[libcxx-commits] [libcxx] [libc++][ranges] implement LWG3715 (PR #85004)

[Hristo Hristov via libcxx-commits]

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+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// LWG 3715: `view_interface::empty` is overconstrained
+
+#include <cassert>
+#include <ranges>
+#include <sstream>
+
+bool test() {
+  std::istringstream input("1 2 3 4 5");
+  auto i = std::views::istream<int>(input);
+  auto r = std::views::counted(i.begin(), 4) | std::views::take(2);
+  static_assert(std::ranges::input_range<decltype(r)>);
+  static_assert(!std::ranges::forward_range<decltype(r)>);
+  static_assert(std::ranges::sized_range<decltype(r)>);
+  assert(!r.empty());
+  return true;
+}
+
+int main(int, char**) {
+  test();
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Zingam wrote:

We need a constexpr test too probably.

https://github.com/llvm/llvm-project/pull/85004