[libc++] Implementing ranges::iota: Cleanup and addressing comments from @strega-nil

Author: jamesETsmith

libcxx/docs/Status/RangesAlgorithms.csv

@@ -9,7 +9,6 @@ C++23,`shift_left <https://wg21.link/p2440r1>`_,Unassigned,No patch yet,Not star
 C++23,`shift_right <https://wg21.link/p2440r1>`_,Unassigned,No patch yet,Not started
 C++23,`iota (algorithm) <https://wg21.link/p2440r1>`_,Unassigned,No patch yet,Not started
 C++23,`fold <https://wg21.link/p2322r5>`_,Unassigned,No patch yet,Not started
-C++23,`contains <https://wg21.link/p2302r2>`_,Zijun Zhao,No patch yet,In Progress
 C++23,`ranges::iota <https://wg21.link/P2440R1>`_, James E T Smith, `PR68494 <https://github.com/llvm/llvm-project/pull/68494>`_, In Progress
 C++23,`contains <https://wg21.link/p2302r2>`_,Zijun Zhao, `#65148 <https://github.com/llvm/llvm-project/pull/65148>`_,Complete
 C++23,`fold_left_with_iter <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,Complete

libcxx/docs/Status/RangesMajorFeatures.csv

@@ -2,5 +2,4 @@ Standard,Name,Assignee,CL,Status
 C++23,`ranges::to <https://wg21.link/P1206R7>`_,Konstantin Varlamov,`D142335 <https://reviews.llvm.org/D142335>`_,Complete
 C++23,`Pipe support for user-defined range adaptors <https://wg21.link/P2387R3>`_,"Louis Dionne, Jakub Mazurkiewicz, and Xiaoyang Liu",Various,Complete
 C++23,`Formatting Ranges <https://wg21.link/P2286R8>`_,Mark de Wever,Various,Complete
-C++23, `ranges::iota <https://wg21.link/P2440R1>`_, James E T Smith, `PR68494 <https://github.com/llvm/llvm-project/pull/68494>`_, In Progress
 C++20,`Stashing stashing iterators for proper flattening <https://wg21.link/P2770R0>`_,Jakub Mazurkiewicz,Various,In progress

libcxx/include/__numeric/ranges_iota.h

@@ -48,7 +48,7 @@ struct __iota_fn {
   template <weakly_incrementable _Tp, ranges::output_range<const _Tp&> _Range>
   _LIBCPP_HIDE_FROM_ABI static constexpr iota_result<ranges::borrowed_iterator_t<_Range>, _Tp>
   operator()(_Range&& __r, _Tp __value) {
-    return __iota_fn::operator()(ranges::begin(__r), ranges::end(__r), std::move(__value));
+    return operator()(ranges::begin(__r), ranges::end(__r), std::move(__value));
   }
 };
 

libcxx/include/algorithm

@@ -42,12 +42,12 @@ namespace ranges {
   template <class I>
     struct in_found_result;              // since C++20
 
-  template <class O, class T>
-    struct out_value_result;             // since C++23
-
   template <class I, class T>
     struct in_value_result;              // since C++23
 
+  template <class O, class T>
+    struct out_value_result;             // since C++23
+
   template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
     indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>                                   // since C++20
   constexpr I min_element(I first, S last, Comp comp = {}, Proj proj = {});

libcxx/test/std/algorithms/ranges_result_alias_declarations.compile.pass.cpp

@@ -63,7 +63,6 @@ static_assert(std::is_same_v<in_found_result<int>, next_permutation_result<int>>
 static_assert(std::is_same_v<in_found_result<int>, prev_permutation_result<int>>);
 
 #if TEST_STD_VER >= 23
-static_assert(std::is_same_v<out_value_result<int, int>, iota_result<int, int>>);
-
 static_assert(std::is_same_v<in_value_result<int, long>, fold_left_with_iter_result<int, long>>);
+static_assert(std::is_same_v<out_value_result<int, int>, iota_result<int, int>>);
 #endif // TEST_STD_VER

libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp

@@ -108,7 +108,7 @@ constexpr void run_tests() {
   test(std::ranges::search_n, in, count, x);
   test(std::ranges::find_end, in, in2);
 #if TEST_STD_VER >= 23
-  if constexpr (std::copyable<T>) {
+  if constexpr (std::weakly_incrementable<T>) {
     test(std::ranges::iota, in, x);
   }
 #endif

libcxx/test/support/test_iterators.h

@@ -1198,7 +1198,7 @@ struct Proxy : ProxyDiffTBase<T> {
   // Calling swap(Proxy<T>{}, Proxy<T>{}) would fail (pass prvalues)
 
   // Compare operators are defined for the convenience of the tests
-  friend constexpr bool operator==(const Proxy& lhs, const Proxy& rhs)
+  friend constexpr bool operator==(const Proxy&, const Proxy&)
     requires(std::equality_comparable<T> && !std::is_reference_v<T>)
   = default;
 
@@ -1210,7 +1210,7 @@ struct Proxy : ProxyDiffTBase<T> {
     return lhs.data == rhs.data;
   }
 
-  friend constexpr auto operator<=>(const Proxy& lhs, const Proxy& rhs)
+  friend constexpr auto operator<=>(const Proxy&, const Proxy&)
     requires(std::three_way_comparable<T> && !std::is_reference_v<T>)
   = default;