Implement N4606 optional
Summary:
Adapt implementation of Library Fundamentals TS optional into an implementation of N4606 optional.
- Update relational operators per http://wg21.link/P0307
- Update to requirements of http://wg21.link/P0032
- Extension: Implement trivial copy/move construction/assignment for `optional<T>` when `T` is trivially copyable.
Audit P/Rs for optional LWG issues:
- 2756 "C++ WP optional<T> should 'forward' T's implicit conversions" Implemented, which also resolves 2753 "Optional's constructors and assignments need constraints" (modulo my refusal to explicitly delete the move operations, which is a design error that I'm working on correcting in the 2756 P/R).
- 2736 "nullopt_t insufficiently constrained" Already conforming. I've added a test ensuring that `nullopt_t` is not copy-initializable from an empty braced-init-list, which I believe is the root intent of the issue, to avoid regression.
- 2740 "constexpr optional<T>::operator->" Already conforming.
- 2746 "Inconsistency between requirements for emplace between optional and variant" No P/R, but note that the author's '"suggested resolution" is already implemented.
- 2748 "swappable traits for optionals" Already conforming.
- 2753 "Optional's constructors and assignments need constraints" Implemented.
Most of the work for this patch was done by Casey Carter @ Microsoft. Thank you Casey!
Reviewers: mclow.lists, CaseyCarter, EricWF
Differential Revision: https://reviews.llvm.org/D22741
llvm-svn: 283980
diff --git a/libcxx/test/std/utilities/optional/optional.nullops/greater.pass.cpp b/libcxx/test/std/utilities/optional/optional.nullops/greater.pass.cpp
new file mode 100644
index 0000000..3986a0a
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.nullops/greater.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+// template <class T> constexpr bool operator>(const optional<T>& x, nullopt_t) noexcept;
+// template <class T> constexpr bool operator>(nullopt_t, const optional<T>& x) noexcept;
+
+#include <optional>
+
+int main()
+{
+ using std::optional;
+ using std::nullopt_t;
+ using std::nullopt;
+
+ {
+ typedef int T;
+ typedef optional<T> O;
+
+ constexpr O o1; // disengaged
+ constexpr O o2{1}; // engaged
+
+ static_assert ( !(nullopt > o1), "" );
+ static_assert ( !(nullopt > o2), "" );
+ static_assert ( !(o1 > nullopt), "" );
+ static_assert ( (o2 > nullopt), "" );
+
+ static_assert (noexcept(nullopt > o1), "");
+ static_assert (noexcept(o1 > nullopt), "");
+ }
+}