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[libc++] [string_view] Remove operators made redundant by C++20 (#66206)

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Thanks to Giuseppe D'Angelo for pointing this out on the cpplang Slack!

The example implementation in https://eel.is/c++draft/string.view.comparison#example-1
was necessary when it was written, in C++17, but in C++20 we don't need that
complexity anymore, because of the reversed candidates that are
synthesized by the compiler.
This commit is contained in:
Amirreza Ashouri 2023-09-18 18:00:44 +03:30 committed by GitHub
parent a2bb365733
commit aa8601dc6d
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1 changed files with 28 additions and 37 deletions
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65
libcxx/include/string_view
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@ -776,7 +776,35 @@ template <ranges::contiguous_range _Range>
#endif
// [string.view.comparison]
#if _LIBCPP_STD_VER >= 20
template<class _CharT, class _Traits>
_LIBCPP_HIDE_FROM_ABI constexpr
bool operator==(basic_string_view<_CharT, _Traits> __lhs,
type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) noexcept {
if (__lhs.size() != __rhs.size()) return false;
return __lhs.compare(__rhs) == 0;
}
template <class _CharT, class _Traits>
_LIBCPP_HIDE_FROM_ABI constexpr auto operator<=>(
basic_string_view<_CharT, _Traits> __lhs, type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) noexcept {
if constexpr (requires { typename _Traits::comparison_category; }) {
// [string.view]/4
static_assert(
__comparison_category<typename _Traits::comparison_category>,
"return type is not a comparison category type");
return static_cast<typename _Traits::comparison_category>(__lhs.compare(__rhs) <=> 0);
} else {
return static_cast<weak_ordering>(__lhs.compare(__rhs) <=> 0);
}
}
#else
// operator ==
template<class _CharT, class _Traits>
_LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
bool operator==(basic_string_view<_CharT, _Traits> __lhs,
@ -797,8 +825,6 @@ bool operator==(basic_string_view<_CharT, _Traits> __lhs,
return __lhs.compare(__rhs) == 0;
}
#if _LIBCPP_STD_VER < 20
// This overload is automatically generated in C++20.
template<class _CharT, class _Traits, int = 2>
_LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
bool operator==(__type_identity_t<basic_string_view<_CharT, _Traits> > __lhs,
@ -807,41 +833,6 @@ bool operator==(__type_identity_t<basic_string_view<_CharT, _Traits> > __lhs,
if (__lhs.size() != __rhs.size()) return false;
return __lhs.compare(__rhs) == 0;
}
#endif // _LIBCPP_STD_VER >= 20
// operator <=>
#if _LIBCPP_STD_VER >= 20
template <class _CharT, class _Traits>
_LIBCPP_HIDE_FROM_ABI constexpr auto
operator<=>(basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) noexcept {
if constexpr (requires { typename _Traits::comparison_category; }) {
// [string.view]/4
static_assert(
__comparison_category<typename _Traits::comparison_category>,
"return type is not a comparison category type");
return static_cast<typename _Traits::comparison_category>(__lhs.compare(__rhs) <=> 0);
} else {
return static_cast<weak_ordering>(__lhs.compare(__rhs) <=> 0);
}
}
template <class _CharT, class _Traits, int = 1>
_LIBCPP_HIDE_FROM_ABI constexpr auto operator<=>(
basic_string_view<_CharT, _Traits> __lhs, type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) noexcept {
if constexpr (requires { typename _Traits::comparison_category; }) {
// [string.view]/4
static_assert(
__comparison_category<typename _Traits::comparison_category>,
"return type is not a comparison category type");
return static_cast<typename _Traits::comparison_category>(__lhs.compare(__rhs) <=> 0);
} else {
return static_cast<weak_ordering>(__lhs.compare(__rhs) <=> 0);
}
}
#else // _LIBCPP_STD_VER >= 20
// operator !=
template<class _CharT, class _Traits>