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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
// <expected>
// template<class F> constexpr auto and_then(F&& f) &;
// template<class F> constexpr auto and_then(F&& f) const &;
// template<class F> constexpr auto and_then(F&& f) &&;
// template<class F> constexpr auto and_then(F&& f) const &&;
#include <cassert>
#include <concepts>
#include <expected>
#include <memory>
#include <type_traits>
#include <utility>
struct LVal {
constexpr std::expected<int, int> operator()(int&) { return 1; }
std::expected<int, int> operator()(const int&) = delete;
std::expected<int, int> operator()(int&&) = delete;
std::expected<int, int> operator()(const int&&) = delete;
};
struct CLVal {
std::expected<int, int> operator()(int&) = delete;
constexpr std::expected<int, int> operator()(const int&) { return 1; }
std::expected<int, int> operator()(int&&) = delete;
std::expected<int, int> operator()(const int&&) = delete;
};
struct RVal {
std::expected<int, int> operator()(int&) = delete;
std::expected<int, int> operator()(const int&) = delete;
constexpr std::expected<int, int> operator()(int&&) { return 1; }
std::expected<int, int> operator()(const int&&) = delete;
};
struct CRVal {
std::expected<int, int> operator()(int&) = delete;
std::expected<int, int> operator()(const int&) = delete;
std::expected<int, int> operator()(int&&) = delete;
constexpr std::expected<int, int> operator()(const int&&) { return 1; }
};
struct RefQual {
constexpr std::expected<int, int> operator()(int) & { return 1; }
std::expected<int, int> operator()(int) const& = delete;
std::expected<int, int> operator()(int) && = delete;
std::expected<int, int> operator()(int) const&& = delete;
};
struct CRefQual {
std::expected<int, int> operator()(int) & = delete;
constexpr std::expected<int, int> operator()(int) const& { return 1; }
std::expected<int, int> operator()(int) && = delete;
std::expected<int, int> operator()(int) const&& = delete;
};
struct RVRefQual {
std::expected<int, int> operator()(int) & = delete;
std::expected<int, int> operator()(int) const& = delete;
constexpr std::expected<int, int> operator()(int) && { return 1; }
std::expected<int, int> operator()(int) const&& = delete;
};
struct RVCRefQual {
std::expected<int, int> operator()(int) & = delete;
std::expected<int, int> operator()(int) const& = delete;
std::expected<int, int> operator()(int) && = delete;
constexpr std::expected<int, int> operator()(int) const&& { return 1; }
};
struct UnexpectedLVal {
constexpr std::expected<int, int> operator()(int&) { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(const int&) = delete;
std::expected<int, int> operator()(int&&) = delete;
std::expected<int, int> operator()(const int&&) = delete;
};
struct UnexpectedCLVal {
std::expected<int, int> operator()(int&) = delete;
constexpr std::expected<int, int> operator()(const int&) { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(int&&) = delete;
std::expected<int, int> operator()(const int&&) = delete;
};
struct UnexpectedRVal {
std::expected<int, int> operator()(int&) = delete;
std::expected<int, int> operator()(const int&) = delete;
constexpr std::expected<int, int> operator()(int&&) { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(const int&&) = delete;
};
struct UnexpectedCRVal {
std::expected<int, int> operator()(int&) = delete;
std::expected<int, int> operator()(const int&) = delete;
std::expected<int, int> operator()(int&&) = delete;
constexpr std::expected<int, int> operator()(const int&&) { return std::expected<int, int>(std::unexpected<int>(5)); }
};
struct UnexpectedRefQual {
constexpr std::expected<int, int> operator()(int) & { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(int) const& = delete;
std::expected<int, int> operator()(int) && = delete;
std::expected<int, int> operator()(int) const&& = delete;
};
struct UnexpectedCRefQual {
std::expected<int, int> operator()(int) & = delete;
constexpr std::expected<int, int> operator()(int) const& { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(int) && = delete;
std::expected<int, int> operator()(int) const&& = delete;
};
struct UnexpectedRVRefQual {
std::expected<int, int> operator()(int) & = delete;
std::expected<int, int> operator()(int) const& = delete;
constexpr std::expected<int, int> operator()(int) && { return std::expected<int, int>(std::unexpected<int>(5)); }
std::expected<int, int> operator()(int) const&& = delete;
};
struct UnexpectedRVCRefQual {
std::expected<int, int> operator()(int) & = delete;
