Add DaydreamVR native libraries and services

Upstreaming the main VR system components from master-dreamos-dev
into goog/master.

Bug: None
Test: `m -j32` succeeds. Sailfish boots and basic_vr sample app works
Change-Id: I853015872afc443aecee10411ef2d6b79184d051
diff --git a/libs/vr/libpdx/variant_tests.cpp b/libs/vr/libpdx/variant_tests.cpp
new file mode 100644
index 0000000..c30c055
--- /dev/null
+++ b/libs/vr/libpdx/variant_tests.cpp
@@ -0,0 +1,1087 @@
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <string>
+#include <type_traits>
+
+#include <gtest/gtest.h>
+#include <pdx/rpc/variant.h>
+
+using namespace android::pdx;
+using namespace android::pdx::rpc;
+
+namespace {
+
+struct BaseType {
+  BaseType(int value) : value(value) {}
+  int value;
+};
+
+struct DerivedType : BaseType {
+  DerivedType(int value) : BaseType{value} {};
+};
+
+template <typename T>
+class TestType {
+ public:
+  TestType(const T& value) : value_(value) {}
+  TestType(T&& value) : value_(std::move(value)) {}
+  TestType(const TestType&) = default;
+  TestType(TestType&&) = default;
+
+  TestType& operator=(const TestType&) = default;
+  TestType& operator=(TestType&&) = default;
+
+  const T& get() const { return value_; }
+  T&& take() { return std::move(value_); }
+
+ private:
+  T value_;
+};
+
+template <typename T>
+class InstrumentType {
+ public:
+  InstrumentType(const T& value) : value_(value) { constructor_count_++; }
+  InstrumentType(T&& value) : value_(std::move(value)) { constructor_count_++; }
+  InstrumentType(const InstrumentType& other) : value_(other.value_) {
+    constructor_count_++;
+  }
+  InstrumentType(InstrumentType&& other) : value_(std::move(other.value_)) {
+    constructor_count_++;
+  }
+  InstrumentType(const TestType<T>& other) : value_(other.get()) {
+    constructor_count_++;
+  }
+  InstrumentType(TestType<T>&& other) : value_(other.take()) {
+    constructor_count_++;
+  }
+  ~InstrumentType() { destructor_count_++; }
+
+  InstrumentType& operator=(const InstrumentType& other) {
+    copy_assignment_count_++;
+    value_ = other.value_;
+    return *this;
+  }
+  InstrumentType& operator=(InstrumentType&& other) {
+    move_assignment_count_++;
+    value_ = std::move(other.value_);
+    return *this;
+  }
+
+  InstrumentType& operator=(const TestType<T>& other) {
+    copy_assignment_count_++;
+    value_ = other.get();
+    return *this;
+  }
+  InstrumentType& operator=(TestType<T>&& other) {
+    move_assignment_count_++;
+    value_ = other.take();
+    return *this;
+  }
+
+  static std::size_t constructor_count() { return constructor_count_; }
+  static std::size_t destructor_count() { return destructor_count_; }
+  static std::size_t move_assignment_count() { return move_assignment_count_; }
+  static std::size_t copy_assignment_count() { return copy_assignment_count_; }
+
+  const T& get() const { return value_; }
+  T&& take() { return std::move(value_); }
+
+  static void clear() {
+    constructor_count_ = 0;
+    destructor_count_ = 0;
+    move_assignment_count_ = 0;
+    copy_assignment_count_ = 0;
+  }
+
+ private:
+  T value_;
+
+  static std::size_t constructor_count_;
+  static std::size_t destructor_count_;
+  static std::size_t move_assignment_count_;
+  static std::size_t copy_assignment_count_;
+};
+
+template <typename T>
+std::size_t InstrumentType<T>::constructor_count_ = 0;
+template <typename T>
+std::size_t InstrumentType<T>::destructor_count_ = 0;
+template <typename T>
+std::size_t InstrumentType<T>::move_assignment_count_ = 0;
+template <typename T>
+std::size_t InstrumentType<T>::copy_assignment_count_ = 0;
+
+}  // anonymous namespace
+
+TEST(Variant, Assignment) {
+  // Assert basic type properties.
