[clang-tools-extra] [compiler-rt] [clang] [flang] [lld] [llvm] [libcxx] [libc++][ranges] P2116R9: Implements `views::enumerate` (PR #73617)

[Christopher Di Bella via cfe-commits]

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@@ -0,0 +1,75 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <ranges>
+
+// class enumerate_view
+
+// class enumerate_view::iterator
+
+// friend constexpr auto iter_move(const iterator& i)
+//   noexcept(noexcept(ranges::iter_move(i.current_)) &&
+//             is_nothrow_move_constructible_v<range_rvalue_reference_t<Base>>);
+
+#include <array>
+#include <cassert>
+#include <ranges>
+#include <type_traits>
+#include <utility>
+
+#include "test_iterators.h"
+#include "../types.h"
+
+template <class Iterator, bool HasNoexceptIterMove>
+constexpr void test() {
+  using Sentinel          = sentinel_wrapper<Iterator>;
+  using View              = MinimalView<Iterator, Sentinel>;
+  using EnumerateView     = std::ranges::enumerate_view<View>;
+  using EnumerateIterator = std::ranges::iterator_t<EnumerateView>;
+
+  std::array array{0, 1, 2, 3, 4};
+
+  View view{Iterator(array.begin()), Sentinel(Iterator(array.end()))};
+  EnumerateView ev{std::move(view)};
+  EnumerateIterator const it = ev.begin();
+
+  auto&& result = iter_move(it);
+
+  static_assert(std::is_same_v<decltype(result),
+                               std::tuple<typename std::ranges::iterator_t<EnumerateView>::difference_type, int&&>&&>);
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cjdb wrote:

Consider using `ranges::range_difference_t`.

https://github.com/llvm/llvm-project/pull/73617