_ASSERT(v.extract<1>() == 1);
}

static void testConstructionWithVariantType() {
  Variant<uint32_t, uint64_t, uint32_t> v(mozilla::VariantType<uint64_t>{}, 3);
  MOZ_RELEASE_ASSERT(v.is<uint64_t>());
  // MOZ_RELEASE_ASSERT(!v.is<uint32_t>()); // uint32_t is not unique!
  MOZ_RELEASE_ASSERT(v.as<uint64_t>() == 3);
}

static void testConstructionWithVariantIndex() {
  Variant<uint32_t, uint64_t, uint32_t> v(mozilla::VariantIndex<2>{}, 2);
  MOZ_RELEASE_ASSERT(!v.is<uint64_t>());
  // Note: uint32_t is not unique, so `v.is<uint32_t>()` is not allowed.

  MOZ_RELEASE_ASSERT(!v.is<1>());
  MOZ_RELEASE_ASSERT(!v.is<0>());
  MOZ_RELEASE_ASSERT(v.is<2>());
  MOZ_RELEASE_ASSERT(v.as<2>() == 2);
  MOZ_RELEASE_ASSERT(v.extract<2>() == 2);
}

static void testEmplaceWithType() {
  printf("testEmplaceWithType\n");
  Variant<uint32_t, uint64_t, uint32_t> v1(mozilla::VariantIndex<0>{}, 0);
  v1.emplace<uint64_t>(3);
  MOZ_RELEASE_ASSERT(v1.is<uint64_t>());
  MOZ_RELEASE_ASSERT(v1.as<uint64_t>() == 3);

  Variant<UniquePtr<int>, char> v2('a');
  v2.emplace<UniquePtr<int>>();
  MOZ_RELEASE_ASSERT(v2.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(!v2.as<UniquePtr<int>>().get());

  Variant<UniquePtr<int>, char> v3('a');
  v3.emplace<UniquePtr<int>>(MakeUnique<int>(4));
  MOZ_RELEASE_ASSERT(v3.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(*v3.as<UniquePtr<int>>().get() == 4);
}

static void testEmplaceWithIndex() {
  printf("testEmplaceWithIndex\n");
  Variant<uint32_t, uint64_t, uint32_t> v1(mozilla::VariantIndex<1>{}, 0);
  v1.emplace<2>(2);
  MOZ_RELEASE_ASSERT(!v1.is<uint64_t>());
  MOZ_RELEASE_ASSERT(!v1.is<1>());
  MOZ_RELEASE_ASSERT(!v1.is<0>());
  MOZ_RELEASE_ASSERT(v1.is<2>());
  MOZ_RELEASE_ASSERT(v1.as<2>() == 2);
  MOZ_RELEASE_ASSERT(v1.extract<2>() == 2);

  Variant<UniquePtr<int>, char> v2('a');
  v2.emplace<0>();
  MOZ_RELEASE_ASSERT(v2.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(!v2.is<1>());
  MOZ_RELEASE_ASSERT(v2.is<0>());
  MOZ_RELEASE_ASSERT(!v2.as<0>().get());
  MOZ_RELEASE_ASSERT(!v2.extract<0>().get());

  Variant<UniquePtr<int>, char> v3('a');
  v3.emplace<0>(MakeUnique<int>(4));
  MOZ_RELEASE_ASSERT(v3.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(!v3.is<1>());
  MOZ_RELEASE_ASSERT(v3.is<0>());
  MOZ_RELEASE_ASSERT(*v3.as<0>().get() == 4);
  MOZ_RELEASE_ASSERT(*v3.extract<0>().get() == 4);
}

static void testCopy() {
  printf("testCopy\n");
  Variant<uint32_t, uint64_t> v1(uint64_t(1));
  Variant<uint32_t, uint64_t> v2(v1);
  MOZ_RELEASE_ASSERT(v2.is<uint64_t>());
  MOZ_RELEASE_ASSERT(!v2.is<uint32_t>());
  MOZ_RELEASE_ASSERT(v2.as<uint64_t>() == 1);

