src/tint/castable_test.cc

// Copyright 2020 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "src/tint/castable.h"

#include <memory>
#include <string>

#include "gtest/gtest.h"

namespace tint {

struct Animal : public tint::Castable<Animal> {};
struct Amphibian : public tint::Castable<Amphibian, Animal> {};
struct Mammal : public tint::Castable<Mammal, Animal> {};
struct Reptile : public tint::Castable<Reptile, Animal> {};
struct Frog : public tint::Castable<Frog, Amphibian> {};
struct Bear : public tint::Castable<Bear, Mammal> {};
struct Lizard : public tint::Castable<Lizard, Reptile> {};
struct Gecko : public tint::Castable<Gecko, Lizard> {};
struct Iguana : public tint::Castable<Iguana, Lizard> {};

namespace {

TEST(CastableBase, Is) {
    std::unique_ptr<CastableBase> frog = std::make_unique<Frog>();
    std::unique_ptr<CastableBase> bear = std::make_unique<Bear>();
    std::unique_ptr<CastableBase> gecko = std::make_unique<Gecko>();

    ASSERT_TRUE(frog->Is<Animal>());
    ASSERT_TRUE(bear->Is<Animal>());
    ASSERT_TRUE(gecko->Is<Animal>());

    ASSERT_TRUE(frog->Is<Amphibian>());
    ASSERT_FALSE(bear->Is<Amphibian>());
    ASSERT_FALSE(gecko->Is<Amphibian>());

    ASSERT_FALSE(frog->Is<Mammal>());
    ASSERT_TRUE(bear->Is<Mammal>());
    ASSERT_FALSE(gecko->Is<Mammal>());

    ASSERT_FALSE(frog->Is<Reptile>());
    ASSERT_FALSE(bear->Is<Reptile>());
    ASSERT_TRUE(gecko->Is<Reptile>());
}

TEST(CastableBase, Is_kDontErrorOnImpossibleCast) {
    // Unlike TEST(CastableBase, Is), we're dynamically querying [A -> B] without
    // going via CastableBase.
    auto frog = std::make_unique<Frog>();
    auto bear = std::make_unique<Bear>();
    auto gecko = std::make_unique<Gecko>();

    ASSERT_TRUE((frog->Is<Animal, kDontErrorOnImpossibleCast>()));
    ASSERT_TRUE((bear->Is<Animal, kDontErrorOnImpossibleCast>()));
    ASSERT_TRUE((gecko->Is<Animal, kDontErrorOnImpossibleCast>()));

    ASSERT_TRUE((frog->Is<Amphibian, kDontErrorOnImpossibleCast>()));
    ASSERT_FALSE((bear->Is<Amphibian, kDontErrorOnImpossibleCast>()));
    ASSERT_FALSE((gecko->Is<Amphibian, kDontErrorOnImpossibleCast>()));

    ASSERT_FALSE((frog->Is<Mammal, kDontErrorOnImpossibleCast>()));
    ASSERT_TRUE((bear->Is<Mammal, kDontErrorOnImpossibleCast>()));
    ASSERT_FALSE((gecko->Is<Mammal, kDontErrorOnImpossibleCast>()));

    ASSERT_FALSE((frog->Is<Reptile, kDontErrorOnImpossibleCast>()));
    ASSERT_FALSE((bear->Is<Reptile, kDontErrorOnImpossibleCast>()));
    ASSERT_TRUE((gecko->Is<Reptile, kDontErrorOnImpossibleCast>()));
}

TEST(CastableBase, IsWithPredicate) {
    std::unique_ptr<CastableBase> frog = std::make_unique<Frog>();

    frog->Is<Animal>([&frog](const Animal* a) {
        EXPECT_EQ(a, frog.get());
        return true;
    });

    ASSERT_TRUE((frog->Is<Animal>([](const Animal*) { return true; })));
    ASSERT_FALSE((frog->Is<Animal>([](const Animal*) { return false; })));

    // Predicate not called if cast is invalid
    auto expect_not_called = [] { FAIL() << "Should not be called"; };
    ASSERT_FALSE((frog->Is<Bear>([&](const Animal*) {
        expect_not_called();
        return true;
    })));
}

