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

1 files changed, 174 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/move.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/move.pass.cpp
new file mode 100644
index 00000000000..3ba261b5246
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/move.pass.cpp
@@ -0,0 +1,174 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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=(optional<T>&& rhs)
+//     noexcept(is_nothrow_move_assignable<T>::value &&
+//              is_nothrow_move_constructible<T>::value);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+struct X
+{
+    static bool throw_now;
+    static int alive;
+
+    X() { ++alive; }
+    X(X&&)
+    {
+        if (throw_now)
+            TEST_THROW(6);
+        ++alive;
+    }
+
+    X& operator=(X&&)
+    {
+        if (throw_now)
+            TEST_THROW(42);
+        return *this;
+    }
+
+    ~X() { assert(alive > 0); --alive; }
+};
+
+struct Y {};
+
+bool X::throw_now = false;
+int X::alive = 0;
+
+int main()
+{
+    {
+        static_assert(std::is_nothrow_move_assignable<optional<int>>::value, "");
+        optional<int> opt;
+        constexpr optional<int> opt2;
+        opt = std::move(opt2);
+        static_assert(static_cast<bool>(opt2) == false, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt;
+        constexpr optional<int> opt2(2);
+        opt = std::move(opt2);
+        static_assert(static_cast<bool>(opt2) == true, "");
+        static_assert(*opt2 == 2, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+        assert(*opt == *opt2);
+    }
+    {
+        optional<int> opt(3);
+        constexpr optional<int> opt2;
+        opt = std::move(opt2);
+        static_assert(static_cast<bool>(opt2) == false, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        optional<T> opt(3);
+        optional<T> opt2;
+        assert(T::alive == 1);
+        opt = std::move(opt2);
+        assert(T::alive == 0);
+        assert(static_cast<bool>(opt2) == false);
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt(3);
+        constexpr optional<int> opt2(2);
+        opt = std::move(opt2);
+        static_assert(static_cast<bool>(opt2) == true, "");
+        static_assert(*opt2 == 2, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+        assert(*opt == *opt2);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        static_assert(!std::is_nothrow_move_assignable<optional<X>>::value, "");
+        X::alive = 0;
+        X::throw_now = false;
+        optional<X> opt;
+        optional<X> opt2(X{});
+        assert(X::alive == 1);
+        assert(static_cast<bool>(opt2) == true);
+        try
+        {
+            X::throw_now = true;
+            opt = std::move(opt2);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+            assert(static_cast<bool>(opt) == false);
+        }
+        assert(X::alive == 1);
+    }
+    assert(X::alive == 0);
+    {
+        static_assert(!std::is_nothrow_move_assignable<optional<X>>::value, "");
+        X::throw_now = false;
+        optional<X> opt(X{});
+        optional<X> opt2(X{});
+        assert(X::alive == 2);
+        assert(static_cast<bool>(opt2) == true);
+        try
+        {
+            X::throw_now = true;
+            opt = std::move(opt2);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 42);
+            assert(static_cast<bool>(opt) == true);
+        }
+        assert(X::alive == 2);
+    }
+    assert(X::alive == 0);
+#endif // TEST_HAS_NO_EXCEPTIONS
+    {
+        static_assert(std::is_nothrow_move_assignable<optional<Y>>::value, "");
+    }
+    {
+        struct ThrowsMove {
+          ThrowsMove() noexcept {}
+          ThrowsMove(ThrowsMove const&) noexcept {}
+          ThrowsMove(ThrowsMove &&) noexcept(false) {}
+          ThrowsMove& operator=(ThrowsMove const&) noexcept { return *this; }
+          ThrowsMove& operator=(ThrowsMove &&) noexcept { return *this; }
+        };
+        static_assert(!std::is_nothrow_move_assignable<optional<ThrowsMove>>::value, "");
+        struct ThrowsMoveAssign {
+          ThrowsMoveAssign() noexcept {}
+          ThrowsMoveAssign(ThrowsMoveAssign const&) noexcept {}
+          ThrowsMoveAssign(ThrowsMoveAssign &&) noexcept {}
+          ThrowsMoveAssign& operator=(ThrowsMoveAssign const&) noexcept { return *this; }
+          ThrowsMoveAssign& operator=(ThrowsMoveAssign &&) noexcept(false) { return *this; }
+        };
+        static_assert(!std::is_nothrow_move_assignable<optional<ThrowsMoveAssign>>::value, "");
+        struct NoThrowMove {
+          NoThrowMove() noexcept(false) {}
+          NoThrowMove(NoThrowMove const&) noexcept(false) {}
+          NoThrowMove(NoThrowMove &&) noexcept {}
+          NoThrowMove& operator=(NoThrowMove const&) noexcept { return *this; }
+          NoThrowMove& operator=(NoThrowMove&&) noexcept { return *this; }
+        };
+        static_assert(std::is_nothrow_move_assignable<optional<NoThrowMove>>::value, "");
+    }
+}