  Variant<uint32_t, uint64_t> v3(uint32_t(10));
  v3 = v2;
  MOZ_RELEASE_ASSERT(v3.is<uint64_t>());
  MOZ_RELEASE_ASSERT(v3.as<uint64_t>() == 1);
}

static void testMove() {
  printf("testMove\n");
  Variant<UniquePtr<int>, char> v1(MakeUnique<int>(5));
  Variant<UniquePtr<int>, char> v2(std::move(v1));

  MOZ_RELEASE_ASSERT(v2.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(*v2.as<UniquePtr<int>>() == 5);

  MOZ_RELEASE_ASSERT(v1.is<UniquePtr<int>>());
  MOZ_RELEASE_ASSERT(v1.as<UniquePtr<int>>() == nullptr);

  Destroyer::destroyedCount = 0;
  {
    Variant<char, UniquePtr<Destroyer>> v3(MakeUnique<Destroyer>());
    Variant<char, UniquePtr<Destroyer>> v4(std::move(v3));

    Variant<char, UniquePtr<Destroyer>> v5('a');
    v5 = std::move(v4);

    auto ptr = v5.extract<UniquePtr<Destroyer>>();
    MOZ_RELEASE_ASSERT(Destroyer::destroyedCount == 0);
  }
  MOZ_RELEASE_ASSERT(Destroyer::destroyedCount == 1);
}

static void testDestructor() {
  printf("testDestructor\n");
  Destroyer::destroyedCount = 0;

  {
    Destroyer d;

    {
      Variant<char, UniquePtr<char[]>, Destroyer> v1(d);
      MOZ_RELEASE_ASSERT(Destroyer::destroyedCount ==
                         0);  // None destroyed yet.
    }

    MOZ_RELEASE_ASSERT(Destroyer::destroyedCount ==
                       1);  // v1's copy of d is destroyed.

    {
      Variant<char, UniquePtr<char[]>, Destroyer> v2(
          mozilla::VariantIndex<2>{});
      v2.emplace<Destroyer>(d);
      MOZ_RELEASE_ASSERT(Destroyer::destroyedCount ==
                         2);  // v2's initial value is destroyed.
    }

    MOZ_RELEASE_ASSERT(Destroyer::destroyedCount ==
                       3);  // v2's second value is destroyed.
  }

  MOZ_RELEASE_ASSERT(Destroyer::destroyedCount == 4);  // d is destroyed.
}

static void testEquality() {
  printf("testEquality\n");
  using V = Variant<char, int>;

  V v0('a');
  V v1('b');
  V v2('b');
  V v3(42);
  V v4(27);
  V v5(27);
  V v6(int('b'));

  MOZ_RELEASE_ASSERT(v0 != v1);
  MOZ_RELEASE_ASSERT(v1 == v2);
  MOZ_RELEASE_ASSERT(v2 != v3);
  MOZ_RELEASE_ASSERT(v3 != v4);
  MOZ_RELEASE_ASSERT(v4 == v5);
  MOZ_RELEASE_ASSERT(v1 != v6);

  MOZ_RELEASE_ASSERT(v0 == v0);
  MOZ_RELEASE_ASSERT(v1 == v1);
  MOZ_RELEASE_ASSERT(v2 == v2);
  MOZ_RELEASE_ASSERT(v3 == v3);
  MOZ_RELEASE_ASSERT(v4 == v4);
  MOZ_RELEASE_ASSERT(v5 == v5);
  MOZ_RELEASE_ASSERT(v6 == v6);
}

// Matcher that returns a description of how its call-operator was invoked.
struct Describer {
  enum class ParameterSize { NA, U8, U32, U64 };
  enum class ParameterQualifier {
    NA,
    ParamLREF,
    ParamCLREF,
    ParamRREF,
    ParamCRREF
  };
  enum class ThisQualifier { NA, ThisLREF, ThisCLREF, ThisRREF, ThisCRREF };

  using Result =
      std::tuple<ParameterSize, ParameterQualifier, ThisQualifier, uint64_t>;