TEST(CastableBase, IsAnyOf) {
    std::unique_ptr<CastableBase> frog = std::make_unique<Frog>();
    std::unique_ptr<CastableBase> bear = std::make_unique<Bear>();
    std::unique_ptr<CastableBase> gecko = std::make_unique<Gecko>();

    ASSERT_TRUE((frog->IsAnyOf<Animal, Mammal, Amphibian, Reptile>()));
    ASSERT_TRUE((frog->IsAnyOf<Mammal, Amphibian>()));
    ASSERT_TRUE((frog->IsAnyOf<Amphibian, Reptile>()));
    ASSERT_FALSE((frog->IsAnyOf<Mammal, Reptile>()));

    ASSERT_TRUE((bear->IsAnyOf<Animal, Mammal, Amphibian, Reptile>()));
    ASSERT_TRUE((bear->IsAnyOf<Mammal, Amphibian>()));
    ASSERT_TRUE((bear->IsAnyOf<Mammal, Reptile>()));
    ASSERT_FALSE((bear->IsAnyOf<Amphibian, Reptile>()));

    ASSERT_TRUE((gecko->IsAnyOf<Animal, Mammal, Amphibian, Reptile>()));
    ASSERT_TRUE((gecko->IsAnyOf<Mammal, Reptile>()));
    ASSERT_TRUE((gecko->IsAnyOf<Amphibian, Reptile>()));
    ASSERT_FALSE((gecko->IsAnyOf<Mammal, Amphibian>()));
}

TEST(CastableBase, As) {
    std::unique_ptr<CastableBase> frog = std::make_unique<Frog>();
    std::unique_ptr<CastableBase> bear = std::make_unique<Bear>();
    std::unique_ptr<CastableBase> gecko = std::make_unique<Gecko>();

    ASSERT_EQ(frog->As<Animal>(), static_cast<Animal*>(frog.get()));
    ASSERT_EQ(bear->As<Animal>(), static_cast<Animal*>(bear.get()));
    ASSERT_EQ(gecko->As<Animal>(), static_cast<Animal*>(gecko.get()));

    ASSERT_EQ(frog->As<Amphibian>(), static_cast<Amphibian*>(frog.get()));
    ASSERT_EQ(bear->As<Amphibian>(), nullptr);
    ASSERT_EQ(gecko->As<Amphibian>(), nullptr);

    ASSERT_EQ(frog->As<Mammal>(), nullptr);
    ASSERT_EQ(bear->As<Mammal>(), static_cast<Mammal*>(bear.get()));
    ASSERT_EQ(gecko->As<Mammal>(), nullptr);

    ASSERT_EQ(frog->As<Reptile>(), nullptr);
    ASSERT_EQ(bear->As<Reptile>(), nullptr);
    ASSERT_EQ(gecko->As<Reptile>(), static_cast<Reptile*>(gecko.get()));
}

TEST(CastableBase, As_kDontErrorOnImpossibleCast) {
    // Unlike TEST(CastableBase, As), we're dynamically casting [A -> B] without
    // going via CastableBase.
    auto frog = std::make_unique<Frog>();
    auto bear = std::make_unique<Bear>();
    auto gecko = std::make_unique<Gecko>();

    ASSERT_EQ((frog->As<Animal, kDontErrorOnImpossibleCast>()), static_cast<Animal*>(frog.get()));
    ASSERT_EQ((bear->As<Animal, kDontErrorOnImpossibleCast>()), static_cast<Animal*>(bear.get()));
    ASSERT_EQ((gecko->As<Animal, kDontErrorOnImpossibleCast>()), static_cast<Animal*>(gecko.get()));

    ASSERT_EQ((frog->As<Amphibian, kDontErrorOnImpossibleCast>()),
              static_cast<Amphibian*>(frog.get()));
    ASSERT_EQ((bear->As<Amphibian, kDontErrorOnImpossibleCast>()), nullptr);
    ASSERT_EQ((gecko->As<Amphibian, kDontErrorOnImpossibleCast>()), nullptr);

    ASSERT_EQ((frog->As<Mammal, kDontErrorOnImpossibleCast>()), nullptr);
    ASSERT_EQ((bear->As<Mammal, kDontErrorOnImpossibleCast>()), static_cast<Mammal*>(bear.get()));
    ASSERT_EQ((gecko->As<Mammal, kDontErrorOnImpossibleCast>()), nullptr);