+  {
+    Variant<int, bool, float> v;
+    ASSERT_EQ(-1, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_FALSE(v.is<bool>());
+    ASSERT_FALSE(v.is<float>());
+  }
+
+  {
+    Variant<int, bool, float> v;
+    v = 10;
+    ASSERT_EQ(0, v.index());
+    ASSERT_TRUE(v.is<int>());
+    ASSERT_FALSE(v.is<bool>());
+    ASSERT_FALSE(v.is<float>());
+    EXPECT_EQ(10, std::get<int>(v));
+  }
+
+  {
+    Variant<int, bool, float> v;
+    v = false;
+    ASSERT_EQ(1, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_TRUE(v.is<bool>());
+    ASSERT_FALSE(v.is<float>());
+    EXPECT_EQ(false, std::get<bool>(v));
+  }
+
+  {
+    Variant<int, bool, float> v;
+    v = 1.0f;
+    ASSERT_EQ(2, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_FALSE(v.is<bool>());
+    ASSERT_TRUE(v.is<float>());
+    EXPECT_FLOAT_EQ(1.0f, std::get<float>(v));
+  }
+
+  {
+    Variant<int, bool, float> v;
+    // ERROR: More than one type is implicitly convertible from double.
+    // v = 1.0;
+    v = static_cast<float>(1.0);
+  }
+
+  {
+    Variant<int, bool, float> v;
+
+    double x = 1.1;
+    v = static_cast<float>(x);
+    ASSERT_EQ(2, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_FALSE(v.is<bool>());
+    ASSERT_TRUE(v.is<float>());
+    EXPECT_FLOAT_EQ(1.1, std::get<float>(v));
+  }
+
+  {
+    Variant<int, std::string> v;
+    ASSERT_EQ(-1, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_FALSE(v.is<std::string>());
+  }
+
+  {
+    Variant<int, std::string> v;
+    v = 20;
+    ASSERT_EQ(0, v.index());
+    ASSERT_TRUE(v.is<int>());
+    ASSERT_FALSE(v.is<std::string>());
+    EXPECT_EQ(20, std::get<int>(v));
+  }
+
+  {
+    Variant<int, std::string> v;
+    v = std::string("test");
+    ASSERT_EQ(1, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(v));
+  }
+
+  {
+    Variant<int, std::string> v;
+    v = "test";
+    ASSERT_EQ(1, v.index());
+    ASSERT_FALSE(v.is<int>());
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(v));
+  }
+
+  {
+    Variant<const char*> v1;
+    Variant<std::string> v2;
+
+    v1 = "test";
+    ASSERT_TRUE(v1.is<const char*>());
+    v2 = v1;
+    ASSERT_TRUE(v2.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(v2));
+  }
+
+  {
+    Variant<int> a(1);
+    Variant<int> b;
+    ASSERT_TRUE(!a.empty());
+    ASSERT_TRUE(b.empty());
+
+    a = b;
+    ASSERT_TRUE(a.empty());
+    ASSERT_TRUE(b.empty());
+  }
+
+  {
+    Variant<int*, char*> v;
+
+    // ERROR: More than one type is implicitly convertible from nullptr.