#define RESULT(SIZE, PQUAL, TQUAL, VALUE)                 \
  Describer::Result(Describer::ParameterSize::SIZE,       \
                    Describer::ParameterQualifier::PQUAL, \
                    Describer::ThisQualifier::TQUAL, VALUE)

#define CALL(TYPE, SIZE, PQUAL, TREF, TQUAL)   \
  Result operator()(TYPE aValue) TREF {        \
    return RESULT(SIZE, PQUAL, TQUAL, aValue); \
  }

  // All combinations of possible call operators:
  // Every line, the parameter integer type changes.
  // Every 3 lines, the parameter type changes constness.
  // Every 6 lines, the parameter changes reference l/r-valueness.
  // Every 12 lines, the member function qualifier changes constness.
  // After 24 lines, the member function qualifier changes ref l/r-valueness.
  CALL(uint8_t&, U8, ParamLREF, &, ThisLREF)
  CALL(uint32_t&, U32, ParamLREF, &, ThisLREF)
  CALL(uint64_t&, U64, ParamLREF, &, ThisLREF)

  CALL(const uint8_t&, U8, ParamCLREF, &, ThisLREF)
  CALL(const uint32_t&, U32, ParamCLREF, &, ThisLREF)
  CALL(const uint64_t&, U64, ParamCLREF, &, ThisLREF)

  CALL(uint8_t&&, U8, ParamRREF, &, ThisLREF)
  CALL(uint32_t&&, U32, ParamRREF, &, ThisLREF)
  CALL(uint64_t&&, U64, ParamRREF, &, ThisLREF)

  CALL(const uint8_t&&, U8, ParamCRREF, &, ThisLREF)
  CALL(const uint32_t&&, U32, ParamCRREF, &, ThisLREF)
  CALL(const uint64_t&&, U64, ParamCRREF, &, ThisLREF)

  CALL(uint8_t&, U8, ParamLREF, const&, ThisCLREF)
  CALL(uint32_t&, U32, ParamLREF, const&, ThisCLREF)
  CALL(uint64_t&, U64, ParamLREF, const&, ThisCLREF)

  CALL(const uint8_t&, U8, ParamCLREF, const&, ThisCLREF)
  CALL(const uint32_t&, U32, ParamCLREF, const&, ThisCLREF)
  CALL(const uint64_t&, U64, ParamCLREF, const&, ThisCLREF)

  CALL(uint8_t&&, U8, ParamRREF, const&, ThisCLREF)
  CALL(uint32_t&&, U32, ParamRREF, const&, ThisCLREF)
  CALL(uint64_t&&, U64, ParamRREF, const&, ThisCLREF)

  CALL(const uint8_t&&, U8, ParamCRREF, const&, ThisCLREF)
  CALL(const uint32_t&&, U32, ParamCRREF, const&, ThisCLREF)
  CALL(const uint64_t&&, U64, ParamCRREF, const&, ThisCLREF)

  CALL(uint8_t&, U8, ParamLREF, &&, ThisRREF)
  CALL(uint32_t&, U32, ParamLREF, &&, ThisRREF)
  CALL(uint64_t&, U64, ParamLREF, &&, ThisRREF)

  CALL(const uint8_t&, U8, ParamCLREF, &&, ThisRREF)
  CALL(const uint32_t&, U32, ParamCLREF, &&, ThisRREF)
  CALL(const uint64_t&, U64, ParamCLREF, &&, ThisRREF)

  CALL(uint8_t&&, U8, ParamRREF, &&, ThisRREF)
  CALL(uint32_t&&, U32, ParamRREF, &&, ThisRREF)
  CALL(uint64_t&&, U64, ParamRREF, &&, ThisRREF)

  CALL(const uint8_t&&, U8, ParamCRREF, &&, ThisRREF)
  CALL(const uint32_t&&, U32, ParamCRREF, &&, ThisRREF)
  CALL(const uint64_t&&, U64, ParamCRREF, &&, ThisRREF)