    ASSERT_EQ((frog->As<Reptile, kDontErrorOnImpossibleCast>()), nullptr);
    ASSERT_EQ((bear->As<Reptile, kDontErrorOnImpossibleCast>()), nullptr);
    ASSERT_EQ((gecko->As<Reptile, kDontErrorOnImpossibleCast>()),
              static_cast<Reptile*>(gecko.get()));
}

TEST(Castable, Is) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();

    ASSERT_TRUE(frog->Is<Animal>());
    ASSERT_TRUE(bear->Is<Animal>());
    ASSERT_TRUE(gecko->Is<Animal>());

    ASSERT_TRUE(frog->Is<Amphibian>());
    ASSERT_FALSE(bear->Is<Amphibian>());
    ASSERT_FALSE(gecko->Is<Amphibian>());

    ASSERT_FALSE(frog->Is<Mammal>());
    ASSERT_TRUE(bear->Is<Mammal>());
    ASSERT_FALSE(gecko->Is<Mammal>());

    ASSERT_FALSE(frog->Is<Reptile>());
    ASSERT_FALSE(bear->Is<Reptile>());
    ASSERT_TRUE(gecko->Is<Reptile>());
}

TEST(Castable, IsWithPredicate) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();

    frog->Is([&frog](const Animal* a) {
        EXPECT_EQ(a, frog.get());
        return true;
    });

    ASSERT_TRUE((frog->Is([](const Animal*) { return true; })));
    ASSERT_FALSE((frog->Is([](const Animal*) { return false; })));

    // Predicate not called if cast is invalid
    auto expect_not_called = [] { FAIL() << "Should not be called"; };
    ASSERT_FALSE((frog->Is([&](const Bear*) {
        expect_not_called();
        return true;
    })));
}

TEST(Castable, As) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();

    ASSERT_EQ(frog->As<Animal>(), static_cast<Animal*>(frog.get()));
    ASSERT_EQ(bear->As<Animal>(), static_cast<Animal*>(bear.get()));
    ASSERT_EQ(gecko->As<Animal>(), static_cast<Animal*>(gecko.get()));

    ASSERT_EQ(frog->As<Amphibian>(), static_cast<Amphibian*>(frog.get()));
    ASSERT_EQ(bear->As<Amphibian>(), nullptr);
    ASSERT_EQ(gecko->As<Amphibian>(), nullptr);

    ASSERT_EQ(frog->As<Mammal>(), nullptr);
    ASSERT_EQ(bear->As<Mammal>(), static_cast<Mammal*>(bear.get()));
    ASSERT_EQ(gecko->As<Mammal>(), nullptr);

    ASSERT_EQ(frog->As<Reptile>(), nullptr);
    ASSERT_EQ(bear->As<Reptile>(), nullptr);
    ASSERT_EQ(gecko->As<Reptile>(), static_cast<Reptile*>(gecko.get()));
}

TEST(Castable, SwitchNoDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        bool frog_matched_amphibian = false;
        Switch(
            frog.get(),  //
            [&](Reptile*) { FAIL() << "frog is not reptile"; },
            [&](Mammal*) { FAIL() << "frog is not mammal"; },
            [&](Amphibian* amphibian) {
                EXPECT_EQ(amphibian, frog.get());
                frog_matched_amphibian = true;
            });
        EXPECT_TRUE(frog_matched_amphibian);
    }
    {
        bool bear_matched_mammal = false;
        Switch(
            bear.get(),  //
            [&](Reptile*) { FAIL() << "bear is not reptile"; },
            [&](Amphibian*) { FAIL() << "bear is not amphibian"; },
            [&](Mammal* mammal) {
                EXPECT_EQ(mammal, bear.get());
                bear_matched_mammal = true;
            });
        EXPECT_TRUE(bear_matched_mammal);
    }
    {
        bool gecko_matched_reptile = false;
        Switch(
            gecko.get(),  //
            [&](Mammal*) { FAIL() << "gecko is not mammal"; },
            [&](Amphibian*) { FAIL() << "gecko is not amphibian"; },
            [&](Reptile* reptile) {
                EXPECT_EQ(reptile, gecko.get());
                gecko_matched_reptile = true;
            });
        EXPECT_TRUE(gecko_matched_reptile);
    }
}

