[libcxx-commits] [libcxx] [libc++][tuple][utility] P2968R2 Make `std::ignore` a first-class object (PR #97401)

[S. B. Tam via libcxx-commits]

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@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___TUPLE_IGNORE_H
+#define _LIBCPP___TUPLE_IGNORE_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifndef _LIBCPP_CXX03_LANG
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct __ignore_type {
+  template <class _Tp>
+  _LIBCPP_HIDE_FROM_ABI constexpr const __ignore_type& operator=(const _Tp&) const noexcept {
+    return *this;
+  }
+};
+
+inline constexpr __ignore_type ignore;
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cpplearner wrote:

> This is backporting a change in C++17 ([P0607R0](https://wg21.link/p0607r0))... I think in C++11/14 `std::ignore` was supported to have internal linkage (and thus denoted different objects in different TUs).

What's the benefit of doing this?

https://github.com/llvm/llvm-project/pull/97401