  CALL(uint8_t&, U8, ParamLREF, const&&, ThisCRREF)
  CALL(uint32_t&, U32, ParamLREF, const&&, ThisCRREF)
  CALL(uint64_t&, U64, ParamLREF, const&&, ThisCRREF)

  CALL(const uint8_t&, U8, ParamCLREF, const&&, ThisCRREF)
  CALL(const uint32_t&, U32, ParamCLREF, const&&, ThisCRREF)
  CALL(const uint64_t&, U64, ParamCLREF, const&&, ThisCRREF)

  CALL(uint8_t&&, U8, ParamRREF, const&&, ThisCRREF)
  CALL(uint32_t&&, U32, ParamRREF, const&&, ThisCRREF)
  CALL(uint64_t&&, U64, ParamRREF, const&&, ThisCRREF)

  CALL(const uint8_t&&, U8, ParamCRREF, const&&, ThisCRREF)
  CALL(const uint32_t&&, U32, ParamCRREF, const&&, ThisCRREF)
  CALL(const uint64_t&&, U64, ParamCRREF, const&&, ThisCRREF)

#undef CALL

  // Catch-all, to verify that there is no call with any type other than the
  // expected ones above.
  template <typename Other>
  Result operator()(const Other&) {
    MOZ_RELEASE_ASSERT(false);
    return RESULT(NA, NA, NA, 0);
  }
};

static void testMatching() {
  printf("testMatching\n");
  using V = Variant<uint8_t, uint32_t, uint64_t>;

  Describer desc;
  const Describer descConst;
  auto MakeDescriber = []() { return Describer(); };
  auto MakeConstDescriber = []() -> const Describer { return Describer(); };

  V v1(uint8_t(1));
  V v2(uint32_t(2));
  V v3(uint64_t(3));

  const V& constRef1 = v1;
  const V& constRef2 = v2;
  const V& constRef3 = v3;

  // Create a temporary variant by returning a copy of one.
  auto CopyV = [](const V& aV) { return aV; };

  // Create a temporary variant by returning a const copy of one.
  auto CopyConstV = [](const V& aV) -> const V { return aV; };

  // All combinations of possible calls:
  // Every line, the variant integer type changes.
  // Every 3 lines, the variant type changes constness.
  // Every 6 lines, the variant changes reference l/r-valueness.
  // Every 12 lines, the matcher changes constness.
  // After 24 lines, the matcher changes ref l/r-valueness.
  MOZ_RELEASE_ASSERT(v1.match(desc) == RESULT(U8, ParamLREF, ThisLREF, 1));
  MOZ_RELEASE_ASSERT(v2.match(desc) == RESULT(U32, ParamLREF, ThisLREF, 2));
  MOZ_RELEASE_ASSERT(v3.match(desc) == RESULT(U64, ParamLREF, ThisLREF, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(desc) ==
                     RESULT(U8, ParamCLREF, ThisLREF, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(desc) ==
                     RESULT(U32, ParamCLREF, ThisLREF, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(desc) ==
                     RESULT(U64, ParamCLREF, ThisLREF, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(desc) ==
                     RESULT(U8, ParamRREF, ThisLREF, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(desc) ==
                     RESULT(U32, ParamRREF, ThisLREF, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(desc) ==
                     RESULT(U64, ParamRREF, ThisLREF, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(desc) ==
                     RESULT(U8, ParamCRREF, ThisLREF, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(desc) ==
                     RESULT(U32, ParamCRREF, ThisLREF, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(desc) ==
                     RESULT(U64, ParamCRREF, ThisLREF, 3));