+    // v = nullptr;
+
+    v = static_cast<int*>(nullptr);
+    EXPECT_TRUE(v.is<int*>());
+
+    v = static_cast<char*>(nullptr);
+    EXPECT_TRUE(v.is<char*>());
+  }
+
+  {
+    Variant<int*, char*> v;
+    int a = 10;
+    char b = 20;
+
+    v = &b;
+    ASSERT_TRUE(v.is<char*>());
+    EXPECT_EQ(&b, std::get<char*>(v));
+    EXPECT_EQ(b, *std::get<char*>(v));
+
+    v = &a;
+    ASSERT_TRUE(v.is<int*>());
+    EXPECT_EQ(&a, std::get<int*>(v));
+    EXPECT_EQ(a, *std::get<int*>(v));
+  }
+
+  {
+    using IntRef = std::reference_wrapper<int>;
+    Variant<IntRef> v;
+    int a = 10;
+
+    v = a;
+    ASSERT_TRUE(v.is<IntRef>());
+    EXPECT_EQ(a, std::get<IntRef>(v));
+
+    a = 20;
+    EXPECT_EQ(a, std::get<IntRef>(v));
+  }
+}
+
+TEST(Variant, MoveAssignment) {
+  {
+    Variant<std::string> v;
+    std::string s = "test";
+    v = std::move(s);
+
+    EXPECT_TRUE(s.empty());
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(v));
+  }
+
+  {
+    Variant<std::string> v("test");
+    std::string s = "fizz";
+    s = std::move(std::get<std::string>(v));
+
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(v).empty());
+    EXPECT_EQ("test", s);
+  }
+
+  {
+    Variant<std::string> a("test");
+    Variant<std::string> b;
+
+    b = std::move(a);
+    ASSERT_TRUE(a.is<std::string>());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(a).empty());
+    EXPECT_EQ("test", std::get<std::string>(b));
+  }
+
+  {
+    Variant<std::string> a("test");
+    Variant<std::string> b("fizz");
+
+    b = std::move(a);
+    ASSERT_TRUE(a.is<std::string>());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(a).empty());
+    EXPECT_EQ("test", std::get<std::string>(b));
+  }
+
+  {
+    Variant<int, std::string> a("test");
+    Variant<int, std::string> b(10);
+
+    b = std::move(a);
+    ASSERT_TRUE(a.is<std::string>());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(a).empty());
+    EXPECT_EQ("test", std::get<std::string>(b));
+  }
+
+  {
+    Variant<int, std::string> a(10);
+    Variant<int, std::string> b("test");
+
+    b = std::move(a);
+    ASSERT_TRUE(a.is<int>());
+    ASSERT_TRUE(b.is<int>());
+    EXPECT_EQ(10, std::get<int>(a));
+    EXPECT_EQ(10, std::get<int>(b));
+  }
+}
+
+TEST(Variant, Constructor) {
+  {
+    Variant<int, bool, float> v(true);
+    EXPECT_TRUE(v.is<bool>());
+  }
+
+  {
+    Variant<int, bool, float> v(10);
+    EXPECT_TRUE(v.is<int>());
+  }
+
+  {
+    Variant<int, bool, float> v(10.1f);
+    EXPECT_TRUE(v.is<float>());
+  }
+
+  {
+    Variant<float, std::string> v(10.);
+    EXPECT_TRUE(v.is<float>());
+  }
+
+  {
+    TestType<int> i(1);
+    Variant<int, bool, float> v(i.take());
+    ASSERT_TRUE(v.is<int>());
+    EXPECT_EQ(1, std::get<int>(v));
+  }
+
+  {
+    TestType<bool> b(true);
+    Variant<int, bool, float> v(b.take());
+    ASSERT_TRUE(v.is<bool>());
+    EXPECT_EQ(true, std::get<bool>(v));
+  }
+
+  {
+    Variant<const char*> c("test");
+    Variant<std::string> s(c);
+    ASSERT_TRUE(s.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(s));
+  }
+
+  {
+    Variant<int, bool, float> a(true);
+    Variant<int, bool, float> b(a);
+
+    ASSERT_TRUE(b.is<bool>());
+  }
+
+  {
+    using IntRef = std::reference_wrapper<int>;
+    int a = 10;
+    Variant<IntRef> v(a);
+    TestType<IntRef> t(a);
+
+    ASSERT_TRUE(v.is<IntRef>());
+    EXPECT_EQ(a, std::get<IntRef>(v));
+    EXPECT_EQ(a, t.get());
+
+    a = 20;
+    EXPECT_EQ(a, std::get<IntRef>(v));
+    EXPECT_EQ(a, t.get());
+  }
+}
+
+// Verify correct ctor/dtor and assignment behavior used an instrumented type.
+TEST(Variant, CopyMoveConstructAssign) {
+  {
+    InstrumentType<int>::clear();
+
+    // Default construct to empty, no InstrumentType activity.
+    Variant<int, InstrumentType<int>> v;
+    ASSERT_EQ(0u, InstrumentType<int>::constructor_count());
+    ASSERT_EQ(0u, InstrumentType<int>::destructor_count());
+    ASSERT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    ASSERT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from int type, no InstrumentType activity.
+    Variant<int, InstrumentType<int>> v;
+    v = 10;
+    EXPECT_EQ(0u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from int type, no InstrumentType activity.
+    Variant<int, InstrumentType<int>> v(10);
+    EXPECT_EQ(0u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from temporary, temporary ctor/dtor.
