zircon/system/utest/fit/variant_tests.cpp

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <string>
#include <type_traits>

#include <lib/fit/variant.h>
#include <unittest/unittest.h>

namespace {

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

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

struct no_copy_no_move {
    no_copy_no_move(const no_copy_no_move&) = delete;
    no_copy_no_move(no_copy_no_move&&) = delete;
    no_copy_no_move& operator=(const no_copy_no_move&) = delete;
    no_copy_no_move& operator=(no_copy_no_move&&) = delete;
};

struct non_trivial_destructor {
    ~non_trivial_destructor() {}
};

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

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

struct literal_traits {
    using variant = fit::internal::variant<
        fit::internal::monostate, int, double>;

    static constexpr fit::internal::monostate a_value{};
    static constexpr int b_value = 10;
    static constexpr double c_value = 2.5;
    static constexpr double c2_value = 4.2;

    static variant a, b, c;
    static constexpr variant const_a;
    static constexpr variant const_b{fit::internal::in_place_index<1>,
                                     b_value};
    static constexpr variant const_c{fit::internal::in_place_index<2>,
                                     c_value};
};

literal_traits::variant literal_traits::a;
literal_traits::variant literal_traits::b{fit::internal::in_place_index<1>,
                                          literal_traits::b_value};
literal_traits::variant literal_traits::c{fit::internal::in_place_index<2>,
                                          literal_traits::c_value};

struct complex_traits {
    using variant = fit::internal::variant<
        fit::internal::monostate, int, std::string>;

    static const fit::internal::monostate a_value;
    static const int b_value;
    static const std::string c_value;
    static const std::string c2_value;

    static variant a, b, c;
    static const variant const_a;
    static const variant const_b;
    static const variant const_c;
};

const fit::internal::monostate complex_traits::a_value{};
const int complex_traits::b_value = 10;
const std::string complex_traits::c_value = "test";
const std::string complex_traits::c2_value = "another";

complex_traits::variant complex_traits::a;
complex_traits::variant complex_traits::b{fit::internal::in_place_index<1>,
                                          complex_traits::b_value};
complex_traits::variant complex_traits::c{fit::internal::in_place_index<2>,
                                          complex_traits::c_value};

const complex_traits::variant complex_traits::const_a;
const complex_traits::variant complex_traits::const_b{fit::internal::in_place_index<1>,
                                                      complex_traits::b_value};
const complex_traits::variant complex_traits::const_c{fit::internal::in_place_index<2>,
                                                      complex_traits::c_value};

template <typename T>
bool accessors() {
    BEGIN_TEST;

    EXPECT_EQ(0, T::a.index());
    EXPECT_TRUE(T::a_value == T::a.template get<0>());
    EXPECT_TRUE(T::a_value == T::const_a.template get<0>());

    EXPECT_EQ(1, T::b.index());
    EXPECT_TRUE(T::b_value == T::b.template get<1>());
    EXPECT_TRUE(T::b_value == T::const_b.template get<1>());

    EXPECT_EQ(2, T::c.index());
    EXPECT_TRUE(T::c_value == T::c.template get<2>());
    EXPECT_TRUE(T::c_value == T::const_c.template get<2>());

    END_TEST;
}

template <typename T>
bool copy_move_assign() {
    BEGIN_TEST;

    typename T::variant x;
    EXPECT_EQ(0, x.index());
    EXPECT_TRUE(T::a_value == x.template get<0>());

    x = T::b;
    EXPECT_EQ(1, x.index());
    EXPECT_TRUE(T::b_value == x.template get<1>());

    x.template emplace<2>(T::c_value);
    EXPECT_EQ(2, x.index());
    EXPECT_TRUE(T::c_value == x.template get<2>());

    typename T::variant y(T::b);
    EXPECT_EQ(1, y.index());
    EXPECT_TRUE(T::b_value == y.template get<1>());

    x = std::move(y);
    EXPECT_EQ(1, x.index());
    EXPECT_TRUE(T::b_value == x.template get<1>());

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wself-assign-overloaded"
#endif

    x = x;
    EXPECT_EQ(1, x.index());
    EXPECT_TRUE(T::b_value == x.template get<1>());

#ifdef __clang__
#pragma clang diagnostic pop
#endif

    x = std::move(x);
    EXPECT_EQ(1, x.index());
    EXPECT_TRUE(T::b_value == x.template get<1>());

    x = T::a;
    EXPECT_EQ(0, x.index());
    EXPECT_TRUE(T::a_value == x.template get<0>());

    x = T::c;
    typename T::variant z(std::move(x));
    EXPECT_EQ(2, z.index());
    EXPECT_TRUE(T::c_value == z.template get<2>());

