[libcxx-commits] [libcxx] [libc++][ranges] implement `ranges::elements_of` (PR #91414)

[Mark de Wever via libcxx-commits]

================
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// std::ranges::elements_of;
+
+#include <ranges>
+
+#include <concepts>
+#include <memory>
+#include <vector>
+
+constexpr bool test() {
+  {
+    auto elements_of = std::ranges::elements_of(std::vector<int>());
+    static_assert(
+        std::same_as<decltype(elements_of), std::ranges::elements_of<std::vector<int>&&, std::allocator<std::byte>>>);
+    static_assert(std::same_as<decltype(elements_of.range), std::vector<int>&&>);
+    static_assert(std::same_as<decltype(elements_of.allocator), std::allocator<std::byte>>);
+  }
+  {
+    auto elements_of = std::ranges::elements_of(std::vector<int>(), std::allocator<int>());
+    static_assert(
+        std::same_as<decltype(elements_of), std::ranges::elements_of<std::vector<int>&&, std::allocator<int>>>);
+    static_assert(std::same_as<decltype(elements_of.range), std::vector<int>&&>);
+    static_assert(std::same_as<decltype(elements_of.allocator), std::allocator<int>>);
+  }
+  return true;
+}
+
+int main() {
+  test();
+  static_assert(test());
+}
----------------
mordante wrote:

This signature and the `return` is required on some platforms where libc++ is tested.
```suggestion
int main(int, char**) {
  test();
  static_assert(test());
  
  return 0;
}
```

https://github.com/llvm/llvm-project/pull/91414