Implement N4606 optional

[EricWF]

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!

[EricWF]

We should consider adding a storage specialization for trivially copyable types. It's important to do it now because it would be an ABI breaking change later. It would also be possible to provide constexpr optional<T> copy/move operations for such a specialization.

More comments to come.

include/optional

175

I really don't like this constructor. I can see plenty of places where it could get constructed accidentally.
Let's find another way to (A) get rid of the default constructor and (B) privately initialize nullopt_t.

202

Or just __null_state_(0)

259

I've never seen variable template specialization, but I like it :-)

346

It seems like this implementation should support references fine, no? It might be one of those cases that needs std::launder, but __optional_storage looks like it could handle it.

Do you know what the status of optional<T&>is? Is LEWG working on it?

420

There are not constexpr in the spec, and it can't be implemented as a constexpr operation in the vast majority* of cases AFAIK.

[1] http://stackoverflow.com/questions/30632442/c14-constexpr-union-conditional-initialization-in-constructor

[CaseyCarter]

We should consider adding a storage specialization for trivially copyable types. It's important to do it now because it would be an ABI breaking change later. It would also be possible to provide constexpr optional<T> copy/move operations for such a specialization.

Intent of this change was to perform the minimum changes necessary to bring the existing LibFund optional implementation into spec with the WP, so I didn't mess about with the existing design at all, really. That said, I put a bit of effort into providing trivial-and-therefor-constexpr copy/move constructors/assignments for MSVC's optional implementation, so I obviously agree it's a good idea. If you're interested I'd be happy to implement it here as well.

include/optional

175

How about an unspeakable tag argument, e.g.:

struct nullopt_t
{
    struct __secret_tag { explicit __secret_tag() = default; };
    explicit constexpr nullopt_t(__secret_tag, __secret_tag) noexcept {}
};

constexpr nullopt_t nullopt{nullopt_t::__secret_tag{}, nullopt_t::__secret_tag{}};

202

I would have simply value-initialized; I didn't change anything pre-existing that was not necessary to accommodate the spec changes from TS2 to WP optional.

'E' for "empty" would be a good choice as well. It's a shame "Ø" isn't in the basic source character set. ;)

210

There are *four* virtually identical constructors with this same pattern; consider refactoring.

259

I use it *very* extensively in cmcstl2 to workaround performance deficiencies in GCC's concepts implementation, so I've enjoyed riding a roller coaster of bugs for the last year. I can now confidently say that GCC & Clang both have good support for partial specialization of variable templates.

346

It's an explicit requirement in N4606 that optional references are verboten. Yes, that is inconsistent with variant which explicitly *does* support references. I don't know if anyone has been working on it. Hopefully we'll get the differences ironed out sometime before C++20.

Psuedo-destructor syntax isn't valid for reference types, so e.g. __optional_storage's destructor would need a bit of work to support them.

I would want a specialized representation for optional<T&> that stores only a pointer and uses nullptr for the empty state so the general implementation of __optional_storage wouldn't need to support them anyway.

420

These *are* constexpr in Library Fundamentals TS2 (para 44 & 49) just as specified in the resolution of LWG2451. I agree they cannot be implemented as constexpr; I submitted LWG2745 to remove the constexpr and "shall be constexpr if ..." wording.

[CaseyCarter]

Address review comments:

• Defend nullopt_t constructor against Murphy.
• Refactor __optional_storage into three class templates:
  • __optional_destruct_base: conditionally implements non-trivial destruction
  • __optional_copy_base: conditionally implements non-trivial copy/move construction/assignment
  • __optional_storage: presents a clean API to insulate optional from the storage representation. (In theory, specializations of this class can provide novel representations, e.g., optional<T&> could use a T* for its representation with (T*)0 as the empty state.)

[CaseyCarter]

include/optional

315

Where are the tests to validate trivial/constexpr move/copy construct/assign for optional of trivial types?

optional

2 ↗

(On Diff #66142)

It bears repeating. An implementation just can't have too many files named "optional."

Delete this and re-push.

[CaseyCarter]

Remove the extra "optional" file that I somehow managed to add at the top of the directory tree.

[CaseyCarter]

NOTE WELL: This implementation of the "trivially copyable type" optimization critically fails to SFINAE the special member functions. I suggest you put off reviewing until I update the diff again.

include/optional

316

Those tests also validate that the special members don't participate in overload resolution when they're not valid for T, which I haven't implemented here, and is IMO critical for optional to be useful (LWG2753).

[EricWF]

Adding a bunch of inline comments. This looks really great. I should finish the review tommorow.

The biggest problem, which you already noted, is that the special members still lack SFINAE. We need to make sure they are correctly generated. Here's the test case I wrote for it.

include/experimental/optional

11 ↗

(On Diff #66145)

Let's go with the full _LIBCPP_EXPERIMENTAL_OPTIONAL.

include/optional

144

bad_optional_access should go directly into namespace std, not the versioning namespace, because we don't version exceptions.

159

Just put these includes at the top. If you include <optional> when it's not available then it's your fault. We don't need to optimize for it.

167

Put this right after the first includes.

320

What's up with this default template argument?

406

I don't think we want to check this. Sometime's the implicitly generated destructor is not noexcept.

409

= default;?

412

Don't even declare the destructor.

416

I think we probably want to constrain these or is_constructible<value_type, value_type&&> even though the standard doesn't require it.