    END_TEST;
}

template <typename T>
bool swapping() {
    BEGIN_TEST;

    typename T::variant x;
    EXPECT_EQ(0, x.index());
    EXPECT_TRUE(T::a_value == x.template get<0>());

    typename T::variant y(T::c);
    y.swap(y);
    EXPECT_EQ(2, y.index());
    EXPECT_TRUE(T::c_value == y.template get<2>());

    x.swap(y);
    EXPECT_EQ(2, x.index());
    EXPECT_TRUE(T::c_value == x.template get<2>());
    EXPECT_EQ(0, y.index());
    EXPECT_TRUE(T::a_value == y.template get<0>());

    y.template emplace<2>(T::c2_value);
    x.swap(y);
    EXPECT_EQ(2, x.index());
    EXPECT_TRUE(T::c2_value == x.template get<2>());
    EXPECT_EQ(2, y.index());
    EXPECT_TRUE(T::c_value == y.template get<2>());

    x = T::b;
    y.swap(x);
    EXPECT_EQ(2, x.index());
    EXPECT_TRUE(T::c_value == x.template get<2>());
    EXPECT_EQ(1, y.index());
    EXPECT_TRUE(T::b_value == y.template get<1>());

    x = T::a;
    y.swap(x);
    EXPECT_EQ(1, x.index());
    EXPECT_TRUE(T::b_value == x.template get<1>());
    EXPECT_EQ(0, y.index());
    EXPECT_TRUE(T::a_value == y.template get<0>());

    END_TEST;
}

// Test constexpr behavior.
namespace constexpr_test {
static_assert(literal_traits::variant().index() == 0, "");
static_assert(literal_traits::const_a.index() == 0, "");
static_assert(literal_traits::const_a.get<0>() == literal_traits::a_value, "");
static_assert(literal_traits::const_b.index() == 1, "");
static_assert(literal_traits::const_b.get<1>() == literal_traits::b_value, "");
static_assert(literal_traits::const_c.index() == 2, "");
static_assert(literal_traits::const_c.get<2>() == literal_traits::c_value, "");
} // namespace constexpr_test

// Ensure the variant is copy-constructible only when the types are copyable.
namespace copy_construction_test {
static_assert(
    std::is_copy_constructible<
        fit::internal::variant<fit::internal::monostate>>::value,
    "");
static_assert(
    !std::is_copy_constructible<
        fit::internal::variant<fit::internal::monostate, no_copy>>::value,
    "");
static_assert(
    std::is_copy_constructible<
        fit::internal::variant<fit::internal::monostate, no_move>>::value,
    "");
static_assert(
    !std::is_copy_constructible<
        fit::internal::variant<fit::internal::monostate, no_copy_no_move>>::value,
    "");
static_assert(
    std::is_copy_constructible<
        literal_traits::variant>::value,
    "");
static_assert(
    std::is_copy_constructible<
        complex_traits::variant>::value,
    "");
} // namespace copy_construction_test

// Ensure the variant is copy-assignable only when the types are copyable.
namespace copy_assignment_test {
static_assert(
    std::is_copy_assignable<
        fit::internal::variant<fit::internal::monostate>>::value,
    "");
static_assert(
    !std::is_copy_assignable<
        fit::internal::variant<fit::internal::monostate, no_copy>>::value,
    "");
static_assert(
    std::is_copy_assignable<
        fit::internal::variant<fit::internal::monostate, no_move>>::value,
    "");
static_assert(
    !std::is_copy_assignable<
        fit::internal::variant<fit::internal::monostate, no_copy_no_move>>::value,
    "");
static_assert(
    std::is_copy_assignable<
        literal_traits::variant>::value,
    "");
static_assert(
    std::is_copy_assignable<
        complex_traits::variant>::value,
    "");
} // namespace copy_assignment_test

// Ensure the variant is move-constructible only when the types are movable.
// Note that copy-constructible types are also considered movable.
namespace move_construction_test {
static_assert(
    std::is_move_constructible<
        fit::internal::variant<fit::internal::monostate>>::value,
    "");
static_assert(
    std::is_move_constructible<
        fit::internal::variant<fit::internal::monostate, no_copy>>::value,
    "");
static_assert(
    std::is_move_constructible<
        fit::internal::variant<fit::internal::monostate, no_move>>::value,
    "");
static_assert(
    !std::is_move_constructible<
        fit::internal::variant<fit::internal::monostate, no_copy_no_move>>::value,
    "");
static_assert(
    std::is_move_constructible<
        literal_traits::variant>::value,
    "");
static_assert(
    std::is_move_constructible<
        complex_traits::variant>::value,
    "");
} // namespace move_construction_test

// Ensure the variant is move-assignable only when the types are movable.
// Note that copy-assignable types are also considered movable.
namespace move_assignment_test {
static_assert(
    std::is_move_assignable<
        fit::internal::variant<fit::internal::monostate>>::value,
    "");
static_assert(
    std::is_move_assignable<
        fit::internal::variant<fit::internal::monostate, no_copy>>::value,
    "");
static_assert(
    std::is_move_assignable<
        fit::internal::variant<fit::internal::monostate, no_move>>::value,
    "");
static_assert(
    !std::is_move_assignable<
        fit::internal::variant<fit::internal::monostate, no_copy_no_move>>::value,
    "");
static_assert(
    std::is_move_assignable<
        literal_traits::variant>::value,
    "");
static_assert(
    std::is_move_assignable<
        complex_traits::variant>::value,
    "");
} // namespace move_assignment_test

