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

[Christopher Di Bella via cfe-commits]

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@@ -0,0 +1,96 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 bool operator==(const iterator& x, const iterator& y) noexcept;
+
+#include <cassert>
+#include <ranges>
+
+#include "test_iterators.h"
+#include "../types.h"
+// #include "../types_iterators.h"
+
+// template <bool Const>
+// struct Iterator {
+//   using value_type       = int
+//   using difference_type  = std::std::ptrdiff_t;
+//   using iterator_concept = std::input_iterator_tag;
+
+//   constexpr decltype(auto) operator*() const { return *it_; }
+//   constexpr Iterator& operator++() {
+//     ++it_;
+
+//     return *this;
+//   }
+//   constexpr void operator++(int) { ++it_; }
+
+//   std::tuple<std::ptrdiff_t, int>* it_;
+// };
+
+// template <bool Const>
+// struct Sentinel {
+//   constexpr bool operator==(const Iterator<Const>& i) const { return i.it_ == end_; }
+
+//   std::tuple<std::ptrdiff_t, int>* end_;
+// };
+
+// template <bool Const>
+// struct CrossComparableSentinel {
+//   template <bool C>
+//   constexpr bool operator==(const Iterator<C>& i) const {
+//     return i.it_ == end_;
+//   }
+
+//   std::tuple<std::ptrdiff_t, int>* end_;
+// };
+
+constexpr bool test() {
+  int buff[] = {0, 1, 2, 3, 5};
+  {
+    using View = std::ranges::enumerate_view<RangeView>;
+    RangeView const range(buff, buff + 5);
+
+    std::same_as<View> decltype(auto) ev = std::views::enumerate(range);
+
+    auto it1 = ev.begin();
+    auto it2 = it1 + 5;
+
+    assert(it1 == it1);
+    ASSERT_NOEXCEPT(it1 == it1);
+    assert(it1 != it2);
+    ASSERT_NOEXCEPT(it1 != it2);
+    assert(it2 != it1);
+    ASSERT_NOEXCEPT(it2 != it1);
+    assert(it2 == ev.end());
+    assert(ev.end() == it2);
+
+    for (std::size_t index = 0; index != 5; ++index) {
+      ++it1;
+    }
----------------
cjdb wrote:

Please hand-roll.

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