784

Urg this is unfortunate. Clang provides a constexpr addressof, but GCC doesn't yet.

Even worse is that this technique doesn't detect explicitly deleted operator& overloads.

803

Calls to declval *need* to be qualified to avoid ADL hijacking.

1168

decay_t is now available :-)

1203

_LIBCPP_STD_VER > 14

test/libcxx/optional/version.pass.cpp

1 ↗

(On Diff #66145)

test/libcxx/utilities/optional is the correct path for this.

[CaseyCarter]

I should have time to finish up this week.

include/optional

320

I foresee wanting to specialize __optional_storage for types with a built-in invalid state / sentinel value some time, especially if/when the committee decides to allow optional<T&>. This parameter is here *now* so that when that time comes it can be used for selecting specializations without ABI breaking.

406

This was pre-existing in experimental/optional, but I agree. Will remove.

409

This was pre-existing, and it confused me as well, until I recalled [dcl.init]/7: "If a program calls for the default-initialization of an object of a const-qualified type T, T shall be a class type with a user-provided default constructor." I see no reason not to allow e.g. constexpr optional<foo> o;

416

Yes, constraining the constructors and assignments is LWG2753. I'll be sure to implement all the issues that are Tentatively Ready from Chicago.

[CaseyCarter]

Implements the most recent PR for LWG2756 - which also resolves LWG2753 - except that optional<T>'s move operations are not defined as deleted when T is not movable. They instead do not participate in overload resolution. Copyable-but-not-Movable types are an abomination that optional should not propagate. Consequently, optional<T> is both copyable and movable when T is Copyable-but-not-Movable; this is a feature, not a bug ;)

I split Eric's special-member-function triviality/SFINAE test into separate tests:

• An SFINAE test under std, since LWG2753 is Tentatively Ready
• A triviality test under libcxx, since no one has shown an interest in standardizing the triviality of optional<T>'s SMFs.

Implemented a test for LWG2736 "nullopt_t insufficiently constrained." nullopt_t already conformed, but it never hurts to guard against regression.

Wrapped all the everything at 100-ish columns.

[CaseyCarter]

That's everything I'm planning to do for now. Review away.

include/optional

785

I can live with this nearly-pathological corner case being broken without intrinsic addressof.

[CaseyCarter]

Fix triviality impl and tests (you know, because you tend to find errors when you actually *run* the tests)

• Add trivially_assignable tests
• Cleanup:
  • add some missing _LIBCPP_INLINE_VISIBILITY specifiers
  • We're inside _LIBCPP_STD_VER > 14, so use trait_v everywhere instead of trait::value.
  • Use is_trivially_copyable<T> directly, instead of the equivalent but longer is_trivially_copyable<__optional_destruct_base<T>>.
  • "inline constexpr" => "constexpr"

[CaseyCarter]

Nitpicks.

include/optional

168

Why is "Access" capitalized?

648

Again, you've written four nearly identical constructor bodies. This cries out for DRY.

test/libcxx/utilities/optional/optional.object/special_member_gen.pass.cpp

38

Needs to check triviality of copy/move assignment as well.

[CaseyCarter]

Apply Eric's refactoring to separate the SFINAE constraints from the implementation of the special member functions.

[CaseyCarter]

include/optional

389

Note the intentional difference from Eric's patch: this class deletes the *assignments* as well as the constructions when T is not movable and/or copyable, so that optional<T> is foo_assignable iff T is foo_constructible and foo_copyable.

Given that constructibility partially determines assignment, it may be possible to combine the two sfinae bases cleanly.

[EricWF]

Hi Casey? Sorry about this, but I actually just factored out the __optional_sfinae_ctor_base and __optional_sfinae_assign_base since we'll need them in optional. Could you please apply this patch to yours?

https://gist.github.com/EricWF/49ffb06a2ac904b5f4729c1e72725fbe

include/optional

168

Just make it "bad optional access". I don't think diagnostics should ever be capitalized.

321

I suspect we could make the change is a mostly non-abi breaking change without it, but I'm OK with it in general.
Just add a comment along the lines of "For future specialization."

648

I think we could just lower it to an __optional_storage constructor using

optional(optional<U>&& u) : __base(std::move(u)) {}

or similar

[EricWF]

Additionally I'm perfectly happy to take over this change if you don't want to continue. If you do then thank you very much! I understand it's a lot of work.

[EricWF]

include/optional

752

Please replace this with:

if (!this->has_value())
  __libcpp_throw(bad_optional_access());

764

Same here.

776

Same here.

788

Same here.

[CaseyCarter]

include/optional

389

Given that constructibility partially determines assignment, it may be possible to combine the two sfinae bases cleanly.

This results in 9 specializations of 1 class instead of 4 specializations * 2 classes. I'd call it a wash.

474

I moved these here so there would be one private section, but I'm now thinking it would be cleaner to make __base public and move these __operator_arrow overloads back into a private section at the end of the class body.

[EricWF]

include/optional

389

I actually changed how it was done. Now __optional_sfinae_assign_base_t selects the correct copy/assignment operator definitions based on the copy/move constructor availability. Sorry I missed that in the first patch.

[CaseyCarter]

Hi Casey? Sorry about this, but I actually just factored out the __optional_sfinae_ctor_base and __optional_sfinae_assign_base since we'll need them in optional. Could you please apply this patch to yours?

