Add <optional> header.

This patch is largely thanks to Casey Carter @ Microsoft. He did the initial
work of porting our experimental implementation and tests over to namespace
std.

llvm-svn: 283977

1 files changed, 25 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/optional/optional.nullopt/not_brace_initializable.fail.cpp b/libcxx/test/std/utilities/optional/optional.nullopt/not_brace_initializable.fail.cpp
new file mode 100644
index 00000000000..86da5054a70
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.nullopt/not_brace_initializable.fail.cpp
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// <optional>
+
+// struct nullopt_t{see below};
+
+#include <optional>
+
+using std::optional;
+using std::nullopt_t;
+
+int main()
+{
+    // I roughly interpret LWG2736 as "it shall not be possible to copy-list-initialize nullopt_t with an
+    // empty braced-init-list."
+    nullopt_t foo = {};
+}