std::expected<int, int> operator()(int) const& = delete;
std::expected<int, int> operator()(int) && = delete;
constexpr std::expected<int, int> operator()(int) const&& { return std::expected<int, int>(std::unexpected<int>(5)); }
};
struct NonCopyable {
constexpr NonCopyable(int) {}
NonCopyable(const NonCopyable&) = delete;
};
struct NonMovable {
constexpr NonMovable(int) {}
NonMovable(NonMovable&&) = delete;
};
struct NonConst {
std::expected<int, int> non_const() { return 1; }
};
template <class E, class F>
concept has_and_then = requires(E&& e, F&& f) {
{std::forward<E>(e).and_then(std::forward<F>(f))};
};
static_assert( has_and_then<std::expected<int, int>&, std::expected<int, int>(int&)>);
static_assert(!has_and_then<std::expected<int, NonCopyable>&, std::expected<int, NonCopyable>(int&)>);
static_assert( has_and_then<const std::expected<int, int>&, std::expected<int, int>(const int&)>);
static_assert(!has_and_then<const std::expected<int, NonCopyable>&, std::expected<int, NonCopyable>(const int&)>);
static_assert( has_and_then<std::expected<int, int>&&, std::expected<int, int>(int)>);
static_assert(!has_and_then<std::expected<int, NonMovable>&&, std::expected<int, NonMovable>(int)>);
static_assert( has_and_then<const std::expected<int, int>&&, std::expected<int, int>(const int)>);
static_assert(!has_and_then<const std::expected<int, NonMovable>&&, std::expected<int, NonMovable>(const int)>);
// [LWG 3877] https://cplusplus.github.io/LWG/issue3877, check constraint failing but not compile error inside the function body.
static_assert(!has_and_then<const std::expected<int, std::unique_ptr<int>>&, int()>);
static_assert(!has_and_then<const std::expected<int, std::unique_ptr<int>>&&, int()>);
// clang-format off
constexpr void test_val_types() {
// Test & overload
{
// Without &qualifier on F'soperator()
{
std::expected<int, int> e{0};
std::same_as<std::expected<int, int>> decltype(auto) val = e.and_then(LVal{});
assert(val == 1);
assert(e.and_then(UnexpectedLVal{}).error() == 5);
}
// With & qualifier on F's operator()
{
std::expected<int, int> e{0};
RefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = e.and_then(l);
assert(val == 1);
UnexpectedRefQual nl{};
assert(e.and_then(nl).error() == 5);
}
}
// Test const& overload
{
// Without & qualifier on F's operator()
{
const std::expected<int, int> e{0};
std::same_as<std::expected<int, int>> decltype(auto) val = e.and_then(CLVal{});
assert(val == 1);
assert(e.and_then(UnexpectedCLVal{}).error() == 5);
}
// With & qualifier on F's operator()
{
const std::expected<int, int> e{0};
const CRefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = e.and_then(l);
assert(val == 1);
const UnexpectedCRefQual nl{};
assert(e.and_then(nl).error() == 5);
}
}
// Test && overload
{
// Without & qualifier on F's operator()
{
std::expected<int, int> e{0};
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).and_then(RVal{});
assert(val == 1);
assert(std::move(e).and_then(UnexpectedRVal{}).error() == 5);
}
// With & qualifier on F's operator()
{
std::expected<int, int> e{0};
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).and_then(RVRefQual{});
assert(val == 1);
assert(e.and_then(UnexpectedRVRefQual{}).error() == 5);
}
}
// Test const&& overload
{
// Without & qualifier on F's operator()
{
const std::expected<int, int> e{0};
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).and_then(CRVal{});
assert(val == 1);
assert(std::move(e).and_then(UnexpectedCRVal{}).error() == 5);
}
// With & qualifier on F's operator()
{
const std::expected<int, int> e{0};
const RVCRefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).and_then(std::move(l));
assert(val == 1);
const UnexpectedRVCRefQual nl{};
assert(std::move(e).and_then(std::move(nl)).error() == 5);
}
}
}
// clang-format on
// check that the lambda body is not instantiated during overload resolution
constexpr void test_sfinae() {
std::expected<NonConst, int> e(std::unexpected<int>(2));
auto l = [](auto&& x) { return x.non_const(); };
e.and_then(l);
std::move(e).and_then(l);
}
constexpr bool test() {
test_sfinae();
test_val_types();
std::expected<int, int> e(std::unexpected<int>(1));
const auto& ce = e;
const auto never_called = [](int) {
assert(false);
return std::expected<int, int>();
};
e.and_then(never_called);
std::move(e).and_then(never_called);
ce.and_then(never_called);
std::move(ce).and_then(never_called);
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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