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

4 files changed, 501 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/optional/optional.specalg/make_optional.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/make_optional.pass.cpp
new file mode 100644
index 00000000000..3fbf19f8ee1
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.specalg/make_optional.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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 optional<decay_t<T>> make_optional(T&& v);
+
+#include <optional>
+#include <string>
+#include <memory>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using std::optional;
+    using std::make_optional;
+    {
+        int arr[10]; ((void)arr);
+        ASSERT_SAME_TYPE(decltype(make_optional(arr)), optional<int*>);
+    }
+    {
+        constexpr auto opt = make_optional(2);
+        ASSERT_SAME_TYPE(decltype(opt), const optional<int>);
+        static_assert(opt.value() == 2);
+    }
+    {
+        optional<int> opt = make_optional(2);
+        assert(*opt == 2);
+    }
+    {
+        std::string s("123");
+        optional<std::string> opt = make_optional(s);
+        assert(*opt == s);
+    }
+    {
+        std::unique_ptr<int> s(new int(3));
+        optional<std::unique_ptr<int>> opt = make_optional(std::move(s));
+        assert(**opt == 3);
+        assert(s == nullptr);
+    }
+}
diff --git a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp
new file mode 100644
index 00000000000..bdfeefbcc1d
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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, class... Args>
+//   constexpr optional<T> make_optional(Args&&... args);
+
+#include <optional>
+#include <string>
+#include <memory>
+#include <cassert>
+
+int main()
+{
+    using std::optional;
+    using std::make_optional;
+
+    {
+        constexpr auto opt = make_optional<int>('a');
+        static_assert(*opt == int('a'), "");
+    }
+    {
+        std::string s("123");
+        auto opt = make_optional<std::string>(s);
+        assert(*opt == s);
+    }
+    {
+        std::unique_ptr<int> s(new int(3));
+        auto opt = make_optional<std::unique_ptr<int>>(std::move(s));
+        assert(**opt == 3);
+        assert(s == nullptr);
+    }
+    {
+        auto opt = make_optional<std::string>(4, 'X');
+        assert(*opt == "XXXX");
+    }
+}
diff --git a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp
new file mode 100644
index 00000000000..f17f5820d20
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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, class U, class... Args>
+//   constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);
+
+#include <optional>
+#include <string>
+#include <memory>
+#include <cassert>
+
+#include "test_macros.h"
+
+struct TestT {
+  int x;
+  int size;
+  constexpr TestT(std::initializer_list<int> il) : x(*il.begin()), size(il.size()) {}
+  constexpr TestT(std::initializer_list<int> il, const int*)
+      : x(*il.begin()), size(il.size()) {}
+};
+
+int main()
+{
+    using std::make_optional;
+    {
+        constexpr auto opt = make_optional<TestT>({42, 2, 3});
+        ASSERT_SAME_TYPE(decltype(opt), const std::optional<TestT>);
+        static_assert(opt->x == 42, "");
+        static_assert(opt->size == 3, "");
+    }
+    {
+        constexpr auto opt = make_optional<TestT>({42, 2, 3}, nullptr);
+        static_assert(opt->x == 42, "");
+        static_assert(opt->size == 3, "");
+    }
+    {
+        auto opt = make_optional<std::string>({'1', '2', '3'});
+        assert(*opt == "123");
+    }
+    {
+        auto opt = make_optional<std::string>({'a', 'b', 'c'}, std::allocator<char>{});
+        assert(*opt == "abc");
+    }
+}
diff --git a/libcxx/test/std/utilities/optional/optional.specalg/swap.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/swap.pass.cpp
new file mode 100644
index 00000000000..9f1d0305022
--- /dev/null
+++ b/libcxx/test/std/utilities/optional/optional.specalg/swap.pass.cpp
@@ -0,0 +1,352 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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> void swap(optional<T>& x, optional<T>& y)
+//     noexcept(noexcept(x.swap(y)));
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+class X
+{
+    int i_;
+public:
+    static unsigned dtor_called;
+    X(int i) : i_(i) {}
+    X(X&& x) = default;
+    X& operator=(X&&) = default;
+    ~X() {++dtor_called;}
+
+    friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
+};
+
+unsigned X::dtor_called = 0;
+
+class Y
+{
+    int i_;
+public:
+    static unsigned dtor_called;
+    Y(int i) : i_(i) {}
+    Y(Y&&) = default;
+    ~Y() {++dtor_called;}
+
+    friend constexpr bool operator==(const Y& x, const Y& y) {return x.i_ == y.i_;}
+    friend void swap(Y& x, Y& y) {std::swap(x.i_, y.i_);}
+};
+
+unsigned Y::dtor_called = 0;
+
+class Z
+{
+    int i_;
+public:
+    Z(int i) : i_(i) {}