+    Variant<int, InstrumentType<int>> v;
+    v = InstrumentType<int>(25);
+    EXPECT_EQ(2u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from temporary, temporary ctor/dtor.
+    Variant<int, InstrumentType<int>> v(InstrumentType<int>(25));
+    EXPECT_EQ(2u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from temporary, temporary ctor/dtor.
+    Variant<int, InstrumentType<int>> v(InstrumentType<int>(25));
+
+    // Assign from temporary, temporary ctor/dtor.
+    v = InstrumentType<int>(35);
+    EXPECT_EQ(3u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(2u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from temporary, temporary ctor/dtor.
+    Variant<int, InstrumentType<int>> v(InstrumentType<int>(25));
+
+    // dtor.
+    v = 10;
+    EXPECT_EQ(2u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(2u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from temporary, temporary ctor/dtor.
+    Variant<int, InstrumentType<int>> v(InstrumentType<int>(25));
+
+    EXPECT_EQ(2u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+  EXPECT_EQ(2u, InstrumentType<int>::constructor_count());
+  EXPECT_EQ(2u, InstrumentType<int>::destructor_count());
+  EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+  EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from other temporary.
+    Variant<int, InstrumentType<int>> v(TestType<int>(10));
+    EXPECT_EQ(1u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from other temporary.
+    Variant<int, InstrumentType<int>> v(TestType<int>(10));
+    // Assign from other temporary.
+    v = TestType<int>(11);
+    EXPECT_EQ(1u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from other temporary.
+    Variant<int, InstrumentType<int>> v(TestType<int>(10));
+    // Assign from empty Variant.
+    v = Variant<int, InstrumentType<int>>();
+    EXPECT_EQ(1u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(1u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    TestType<int> other(10);
+    // Construct from other.
+    Variant<int, InstrumentType<int>> v(other);
+
+    EXPECT_EQ(1u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(0u, InstrumentType<int>::copy_assignment_count());
+  }
+
+  {
+    InstrumentType<int>::clear();
+
+    // Construct from other temporary.
+    Variant<int, InstrumentType<int>> v(TestType<int>(0));
+    TestType<int> other(10);
+    // Assign from other.
+    v = other;
+    EXPECT_EQ(1u, InstrumentType<int>::constructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::destructor_count());
+    EXPECT_EQ(0u, InstrumentType<int>::move_assignment_count());
+    EXPECT_EQ(1u, InstrumentType<int>::copy_assignment_count());
+  }
+}
+
+TEST(Variant, MoveConstructor) {
+  {
+    std::unique_ptr<int> pointer = std::make_unique<int>(10);
+    Variant<std::unique_ptr<int>> v(std::move(pointer));
+    ASSERT_TRUE(v.is<std::unique_ptr<int>>());
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(v) != nullptr);
+    EXPECT_TRUE(pointer == nullptr);
+  }
+
+  {
+    Variant<std::unique_ptr<int>> a(std::make_unique<int>(10));
+    Variant<std::unique_ptr<int>> b(std::move(a));
+
+    ASSERT_TRUE(a.is<std::unique_ptr<int>>());
+    ASSERT_TRUE(b.is<std::unique_ptr<int>>());
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(a) == nullptr);
