зеркало из https://github.com/microsoft/STL.git
Implement LWG-3877 Incorrect constraints on `const`-qualified monadic overloads for `std::expected` (#3504)
Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
This commit is contained in:
A. Jiang
GitHub
Родитель
7155ea6f88
Коммит
882d92ec47
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@ -732,7 +732,7 @@ public:
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// [expected.object.monadic]
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template <class _Fn>
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requires is_copy_constructible_v<_Err>
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requires is_constructible_v<_Err, _Err&>
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constexpr auto and_then(_Fn&& _Func) & {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn, _Ty&>>;
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@ -789,7 +789,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Err>
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requires is_constructible_v<_Err, const _Err>
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constexpr auto and_then(_Fn&& _Func) const&& {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn, const _Ty>>;
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@ -808,7 +808,7 @@ public:
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}
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template <class _Fn>
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requires is_copy_constructible_v<_Ty>
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requires is_constructible_v<_Ty, _Ty&>
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constexpr auto or_else(_Fn&& _Func) & {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn, _Err&>>;
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@ -865,7 +865,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Ty>
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requires is_constructible_v<_Ty, const _Ty>
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constexpr auto or_else(_Fn&& _Func) const&& {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn, const _Err>>;
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@ -884,7 +884,7 @@ public:
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}
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template <class _Fn>
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requires is_copy_constructible_v<_Err>
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requires is_constructible_v<_Err, _Err&>
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constexpr auto transform(_Fn&& _Func) & {
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static_assert(invocable<_Fn, _Ty&>, "expected<T, E>::transform(F) requires that F is invocable with T. "
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"(N4928 [expected.object.monadic]/19)");
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@ -965,7 +965,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Err>
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requires is_constructible_v<_Err, const _Err>
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constexpr auto transform(_Fn&& _Func) const&& {
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static_assert(invocable<_Fn, const _Ty>, "expected<T, E>::transform(F) requires that F is invocable with T. "
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"(N4928 [expected.object.monadic]/23)");
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@ -992,7 +992,7 @@ public:
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}
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template <class _Fn>
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requires is_copy_constructible_v<_Ty>
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requires is_constructible_v<_Ty, _Ty&>
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constexpr auto transform_error(_Fn&& _Func) & {
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static_assert(invocable<_Fn, _Err&>, "expected<T, E>::transform_error(F) requires that F is invocable with E. "
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"(N4928 [expected.object.monadic]/27)");
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@ -1053,7 +1053,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Ty>
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requires is_constructible_v<_Ty, const _Ty>
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constexpr auto transform_error(_Fn&& _Func) const&& {
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static_assert(invocable<_Fn, const _Err>,
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"expected<T, E>::transform_error(F) requires that F is invocable with E. "
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@ -1470,7 +1470,7 @@ public:
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// [expected.void.monadic]
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template <class _Fn>
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requires is_copy_constructible_v<_Err>
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requires is_constructible_v<_Err, _Err&>
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constexpr auto and_then(_Fn&& _Func) & {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn>>;
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@ -1527,7 +1527,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Err>
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requires is_constructible_v<_Err, const _Err>
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constexpr auto and_then(_Fn&& _Func) const&& {
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using _Uty = remove_cvref_t<invoke_result_t<_Fn>>;
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@ -1618,7 +1618,7 @@ public:
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}
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template <class _Fn>
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requires is_copy_constructible_v<_Err>
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requires is_constructible_v<_Err, _Err&>
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constexpr auto transform(_Fn&& _Func) & {
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static_assert(invocable<_Fn>, "expected<void, E>::transform(F) requires that F is invocable with no arguments. "
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"(N4928 [expected.void.monadic]/17)");
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@ -1696,7 +1696,7 @@ public:
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}
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template <class _Fn>
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requires is_move_constructible_v<_Err>
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requires is_constructible_v<_Err, const _Err>
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constexpr auto transform(_Fn&& _Func) const&& {
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static_assert(invocable<_Fn>, "expected<void, E>::transform(F) requires that F is invocable with no arguments. "
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"(N4928 [expected.void.monadic]/21)");
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@ -375,7 +375,153 @@ constexpr bool test() {
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return true;
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}
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template <class T, template <class...> class Tmpl>
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constexpr bool is_specialization_of = false;
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template <template <class...> class Tmpl, class... Args>
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constexpr bool is_specialization_of<Tmpl<Args...>, Tmpl> = true;
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template <class T>
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requires is_specialization_of<remove_cvref_t<T>, expected>
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using expected_value_t = typename remove_cvref_t<T>::value_type;
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template <class T>
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requires is_specialization_of<remove_cvref_t<T>, expected>
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using expected_error_t = typename remove_cvref_t<T>::error_type;
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template <class R>
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struct DefaultTransformer {
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constexpr R operator()() const {
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return R();
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}
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constexpr R operator()(auto&&) const {
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return R();
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}
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};
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template <class T>
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concept CanAndThen =
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is_specialization_of<remove_cvref_t<T>, expected>
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&& requires(T&& t) { forward<T>(t).and_then(DefaultTransformer<expected<void, expected_error_t<T>>>{}); };
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template <class T>
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concept CanOrElse =
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is_specialization_of<remove_cvref_t<T>, expected>