I could, but then the tests won't run. Could you include the destination of the refactoring in the patch as well?

include/optional

322

Already removed during the sfinae refactor - whoever specializes optional_storage for references will have to specialize it separately for lvalue and rvalue references ;)

649

Already done.

[EricWF]

In D22741#515018, @CaseyCarter wrote:

Hi Casey? Sorry about this, but I actually just factored out the __optional_sfinae_ctor_base and __optional_sfinae_assign_base since we'll need them in optional. Could you please apply this patch to yours?

I could, but then the tests won't run. Could you include the destination of the refactoring in the patch as well?

I already pushed the destination to master. The definitions are at the bottom of __tuple.

[CaseyCarter]

Relocate __operator_arrow; __libcpp_throw; __sfinae_XXX_base relocation.

[EricWF]

The summary says:

Speculatively apply resolution of http://wg21.link/lwg2451 from the TS

It we want to apply the defect report for the WP, not the TS. IE:

2756. C++ WP optional<T> should 'forward' T's implicit conversions

[EricWF]

include/optional

738

These need non-const overloads as well.

[EricWF]

Side note: The current patch make clang ICE a bunch. I've filed a bug against Clang here: https://llvm.org/bugs/show_bug.cgi?id=28978

This bug doesn't seem to affect 3.9 or 3.8 so we shouldn't have a real issue.

[CaseyCarter]

It we want to apply the defect report for the WP, not the TS.

Yes, I implemented 2756 today and did a full audit of all the active optional issues, but forgot to update the Summary.

[CaseyCarter]

__operator_arrow needs to work for *mutable* objects as well as constant objects.

[EricWF]

@CaseyCarter I've updated the implementation for references according to your feedback. optional<T&> and optional<T&&> now have sizeof(void*). What do you think of this patch:

https://gist.github.com/EricWF/a43e98641c3270b411a9358601bc2f0d

[EricWF]

Updating with the final revision.

.gitignore

 docs/_build/
 
 # PyBuilder
 target/
 
 # MSVC libraries test harness
 env.lst
 keep.lst
+
+# Editor by-products
+.vscode/

include/__config

 #endif
 
 #if __has_attribute(require_constant_initialization)
 #define _LIBCPP_SAFE_STATIC __attribute__((__require_constant_initialization__))
 #else
 #define _LIBCPP_SAFE_STATIC
 #endif
 
+#if !__has_builtin(__builtin_addressof) && _GNUC_VER < 700
+#define _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG

