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Differential D113408 Diff 394654 libcxx/test/std/utilities/optional/optional.monadic/or_else.pass.cpp

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libcxx/test/std/utilities/optional/optional.monadic/or_else.pass.cpp

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//===----------------------------------------------------------------------===//
//
ldionneUnsubmitted
Done
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Please add tests for SFINAE friendliness when the Constraints: are not met.

ldionne: Please add tests for SFINAE friendliness when the `Constraints:` are not met.
philnikAuthorUnsubmitted
Done
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Could you reference something where that is done? I have no idea what you are asking for.

philnik: Could you reference something where that is done? I have no idea what you are asking for.
QuuxplusoneUnsubmitted
Done
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Something like libcxx/test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_size_value_sfinae.pass.cpp. Basically:

#include "MoveOnly.h"

struct NonMovable {
    NonMovable() = default;
    NonMovable(NonMovable&&) = delete;
};

// TODO: rewrite to use 'requires' when _LIBCPP_HAS_NO_CONCEPTS goes away
template<class O, class F>
auto has_or_else(int, O&& o, F&& f)
    -> decltype(static_cast<O&&>(o).or_else(static_cast<F&&>(f)), true)
    { return true; }

template<class O, class F>
bool has_or_else(long, O&& o, F&& f)
    { return false; }

void test_sfinae() {
    std::optional<int> o1;
    std::optional<MoveOnly> o2;
    std::optional<NonMovable> o3;
    assert( has_or_else(0, o1, [&](){ return std::optional<int>(); }));
    assert( has_or_else(0, std::move(o1), [&](){ return std::optional<int>(); }));
    assert(!has_or_else(0, o2, [&](){ return std::optional<MoveOnly>(); }));
    assert( has_or_else(0, std::move(o2), [&](){ return std::optional<MoveOnly>(); }));
    assert(!has_or_else(0, o3, [&](){ return std::optional<NonMovable>(); }));
    assert(!has_or_else(0, std::move(o3), [&](){ return std::optional<NonMovable>(); }));

    assert(!has_or_else(0, o1, [&](int){ return std::optional<int>(); }));
    assert(!has_or_else(0, o1, [&](int){}));
    assert(!has_or_else(0, o1, 42));
}
Quuxplusone: Something like `libcxx/test/std/utilities/tuple/tuple.tuple/tuple.
// 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
// <optional>
// template<class F> constexpr optional or_else(F&&) &&;
// template<class F> constexpr optional or_else(F&&) const&;
#include "MoveOnly.h"
#include <cassert>
#include <optional>
struct NonMovable {
NonMovable() = default;
NonMovable(NonMovable&&) = delete;
};
template <class Opt, class F>
concept has_or_else = requires(Opt&& opt, F&& f) {
{std::forward<Opt>(opt).or_else(std::forward<F>(f))};
};
template <class T>
std::optional<T> return_optional() {}
static_assert(has_or_else<std::optional<int>&, decltype(return_optional<int>)>);
ldionneUnsubmitted
Done
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I believe this would work and be equivalent:

template <class Opt, class F>
concept has_or_else = requires(Opt&& opt, F&& f) {
  { std::forward<Opt>(opt).or_else(std::forward<F>(f)) };
};
ldionne: I believe this would work and be equivalent: ``` template <class Opt, class F> concept…
static_assert(has_or_else<std::optional<int>&&, decltype(return_optional<int>)>);
static_assert(!has_or_else<std::optional<MoveOnly>&, decltype(return_optional<MoveOnly>)>);
static_assert(has_or_else<std::optional<MoveOnly>&&, decltype(return_optional<MoveOnly>)>);
static_assert(!has_or_else<std::optional<NonMovable>&, decltype(return_optional<NonMovable>)>);
static_assert(!has_or_else<std::optional<NonMovable>&&, decltype(return_optional<NonMovable>)>);
std::optional<int> take_int(int) { return 0; }
void take_int_return_void(int) {}
static_assert(!has_or_else<std::optional<int>, decltype(take_int)>);
static_assert(!has_or_else<std::optional<int>, decltype(take_int_return_void)>);
static_assert(!has_or_else<std::optional<int>, int>);
constexpr bool test() {
{
std::optional<int> opt;
assert(opt.or_else([] { return std::optional<int>{0}; }) == 0);
opt = 1;
opt.or_else([] {
assert(false);
return std::optional<int>{};
});
}
{
std::optional<MoveOnly> opt;
opt = std::move(opt).or_else([] { return std::optional<MoveOnly>{MoveOnly{}}; });
std::move(opt).or_else([] {
assert(false);
return std::optional<MoveOnly>{};
});
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
}