+    Z(Z&&) { TEST_THROW(7);}
+
+    friend constexpr bool operator==(const Z& x, const Z& y) {return x.i_ == y.i_;}
+    friend void swap(Z& x, Z& y) { TEST_THROW(6);}
+};
+
+
+struct NonSwappable {
+    NonSwappable(NonSwappable const&) = delete;
+};
+void swap(NonSwappable&, NonSwappable&) = delete;
+
+void test_swap_sfinae() {
+    using std::optional;
+    {
+        using T = TestTypes::TestType;
+        static_assert(std::is_swappable_v<optional<T>>, "");
+    }
+    {
+        using T = TestTypes::MoveOnly;
+        static_assert(std::is_swappable_v<optional<T>>, "");
+    }
+    {
+        using T = TestTypes::Copyable;
+        static_assert(std::is_swappable_v<optional<T>>, "");
+    }
+    {
+        using T = TestTypes::NoCtors;
+        static_assert(!std::is_swappable_v<optional<T>>, "");
+    }
+    {
+        using T = NonSwappable;
+        static_assert(!std::is_swappable_v<optional<T>>, "");
+    }
+    {
+        // Even thought CopyOnly has deleted move operations, those operations
+        // cause optional<CopyOnly> to have implicitly deleted move operations
+        // that decay into copies.
+        using T = TestTypes::CopyOnly;
+        using Opt = optional<T>;
+        T::reset();
+        Opt L(101), R(42);
+        T::reset_constructors();
+        std::swap(L, R);
+        assert(L->value == 42);
+        assert(R->value == 101);
+        assert(T::copy_constructed == 1);
+        assert(T::constructed == T::copy_constructed);
+        assert(T::assigned == 2);
+        assert(T::assigned == T::copy_assigned);
+    }
+}
+
+int main()
+{
+    test_swap_sfinae();
+    {
+        optional<int> opt1;
+        optional<int> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<int> opt1(1);
+        optional<int> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<int> opt1;
+        optional<int> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<int> opt1(1);
+        optional<int> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<X> opt1;
+        optional<X> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        assert(X::dtor_called == 0);
+    }
+    {
+        optional<X> opt1(1);
+        optional<X> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        X::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(X::dtor_called == 1);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<X> opt1;
+        optional<X> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        X::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(X::dtor_called == 1);
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<X> opt1(1);
+        optional<X> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        X::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(X::dtor_called == 1);  // from inside std::swap
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<Y> opt1;
+        optional<Y> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        assert(Y::dtor_called == 0);
+    }
+    {
+        optional<Y> opt1(1);
+        optional<Y> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        Y::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(Y::dtor_called == 1);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<Y> opt1;
+        optional<Y> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        Y::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(Y::dtor_called == 1);
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<Y> opt1(1);
+        optional<Y> opt2(2);
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        Y::dtor_called = 0;
+        swap(opt1, opt2);
+        assert(Y::dtor_called == 0);
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 2);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 1);
+    }
+    {
+        optional<Z> opt1;
+        optional<Z> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        swap(opt1, opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        optional<Z> opt1;
+        opt1.emplace(1);
+        optional<Z> opt2;
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        try
+        {
+            swap(opt1, opt2);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 7);
+        }
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<Z> opt1;
+        optional<Z> opt2;
+        opt2.emplace(2);
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        try
+        {
+            swap(opt1, opt2);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 7);
+        }
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+    }
+    {
+        optional<Z> opt1;
+        opt1.emplace(1);
+        optional<Z> opt2;
+        opt2.emplace(2);
+        static_assert(noexcept(swap(opt1, opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        try
+        {
+            swap(opt1, opt2);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+        }
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+    }
+#endif // TEST_HAS_NO_EXCEPTIONS
+}