include/optional

+// -*- C++ -*-
+//===-------------------------- optional ----------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_OPTIONAL
+#define _LIBCPP_OPTIONAL
+
+/*
+    optional synopsis
+
+// C++1z
+
+namespace std {
+  // 20.6.3, optional for object types
+  template <class T> class optional;
+
+  // 20.6.4, no-value state indicator
+  struct nullopt_t{see below };
+  constexpr nullopt_t nullopt(unspecified );
+
+  // 20.6.5, class bad_optional_access
+  class bad_optional_access;
+
+  // 20.6.6, relational operators
+  template <class T>
+  constexpr bool operator==(const optional<T>&, const optional<T>&);
+  template <class T>
+  constexpr bool operator!=(const optional<T>&, const optional<T>&);
+  template <class T>
+  constexpr bool operator<(const optional<T>&, const optional<T>&);
+  template <class T>
+  constexpr bool operator>(const optional<T>&, const optional<T>&);
+  template <class T>
+  constexpr bool operator<=(const optional<T>&, const optional<T>&);
+  template <class T>
+  constexpr bool operator>=(const optional<T>&, const optional<T>&);
+  template <class T> constexpr bool operator==(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator==(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator!=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator!=(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator<(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator<(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator<=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator<=(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator>(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator>(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator>=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator>=(nullopt_t, const optional<T>&) noexcept;
+
+  // 20.6.8, comparison with T
+  template <class T> constexpr bool operator==(const optional<T>&, const T&);
+  template <class T> constexpr bool operator==(const T&, const optional<T>&);
+  template <class T> constexpr bool operator!=(const optional<T>&, const T&);
+  template <class T> constexpr bool operator!=(const T&, const optional<T>&);
+  template <class T> constexpr bool operator<(const optional<T>&, const T&);
+  template <class T> constexpr bool operator<(const T&, const optional<T>&);
+  template <class T> constexpr bool operator<=(const optional<T>&, const T&);
+  template <class T> constexpr bool operator<=(const T&, const optional<T>&);
+  template <class T> constexpr bool operator>(const optional<T>&, const T&);
+  template <class T> constexpr bool operator>(const T&, const optional<T>&);
+  template <class T> constexpr bool operator>=(const optional<T>&, const T&);
+  template <class T> constexpr bool operator>=(const T&, const optional<T>&);
+
+  // 20.6.9, specialized algorithms
+  template <class T> void swap(optional<T>&, optional<T>&) noexcept(see below );
+  template <class T> constexpr optional<see below > make_optional(T&&);
+  template <class T, class... Args>
+    constexpr optional<T> make_optional(Args&&... args);
+  template <class T, class U, class... Args>
+    constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);
+
+  // 20.6.10, hash support
+  template <class T> struct hash;
+  template <class T> struct hash<optional<T>>;
+
+  template <class T> class optional {
+  public:
+    using value_type = T;
+
+    // 20.6.3.1, constructors
+    constexpr optional() noexcept;
+    constexpr optional(nullopt_t) noexcept;
+    optional(const optional &);
+    optional(optional &&) noexcept(see below );
+    template <class... Args> constexpr explicit optional(in_place_t, Args &&...);
+    template <class U, class... Args>
+      constexpr explicit optional(in_place_t, initializer_list<U>, Args &&...);
+    template <class U = T>
+      constexpr EXPLICIT optional(U &&);
+    template <class U>
+      constexpr EXPLICIT optional(const optional<U> &);
+    template <class U>
+      constexpr EXPLICIT optional(optional<U> &&);
+
+    // 20.6.3.2, destructor
+    ~optional();
+
+    // 20.6.3.3, assignment
+    optional &operator=(nullopt_t) noexcept;
+    optional &operator=(const optional &);
+    optional &operator=(optional &&) noexcept(see below );
+    template <class U = T> optional &operator=(U &&);
+    template <class U> optional &operator=(const optional<U> &);
+    template <class U> optional &operator=(optional<U> &&);
+    template <class... Args> void emplace(Args &&...);
+    template <class U, class... Args>
+      void emplace(initializer_list<U>, Args &&...);
+
+    // 20.6.3.4, swap
+    void swap(optional &) noexcept(see below );
+
+    // 20.6.3.5, observers
+    constexpr T const *operator->() const;
+    constexpr T *operator->();
+    constexpr T const &operator*() const &;
+    constexpr T &operator*() &;
+    constexpr T &&operator*() &&;
+    constexpr const T &&operator*() const &&;
+    constexpr explicit operator bool() const noexcept;
+    constexpr bool has_value() const noexcept;
+    constexpr T const &value() const &;
+    constexpr T &value() &;
+    constexpr T &&value() &&;
+    constexpr const T &&value() const &&;
+    template <class U> constexpr T value_or(U &&) const &;
+    template <class U> constexpr T value_or(U &&) &&;
+
+    // 20.6.3.6, modifiers
+    void reset() noexcept;
+
+  private:
+    T *val; // exposition only
+  };
+} // namespace std
+
+*/
+
+#include <__config>
+#include <__debug>
+#include <__functional_base>
+#include <__undef_min_max>
+#include <functional>
+#include <initializer_list>
+#include <new>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+namespace std  // purposefully not using versioning namespace
+{
+
+class _LIBCPP_EXCEPTION_ABI bad_optional_access
+    : public logic_error
+{
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    bad_optional_access() : logic_error("bad optional access") {}
+
+    // Get the key function ~bad_optional_access() into the dylib
+    _LIBCPP_FUNC_VIS
+    virtual ~bad_optional_access() _NOEXCEPT;
+};
+
+}  // std
+
+#if _LIBCPP_STD_VER > 14
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_NORETURN
+inline _LIBCPP_INLINE_VISIBILITY
+void __throw_bad_optional_access() {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+        throw bad_optional_access();
+#else
+        _VSTD::abort();
+#endif
+}
+
+struct nullopt_t
+{
+    struct __secret_tag { _LIBCPP_INLINE_VISIBILITY explicit __secret_tag() = default; };
+    _LIBCPP_INLINE_VISIBILITY constexpr explicit nullopt_t(__secret_tag, __secret_tag) noexcept {}
+};
+
+/* inline */ constexpr nullopt_t nullopt{nullopt_t::__secret_tag{}, nullopt_t::__secret_tag{}};
+
+template <class _Tp, bool = is_trivially_destructible<_Tp>::value>
+struct __optional_destruct_base;
+
+template <class _Tp>
+struct __optional_destruct_base<_Tp, false>
+{
+    typedef _Tp value_type;
+    static_assert(is_object_v<value_type>,
+        "instantiation of optional with a non-object type is undefined behavior");
+    union
+    {
+        char __null_state_;
+        value_type __val_;
+    };
+    bool __engaged_;
+
+    _LIBCPP_INLINE_VISIBILITY
+    ~__optional_destruct_base()
+    {
+        if (__engaged_)
+            __val_.~value_type();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_destruct_base() noexcept
+        :  __null_state_(),
+           __engaged_(false) {}
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_destruct_base(in_place_t, _Args&&... __args)
+        :  __val_(_VSTD::forward<_Args>(__args)...),
+           __engaged_(true) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept
+    {
+        if (__engaged_)
+        {
+            __val_.~value_type();
+            __engaged_ = false;
+        }
+    }
+};
+
+template <class _Tp>
+struct __optional_destruct_base<_Tp, true>
+{
+    typedef _Tp value_type;
+    static_assert(is_object_v<value_type>,
