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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
// GCC has a issue for `Guaranteed copy elision for potentially-overlapping non-static data members`,
// please refer to: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108333, but we have a workaround to
// avoid this issue.
// <expected>
// template<class F> constexpr auto transform(F&& f) &;
// template<class F> constexpr auto transform(F&& f) const &;
// template<class F> constexpr auto transform(F&& f) &&;
// template<class F> constexpr auto transform(F&& f) const &&;
#include <expected>
#include <concepts>
#include <cassert>
#include <memory>
#include <type_traits>
#include <utility>
#include "../../types.h"
struct LVal {
constexpr int operator()(int&) { return 1; }
int operator()(const int&) = delete;
int operator()(int&&) = delete;
int operator()(const int&&) = delete;
};
struct CLVal {
int operator()(int&) = delete;
constexpr int operator()(const int&) { return 1; }
int operator()(int&&) = delete;
int operator()(const int&&) = delete;
};
struct RVal {
int operator()(int&) = delete;
int operator()(const int&) = delete;
constexpr int operator()(int&&) { return 1; }
int operator()(const int&&) = delete;
};
struct CRVal {
int operator()(int&) = delete;
int operator()(const int&) = delete;
int operator()(int&&) = delete;
constexpr int operator()(const int&&) { return 1; }
};
struct RefQual {
constexpr int operator()(int) & { return 1; }
int operator()(int) const& = delete;
int operator()(int) && = delete;
int operator()(int) const&& = delete;
};
struct CRefQual {
int operator()(int) & = delete;
constexpr int operator()(int) const& { return 1; }
int operator()(int) && = delete;
int operator()(int) const&& = delete;
};
struct RVRefQual {
int operator()(int) & = delete;
int operator()(int) const& = delete;
constexpr int operator()(int) && { return 1; }
int operator()(int) const&& = delete;
};
struct RVCRefQual {
int operator()(int) & = delete;
int operator()(int) const& = delete;
int operator()(int) && = delete;
constexpr int operator()(int) const&& { return 1; }
};
struct NonCopy {
int value;
constexpr explicit NonCopy(int val) : value(val) {}
NonCopy(const NonCopy&) = delete;
};
struct NonConst {
int non_const() { return 1; }
};
template <class E, class F>
concept has_transform =
requires(E&& e, F&& f) {
{ std::forward<E>(e).transform(std::forward<F>(f)) };
};
// clang-format off
// [LWG 3877] https://cplusplus.github.io/LWG/issue3877, check constraint failing but not compile error inside the function body.
static_assert(!has_transform<const std::expected<int, std::unique_ptr<int>>&, int()>);
static_assert(!has_transform<const std::expected<int, std::unique_ptr<int>>&&, int()>);
// [LWG 3983] https://cplusplus.github.io/LWG/issue3938, check std::expected monadic ops well-formed with move-only error_type.
// There are no effects for `&` and `const &` overload, because the constraints requires is_constructible_v<E, decltype(error())> is true.
static_assert(has_transform<std::expected<int, MoveOnlyErrorType>&&, int(int)>);
static_assert(has_transform<const std::expected<int, MoveOnlyErrorType>&&, int(const int)>);
constexpr void test_val_types() {
// Test & overload
{
// Without & qualifier on F's operator()
{
std::expected<int, int> e(0);
std::same_as<std::expected<int, int>> decltype(auto) val = e.transform(LVal{});
assert(val == 1);
}
// 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.transform(l);
assert(val == 1);
}
}
// 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.transform(CLVal{});
assert(val == 1);
}
// 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.transform(l);
assert(val == 1);
}
}
// 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).transform(RVal{});
assert(val == 1);
}
// 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).transform(RVRefQual{});
assert(val == 1);
}
}
// 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).transform(CRVal{});
assert(val == 1);
}
// 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 = e.transform(std::move(l));
assert(val == 1);
}
}
}
// clang-format on
constexpr void test_take_val_return_void() {
std::expected<int, int> e(1);
int val = 0;
e.transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, int&>);
assert(val == 0);
val = 1;
});
assert(val == 1);
std::move(e).transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, int>);
assert(val == 1);
val = 2;
});
const auto& ce = e;
assert(val == 2);
ce.transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, const int&>);
assert(val == 2);
val = 3;
});
assert(val == 3);
std::move(ce).transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, const int>);
assert(val == 3);
val = 4;
});
assert(val == 4);
}
// check val member is direct-non-list-initialized with invoke(std::forward<F>(f), value())
constexpr void test_direct_non_list_init() {
auto xform = [](int i) { return NonCopy(i); };
std::expected<int, int> e(2);
std::expected<NonCopy, int> n = e.transform(xform);
assert(n.value().value == 2);
}
// 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.transform(l);
std::move(e).transform(l);
std::expected<int, int> e1(std::unexpected<int>(1));
const auto& ce1 = e1;
const auto never_called = [](int) {
assert(false);
return std::expected<int, int>();
};
e1.transform(never_called);
std::move(e1).transform(never_called);
ce1.and_then(never_called);
std::move(ce1).transform(never_called);
}
constexpr void test_move_only_error_type() {
// Test &&
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](int) { return 0; };
std::move(e).transform(l);
}
// Test const&&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const int) { return 0; };
std::move(e).transform(l);
}
}
constexpr bool test() {
test_sfinae();
test_val_types();
test_direct_non_list_init();
test_move_only_error_type();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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