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(b) != nullptr);
+  }
+}
+
+TEST(Variant, IndexOf) {
+  Variant<int, bool, float> v1;
+
+  EXPECT_EQ(0, v1.index_of<int>());
+  EXPECT_EQ(1, v1.index_of<bool>());
+  EXPECT_EQ(2, v1.index_of<float>());
+
+  Variant<int, bool, float, int> v2;
+
+  EXPECT_EQ(0, v2.index_of<int>());
+  EXPECT_EQ(1, v2.index_of<bool>());
+  EXPECT_EQ(2, v2.index_of<float>());
+}
+
+struct Visitor {
+  int int_value = 0;
+  bool bool_value = false;
+  float float_value = 0.0;
+  bool empty_value = false;
+
+  void Visit(int value) { int_value = value; }
+  void Visit(bool value) { bool_value = value; }
+  void Visit(float value) { float_value = value; }
+  void Visit(EmptyVariant) { empty_value = true; }
+};
+
+TEST(Variant, Visit) {
+  {
+    Variant<int, bool, float> v(10);
+    EXPECT_TRUE(v.is<int>());
+
+    Visitor visitor;
+    v.Visit([&visitor](const auto& value) { visitor.Visit(value); });
+    EXPECT_EQ(10, visitor.int_value);
+
+    visitor = {};
+    v = true;
+    v.Visit([&visitor](const auto& value) { visitor.Visit(value); });
+    EXPECT_EQ(true, visitor.bool_value);
+  }
+
+  {
+    Variant<int, bool, float> v;
+    EXPECT_EQ(-1, v.index());
+
+    Visitor visitor;
+    v.Visit([&visitor](const auto& value) { visitor.Visit(value); });
+    EXPECT_TRUE(visitor.empty_value);
+  }
+
+  {
+    Variant<std::string> v("test");
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_FALSE(std::get<std::string>(v).empty());
+
+    v.Visit([](auto&& value) {
+      std::remove_reference_t<decltype(value)> empty;
+      std::swap(empty, value);
+    });
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(v).empty());
+  }
+}
+
+TEST(Variant, Become) {
+  {
+    Variant<int, bool, float> v;
+
+    v.Become(0);
+    EXPECT_TRUE(v.is<int>());
+
+    v.Become(1);
+    EXPECT_TRUE(v.is<bool>());
+
+    v.Become(2);
+    EXPECT_TRUE(v.is<float>());
+
+    v.Become(3);
+    EXPECT_TRUE(v.empty());
+
+    v.Become(-1);
+    EXPECT_TRUE(v.empty());
+
+    v.Become(-2);
+    EXPECT_TRUE(v.empty());
+  }
+
+  {
+    Variant<int, bool, float> v;
+
+    v.Become(0, 10);
+    ASSERT_TRUE(v.is<int>());
+    EXPECT_EQ(10, std::get<int>(v));
+
+    v.Become(1, true);
+    ASSERT_TRUE(v.is<bool>());
+    EXPECT_EQ(true, std::get<bool>(v));
+
+    v.Become(2, 2.0f);
+    ASSERT_TRUE(v.is<float>());
+    EXPECT_FLOAT_EQ(2.0f, std::get<float>(v));
+
+    v.Become(3, 10);
+    EXPECT_TRUE(v.empty());
+
+    v.Become(-1, 10);
+    EXPECT_TRUE(v.empty());
+
+    v.Become(-2, 20);
+    EXPECT_TRUE(v.empty());
+  }
+
+  {
+    Variant<std::string> v;
+
+    v.Become(0);
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_TRUE(std::get<std::string>(v).empty());
+  }
+
+  {
+    Variant<std::string> v;
+
+    v.Become(0, "test");
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("test", std::get<std::string>(v));
+  }
+
+  {
+    Variant<std::string> v("foo");
+
+    v.Become(0, "bar");
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("foo", std::get<std::string>(v));
+  }
+}
+
+TEST(Variant, Swap) {
+  {
+    Variant<std::string> a;
+    Variant<std::string> b;
+
+    std::swap(a, b);
+    EXPECT_TRUE(a.empty());
+    EXPECT_TRUE(b.empty());
+  }
+
+  {
+    Variant<std::string> a("1");
+    Variant<std::string> b;
+
+    std::swap(a, b);
+    EXPECT_TRUE(!a.empty());