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&& requires(T&& t) { forward<T>(t).or_else(DefaultTransformer<expected<expected_value_t<T>, char>>{}); };
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template <class T>
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concept CanTransform = is_specialization_of<remove_cvref_t<T>, expected>
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&& requires(T&& t) { forward<T>(t).transform(DefaultTransformer<expected_value_t<T>>{}); };
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template <class T>
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concept CanTransformError =
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is_specialization_of<remove_cvref_t<T>, expected>
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&& requires(T&& t) { forward<T>(t).transform_error(DefaultTransformer<expected_error_t<T>>{}); };
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enum class HasMutCopy : bool { No, Yes };
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enum class HasConstCopy : bool { No, Yes };
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enum class HasMutMove : bool { No, Yes };
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enum class HasConstMove : bool { No, Yes };
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template <HasMutCopy MutCopyStatus, HasConstCopy ConstCopyStatus, HasMutMove MutMoveStatus,
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HasConstMove ConstMoveStatus>
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struct State {
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State() = default;
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// clang-format off
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State(State&) requires (static_cast<bool>(MutCopyStatus)) = default;
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State(State&) requires (!static_cast<bool>(MutCopyStatus)) = delete;
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State(const State&) requires (static_cast<bool>(ConstCopyStatus)) = default;
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State(const State&) requires (!static_cast<bool>(ConstCopyStatus)) = delete;
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State(State&&) requires (static_cast<bool>(MutMoveStatus)) = default;
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State(State&&) requires (!static_cast<bool>(MutMoveStatus)) = delete;
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State(const State&&) requires (!static_cast<bool>(ConstMoveStatus)) = delete;
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// clang-format on
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template <class U = State>
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requires (!static_cast<bool>(ConstCopyStatus) && static_cast<bool>(ConstMoveStatus))
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constexpr State(const type_identity_t<U>&&) noexcept {}
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State& operator=(const State&) = default;
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State& operator=(State&&) = default;
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};
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template <int N>
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constexpr bool test_monadic_constraints_impl() {
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constexpr bool MutCopyStatus = static_cast<bool>(N & 0b0001);
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constexpr bool ConstCopyStatus = static_cast<bool>(N & 0b0010);
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constexpr bool MutMoveStatus = static_cast<bool>(N & 0b0100);
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constexpr bool ConstMoveStatus = static_cast<bool>(N & 0b1000);
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using T = State<static_cast<HasMutCopy>(MutCopyStatus), static_cast<HasConstCopy>(ConstCopyStatus),
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static_cast<HasMutMove>(MutMoveStatus), static_cast<HasConstMove>(ConstMoveStatus)>;
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static_assert(is_constructible_v<T, T&> == MutCopyStatus);
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static_assert(is_constructible_v<T, const T&> == ConstCopyStatus);
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static_assert(is_constructible_v<T, T> == MutMoveStatus);
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static_assert(is_constructible_v<T, const T> == ConstMoveStatus);
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static_assert(CanAndThen<expected<int, T>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanAndThen<const expected<int, T>&> == ConstCopyStatus);
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static_assert(CanAndThen<expected<int, T>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanAndThen<const expected<int, T>> == ConstMoveStatus || ConstCopyStatus);
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static_assert(CanAndThen<expected<void, T>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanAndThen<const expected<void, T>&> == ConstCopyStatus);
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static_assert(CanAndThen<expected<void, T>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanAndThen<const expected<void, T>> == ConstMoveStatus || ConstCopyStatus);
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static_assert(CanOrElse<expected<T, char>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanOrElse<const expected<T, char>&> == ConstCopyStatus);
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static_assert(CanOrElse<expected<T, char>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanOrElse<const expected<T, char>> == ConstMoveStatus || ConstCopyStatus);
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static_assert(CanTransform<expected<int, T>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanTransform<const expected<int, T>&> == ConstCopyStatus);
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static_assert(CanTransform<expected<int, T>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanTransform<const expected<int, T>> == ConstMoveStatus || ConstCopyStatus);
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static_assert(CanTransform<expected<void, T>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanTransform<const expected<void, T>&> == ConstCopyStatus);
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static_assert(CanTransform<expected<void, T>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanTransform<const expected<void, T>> == ConstMoveStatus || ConstCopyStatus);
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static_assert(CanTransformError<expected<T, char>&> == MutCopyStatus || ConstCopyStatus);
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static_assert(CanTransformError<const expected<T, char>&> == ConstCopyStatus);
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static_assert(CanTransformError<expected<T, char>> == MutMoveStatus || ConstCopyStatus || ConstMoveStatus);
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static_assert(CanTransformError<const expected<T, char>> == ConstMoveStatus || ConstCopyStatus);
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return true;
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}
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constexpr bool test_monadic_constraints() {
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static_assert(test_monadic_constraints_impl<0b0000>());
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static_assert(test_monadic_constraints_impl<0b0001>());
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static_assert(test_monadic_constraints_impl<0b0010>());
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static_assert(test_monadic_constraints_impl<0b0011>());
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static_assert(test_monadic_constraints_impl<0b0100>());
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static_assert(test_monadic_constraints_impl<0b0101>());
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static_assert(test_monadic_constraints_impl<0b0110>());
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static_assert(test_monadic_constraints_impl<0b0111>());
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static_assert(test_monadic_constraints_impl<0b1000>());
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static_assert(test_monadic_constraints_impl<0b1001>());
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static_assert(test_monadic_constraints_impl<0b1010>());
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static_assert(test_monadic_constraints_impl<0b1011>());
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static_assert(test_monadic_constraints_impl<0b1100>());
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static_assert(test_monadic_constraints_impl<0b1101>());
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static_assert(test_monadic_constraints_impl<0b1110>());
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static_assert(test_monadic_constraints_impl<0b1111>());
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return true;
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}
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int main() {
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test();
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static_assert(test());
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assert(test_monadic_constraints());
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static_assert(test_monadic_constraints());
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}
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