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[libc++][NFC] Use __copy_cv to implement __apply_cv #86477

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Merged
merged 1 commit into from
Mar 29, 2024
+5 −45
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[libc++][NFC] Use __copy_cv to implement __apply_cv #86477

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50 changes: 5 additions & 45 deletions libcxx/include/__type_traits/apply_cv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,64 +10,24 @@
#define _LIBCPP___TYPE_TRAITS_APPLY_CV_H

#include <__config>
#include <__type_traits/is_const.h>
#include <__type_traits/is_volatile.h>
#include <__type_traits/remove_reference.h>
#include <__type_traits/copy_cv.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Tp,
bool = is_const<__libcpp_remove_reference_t<_Tp> >::value,
bool = is_volatile<__libcpp_remove_reference_t<_Tp> >::value>
struct __apply_cv_impl {
template <class _Up>
using __apply _LIBCPP_NODEBUG = _Up;
};

template <class _Tp>
struct __apply_cv_impl<_Tp, true, false> {
template <class _Up>
using __apply _LIBCPP_NODEBUG = const _Up;
};

template <class _Tp>
struct __apply_cv_impl<_Tp, false, true> {
template <class _Up>
using __apply _LIBCPP_NODEBUG = volatile _Up;
};

template <class _Tp>
struct __apply_cv_impl<_Tp, true, true> {
template <class _Up>
using __apply _LIBCPP_NODEBUG = const volatile _Up;
};

template <class _Tp>
struct __apply_cv_impl<_Tp&, false, false> {
template <class _Up>
using __apply _LIBCPP_NODEBUG = _Up&;
};

template <class _Tp>
struct __apply_cv_impl<_Tp&, true, false> {
template <class _Up>
using __apply _LIBCPP_NODEBUG = const _Up&;
};

template <class _Tp>
struct __apply_cv_impl<_Tp&, false, true> {
struct __apply_cv_impl {
template <class _Up>
using __apply _LIBCPP_NODEBUG = volatile _Up&;
using __apply _LIBCPP_NODEBUG = __copy_cv_t<_Tp, _Up>;
};

template <class _Tp>
struct __apply_cv_impl<_Tp&, true, true> {
struct __apply_cv_impl<_Tp&> {
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An improvement to __copy_cv_ref_t we could maybe do is

template <bool _Ref>
struct __copy_cv_ref_impl;

template <>
struct __copy_cv_ref_impl<true> {
  template <class _Tp>
  using __apply _LIBCPP_NODEBUG = _Tp&;
};

template <>
struct __copy_cv_ref_impl<false> {
  template <class _Tp>
  using __apply _LIBCPP_NODEBUG = _Tp;
};

template <class _Tp>
using __copy_cvref_t = typename __copy_cv_ref_impl<is_lvalue_reference_v<_Tp>>::template __apply<_Tp>;

template <class _Up>
using __apply _LIBCPP_NODEBUG = const volatile _Up&;
using __apply _LIBCPP_NODEBUG = __copy_cv_t<_Tp, _Up>&;
};

template <class _Tp, class _Up>
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