TEST(Castable, SwitchWithUnusedDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        bool frog_matched_amphibian = false;
        Switch(
            frog.get(),  //
            [&](Reptile*) { FAIL() << "frog is not reptile"; },
            [&](Mammal*) { FAIL() << "frog is not mammal"; },
            [&](Amphibian* amphibian) {
                EXPECT_EQ(amphibian, frog.get());
                frog_matched_amphibian = true;
            },
            [&](Default) { FAIL() << "default should not have been selected"; });
        EXPECT_TRUE(frog_matched_amphibian);
    }
    {
        bool bear_matched_mammal = false;
        Switch(
            bear.get(),  //
            [&](Reptile*) { FAIL() << "bear is not reptile"; },
            [&](Amphibian*) { FAIL() << "bear is not amphibian"; },
            [&](Mammal* mammal) {
                EXPECT_EQ(mammal, bear.get());
                bear_matched_mammal = true;
            },
            [&](Default) { FAIL() << "default should not have been selected"; });
        EXPECT_TRUE(bear_matched_mammal);
    }
    {
        bool gecko_matched_reptile = false;
        Switch(
            gecko.get(),  //
            [&](Mammal*) { FAIL() << "gecko is not mammal"; },
            [&](Amphibian*) { FAIL() << "gecko is not amphibian"; },
            [&](Reptile* reptile) {
                EXPECT_EQ(reptile, gecko.get());
                gecko_matched_reptile = true;
            },
            [&](Default) { FAIL() << "default should not have been selected"; });
        EXPECT_TRUE(gecko_matched_reptile);
    }
}

TEST(Castable, SwitchDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        bool frog_matched_default = false;
        Switch(
            frog.get(),  //
            [&](Reptile*) { FAIL() << "frog is not reptile"; },
            [&](Mammal*) { FAIL() << "frog is not mammal"; },
            [&](Default) { frog_matched_default = true; });
        EXPECT_TRUE(frog_matched_default);
    }
    {
        bool bear_matched_default = false;
        Switch(
            bear.get(),  //
            [&](Reptile*) { FAIL() << "bear is not reptile"; },
            [&](Amphibian*) { FAIL() << "bear is not amphibian"; },
            [&](Default) { bear_matched_default = true; });
        EXPECT_TRUE(bear_matched_default);
    }
    {
        bool gecko_matched_default = false;
        Switch(
            gecko.get(),  //
            [&](Mammal*) { FAIL() << "gecko is not mammal"; },
            [&](Amphibian*) { FAIL() << "gecko is not amphibian"; },
            [&](Default) { gecko_matched_default = true; });
        EXPECT_TRUE(gecko_matched_default);
    }
}

TEST(Castable, SwitchMatchFirst) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    {
        bool frog_matched_animal = false;
        Switch(
            frog.get(),
            [&](Animal* animal) {
                EXPECT_EQ(animal, frog.get());
                frog_matched_animal = true;
            },
            [&](Amphibian*) { FAIL() << "animal should have been matched first"; });
        EXPECT_TRUE(frog_matched_animal);
    }
    {
        bool frog_matched_amphibian = false;
        Switch(
            frog.get(),
            [&](Amphibian* amphibain) {
                EXPECT_EQ(amphibain, frog.get());
                frog_matched_amphibian = true;
            },
            [&](Animal*) { FAIL() << "amphibian should have been matched first"; });
        EXPECT_TRUE(frog_matched_amphibian);
    }
}

TEST(Castable, SwitchReturnValueWithDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        const char* result = Switch(
            frog.get(),                              //
            [](Mammal*) { return "mammal"; },        //
            [](Amphibian*) { return "amphibian"; },  //
            [](Default) { return "unknown"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(std::string(result), "amphibian");
    }
    {
        const char* result = Switch(
            bear.get(),                              //
            [](Mammal*) { return "mammal"; },        //
            [](Amphibian*) { return "amphibian"; },  //
            [](Default) { return "unknown"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(std::string(result), "mammal");
    }
    {
        const char* result = Switch(
            gecko.get(),                             //
            [](Mammal*) { return "mammal"; },        //
            [](Amphibian*) { return "amphibian"; },  //
            [](Default) { return "unknown"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(std::string(result), "unknown");
    }
}

TEST(Castable, SwitchReturnValueWithoutDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        const char* result = Switch(
            frog.get(),                        //
            [](Mammal*) { return "mammal"; },  //
            [](Amphibian*) { return "amphibian"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(std::string(result), "amphibian");
    }
    {
        const char* result = Switch(
            bear.get(),                        //
            [](Mammal*) { return "mammal"; },  //
            [](Amphibian*) { return "amphibian"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(std::string(result), "mammal");
    }
    {
        auto* result = Switch(
            gecko.get(),                       //
            [](Mammal*) { return "mammal"; },  //
            [](Amphibian*) { return "amphibian"; });
        static_assert(std::is_same_v<decltype(result), const char*>);
        EXPECT_EQ(result, nullptr);
    }
}

TEST(Castable, SwitchInferPODReturnTypeWithDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto result = Switch(
            frog.get(),                       //
            [](Mammal*) { return 1; },        //
            [](Amphibian*) { return 2.0f; },  //
            [](Default) { return 3.0; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 2.0);
    }
    {
        auto result = Switch(
            bear.get(),                       //
            [](Mammal*) { return 1.0; },      //
            [](Amphibian*) { return 2.0f; },  //
            [](Default) { return 3; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 1.0);
    }
    {
        auto result = Switch(
            gecko.get(),                   //
            [](Mammal*) { return 1.0f; },  //
            [](Amphibian*) { return 2; },  //
            [](Default) { return 3.0; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 3.0);
    }
}

TEST(Castable, SwitchInferPODReturnTypeWithoutDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto result = Switch(
            frog.get(),                 //
            [](Mammal*) { return 1; },  //
            [](Amphibian*) { return 2.0f; });
        static_assert(std::is_same_v<decltype(result), float>);
        EXPECT_EQ(result, 2.0f);
    }
    {
        auto result = Switch(
            bear.get(),                    //
            [](Mammal*) { return 1.0f; },  //
            [](Amphibian*) { return 2; });
        static_assert(std::is_same_v<decltype(result), float>);
        EXPECT_EQ(result, 1.0f);
    }
    {
        auto result = Switch(
            gecko.get(),                  //
            [](Mammal*) { return 1.0; },  //
            [](Amphibian*) { return 2.0f; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 0.0);
    }
}

TEST(Castable, SwitchInferCastableReturnTypeWithDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto* result = Switch(
            frog.get(),                          //
            [](Mammal* p) { return p; },         //
            [](Amphibian*) { return nullptr; },  //
            [](Default) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), Mammal*>);
        EXPECT_EQ(result, nullptr);
    }
    {
        auto* result = Switch(
            bear.get(),                   //
            [](Mammal* p) { return p; },  //
            [](Amphibian* p) { return const_cast<const Amphibian*>(p); },
            [](Default) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), const Animal*>);
        EXPECT_EQ(result, bear.get());
    }
    {
        auto* result = Switch(
            gecko.get(),                     //
            [](Mammal* p) { return p; },     //
            [](Amphibian* p) { return p; },  //
            [](Default) -> CastableBase* { return nullptr; });
        static_assert(std::is_same_v<decltype(result), CastableBase*>);
        EXPECT_EQ(result, nullptr);
    }
}

TEST(Castable, SwitchInferCastableReturnTypeWithoutDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto* result = Switch(
            frog.get(),                   //
            [](Mammal* p) { return p; },  //
            [](Amphibian*) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), Mammal*>);
        EXPECT_EQ(result, nullptr);
    }
    {
        auto* result = Switch(
            bear.get(),                                                     //
            [](Mammal* p) { return p; },                                    //
            [](Amphibian* p) { return const_cast<const Amphibian*>(p); });  //
        static_assert(std::is_same_v<decltype(result), const Animal*>);
        EXPECT_EQ(result, bear.get());
    }
    {
        auto* result = Switch(
            gecko.get(),                  //
            [](Mammal* p) { return p; },  //
            [](Amphibian* p) { return p; });
        static_assert(std::is_same_v<decltype(result), Animal*>);
        EXPECT_EQ(result, nullptr);
    }
}

