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<functional>: Fixes around not_fn #4057

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Oct 4, 2023
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<functional>: Fixes around not_fn #4057

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624b8f5
Fixes around `not_fn`
frederick-vs-ja Sep 28, 2023
1f7241f
Fix typos.
StephanTLavavej Oct 3, 2023
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105 changes: 101 additions & 4 deletions stl/inc/functional
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Original file line number Diff line number Diff line change
Expand Up @@ -585,6 +585,23 @@ _NODISCARD _CONSTEXPR20 _Mem_fn<_Rx _Ty::*> mem_fn(_Rx _Ty::*_Pm) noexcept {
}

#if _HAS_CXX17
#if _HAS_CXX20
#ifdef __cpp_lib_concepts // TRANSITION, GH-395
template <class _Callable, class... _Types>
concept _Can_invoke_then_negate = requires(
_Callable&& _Fx, _Types&&... _Args) { !_STD invoke(_STD forward<_Callable>(_Fx), _STD forward<_Types>(_Args)...); };
#else // ^^^ defined(__cpp_lib_concepts) / !defined(__cpp_lib_concepts) vvv
template <class _Void, class _Callable, class... _Types>
inline constexpr bool _Can_invoke_then_negate_impl = false;
template <class _Callable, class... _Types>
inline constexpr bool _Can_invoke_then_negate_impl<
void_t<decltype(!_STD invoke(_STD declval<_Callable>(), _STD declval<_Types>()...))>, _Callable, _Types...> = true;

template <class _Callable, class... _Types>
inline constexpr bool _Can_invoke_then_negate = _Can_invoke_then_negate_impl<void, _Callable, _Types...>;
#endif // ^^^ !defined(__cpp_lib_concepts) ^^^
#endif // _HAS_CXX20

struct _Not_fn_tag {
explicit _Not_fn_tag() = default;
};
Expand All @@ -603,39 +620,119 @@ public:
constexpr _Not_fn(const _Not_fn&) = default;
constexpr _Not_fn(_Not_fn&&) = default;

#if _HAS_CXX20 && defined(__cpp_lib_concepts) // TRANSITION, GH-395
template <class... _Types>
requires _Can_invoke_then_negate<_Decayed&, _Types...>
constexpr decltype(auto) operator()(_Types&&... _Args) & noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
requires _Can_invoke_then_negate<const _Decayed&, _Types...>
constexpr decltype(auto) operator()(_Types&&... _Args) const& noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
requires _Can_invoke_then_negate<_Decayed, _Types...>
constexpr decltype(auto) operator()(_Types&&... _Args) && noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
requires _Can_invoke_then_negate<const _Decayed, _Types...>
constexpr decltype(auto) operator()(_Types&&... _Args) const&& noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
void operator()(_Types&&...) & = delete;

template <class... _Types>
void operator()(_Types&&...) const& = delete;

template <class... _Types>
void operator()(_Types&&...) && = delete;

template <class... _Types>
void operator()(_Types&&...) const&& = delete;
#elif _HAS_CXX20 // ^^^ _HAS_CXX20 && defined(__cpp_lib_concepts) / _HAS_CXX20 && !defined(__cpp_lib_concepts) vvv
template <class... _Types, enable_if_t<_Can_invoke_then_negate<_Decayed&, _Types...>, int> = 0>
constexpr decltype(auto) operator()(_Types&&... _Args) & noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types, enable_if_t<_Can_invoke_then_negate<const _Decayed&, _Types...>, int> = 0>
constexpr decltype(auto) operator()(_Types&&... _Args) const& noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types, enable_if_t<_Can_invoke_then_negate<_Decayed, _Types...>, int> = 0>
constexpr decltype(auto) operator()(_Types&&... _Args) && noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}

template <class... _Types, enable_if_t<_Can_invoke_then_negate<const _Decayed, _Types...>, int> = 0>
constexpr decltype(auto) operator()(_Types&&... _Args) const&& noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...))) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}

template <class... _Types, enable_if_t<!_Can_invoke_then_negate<_Decayed&, _Types...>, int> = 0>
void operator()(_Types&&...) & = delete;

template <class... _Types, enable_if_t<!_Can_invoke_then_negate<const _Decayed&, _Types...>, int> = 0>
void operator()(_Types&&...) const& = delete;

template <class... _Types, enable_if_t<!_Can_invoke_then_negate<_Decayed, _Types...>, int> = 0>
void operator()(_Types&&...) && = delete;