  MOZ_RELEASE_ASSERT(v1.match(descConst) ==
                     RESULT(U8, ParamLREF, ThisCLREF, 1));
  MOZ_RELEASE_ASSERT(v2.match(descConst) ==
                     RESULT(U32, ParamLREF, ThisCLREF, 2));
  MOZ_RELEASE_ASSERT(v3.match(descConst) ==
                     RESULT(U64, ParamLREF, ThisCLREF, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(descConst) ==
                     RESULT(U8, ParamCLREF, ThisCLREF, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(descConst) ==
                     RESULT(U32, ParamCLREF, ThisCLREF, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(descConst) ==
                     RESULT(U64, ParamCLREF, ThisCLREF, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(descConst) ==
                     RESULT(U8, ParamRREF, ThisCLREF, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(descConst) ==
                     RESULT(U32, ParamRREF, ThisCLREF, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(descConst) ==
                     RESULT(U64, ParamRREF, ThisCLREF, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(descConst) ==
                     RESULT(U8, ParamCRREF, ThisCLREF, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(descConst) ==
                     RESULT(U32, ParamCRREF, ThisCLREF, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(descConst) ==
                     RESULT(U64, ParamCRREF, ThisCLREF, 3));

  MOZ_RELEASE_ASSERT(v1.match(MakeDescriber()) ==
                     RESULT(U8, ParamLREF, ThisRREF, 1));
  MOZ_RELEASE_ASSERT(v2.match(MakeDescriber()) ==
                     RESULT(U32, ParamLREF, ThisRREF, 2));
  MOZ_RELEASE_ASSERT(v3.match(MakeDescriber()) ==
                     RESULT(U64, ParamLREF, ThisRREF, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(MakeDescriber()) ==
                     RESULT(U8, ParamCLREF, ThisRREF, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(MakeDescriber()) ==
                     RESULT(U32, ParamCLREF, ThisRREF, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(MakeDescriber()) ==
                     RESULT(U64, ParamCLREF, ThisRREF, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(MakeDescriber()) ==
                     RESULT(U8, ParamRREF, ThisRREF, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(MakeDescriber()) ==
                     RESULT(U32, ParamRREF, ThisRREF, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(MakeDescriber()) ==
                     RESULT(U64, ParamRREF, ThisRREF, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(MakeDescriber()) ==
                     RESULT(U8, ParamCRREF, ThisRREF, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(MakeDescriber()) ==
                     RESULT(U32, ParamCRREF, ThisRREF, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(MakeDescriber()) ==
                     RESULT(U64, ParamCRREF, ThisRREF, 3));

  MOZ_RELEASE_ASSERT(v1.match(MakeConstDescriber()) ==
                     RESULT(U8, ParamLREF, ThisCRREF, 1));
  MOZ_RELEASE_ASSERT(v2.match(MakeConstDescriber()) ==
                     RESULT(U32, ParamLREF, ThisCRREF, 2));
  MOZ_RELEASE_ASSERT(v3.match(MakeConstDescriber()) ==
                     RESULT(U64, ParamLREF, ThisCRREF, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(MakeConstDescriber()) ==
                     RESULT(U8, ParamCLREF, ThisCRREF, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(MakeConstDescriber()) ==
                     RESULT(U32, ParamCLREF, ThisCRREF, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(MakeConstDescriber()) ==
                     RESULT(U64, ParamCLREF, ThisCRREF, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(MakeConstDescriber()) ==
                     RESULT(U8, ParamRREF, ThisCRREF, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(MakeConstDescriber()) ==
                     RESULT(U32, ParamRREF, ThisCRREF, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(MakeConstDescriber()) ==
                     RESULT(U64, ParamRREF, ThisCRREF, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(MakeConstDescriber()) ==
                     RESULT(U8, ParamCRREF, ThisCRREF, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(MakeConstDescriber()) ==
                     RESULT(U32, ParamCRREF, ThisCRREF, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(MakeConstDescriber()) ==
                     RESULT(U64, ParamCRREF, ThisCRREF, 3));
}

static void testMatchingLambda() {
  printf("testMatchingLambda\n");
  using V = Variant<uint8_t, uint32_t, uint64_t>;

