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, 67 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/nullopt_t.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/nullopt_t.pass.cpp
new file mode 100644
index 00000000000..991f4334304
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/nullopt_t.pass.cpp
@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// optional<T>& operator=(nullopt_t) noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+using std::nullopt_t;
+using std::nullopt;
+
+int main()
+{
+    {
+        optional<int> opt;
+        static_assert(noexcept(opt = nullopt) == true, "");
+        opt = nullopt;
+        assert(static_cast<bool>(opt) == false);
+    }
+    {
+        optional<int> opt(3);
+        opt = nullopt;
+        assert(static_cast<bool>(opt) == false);
+    }
+    using TT = TestTypes::TestType;
+    TT::reset();
+    {
+        optional<TT> opt;
+        static_assert(noexcept(opt = nullopt) == true, "");
+        assert(TT::destroyed == 0);
+        opt = nullopt;
+        assert(TT::constructed == 0);
+        assert(TT::alive == 0);
+        assert(TT::destroyed == 0);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(TT::alive == 0);
+    assert(TT::destroyed == 0);
+    TT::reset();
+    {
+        optional<TT> opt(42);
+        assert(TT::destroyed == 0);
+        TT::reset_constructors();
+        opt = nullopt;
+        assert(TT::constructed == 0);
+        assert(TT::alive == 0);
+        assert(TT::destroyed == 1);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(TT::alive == 0);
+    assert(TT::destroyed == 1);
+    TT::reset();
+}