+    EXPECT_TRUE(!b.empty());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_EQ("1", std::get<std::string>(b));
+  }
+
+  {
+    Variant<std::string> a;
+    Variant<std::string> b("1");
+
+    std::swap(a, b);
+    EXPECT_TRUE(!a.empty());
+    EXPECT_TRUE(!b.empty());
+    ASSERT_TRUE(a.is<std::string>());
+    EXPECT_EQ("1", std::get<std::string>(a));
+  }
+
+  {
+    Variant<std::string> a("1");
+    Variant<std::string> b("2");
+
+    std::swap(a, b);
+    ASSERT_TRUE(a.is<std::string>());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_EQ("2", std::get<std::string>(a));
+    EXPECT_EQ("1", std::get<std::string>(b));
+  }
+
+  {
+    Variant<int, std::string> a(10);
+    Variant<int, std::string> b("1");
+
+    std::swap(a, b);
+    ASSERT_TRUE(a.is<std::string>());
+    ASSERT_TRUE(b.is<int>());
+    EXPECT_EQ("1", std::get<std::string>(a));
+    EXPECT_EQ(10, std::get<int>(b));
+  }
+
+  {
+    Variant<int, std::string> a("1");
+    Variant<int, std::string> b(10);
+
+    std::swap(a, b);
+    ASSERT_TRUE(a.is<int>());
+    ASSERT_TRUE(b.is<std::string>());
+    EXPECT_EQ(10, std::get<int>(a));
+    EXPECT_EQ("1", std::get<std::string>(b));
+  }
+}
+
+TEST(Variant, Get) {
+  {
+    Variant<int, bool, float, int> v;
+
+    EXPECT_EQ(nullptr, &std::get<int>(v));
+    EXPECT_EQ(nullptr, &std::get<bool>(v));
+    EXPECT_EQ(nullptr, &std::get<float>(v));
+    EXPECT_EQ(nullptr, &std::get<0>(v));
+    EXPECT_EQ(nullptr, &std::get<1>(v));
+    EXPECT_EQ(nullptr, &std::get<2>(v));
+    EXPECT_EQ(nullptr, &std::get<3>(v));
+  }
+
+  {
+    Variant<int, bool, float, int> v;
+    v = 9;
+    ASSERT_TRUE(v.is<int>())
+        << "Expected type " << v.index_of<int>() << " got type " << v.index();
+    EXPECT_EQ(9, std::get<int>(v));
+    EXPECT_EQ(9, std::get<0>(v));
+
+    std::get<int>(v) = 10;
+    EXPECT_EQ(10, std::get<int>(v));
+    EXPECT_EQ(10, std::get<0>(v));
+
+    std::get<0>(v) = 11;
+    EXPECT_EQ(11, std::get<int>(v));
+    EXPECT_EQ(11, std::get<0>(v));
+
+    std::get<3>(v) = 12;
+    EXPECT_EQ(12, std::get<int>(v));
+    EXPECT_EQ(12, std::get<3>(v));
+  }
+
+  {
+    Variant<int, bool, float, int> v;
+    v = false;
+    ASSERT_TRUE(v.is<bool>())
+        << "Expected type " << v.index_of<bool>() << " got type " << v.index();
+    EXPECT_EQ(false, std::get<bool>(v));
+    EXPECT_EQ(false, std::get<1>(v));
+
+    std::get<bool>(v) = true;
+    EXPECT_EQ(true, std::get<bool>(v));
+    EXPECT_EQ(true, std::get<1>(v));
+
+    std::get<bool>(v) = false;
+    EXPECT_EQ(false, std::get<bool>(v));
+    EXPECT_EQ(false, std::get<1>(v));
+
+    std::get<1>(v) = true;
+    EXPECT_EQ(true, std::get<bool>(v));
+    EXPECT_EQ(true, std::get<1>(v));
+
+    std::get<1>(v) = false;
+    EXPECT_EQ(false, std::get<bool>(v));
+    EXPECT_EQ(false, std::get<1>(v));
+  }
+
+  {
+    Variant<int, bool, float, int> v;
+    v = 1.0f;
+    ASSERT_TRUE(v.is<float>())
+        << "Expected type " << v.index_of<float>() << " got type " << v.index();
+    EXPECT_EQ(2, v.index());
+    EXPECT_FLOAT_EQ(1.0, std::get<float>(v));
+    EXPECT_FLOAT_EQ(1.0, std::get<2>(v));
+
+    std::get<float>(v) = 1.1;
+    EXPECT_FLOAT_EQ(1.1, std::get<float>(v));
+    EXPECT_FLOAT_EQ(1.1, std::get<2>(v));
+
+    std::get<float>(v) = -3.0;
+    EXPECT_FLOAT_EQ(-3.0, std::get<float>(v));