  // Note: Lambdas' call operators are const by default (unless the lambda is
  // declared `mutable`).
  // There is no need to test mutable lambdas, nor rvalue lambda, because there
  // would be no way to distinguish how each lambda is actually invoked because
  // there is only one choice of call operator in each overload set.
  auto desc = [](auto&& a) {
    if constexpr (std::is_same_v<decltype(a), uint8_t&>) {
      return RESULT(U8, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&>) {
      return RESULT(U8, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint8_t&&>) {
      return RESULT(U8, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&&>) {
      return RESULT(U8, ParamCRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&>) {
      return RESULT(U32, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&>) {
      return RESULT(U32, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&&>) {
      return RESULT(U32, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&&>) {
      return RESULT(U32, ParamCRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&>) {
      return RESULT(U64, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&>) {
      return RESULT(U64, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&&>) {
      return RESULT(U64, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&&>) {
      return RESULT(U64, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };

  V v1(uint8_t(1));
  V v2(uint32_t(2));
  V v3(uint64_t(3));

  const V& constRef1 = v1;
  const V& constRef2 = v2;
  const V& constRef3 = v3;

  // Create a temporary variant by returning a copy of one.
  auto CopyV = [](const V& aV) { return aV; };

  // Create a temporary variant by returning a const copy of one.
  auto CopyConstV = [](const V& aV) -> const V { return aV; };

  MOZ_RELEASE_ASSERT(v1.match(desc) == RESULT(U8, ParamLREF, NA, 1));
  MOZ_RELEASE_ASSERT(v2.match(desc) == RESULT(U32, ParamLREF, NA, 2));
  MOZ_RELEASE_ASSERT(v3.match(desc) == RESULT(U64, ParamLREF, NA, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(desc) == RESULT(U8, ParamCLREF, NA, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(desc) == RESULT(U32, ParamCLREF, NA, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(desc) == RESULT(U64, ParamCLREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(desc) == RESULT(U8, ParamRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(desc) == RESULT(U32, ParamRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(desc) == RESULT(U64, ParamRREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(desc) ==
                     RESULT(U8, ParamCRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(desc) ==
                     RESULT(U32, ParamCRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(desc) ==
                     RESULT(U64, ParamCRREF, NA, 3));
}

static void testMatchingLambdaWithIndex() {
  printf("testMatchingLambdaWithIndex\n");
  using V = Variant<uint8_t, uint32_t, uint64_t>;

  // Note: Lambdas' call operators are const by default (unless the lambda is
  // declared `mutable`), hence the use of "...Const" strings below.
  // There is no need to test mutable lambdas, nor rvalue lambda, because there
  // would be no way to distinguish how each lambda is actually invoked because
  // there is only one choice of call operator in each overload set.
  auto desc = [](auto aIndex, auto&& a) {
    static_assert(
        std::is_same_v<decltype(aIndex), uint_fast8_t>,
        "Expected a uint_fast8_t index for a Variant with 3 alternatives");
    if constexpr (std::is_same_v<decltype(a), uint8_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 0);
      return RESULT(U8, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 0);
      return RESULT(U8, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint8_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 0);
      return RESULT(U8, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 0);
      return RESULT(U8, ParamCRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 1);
      return RESULT(U32, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 1);
      return RESULT(U32, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 1);
      return RESULT(U32, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 1);
      return RESULT(U32, ParamCRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 2);
      return RESULT(U64, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&>) {
      MOZ_RELEASE_ASSERT(aIndex == 2);
      return RESULT(U64, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 2);
      return RESULT(U64, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&&>) {
      MOZ_RELEASE_ASSERT(aIndex == 2);
      return RESULT(U64, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };

  V v1(uint8_t(1));
  V v2(uint32_t(2));
  V v3(uint64_t(3));

  const V& constRef1 = v1;
  const V& constRef2 = v2;
  const V& constRef3 = v3;

  // Create a temporary variant by returning a copy of one.
  auto CopyV = [](const V& aV) { return aV; };

  // Create a temporary variant by returning a const copy of one.
  auto CopyConstV = [](const V& aV) -> const V { return aV; };

