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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 <expected>
#include <concepts>
#include <cassert>
#include <memory>
#include <type_traits>
#include <utility>
struct NonCopyable {
constexpr NonCopyable(int) {}
NonCopyable(const NonCopyable&) = delete;
};
struct NonMovable {
constexpr NonMovable(int) {}
NonMovable(NonMovable&&) = delete;
};
template <class E, class F>
concept has_and_then =
requires(E&& e, F&& f) {
{ std::forward<E>(e).and_then(std::forward<F>(f)) };
};
std::expected<void, int> return_int() { return {}; }
std::expected<void, NonCopyable> return_noncopyable() { return {}; }
std::expected<void, NonMovable> return_nonmovable() { return {}; }
static_assert(has_and_then<std::expected<void, int>&, decltype(return_int)>);
static_assert(!has_and_then<std::expected<void, NonCopyable>&, decltype(return_noncopyable)>);
static_assert(has_and_then<const std::expected<void, int>&, decltype(return_int)>);
static_assert(!has_and_then<const std::expected<void, NonCopyable>&, decltype(return_noncopyable)>);
static_assert(has_and_then<std::expected<void, int>&&, decltype(return_int)>);
static_assert(!has_and_then<std::expected<void, NonMovable>&&, decltype(return_nonmovable)>);
static_assert(has_and_then<const std::expected<void, int>&&, decltype(return_int)>);
static_assert(!has_and_then<const std::expected<void, NonMovable>&&, decltype(return_nonmovable)>);
// [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()>);
constexpr void test_val_types() {
// Test & overload
{
auto l = []() -> std::expected<int, int> { return 2; };
std::expected<void, int> v;
std::same_as<std::expected<int, int>> decltype(auto) val = v.and_then(l);
assert(val == 2);
}
// Test const& overload
{
auto l = []() -> std::expected<int, int> { return 2; };
const std::expected<void, int> v;
assert(v.and_then(l).value() == 2);
static_assert(std::is_same_v< decltype(v.and_then(l)), std::expected<int, int>>);
}
// Test && overload
{
auto l = []() -> std::expected<int, int> { return 2; };
std::expected<void, int> v;
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).and_then(l);
assert(val == 2);
}
// Test const&& overload
{
auto l = []() -> std::expected<int, int> { return 2; };
const std::expected<void, int> v;
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).and_then(l);
assert(val == 2);
}
}
constexpr void test_fail() {
// Test & overload
{
auto f = []() -> std::expected<int, int> {
assert(false);
return 0;
};
std::expected<void, int> v(std::unexpected<int>(2));
std::same_as<std::expected<int, int>> decltype(auto) val = v.and_then(f);
assert(val.error() == 2);
}
// Test const& overload
{
auto f = []() -> std::expected<int, int> {
assert(false);
return 0;
};
const std::expected<void, int> v(std::unexpected<int>(2));
std::same_as<std::expected<int, int>> decltype(auto) val = v.and_then(f);
assert(val.error() == 2);
}
// Test && overload
{
auto f = []() -> std::expected<int, int> {
assert(false);
return 0;
};
std::expected<void, int> v(std::unexpected<int>(2));
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).and_then(f);
assert(val.error() == 2);
}
// Test const&& overload
{
auto f = []() -> std::expected<int, int> {
assert(false);
return 0;
};
const std::expected<void, int> v(std::unexpected<int>(2));
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).and_then(f);
assert(val.error() == 2);
}
}
constexpr bool test() {
test_fail();
test_val_types();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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