+        "instantiation of optional with a non-object type is undefined behavior");
+    union
+    {
+        char __null_state_;
+        value_type __val_;
+    };
+    bool __engaged_;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_destruct_base() noexcept
+        :  __null_state_(),
+           __engaged_(false) {}
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_destruct_base(in_place_t, _Args&&... __args)
+        :  __val_(_VSTD::forward<_Args>(__args)...),
+           __engaged_(true) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept
+    {
+        if (__engaged_)
+        {
+            __engaged_ = false;
+        }
+    }
+};
+
+template <class _Tp, bool = is_reference<_Tp>::value>
+struct __optional_storage_base : __optional_destruct_base<_Tp>
+{
+    using __base = __optional_destruct_base<_Tp>;
+    using value_type = _Tp;
+    using __base::__base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr bool has_value() const noexcept
+    {
+        return this->__engaged_;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& __get() & noexcept
+    {
+        return this->__val_;
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr const value_type& __get() const& noexcept
+    {
+        return this->__val_;
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& __get() && noexcept
+    {
+        return _VSTD::move(this->__val_);
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr const value_type&& __get() const&& noexcept
+    {
+        return _VSTD::move(this->__val_);
+    }
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct(_Args&&... __args)
+    {
+        _LIBCPP_ASSERT(!has_value(), "__construct called for engaged __optional_storage");
+        ::new((void*)_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Args>(__args)...);
+        this->__engaged_ = true;
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct_from(_That&& __opt)
+    {
+        if (__opt.has_value())
+            __construct(_VSTD::forward<_That>(__opt).__get());
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __assign_from(_That&& __opt)
+    {
+        if (this->__engaged_ == __opt.has_value())
+        {
+            if (this->__engaged_)
+                this->__val_ = _VSTD::forward<_That>(__opt).__get();
+        }
+        else
+        {
+            if (this->__engaged_)
+                this->reset();
+            else
+                __construct(_VSTD::forward<_That>(__opt).__get());
+        }
+    }
+};
+
+// optional<T&> is currently required ill-formed, however it may to be in the
+// future. For this reason it has already been implemented to ensure we can
+// make the change in an ABI compatible manner.
+template <class _Tp>
+struct __optional_storage_base<_Tp, true>
+{
+    using value_type = _Tp;
+    using __raw_type = remove_reference_t<_Tp>;
+    __raw_type* __value_;
+
+    template <class _Up>
+    static constexpr bool __can_bind_reference() {
+        using _RawUp = typename remove_reference<_Up>::type;
+        using _UpPtr = _RawUp*;
+        using _RawTp = typename remove_reference<_Tp>::type;
+        using _TpPtr = _RawTp*;
+        using _CheckLValueArg = integral_constant<bool,
+            (is_lvalue_reference<_Up>::value && is_convertible<_UpPtr, _TpPtr>::value)
+        ||  is_same<_RawUp, reference_wrapper<_RawTp>>::value
+        ||  is_same<_RawUp, reference_wrapper<typename remove_const<_RawTp>::type>>::value
+        >;
+        return (is_lvalue_reference<_Tp>::value && _CheckLValueArg::value)
+            || (is_rvalue_reference<_Tp>::value && !is_lvalue_reference<_Up>::value &&
+                is_convertible<_UpPtr, _TpPtr>::value);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_storage_base() noexcept
+        :  __value_(nullptr) {}
+
+    template <class _UArg>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_storage_base(in_place_t, _UArg&& __uarg)
+        :  __value_(_VSTD::addressof(__uarg))
+    {
+      static_assert(__can_bind_reference<_UArg>(),
+        "Attempted to construct a reference element in tuple from a "
+        "possible temporary");
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept { __value_ = nullptr; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr bool has_value() const noexcept
+      { return __value_ != nullptr; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& __get() const& noexcept
+      { return *__value_; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& __get() const&& noexcept
+      { return _VSTD::forward<value_type>(*__value_); }
+
+    template <class _UArg>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct(_UArg&& __val)
+    {
+        _LIBCPP_ASSERT(!has_value(), "__construct called for engaged __optional_storage");
+        static_assert(__can_bind_reference<_UArg>(),
+            "Attempted to construct a reference element in tuple from a "
+            "possible temporary");
+        __value_ = _VSTD::addressof(__val);
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct_from(_That&& __opt)
+    {
+        if (__opt.has_value())
+            __construct(_VSTD::forward<_That>(__opt).__get());
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __assign_from(_That&& __opt)
+    {
+        if (has_value() == __opt.has_value())
+        {
+            if (has_value())
+                *__value_ = _VSTD::forward<_That>(__opt).__get();
+        }
+        else
+        {
+            if (has_value())
+                reset();
+            else
+                __construct(_VSTD::forward<_That>(__opt).__get());
+        }
+    }
+};
+
+template <class _Tp, bool = is_trivially_copyable<_Tp>::value>
+struct __optional_storage;
+
+template <class _Tp>
+struct __optional_storage<_Tp, true> : __optional_storage_base<_Tp>
+{
+    using __optional_storage_base<_Tp>::__optional_storage_base;
+};
+
+template <class _Tp>
+struct __optional_storage<_Tp, false> : __optional_storage_base<_Tp>
+{
+    using value_type = _Tp;
+    using __optional_storage_base<_Tp>::__optional_storage_base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_storage() = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_storage(const __optional_storage& __opt)
+    {
+        this->__construct_from(__opt);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_storage(__optional_storage&& __opt)
+        noexcept(is_nothrow_move_constructible_v<value_type>)
+    {
+        this->__construct_from(_VSTD::move(__opt));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_storage& operator=(const __optional_storage& __opt)
+    {
+        this->__assign_from(__opt);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_storage& operator=(__optional_storage&& __opt)
+        noexcept(is_nothrow_move_assignable_v<value_type> &&
+                 is_nothrow_move_constructible_v<value_type>)
+    {
+        this->__assign_from(_VSTD::move(__opt));
+        return *this;
+    }
+};
+
+template <class _Tp>
+using __optional_sfinae_ctor_base_t = __sfinae_ctor_base<
+    is_copy_constructible<_Tp>::value,
+    is_move_constructible<_Tp>::value
+>;
+
+template <class _Tp>
+using __optional_sfinae_assign_base_t = __sfinae_assign_base<
+    (is_copy_constructible<_Tp>::value && is_copy_assignable<_Tp>::value),
+    (is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value)
+>;
+
+template <class _Tp>
+class optional
+    : private __optional_storage<_Tp>
+    , private __optional_sfinae_ctor_base_t<_Tp>
+    , private __optional_sfinae_assign_base_t<_Tp>
+{
+    using __base = __optional_storage<_Tp>;
+public:
+    using value_type = _Tp;
+
+private:
+     // Disable the reference extension using this static assert.
+    static_assert(!is_same_v<value_type, in_place_t>,
+        "instantiation of optional with in_place_t is ill-formed");
+    static_assert(!is_same_v<__uncvref_t<value_type>, nullopt_t>,
+        "instantiation of optional with nullopt_t is ill-formed");
