[libcxx] Add <experimental/utility> header for LFTS.

[EricWF]

Summary

This patch adds the <experimental/utility> header as specified in the latest draft of the library fundamentals TS.

<experimental/utility> only contains class erased_type.

This patch also updates the documentation to list the erased_type class as "initial implementation complete".

[EricWF]

Hi Marshall,

I'm rudely pinging just this patch. I'm working on polymorphic allocators and they depend on this patch. It would help me a lot if this could be reviewed.

[mclow.lists]

LGTM.

include/experimental/utility

+// -*- C++ -*-
+//===-------------------------- utility ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_UTILITY
+#define _LIBCPP_EXPERIMENTAL_UTILITY
+
+/*
+    experimental/utility synopsis
+
+// C++1y
+
+#include <utility>
+
+namespace std {
+namespace experimental {
+inline namespace fundamentals_v1 {
+
+  3.1.2, erased-type placeholder
+  struct erased_type { };
+
+} // namespace fundamentals_v1
+} // namespace experimental
+} // namespace std
+
+ */
+
+# include <experimental/__config>
+
+#if _LIBCPP_STD_VER > 11
+
+# include <utility>
+
+_LIBCPP_BEGIN_NAMESPACE_LFTS
+
+  struct _LIBCPP_TYPE_VIS_ONLY erased_type { };
+
+_LIBCPP_END_NAMESPACE_LFTS
+
+#endif /* _LIBCPP_STD_VER > 11 */
+
+#endif /* _LIBCPP_EXPERIMENTAL_UTILITY */

test/experimental/utilities/nothing_to_do.pass.cpp

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+int main()
+{
+}

test/experimental/utilities/utility/utility.erased.type/erased_type.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/utility>
+
+#include <experimental/utility>
+
+int main()
+{
+#if _LIBCPP_STD_VER > 11
+    using std::experimental::erased_type;
+    constexpr erased_type e{};
+#endif
+}

test/experimental/utilities/utility/utility.synop/includes.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/utility>
+
+#include <experimental/utility>
+
+int main()
+{
+#if _LIBCPP_STD_VER > 11
+# ifndef _LIBCPP_UTILITY
+#   error "<experimental/utility> must include <utility>"
+# endif
+#endif /* _LIBCPP_STD_VER > 11 */
+}

test/experimental/utilities/utility/version.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/utility>
+
+#include <experimental/utility>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main()
+{
+}

www/ts1z_status.html

   <tr><td>Additions to std::promise</td><td>Not started</td></tr>
   <tr><td>Additions to std::packaged_task</td><td>Not started</td></tr>
   <tr><td></td><td></td></tr>
-  <tr><td>Class erased_type</td><td>Not started</td></tr>
+  <tr><td>Class erased_type</td><td>Initial implementation complete</td></tr>
   <tr><td>Calling a function with a tuple of arguments</td><td>Not started</td></tr>
   <tr><td>Other type transformations</td><td>Not started</td></tr>
   <tr><td>Compile-time Rational Arithmetic</td><td>Not started</td></tr>