+    EXPECT_FLOAT_EQ(-3.0, std::get<2>(v));
+
+    std::get<2>(v) = 1.1;
+    EXPECT_FLOAT_EQ(1.1, std::get<float>(v));
+    EXPECT_FLOAT_EQ(1.1, std::get<2>(v));
+
+    std::get<2>(v) = -3.0;
+    EXPECT_FLOAT_EQ(-3.0, std::get<float>(v));
+    EXPECT_FLOAT_EQ(-3.0, std::get<2>(v));
+  }
+
+  {
+    Variant<std::unique_ptr<int>> v(std::make_unique<int>(10));
+    std::unique_ptr<int> pointer = std::move(std::get<std::unique_ptr<int>>(v));
+    ASSERT_FALSE(v.empty());
+    EXPECT_TRUE(pointer != nullptr);
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(v) == nullptr);
+  }
+
+  {
+    Variant<std::string> v("test");
+    std::string s = std::get<std::string>(std::move(v));
+    EXPECT_EQ("test", s);
+  }
+}
+
+TEST(Variant, IfAnyOf) {
+  {
+    Variant<int, float> v(10);
+    ASSERT_TRUE(v.is<int>());
+
+    bool b = false;
+    EXPECT_TRUE(IfAnyOf<int>::Get(&v, &b));
+    EXPECT_TRUE(b);
+
+    float f = 0.0f;
+    EXPECT_TRUE((IfAnyOf<int, float>::Get(&v, &f)));
+    EXPECT_FLOAT_EQ(10.f, f);
+  }
+
+  {
+    const Variant<int, float> v(10);
+    ASSERT_TRUE(v.is<int>());
+
+    bool b = false;
+    EXPECT_TRUE(IfAnyOf<int>::Get(&v, &b));
+    EXPECT_TRUE(b);
+
+    float f = 0.0f;
+    EXPECT_TRUE((IfAnyOf<int, float>::Get(&v, &f)));
+    EXPECT_FLOAT_EQ(10.f, f);
+  }
+
+  {
+    Variant<int, float> v(10);
+    ASSERT_TRUE(v.is<int>());
+
+    bool b = false;
+    EXPECT_TRUE(IfAnyOf<int>::Call(&v, [&b](const auto& value) { b = value; }));
+    EXPECT_TRUE(b);
+
+    float f = 0.0f;
+    EXPECT_TRUE((
+        IfAnyOf<int, float>::Call(&v, [&f](const auto& value) { f = value; })));
+    EXPECT_FLOAT_EQ(10.f, f);
+  }
+
+  {
+    Variant<std::unique_ptr<int>, int> v(std::make_unique<int>(10));
+    ASSERT_TRUE(v.is<std::unique_ptr<int>>());
+    const int* original_v = std::get<std::unique_ptr<int>>(v).get();
+
+    std::unique_ptr<int> u(std::make_unique<int>(20));
+
+    EXPECT_TRUE(IfAnyOf<std::unique_ptr<int>>::Take(&v, &u));
+    ASSERT_TRUE(v.is<std::unique_ptr<int>>());
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(v) == nullptr);
+    EXPECT_EQ(u.get(), original_v);
+  }
+
+  {
+    Variant<std::unique_ptr<DerivedType>, int> v(
+        std::make_unique<DerivedType>(10));
+    ASSERT_TRUE(v.is<std::unique_ptr<DerivedType>>());
+    const DerivedType* original_v =
+        std::get<std::unique_ptr<DerivedType>>(v).get();
+
+    std::unique_ptr<BaseType> u(std::make_unique<BaseType>(20));
+
+    EXPECT_TRUE(IfAnyOf<std::unique_ptr<DerivedType>>::Take(&v, &u));
+    ASSERT_TRUE(v.is<std::unique_ptr<DerivedType>>());
+    EXPECT_TRUE(std::get<std::unique_ptr<DerivedType>>(v) == nullptr);
+    EXPECT_EQ(u.get(), original_v);
+  }
+
+  {
+    Variant<std::unique_ptr<int>, int> v(std::make_unique<int>(10));
+    ASSERT_TRUE(v.is<std::unique_ptr<int>>());
+    const int* original_v = std::get<std::unique_ptr<int>>(v).get();
+
+    std::unique_ptr<int> u(std::make_unique<int>(20));
+
+    EXPECT_TRUE(IfAnyOf<std::unique_ptr<int>>::Call(
+        &v, [&u](auto&& value) { u = std::move(value); }));
+    ASSERT_TRUE(v.is<std::unique_ptr<int>>());
+    EXPECT_TRUE(std::get<std::unique_ptr<int>>(v) == nullptr);
+    EXPECT_EQ(u.get(), original_v);
+  }
+
+  {
+    Variant<int, bool, float> v(true);
+    ASSERT_TRUE(v.is<bool>());
+
+    float f = 0.f;