+    static_assert(!is_reference_v<value_type>,
+        "instantiation of optional with a reference type is ill-formed");
+    static_assert(is_destructible_v<value_type>,
+        "instantiation of optional with a non-destructible type is ill-formed");
+
+    // LWG2756: conditionally explicit conversion from _Up
+    struct _CheckOptionalArgsConstructor {
+      template <class _Up>
+      static constexpr bool __enable_implicit() {
+          return is_constructible_v<_Tp, _Up&&> &&
+                 is_convertible_v<_Up&&, _Tp>;
+      }
+
+      template <class _Up>
+      static constexpr bool __enable_explicit() {
+          return is_constructible_v<_Tp, _Up&&> &&
+                 !is_convertible_v<_Up&&, _Tp>;
+      }
+    };
+    template <class _Up>
+    using _CheckOptionalArgsCtor = conditional_t<
+        !is_same_v<in_place_t, _Up> &&
+        !is_same_v<decay_t<_Up>, optional>,
+        _CheckOptionalArgsConstructor,
+        __check_tuple_constructor_fail
+    >;
+    template <class _QualUp>
+    struct _CheckOptionalLikeConstructor {
+      template <class _Up, class _Opt = optional<_Up>>
+      using __check_constructible_from_opt = __lazy_or<
+          is_constructible<_Tp, _Opt&>,
+          is_constructible<_Tp, _Opt const&>,
+          is_constructible<_Tp, _Opt&&>,
+          is_constructible<_Tp, _Opt const&&>,
+          is_convertible<_Opt&, _Tp>,
+          is_convertible<_Opt const&, _Tp>,
+          is_convertible<_Opt&&, _Tp>,
+          is_convertible<_Opt const&&, _Tp>
+      >;
+      template <class _Up, class _Opt = optional<_Up>>
+      using __check_assignable_from_opt = __lazy_or<
+          is_assignable<_Tp&, _Opt&>,
+          is_assignable<_Tp&, _Opt const&>,
+          is_assignable<_Tp&, _Opt&&>,
+          is_assignable<_Tp&, _Opt const&&>
+      >;
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_implicit() {
+          return is_convertible<_QUp, _Tp>::value &&
+              !__check_constructible_from_opt<_Up>::value;
+      }
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_explicit() {
+          return !is_convertible<_QUp, _Tp>::value &&
+              !__check_constructible_from_opt<_Up>::value;
+      }
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_assign() {
+          // Construction and assignability of _Qup to _Tp has already been
+          // checked.
+          return !__check_constructible_from_opt<_Up>::value &&
+              !__check_assignable_from_opt<_Up>::value;
+      }
+    };
+
+    template <class _Up, class _QualUp>
+    using _CheckOptionalLikeCtor = conditional_t<
+      __lazy_and<
+          __lazy_not<is_same<_Up, _Tp>>,
+          is_constructible<_Tp, _QualUp>
+      >::value,
+      _CheckOptionalLikeConstructor<_QualUp>,
+      __check_tuple_constructor_fail
+    >;
+    template <class _Up, class _QualUp>
+    using _CheckOptionalLikeAssign = conditional_t<
+      __lazy_and<
+          __lazy_not<is_same<_Up, _Tp>>,
+          is_constructible<_Tp, _QualUp>,
+          is_assignable<_Tp&, _QualUp>
+      >::value,
+      _CheckOptionalLikeConstructor<_QualUp>,
+      __check_tuple_constructor_fail
+    >;
+public:
+
+    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
+    _LIBCPP_INLINE_VISIBILITY optional(const optional&) = default;
+    _LIBCPP_INLINE_VISIBILITY optional(optional&&) = default;
+    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
+
+    template <class... _Args, class = enable_if_t<
+        is_constructible_v<value_type, _Args...>>
+    >
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(in_place_t, _Args&&... __args)
+        : __base(in_place, _VSTD::forward<_Args>(__args)...) {}
+
+    template <class _Up, class... _Args, class = enable_if_t<
+        is_constructible_v<value_type, initializer_list<_Up>&, _Args...>>
+    >
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
+        : __base(in_place, __il, _VSTD::forward<_Args>(__args)...) {}
+
+    template <class _Up = value_type, enable_if_t<
+        _CheckOptionalArgsCtor<_Up>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr optional(_Up&& __v)
+        : __base(in_place, _VSTD::forward<_Up>(__v)) {}
+
+    template <class _Up, enable_if_t<
+        _CheckOptionalArgsCtor<_Up>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(_Up&& __v)
+        : __base(in_place, _VSTD::forward<_Up>(__v)) {}
+
+    // LWG2756: conditionally explicit conversion from const optional<_Up>&
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional(const optional<_Up>& __v)
+    {
+        this->__construct_from(__v);
+    }
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    explicit optional(const optional<_Up>& __v)
+    {
+        this->__construct_from(__v);
+    }
+
+    // LWG2756: conditionally explicit conversion from optional<_Up>&&
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional(optional<_Up>&& __v)
+    {
+        this->__construct_from(_VSTD::move(__v));
+    }
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    explicit optional(optional<_Up>&& __v)
+    {
+        this->__construct_from(_VSTD::move(__v));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    optional& operator=(nullopt_t) noexcept
+    {
+        reset();
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY optional& operator=(const optional&) = default;
+    _LIBCPP_INLINE_VISIBILITY optional& operator=(optional&&) = default;
+
+    // LWG2756
+    template <class _Up = value_type,
+              class = enable_if_t
+                      <
+                          !is_same_v<_Up, optional> &&
+                          !(is_same_v<_Up, value_type> && is_scalar_v<value_type>) &&
+                          is_constructible_v<value_type, _Up> &&
+                          is_assignable_v<value_type&, _Up>
+                      >
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(_Up&& __v)
+    {
+        if (this->has_value())
+            this->__get() = _VSTD::forward<_Up>(__v);
+        else
+            this->__construct(_VSTD::forward<_Up>(__v));
+        return *this;
+    }
+
+    // LWG2756
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeAssign<_Up, _Up const&>::template __enable_assign<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(const optional<_Up>& __v)
+    {
+        this->__assign_from(__v);
+        return *this;
+    }
+
+    // LWG2756
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_assign<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(optional<_Up>&& __v)
+    {
+        this->__assign_from(_VSTD::move(__v));
+        return *this;
+    }
+
+    template <class... _Args,
+              class = enable_if_t
+                      <
+                          is_constructible_v<value_type, _Args...>
+                      >
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    void
+    emplace(_Args&&... __args)
+    {
+        reset();
+        this->__construct(_VSTD::forward<_Args>(__args)...);
+    }
+
+    template <class _Up, class... _Args,
+              class = enable_if_t
+                      <
+                          is_constructible_v<value_type, initializer_list<_Up>&, _Args...>
+                      >
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    void
+    emplace(initializer_list<_Up> __il, _Args&&... __args)
+    {
+        reset();
+        this->__construct(__il, _VSTD::forward<_Args>(__args)...);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void swap(optional& __opt)
+        noexcept(is_nothrow_move_constructible_v<value_type> &&
+                 is_nothrow_swappable_v<value_type>)
+    {
+        if (this->has_value() == __opt.has_value())
+        {
+            using _VSTD::swap;
+            if (this->has_value())
+                swap(this->__get(), __opt.__get());
+        }
+        else
+        {
+            if (this->has_value())
+            {
+                __opt.__construct(_VSTD::move(this->__get()));