TEST(Castable, SwitchExplicitPODReturnTypeWithDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto result = Switch<double>(
            frog.get(),                       //
            [](Mammal*) { return 1; },        //
            [](Amphibian*) { return 2.0f; },  //
            [](Default) { return 3.0; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 2.0f);
    }
    {
        auto result = Switch<double>(
            bear.get(),                    //
            [](Mammal*) { return 1; },     //
            [](Amphibian*) { return 2; },  //
            [](Default) { return 3; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 1.0f);
    }
    {
        auto result = Switch<double>(
            gecko.get(),                      //
            [](Mammal*) { return 1.0f; },     //
            [](Amphibian*) { return 2.0f; },  //
            [](Default) { return 3.0f; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 3.0f);
    }
}

TEST(Castable, SwitchExplicitPODReturnTypeWithoutDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto result = Switch<double>(
            frog.get(),                 //
            [](Mammal*) { return 1; },  //
            [](Amphibian*) { return 2.0f; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 2.0f);
    }
    {
        auto result = Switch<double>(
            bear.get(),                    //
            [](Mammal*) { return 1.0f; },  //
            [](Amphibian*) { return 2; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 1.0f);
    }
    {
        auto result = Switch<double>(
            gecko.get(),                  //
            [](Mammal*) { return 1.0; },  //
            [](Amphibian*) { return 2.0f; });
        static_assert(std::is_same_v<decltype(result), double>);
        EXPECT_EQ(result, 0.0);
    }
}

TEST(Castable, SwitchExplicitCastableReturnTypeWithDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto* result = Switch<Animal>(
            frog.get(),                          //
            [](Mammal* p) { return p; },         //
            [](Amphibian*) { return nullptr; },  //
            [](Default) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), Animal*>);
        EXPECT_EQ(result, nullptr);
    }
    {
        auto* result = Switch<CastableBase>(
            bear.get(),                   //
            [](Mammal* p) { return p; },  //
            [](Amphibian* p) { return const_cast<const Amphibian*>(p); },
            [](Default) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), const CastableBase*>);
        EXPECT_EQ(result, bear.get());
    }
    {
        auto* result = Switch<const Animal>(
            gecko.get(),                     //
            [](Mammal* p) { return p; },     //
            [](Amphibian* p) { return p; },  //
            [](Default) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), const Animal*>);
        EXPECT_EQ(result, nullptr);
    }
}

TEST(Castable, SwitchExplicitCastableReturnTypeWithoutDefault) {
    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    std::unique_ptr<Animal> bear = std::make_unique<Bear>();
    std::unique_ptr<Animal> gecko = std::make_unique<Gecko>();
    {
        auto* result = Switch<Animal>(
            frog.get(),                   //
            [](Mammal* p) { return p; },  //
            [](Amphibian*) { return nullptr; });
        static_assert(std::is_same_v<decltype(result), Animal*>);
        EXPECT_EQ(result, nullptr);
    }
    {
        auto* result = Switch<CastableBase>(
            bear.get(),                                                     //
            [](Mammal* p) { return p; },                                    //
            [](Amphibian* p) { return const_cast<const Amphibian*>(p); });  //
        static_assert(std::is_same_v<decltype(result), const CastableBase*>);
        EXPECT_EQ(result, bear.get());
    }
    {
        auto* result = Switch<const Animal*>(
            gecko.get(),                  //
            [](Mammal* p) { return p; },  //
            [](Amphibian* p) { return p; });
        static_assert(std::is_same_v<decltype(result), const Animal*>);
        EXPECT_EQ(result, nullptr);
    }
}

TEST(Castable, SwitchNull) {
    Animal* null = nullptr;
    Switch(
        null,  //
        [&](Amphibian*) { FAIL() << "should not be called"; },
        [&](Animal*) { FAIL() << "should not be called"; });
}

TEST(Castable, SwitchNullNoDefault) {
    Animal* null = nullptr;
    bool default_called = false;
    Switch(
        null,  //
        [&](Amphibian*) { FAIL() << "should not be called"; },
        [&](Animal*) { FAIL() << "should not be called"; },
        [&](Default) { default_called = true; });
    EXPECT_TRUE(default_called);
}