// Ensure that the correct sequence of base types are considered in the
// implementation of variant to ensure that the right methods participate
// in overload resolution.
namespace impl_test {

// Type with a trivial destructor, move, and copy.
namespace trivial_type {
static_assert(
    std::is_base_of<
        fit::internal::variant_base_impl_trivial<fit::internal::monostate, int>,
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    !std::is_base_of<
        fit::internal::variant_move_impl_non_trivial<fit::internal::monostate, int>,
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    !std::is_base_of<
        fit::internal::variant_copy_impl_non_trivial<fit::internal::monostate, int>,
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    std::is_trivially_destructible<
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    std::is_trivially_move_constructible<
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    std::is_trivially_copy_constructible<
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    std::is_trivially_move_assignable<
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
static_assert(
    std::is_trivially_copy_assignable<
        fit::internal::variant<fit::internal::monostate, int>>::value,
    "");
} // namespace trivial_type

// Type with a non-trivial destructor implies it has non-trivial move and copy too.
namespace non_trivial_destructor_type {
static_assert(
    std::is_base_of<
        fit::internal::variant_base_impl_non_trivial<fit::internal::monostate, non_trivial_destructor>,
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    std::is_base_of<
        fit::internal::variant_move_impl_non_trivial<fit::internal::monostate, non_trivial_destructor>,
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    std::is_base_of<
        fit::internal::variant_copy_impl_non_trivial<fit::internal::monostate, non_trivial_destructor>,
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    !std::is_trivially_destructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    !std::is_trivially_move_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    !std::is_trivially_copy_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    !std::is_trivially_move_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
static_assert(
    !std::is_trivially_copy_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_destructor>>::value,
    "");
} // namespace non_trivial_destructor_type

// Type with a non-trivial move constructor actually ends up being trivially
// movable anyhow if it has a trivial copy constructor and destructor.
namespace non_trivial_move_type {
static_assert(
    std::is_base_of<
        fit::internal::variant_base_impl_trivial<fit::internal::monostate, non_trivial_move>,
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    !std::is_base_of<
        fit::internal::variant_move_impl_non_trivial<fit::internal::monostate, non_trivial_move>,
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    !std::is_base_of<
        fit::internal::variant_copy_impl_non_trivial<fit::internal::monostate, non_trivial_move>,
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    std::is_trivially_destructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    std::is_trivially_move_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    std::is_trivially_copy_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    std::is_trivially_move_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
static_assert(
    std::is_trivially_copy_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_move>>::value,
    "");
} // namespace non_trivial_move_type

// Type with a non-trivial copy constructor may be trivially movable while not
// trivially copyable.
namespace non_trivial_copy_type {
static_assert(
    std::is_base_of<
        fit::internal::variant_base_impl_trivial<fit::internal::monostate, non_trivial_copy>,
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    !std::is_base_of<
        fit::internal::variant_move_impl_non_trivial<fit::internal::monostate, non_trivial_copy>,
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    std::is_base_of<
        fit::internal::variant_copy_impl_non_trivial<fit::internal::monostate, non_trivial_copy>,
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    std::is_trivially_destructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    std::is_trivially_move_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    !std::is_trivially_copy_constructible<
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    std::is_trivially_move_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
static_assert(
    !std::is_trivially_copy_assignable<
        fit::internal::variant<fit::internal::monostate, non_trivial_copy>>::value,
    "");
} // namespace non_trivial_copy_type

// std::string is not trivally destructible, movable, or copyable.
namespace string_type {
static_assert(
    std::is_base_of<
        fit::internal::variant_base_impl_non_trivial<fit::internal::monostate, std::string>,
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    std::is_base_of<
        fit::internal::variant_move_impl_non_trivial<fit::internal::monostate, std::string>,
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    std::is_base_of<
        fit::internal::variant_copy_impl_non_trivial<fit::internal::monostate, std::string>,
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    !std::is_trivially_destructible<
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    !std::is_trivially_move_constructible<
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    !std::is_trivially_copy_constructible<
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    !std::is_trivially_move_assignable<
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
static_assert(
    !std::is_trivially_copy_assignable<
        fit::internal::variant<fit::internal::monostate, std::string>>::value,
    "");
} // namespace string_type
} // namespace impl_test

} // namespace

BEGIN_TEST_CASE(variant_tests)
RUN_TEST(accessors<literal_traits>)
RUN_TEST(accessors<complex_traits>)
RUN_TEST(copy_move_assign<literal_traits>)
RUN_TEST(copy_move_assign<complex_traits>)
RUN_TEST(swapping<literal_traits>)
RUN_TEST(swapping<complex_traits>)
END_TEST_CASE(variant_tests)