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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_error(F&& f) &;
// template<class F> constexpr auto transform_error(F&& f) const &;
// template<class F> constexpr auto transform_error(F&& f) &&;
// template<class F> constexpr auto transform_error(F&& f) const &&;
#include <expected>
#include <concepts>
#include <cassert>
#include <memory>
#include <type_traits>
#include <utility>
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_error =
requires(E&& e, F&& f) {
{ std::forward<E>(e).transform_error(std::forward<F>(f)) };
};
// [LWG 3877] https://cplusplus.github.io/LWG/issue3877, check constraint failing but not compile error inside the function body.
static_assert(!has_transform_error<const std::expected<std::unique_ptr<int>, int>&, int()>);
static_assert(!has_transform_error<const std::expected<std::unique_ptr<int>, int>&&, int()>);
// clang-format off
constexpr void test_val_types() {
// Test & overload
{
// Without & qualifier on F's operator()
{
std::expected<int, int> e(std::unexpected<int>(0));
std::same_as<std::expected<int, int>> decltype(auto) val = e.transform_error(LVal{});
assert(val.error() == 1);
}
// With & qualifier on F's operator()
{
std::expected<int, int> e(std::unexpected<int>(0));
RefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = e.transform_error(l);
assert(val.error() == 1);
}
}
// Test const& overload
{
// Without const& qualifier on F's operator()
{
const std::expected<int, int> e(std::unexpected<int>(0));
std::same_as<std::expected<int, int>> decltype(auto) val = e.transform_error(CLVal{});
assert(val.error() == 1);
}
// With const& qualifier on F's operator()
{
const std::expected<int, int> e(std::unexpected<int>(0));
const CRefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = e.transform_error(l);
assert(val.error() == 1);
}
}
// Test && overload
{
// Without && qualifier on F's operator()
{
std::expected<int, int> e(std::unexpected<int>(0));
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).transform_error(RVal{});
assert(val.error() == 1);
}
// With && qualifier on F's operator()
{
std::expected<int, int> e(std::unexpected<int>(0));
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).transform_error(RVRefQual{});
assert(val.error() == 1);
}
}
// Test const&& overload
{
// Without const&& qualifier on F's operator()
{
const std::expected<int, int> e(std::unexpected<int>(0));
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).transform_error(CRVal{});
assert(val.error() == 1);
}
// With const&& qualifier on F's operator()
{
const std::expected<int, int> e(std::unexpected<int>(0));
const RVCRefQual l{};
std::same_as<std::expected<int, int>> decltype(auto) val = std::move(e).transform_error(std::move(l));
assert(val.error() == 1);
}
}
}
// clang-format on
// check unex member is direct-non-list-initialized with invoke(std::forward<F>(f), error())
constexpr void test_direct_non_list_init() {
auto xform = [](int i) { return NonCopy(i); };
std::expected<int, int> e(std::unexpected<int>(2));
std::expected<int, NonCopy> n = e.transform_error(xform);
assert(n.error().value == 2);
}
// check that the lambda body is not instantiated during overload resolution
constexpr void test_sfinae() {
std::expected<int, NonConst> e(2);
auto l = [](auto&& x) { return x.non_const(); };
e.transform_error(l);
std::move(e).transform_error(l);
std::expected<int, int> e1;
const auto& ce1 = e1;
const auto never_called = [](int) {
assert(false);
return 0;
};
e1.transform_error(never_called);
std::move(e1).transform_error(never_called);
ce1.transform_error(never_called);
std::move(ce1).transform_error(never_called);
}
constexpr bool test() {
test_sfinae();
test_val_types();
test_direct_non_list_init();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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