+                reset();
+            }
+            else
+            {
+                this->__construct(_VSTD::move(__opt.__get()));
+                __opt.reset();
+            }
+        }
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    add_pointer_t<value_type const>
+    operator->() const
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return _VSTD::addressof(this->__get());
+#else
+        return __operator_arrow(__has_operator_addressof<value_type>{}, this->__get());
+#endif
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    add_pointer_t<value_type>
+    operator->()
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return _VSTD::addressof(this->__get());
+#else
+        return __operator_arrow(__has_operator_addressof<value_type>{}, this->__get());
+#endif
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    const value_type&
+    operator*() const&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    value_type&
+    operator*() &
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    value_type&&
+    operator*() &&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    const value_type&&
+    operator*() const&&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit operator bool() const noexcept { return has_value(); }
+
+    using __base::has_value;
+    using __base::__get;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type const& value() const&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& value() &
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& value() &&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type const&& value() const&&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return _VSTD::move(this->__get());
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type value_or(_Up&& __v) const&
+    {
+        static_assert(is_copy_constructible_v<value_type>,
+                      "optional<T>::value_or: T must be copy constructible");
+        static_assert(is_convertible_v<_Up, value_type>,
+                      "optional<T>::value_or: U must be convertible to T");
+        return this->has_value() ? this->__get() :
+                                  static_cast<value_type>(_VSTD::forward<_Up>(__v));
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    value_type value_or(_Up&& __v) &&
+    {
+        static_assert(is_move_constructible_v<value_type>,
+                      "optional<T>::value_or: T must be move constructible");
+        static_assert(is_convertible_v<_Up, value_type>,
+                      "optional<T>::value_or: U must be convertible to T");
+        return this->has_value() ? _VSTD::move(this->__get()) :
+                                  static_cast<value_type>(_VSTD::forward<_Up>(__v));
+    }
+
+    using __base::reset;
+
+private:
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    static _Up*
+    __operator_arrow(true_type, _Up& __x)
+    {
+        return _VSTD::addressof(__x);
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    static constexpr _Up*
+    __operator_arrow(false_type, _Up& __x)
+    {
+        return &__x;
+    }
+};
+
+// Comparisons between optionals
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator==(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (static_cast<bool>(__x) != static_cast<bool>(__y))
+        return false;
+    if (!static_cast<bool>(__x))
+        return true;
+    return *__x == *__y;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator!=(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (static_cast<bool>(__x) != static_cast<bool>(__y))
+        return true;
+    if (!static_cast<bool>(__x))
+        return false;
+    return *__x != *__y;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (!static_cast<bool>(__y))
+        return false;
+    if (!static_cast<bool>(__x))
+        return true;
+    return *__x < *__y;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (!static_cast<bool>(__x))
+        return false;
+    if (!static_cast<bool>(__y))
+        return true;
+    return *__x > *__y;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<=(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (!static_cast<bool>(__x))
+        return true;
+    if (!static_cast<bool>(__y))
+        return false;
+    return *__x <= *__y;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>=(const optional<_Tp>& __x, const optional<_Tp>& __y)
+{
+    if (!static_cast<bool>(__y))
+        return true;
+    if (!static_cast<bool>(__x))
+        return false;
+    return *__x >= *__y;
+}
+
+// Comparisons with nullopt
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator==(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator==(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator!=(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator!=(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<(const optional<_Tp>&, nullopt_t) noexcept
+{
+    return false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<=(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<=(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>=(const optional<_Tp>&, nullopt_t) noexcept
+{
+    return true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>=(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+// Comparisons with T
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator==(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x == __v : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator==(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v == *__x : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator!=(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x != __v : true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator!=(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v != *__x : true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x < __v : true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v < *__x : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<=(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x <= __v : true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator<=(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v <= *__x : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x > __v : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v > *__x : true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>=(const optional<_Tp>& __x, const _Tp& __v)
+{
+    return static_cast<bool>(__x) ? *__x >= __v : false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Tp&>()), bool>,
+    bool
+>
+operator>=(const _Tp& __v, const optional<_Tp>& __x)
+{
+    return static_cast<bool>(__x) ? __v >= *__x : true;
+}
+
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+enable_if_t<
+    is_move_constructible_v<_Tp> && is_swappable_v<_Tp>,
+    void
+>
+swap(optional<_Tp>& __x, optional<_Tp>& __y) noexcept(noexcept(__x.swap(__y)))
+{
+    __x.swap(__y);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<decay_t<_Tp>> make_optional(_Tp&& __v)
+{
+    return optional<decay_t<_Tp>>(_VSTD::forward<_Tp>(__v));
+}
+
+template <class _Tp, class... _Args>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<_Tp> make_optional(_Args&&... __args)
+{
+    return optional<_Tp>(in_place, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _Tp, class _Up, class... _Args>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<_Tp> make_optional(initializer_list<_Up> __il,  _Args&&... __args)
+{
+    return optional<_Tp>(in_place, __il, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY hash<optional<_Tp> >
+{
+    typedef optional<_Tp> argument_type;
+    typedef size_t        result_type;
+
+    _LIBCPP_INLINE_VISIBILITY
+    result_type operator()(const argument_type& __opt) const _NOEXCEPT
+    {
+        return static_cast<bool>(__opt) ? hash<_Tp>()(*__opt) : 0;
+    }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP_STD_VER > 14
+
+#endif  // _LIBCPP_OPTIONAL

