[libcxx-commits] [libcxx] [libc++][RFC] Rewrite CPOs with resolver functions (PR #209104)

[Louis Dionne via libcxx-commits]

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@@ -102,45 +104,53 @@ using iterator_t = decltype(ranges::begin(std::declval<_Tp&>()));
 
 namespace ranges {
 namespace __end {
-template <class _Tp>
-concept __member_end = __can_borrow<_Tp> && requires(_Tp&& __t) {
-  typename iterator_t<_Tp>;
-  { _LIBCPP_AUTO_CAST(__t.end()) } -> sentinel_for<iterator_t<_Tp>>;
-};
-
-void end() = delete;
-
-template <class _Tp>
-concept __unqualified_end =
-    !__member_end<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
-      typename iterator_t<_Tp>;
-      { _LIBCPP_AUTO_CAST(end(__t)) } -> sentinel_for<iterator_t<_Tp>>;
-    };
-
-struct __fn {
-  template <class _Tp, size_t _Np>
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp (&__t)[_Np]) const noexcept
-    requires(sizeof(_Tp) >= 0) // Disallow incomplete element types.
-  {
-    return __t + _Np;
-  }
-
-  template <class _Tp>
-    requires __member_end<_Tp>
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
-      noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.end()))) {
-    return _LIBCPP_AUTO_CAST(__t.end());
+struct __fn : _CPO<[]<class _Ep> consteval noexcept {
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ldionne wrote:

What are the diagnostics like? Can you paste before/after in a reply to this comment just so I get a rough idea?

https://github.com/llvm/llvm-project/pull/209104