  MOZ_RELEASE_ASSERT(v1.match(desc) == RESULT(U8, ParamLREF, NA, 1));
  MOZ_RELEASE_ASSERT(v2.match(desc) == RESULT(U32, ParamLREF, NA, 2));
  MOZ_RELEASE_ASSERT(v3.match(desc) == RESULT(U64, ParamLREF, NA, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(desc) == RESULT(U8, ParamCLREF, NA, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(desc) == RESULT(U32, ParamCLREF, NA, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(desc) == RESULT(U64, ParamCLREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(desc) == RESULT(U8, ParamRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(desc) == RESULT(U32, ParamRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(desc) == RESULT(U64, ParamRREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(desc) ==
                     RESULT(U8, ParamCRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(desc) ==
                     RESULT(U32, ParamCRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(desc) ==
                     RESULT(U64, ParamCRREF, NA, 3));
}

static void testMatchingLambdas() {
  printf("testMatchingLambdas\n");
  using V = Variant<uint8_t, uint32_t, uint64_t>;

  auto desc8 = [](auto&& a) {
    if constexpr (std::is_same_v<decltype(a), uint8_t&>) {
      return RESULT(U8, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&>) {
      return RESULT(U8, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint8_t&&>) {
      return RESULT(U8, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&&>) {
      return RESULT(U8, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };
  auto desc32 = [](auto&& a) {
    if constexpr (std::is_same_v<decltype(a), uint32_t&>) {
      return RESULT(U32, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&>) {
      return RESULT(U32, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&&>) {
      return RESULT(U32, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&&>) {
      return RESULT(U32, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };
  auto desc64 = [](auto&& a) {
    if constexpr (std::is_same_v<decltype(a), uint64_t&>) {
      return RESULT(U64, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&>) {
      return RESULT(U64, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&&>) {
      return RESULT(U64, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&&>) {
      return RESULT(U64, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };

  V v1(uint8_t(1));
  V v2(uint32_t(2));
  V v3(uint64_t(3));

  const V& constRef1 = v1;
  const V& constRef2 = v2;
  const V& constRef3 = v3;

  // Create a temporary variant by returning a copy of one.
  auto CopyV = [](const V& aV) { return aV; };

  // Create a temporary variant by returning a const copy of one.
  auto CopyConstV = [](const V& aV) -> const V { return aV; };

  MOZ_RELEASE_ASSERT(v1.match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamLREF, NA, 1));
  MOZ_RELEASE_ASSERT(v2.match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamLREF, NA, 2));
  MOZ_RELEASE_ASSERT(v3.match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamLREF, NA, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamCLREF, NA, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamCLREF, NA, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamCLREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamRREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamCRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamCRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamCRREF, NA, 3));
}

static void testMatchingLambdasWithIndex() {
  printf("testMatchingLambdasWithIndex\n");
  using V = Variant<uint8_t, uint32_t, uint64_t>;

  auto desc8 = [](size_t aIndex, auto&& a) {
    MOZ_RELEASE_ASSERT(aIndex == 0);
    if constexpr (std::is_same_v<decltype(a), uint8_t&>) {
      return RESULT(U8, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&>) {
      return RESULT(U8, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint8_t&&>) {
      return RESULT(U8, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint8_t&&>) {
      return RESULT(U8, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };
  auto desc32 = [](size_t aIndex, auto&& a) {
    MOZ_RELEASE_ASSERT(aIndex == 1);
    if constexpr (std::is_same_v<decltype(a), uint32_t&>) {
      return RESULT(U32, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&>) {
      return RESULT(U32, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint32_t&&>) {
      return RESULT(U32, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint32_t&&>) {
      return RESULT(U32, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };
  auto desc64 = [](size_t aIndex, auto&& a) {
    MOZ_RELEASE_ASSERT(aIndex == 2);
    if constexpr (std::is_same_v<decltype(a), uint64_t&>) {
      return RESULT(U64, ParamLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&>) {
      return RESULT(U64, ParamCLREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), uint64_t&&>) {
      return RESULT(U64, ParamRREF, NA, a);
    } else if constexpr (std::is_same_v<decltype(a), const uint64_t&&>) {
      return RESULT(U64, ParamCRREF, NA, a);
    } else {
      // We don't expect any other type.
      // Tech note: We can't just do `static_assert(false)` which would always
      // fail during the initial parsing. So we depend on the templated
      // parameter to delay computing `false` until actual instantiation.
      static_assert(sizeof(a) == size_t(-1));
      return RESULT(NA, NA, NA, 0);
    }
  };

