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[libc++] Unify __can_reference and __is_referenceable_v #133278

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Mar 29, 2025
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[libc++] Unify __can_reference and __is_referenceable_v #133278

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3 changes: 2 additions & 1 deletion libcxx/include/__iterator/common_iterator.h
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Expand Up @@ -28,6 +28,7 @@
#include <__memory/addressof.h>
#include <__type_traits/conditional.h>
#include <__type_traits/is_pointer.h>
#include <__type_traits/is_referenceable.h>
#include <__utility/declval.h>
#include <variant>

Expand Down Expand Up @@ -157,7 +158,7 @@ class common_iterator {
++*this;
return __tmp;
} else if constexpr (requires(_Iter& __i) {
{ *__i++ } -> __can_reference;
{ *__i++ } -> __referenceable;
} || !__can_use_postfix_proxy<_Iter>) {
return std::__unchecked_get<_Iter>(__hold_)++;
} else {
Expand Down
3 changes: 2 additions & 1 deletion libcxx/include/__iterator/concepts.h
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Expand Up @@ -38,6 +38,7 @@
#include <__type_traits/is_pointer.h>
#include <__type_traits/is_primary_template.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_referenceable.h>
#include <__type_traits/remove_cv.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/forward.h>
Expand Down Expand Up @@ -132,7 +133,7 @@ concept incrementable = regular<_Ip> && weakly_incrementable<_Ip> && requires(_I
// [iterator.concept.iterator]
template <class _Ip>
concept input_or_output_iterator = requires(_Ip __i) {
{ *__i } -> __can_reference;
{ *__i } -> __referenceable;
} && weakly_incrementable<_Ip>;

// [iterator.concept.sentinel]
Expand Down
3 changes: 2 additions & 1 deletion libcxx/include/__iterator/iter_move.h
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Expand Up @@ -14,6 +14,7 @@
#include <__config>
#include <__iterator/iterator_traits.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_referenceable.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/declval.h>
#include <__utility/forward.h>
Expand Down Expand Up @@ -90,7 +91,7 @@ inline constexpr auto iter_move = __iter_move::__fn{};

template <__dereferenceable _Tp>
requires requires(_Tp& __t) {
{ ranges::iter_move(__t) } -> __can_reference;
{ ranges::iter_move(__t) } -> __referenceable;
}
using iter_rvalue_reference_t = decltype(ranges::iter_move(std::declval<_Tp&>()));

Expand Down
13 changes: 4 additions & 9 deletions libcxx/include/__iterator/iterator_traits.h
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Expand Up @@ -32,6 +32,7 @@
#include <__type_traits/is_object.h>
#include <__type_traits/is_primary_template.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_referenceable.h>
#include <__type_traits/is_valid_expansion.h>
#include <__type_traits/nat.h>
#include <__type_traits/remove_const.h>
Expand All @@ -48,15 +49,9 @@ _LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER >= 20

template <class _Tp>
using __with_reference _LIBCPP_NODEBUG = _Tp&;

template <class _Tp>
concept __can_reference = requires { typename __with_reference<_Tp>; };

template <class _Tp>
concept __dereferenceable = requires(_Tp& __t) {
{ *__t } -> __can_reference; // not required to be equality-preserving
{ *__t } -> __referenceable; // not required to be equality-preserving
};

// [iterator.traits]
Expand Down Expand Up @@ -138,9 +133,9 @@ struct __has_iterator_typedefs {
namespace __iterator_traits_detail {
template <class _Ip>
concept __cpp17_iterator = requires(_Ip __i) {
{ *__i } -> __can_reference;
{ *__i } -> __referenceable;
{ ++__i } -> same_as<_Ip&>;
{ *__i++ } -> __can_reference;
{ *__i++ } -> __referenceable;
} && copyable<_Ip>;

template <class _Ip>
Expand Down
3 changes: 2 additions & 1 deletion libcxx/include/__ranges/transform_view.h
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Expand Up @@ -38,6 +38,7 @@
#include <__type_traits/is_nothrow_constructible.h>
#include <__type_traits/is_object.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_referenceable.h>
#include <__type_traits/maybe_const.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/forward.h>
Expand All @@ -63,7 +64,7 @@ concept __regular_invocable_with_range_ref = regular_invocable<_Fn, range_refere
template <class _View, class _Fn>
concept __transform_view_constraints =
view<_View> && is_object_v<_Fn> && regular_invocable<_Fn&, range_reference_t<_View>> &&
__can_reference<invoke_result_t<_Fn&, range_reference_t<_View>>>;
__is_referenceable_v<invoke_result_t<_Fn&, range_reference_t<_View>>>;

# if _LIBCPP_STD_VER >= 23
template <input_range _View, move_constructible _Fn>
Expand Down
5 changes: 5 additions & 0 deletions libcxx/include/__type_traits/is_referenceable.h
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Expand Up @@ -24,6 +24,11 @@ inline const bool __is_referenceable_v = false;
template <class _Tp>
inline const bool __is_referenceable_v<_Tp, __void_t<_Tp&> > = true;

#if _LIBCPP_STD_VER >= 20
template <class _Tp>
concept __referenceable = __is_referenceable_v<_Tp>;
#endif

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___TYPE_TRAITS_IS_REFERENCEABLE_H