template <class... _Types, enable_if_t<!_Can_invoke_then_negate<const _Decayed, _Types...>, int> = 0>
void operator()(_Types&&...) const&& = delete;
#else // ^^^ _HAS_CXX20 && !defined(__cpp_lib_concepts) / !_HAS_CXX20 vvv
template <class... _Types>
_CONSTEXPR20 auto operator()(_Types&&... _Args) & noexcept(
auto operator()(_Types&&... _Args) & noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...)))
-> decltype(!_STD declval<invoke_result_t<_Decayed&, _Types...>>()) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
_CONSTEXPR20 auto operator()(_Types&&... _Args) const& noexcept(
auto operator()(_Types&&... _Args) const& noexcept(
noexcept(!_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...)))
-> decltype(!_STD declval<invoke_result_t<const _Decayed&, _Types...>>()) {
return !_STD invoke(this->_Get_val(), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
_CONSTEXPR20 auto operator()(_Types&&... _Args) && noexcept(
auto operator()(_Types&&... _Args) && noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...)))
-> decltype(!_STD declval<invoke_result_t<_Decayed, _Types...>>()) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}

template <class... _Types>
_CONSTEXPR20 auto operator()(_Types&&... _Args) const&& noexcept(
auto operator()(_Types&&... _Args) const&& noexcept(
noexcept(!_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...)))
-> decltype(!_STD declval<invoke_result_t<const _Decayed, _Types...>>()) {
return !_STD invoke(_STD move(this->_Get_val()), _STD forward<_Types>(_Args)...);
}
#endif // ^^^ !_HAS_CXX20 ^^^
};

_EXPORT_STD template <class _Callable>
_NODISCARD _CONSTEXPR20 _Not_fn<decay_t<_Callable>> not_fn(_Callable&& _Obj) noexcept(
is_nothrow_constructible_v<decay_t<_Callable>, _Callable>) /* strengthened */ {
// wrap a callable object to be negated
static_assert(is_move_constructible_v<decay_t<_Callable>>,
"the callable type used with std::not_fn should be move constructible.");
return _Not_fn<decay_t<_Callable>>(_STD forward<_Callable>(_Obj), _Not_fn_tag{});
}
#endif // _HAS_CXX17
Expand Down
56 changes: 56 additions & 0 deletions tests/std/tests/Dev11_0535636_functional_overhaul/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2356,6 +2356,62 @@ _CONSTEXPR20 bool test_not_fn() {
return true;
}

// Also test the invocability of the return type of std::not_fn before and after the changes in P0356R5.
#if _HAS_CXX17
struct ConstOnlyFunctor {
bool operator()() = delete;
bool operator()() const {
return true;
}
};

struct ConstOnlyBooleanTester {
void operator()() {}
bool operator()() const {
return true;
}
};

struct GetPinnedNegatable {
struct PinnedNegatable {
PinnedNegatable() = default;

PinnedNegatable(const PinnedNegatable&) = delete;
PinnedNegatable& operator=(const PinnedNegatable&) = delete;

friend bool operator!(PinnedNegatable) {
return false;
}
};

PinnedNegatable operator()() const {
return {};
}
};

using NegatedConstOnlyFunctor = decltype(not_fn(ConstOnlyFunctor{}));
using NegatedConstOnlyBooleanTester = decltype(not_fn(ConstOnlyBooleanTester{}));
using NegatedGetPinnedNegatable = decltype(not_fn(GetPinnedNegatable{}));

#if _HAS_CXX20
constexpr bool not_fn_is_perfect_forwarding = true;
#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
constexpr bool not_fn_is_perfect_forwarding = false;
#endif // ^^^ !_HAS_CXX20 ^^^

static_assert(is_invocable_v<const NegatedConstOnlyFunctor>);
static_assert(is_invocable_v<const NegatedConstOnlyFunctor&>);
static_assert(is_invocable_v<const NegatedConstOnlyBooleanTester>);
static_assert(is_invocable_v<const NegatedConstOnlyBooleanTester&>);

static_assert(is_invocable_v<NegatedConstOnlyFunctor> == !not_fn_is_perfect_forwarding);
static_assert(is_invocable_v<NegatedConstOnlyFunctor&> == !not_fn_is_perfect_forwarding);
static_assert(is_invocable_v<NegatedConstOnlyBooleanTester> == !not_fn_is_perfect_forwarding);
static_assert(is_invocable_v<NegatedConstOnlyBooleanTester&> == !not_fn_is_perfect_forwarding);

static_assert(is_invocable_v<NegatedGetPinnedNegatable> == not_fn_is_perfect_forwarding);
#endif // _HAS_CXX17

int main() {
// Test addressof() with functions.
assert(addressof(triple) == &triple);
Expand Down