+    EXPECT_FALSE((IfAnyOf<int, float>::Get(&v, &f)));
+    EXPECT_FLOAT_EQ(0.f, f);
+  }
+
+  {
+    Variant<std::string, int> v("foo");
+    ASSERT_TRUE(v.is<std::string>());
+
+    std::string s = "bar";
+    EXPECT_TRUE(IfAnyOf<std::string>::Swap(&v, &s));
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("bar", std::get<std::string>(v));
+    EXPECT_EQ("foo", s);
+  }
+
+  {
+    Variant<std::string, const char*> v(static_cast<const char*>("foo"));
+    ASSERT_TRUE(v.is<const char*>());
+
+    std::string s = "bar";
+    EXPECT_TRUE((IfAnyOf<std::string, const char*>::Take(&v, &s)));
+    ASSERT_TRUE(v.is<const char*>());
+    EXPECT_EQ("foo", std::get<const char*>(v));
+    EXPECT_EQ("foo", s);
+
+    v = std::string("bar");
+    ASSERT_TRUE(v.is<std::string>());
+
+    EXPECT_TRUE((IfAnyOf<std::string, const char*>::Take(&v, &s)));
+    ASSERT_TRUE(v.is<std::string>());
+    EXPECT_EQ("bar", s);
+  }
+
+  {
+    Variant<std::string, const char*> v;
+    ASSERT_TRUE(v.empty());
+
+    std::string s = "bar";
+    EXPECT_FALSE((IfAnyOf<std::string, const char*>::Take(&v, &s)));
+    EXPECT_EQ("bar", s);
+  }
+
+  {
+    Variant<std::string, const char*> v(static_cast<const char*>("test"));
+    ASSERT_TRUE(v.is<const char*>());
+
+    std::string s;
+    EXPECT_FALSE(IfAnyOf<>::Take(&v, &s));
+    EXPECT_TRUE(s.empty());
+  }
+}
+
+TEST(Variant, ConstVolatile) {
+  {
+    Variant<const int> v(10);
+    ASSERT_TRUE(v.is<const int>());
+    EXPECT_EQ(10, std::get<const int>(v));
+  }
+
+  {
+    Variant<const std::string> v("test");
+    ASSERT_TRUE(v.is<const std::string>());
+    EXPECT_EQ("test", std::get<const std::string>(v));
+  }
+
+  {
+    Variant<volatile int, std::string> v(10);
+    ASSERT_TRUE(v.is<volatile int>());
+    EXPECT_EQ(10, std::get<volatile int>(v));
+  }
+}
+
+TEST(Variant, HasType) {
+  EXPECT_TRUE((detail::HasType<int, int, float, bool>::value));
+  EXPECT_FALSE((detail::HasType<char, int, float, bool>::value));
+  EXPECT_FALSE(detail::HasType<>::value);
+
+  EXPECT_TRUE((detail::HasTypeIgnoreRef<int&, int, float, bool>::value));
+  EXPECT_FALSE((detail::HasTypeIgnoreRef<char&, int, float, bool>::value));
+}
+
+TEST(Variant, Set) {
+  EXPECT_TRUE((detail::Set<int, bool, float>::template IsSubset<int, bool,
+                                                                float>::value));
+  EXPECT_TRUE(
+      (detail::Set<int, bool, float>::template IsSubset<bool, float>::value));
+  EXPECT_TRUE((detail::Set<int, bool, float>::template IsSubset<float>::value));
+  EXPECT_TRUE((detail::Set<int, bool, float>::template IsSubset<>::value));
+
+  EXPECT_FALSE(
+      (detail::Set<int, bool, float>::template IsSubset<int, bool, float,
+                                                        char>::value));
+  EXPECT_FALSE((detail::Set<int, bool, float>::template IsSubset<bool, float,
+                                                                 char>::value));
+  EXPECT_FALSE(
+      (detail::Set<int, bool, float>::template IsSubset<float, char>::value));
+  EXPECT_FALSE((detail::Set<int, bool, float>::template IsSubset<char>::value));
+
+  EXPECT_TRUE(detail::Set<>::template IsSubset<>::value);
+  EXPECT_FALSE(detail::Set<>::template IsSubset<int>::value);
+  EXPECT_FALSE((detail::Set<>::template IsSubset<int, float>::value));
+}