[clang-tools-extra] [libc++] Implement ranges::contains (PR #65148)

[Konstantin Varlamov via cfe-commits]

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@@ -0,0 +1,61 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_RANGES_CONTAINS_H
+#define _LIBCPP___ALGORITHM_RANGES_CONTAINS_H
+
+#include <__algorithm/in_in_result.h>
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var-const wrote:

Sorry, what I mean is that a good and easy way to see if we're testing every constraint is to simply remove or comment out a constraint, run the tests and see if any tests fail. If we're testing everything properly, at least one test will fail -- conversely, if everything passes, that means a lack of test coverage. So what I'm suggesting is to temporarily remove the `projected` constraint in your local copy, run the tests and see if there are any failures. If there are no failures, please see if it's possible to add a test that checks we are using the `projected` concept there as required by the Standard. Happy to help if this explanation isn't clear!

https://github.com/llvm/llvm-project/pull/65148