[libcxx-commits] [libcxx] [libc++][functional] Implement `not_fn<NTTP>` (PR #86133)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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, c++23
+
+// <functional>
+
+// Type of `std::not_fn<NTTP>()` is always empty.
+
+#include <functional>
+#include <type_traits>
+
+struct NonEmptyFunctionObject {
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ldionne wrote:

I'd also test with a couple of other callables like a function pointer and a pointer to member function.

https://github.com/llvm/llvm-project/pull/86133