TEST(Castable, SwitchReturnNoDefaultInitializer) {
    struct Object {
        explicit Object(int v) : value(v) {}
        int value;
    };

    std::unique_ptr<Animal> frog = std::make_unique<Frog>();
    {
        auto result = Switch(
            frog.get(),                            //
            [](Mammal*) { return Object(1); },     //
            [](Amphibian*) { return Object(2); },  //
            [](Default) { return Object(3); });
        static_assert(std::is_same_v<decltype(result), Object>);
        EXPECT_EQ(result.value, 2);
    }
    {
        auto result = Switch(
            frog.get(),                         //
            [](Mammal*) { return Object(1); },  //
            [](Default) { return Object(3); });
        static_assert(std::is_same_v<decltype(result), Object>);
        EXPECT_EQ(result.value, 3);
    }
}

// IsCastable static tests
static_assert(IsCastable<CastableBase>);
static_assert(IsCastable<Animal>);
static_assert(IsCastable<Ignore, Frog, Bear>);
static_assert(IsCastable<Mammal, Ignore, Amphibian, Gecko>);
static_assert(!IsCastable<Mammal, int, Amphibian, Ignore, Gecko>);
static_assert(!IsCastable<bool>);
static_assert(!IsCastable<int, float>);
static_assert(!IsCastable<Ignore>);

// CastableCommonBase static tests
static_assert(std::is_same_v<Animal, CastableCommonBase<Animal>>);
static_assert(std::is_same_v<Amphibian, CastableCommonBase<Amphibian>>);
static_assert(std::is_same_v<Mammal, CastableCommonBase<Mammal>>);
static_assert(std::is_same_v<Reptile, CastableCommonBase<Reptile>>);
static_assert(std::is_same_v<Frog, CastableCommonBase<Frog>>);
static_assert(std::is_same_v<Bear, CastableCommonBase<Bear>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Lizard>>);
static_assert(std::is_same_v<Gecko, CastableCommonBase<Gecko>>);
static_assert(std::is_same_v<Iguana, CastableCommonBase<Iguana>>);

static_assert(std::is_same_v<Animal, CastableCommonBase<Animal, Animal>>);
static_assert(std::is_same_v<Amphibian, CastableCommonBase<Amphibian, Amphibian>>);
static_assert(std::is_same_v<Mammal, CastableCommonBase<Mammal, Mammal>>);
static_assert(std::is_same_v<Reptile, CastableCommonBase<Reptile, Reptile>>);
static_assert(std::is_same_v<Frog, CastableCommonBase<Frog, Frog>>);
static_assert(std::is_same_v<Bear, CastableCommonBase<Bear, Bear>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Lizard, Lizard>>);
static_assert(std::is_same_v<Gecko, CastableCommonBase<Gecko, Gecko>>);
static_assert(std::is_same_v<Iguana, CastableCommonBase<Iguana, Iguana>>);

static_assert(std::is_same_v<CastableBase, CastableCommonBase<CastableBase, Animal>>);
static_assert(std::is_same_v<CastableBase, CastableCommonBase<Animal, CastableBase>>);
static_assert(std::is_same_v<Amphibian, CastableCommonBase<Amphibian, Frog>>);
static_assert(std::is_same_v<Amphibian, CastableCommonBase<Frog, Amphibian>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Reptile, Frog>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Frog, Reptile>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Bear, Frog>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Frog, Bear>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Gecko, Iguana>>);

static_assert(std::is_same_v<Animal, CastableCommonBase<Bear, Frog, Iguana>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Lizard, Gecko, Iguana>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Gecko, Iguana, Lizard>>);
static_assert(std::is_same_v<Lizard, CastableCommonBase<Gecko, Lizard, Iguana>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Frog, Gecko, Iguana>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Gecko, Iguana, Frog>>);
static_assert(std::is_same_v<Animal, CastableCommonBase<Gecko, Frog, Iguana>>);

static_assert(std::is_same_v<CastableBase, CastableCommonBase<Bear, Frog, Iguana, CastableBase>>);

}  // namespace

TINT_INSTANTIATE_TYPEINFO(Animal);
TINT_INSTANTIATE_TYPEINFO(Amphibian);
TINT_INSTANTIATE_TYPEINFO(Mammal);
TINT_INSTANTIATE_TYPEINFO(Reptile);
TINT_INSTANTIATE_TYPEINFO(Frog);
TINT_INSTANTIATE_TYPEINFO(Bear);
TINT_INSTANTIATE_TYPEINFO(Lizard);
TINT_INSTANTIATE_TYPEINFO(Gecko);

}  // namespace tint