  V v1(uint8_t(1));
  V v2(uint32_t(2));
  V v3(uint64_t(3));

  const V& constRef1 = v1;
  const V& constRef2 = v2;
  const V& constRef3 = v3;

  // Create a temporary variant by returning a copy of one.
  auto CopyV = [](const V& aV) { return aV; };

  // Create a temporary variant by returning a const copy of one.
  auto CopyConstV = [](const V& aV) -> const V { return aV; };

  MOZ_RELEASE_ASSERT(v1.match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamLREF, NA, 1));
  MOZ_RELEASE_ASSERT(v2.match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamLREF, NA, 2));
  MOZ_RELEASE_ASSERT(v3.match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamLREF, NA, 3));

  MOZ_RELEASE_ASSERT(constRef1.match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamCLREF, NA, 1));
  MOZ_RELEASE_ASSERT(constRef2.match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamCLREF, NA, 2));
  MOZ_RELEASE_ASSERT(constRef3.match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamCLREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyV(v1).match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyV(v2).match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyV(v3).match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamRREF, NA, 3));

  MOZ_RELEASE_ASSERT(CopyConstV(v1).match(desc8, desc32, desc64) ==
                     RESULT(U8, ParamCRREF, NA, 1));
  MOZ_RELEASE_ASSERT(CopyConstV(v2).match(desc8, desc32, desc64) ==
                     RESULT(U32, ParamCRREF, NA, 2));
  MOZ_RELEASE_ASSERT(CopyConstV(v3).match(desc8, desc32, desc64) ==
                     RESULT(U64, ParamCRREF, NA, 3));
}

#undef RESULT

static void testAddTagToHash() {
  printf("testAddToHash\n");
  using V = Variant<uint8_t, uint16_t, uint32_t, uint64_t>;

  // We don't know what our hash function is, and these are certainly not all
  // true under all hash functions. But they are probably true under almost any
  // decent hash function, and our aim is simply to establish that the tag
  // *does* influence the hash value.
  {
    mozilla::HashNumber h8 = V(uint8_t(1)).addTagToHash(0);
    mozilla::HashNumber h16 = V(uint16_t(1)).addTagToHash(0);
    mozilla::HashNumber h32 = V(uint32_t(1)).addTagToHash(0);
    mozilla::HashNumber h64 = V(uint64_t(1)).addTagToHash(0);

    MOZ_RELEASE_ASSERT(h8 != h16 && h8 != h32 && h8 != h64);
    MOZ_RELEASE_ASSERT(h16 != h32 && h16 != h64);
    MOZ_RELEASE_ASSERT(h32 != h64);
  }

  {
    mozilla::HashNumber h8 = V(uint8_t(1)).addTagToHash(0x124356);
    mozilla::HashNumber h16 = V(uint16_t(1)).addTagToHash(0x124356);
    mozilla::HashNumber h32 = V(uint32_t(1)).addTagToHash(0x124356);
    mozilla::HashNumber h64 = V(uint64_t(1)).addTagToHash(0x124356);

    MOZ_RELEASE_ASSERT(h8 != h16 && h8 != h32 && h8 != h64);
    MOZ_RELEASE_ASSERT(h16 != h32 && h16 != h64);
    MOZ_RELEASE_ASSERT(h32 != h64);
  }
}

int main() {
  testDetails();
  testSimple();
  testDuplicate();
  testConstructionWithVariantType();
  testConstructionWithVariantIndex();
  testEmplaceWithType();
  testEmplaceWithIndex();
  testCopy();
  testMove();
  testDestructor();
  testEquality();
  testMatching();
  testMatchingLambda();
  testMatchingLambdaWithIndex();
  testMatchingLambdas();
  testMatchingLambdasWithIndex();
  testAddTagToHash();

  printf("TestVariant OK!\n");
  return 0;
}