include/type_traits

 template <bool, class _Tp = void> struct _LIBCPP_TYPE_VIS_ONLY enable_if {};
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY enable_if<true, _Tp> {typedef _Tp type;};
 
 #if _LIBCPP_STD_VER > 11
 template <bool _Bp, class _Tp = void> using enable_if_t = typename enable_if<_Bp, _Tp>::type;
 #endif
 
 // addressof
-#if __has_builtin(__builtin_addressof) || _GNUC_VER >= 700
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 
 template <class _Tp>
 inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 _LIBCPP_NO_CFI _LIBCPP_INLINE_VISIBILITY
 _Tp*
 addressof(_Tp& __x) _NOEXCEPT
 {
     return __builtin_addressof(__x);
 }
 
 #else
 
 template <class _Tp>
 inline _LIBCPP_NO_CFI _LIBCPP_INLINE_VISIBILITY
 _Tp*
 addressof(_Tp& __x) _NOEXCEPT
 {
     return (_Tp*)&reinterpret_cast<const volatile char&>(__x);
 }
 
-#endif // __has_builtin(__builtin_addressof)
+#endif // _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 
 #if defined(_LIBCPP_HAS_OBJC_ARC) && !defined(_LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF)
 // Objective-C++ Automatic Reference Counting uses qualified pointers
 // that require special addressof() signatures. When
 // _LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF is defined, the compiler
 // itself is providing these definitions. Otherwise, we provide them.
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY

src/optional.cpp

 //===------------------------ optional.cpp --------------------------------===//
 //
 //                     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.
 //
 //===----------------------------------------------------------------------===//
 
+#include "optional"
 #include "experimental/optional"
 
-_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
+namespace std
+{
 
-#ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+bad_optional_access::~bad_optional_access() _NOEXCEPT = default;
 
-bad_optional_access::~bad_optional_access() _NOEXCEPT {}
+} // std
 
-#else
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 
 bad_optional_access::~bad_optional_access() _NOEXCEPT = default;
 
-#endif
-
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL

test/libcxx/utilities/optional/optional.object/optional.object.assign/copy.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+// XFAIL: libcpp-no-exceptions
+// <optional>
+
+// optional<T>& operator=(const optional<T>& rhs);
+
+#include <optional>
+#include <string>
+#include <type_traits>
+
+using std::optional;
+
+struct X {};
+
+struct Y
+{
+    Y() = default;
+    Y& operator=(const Y&) { return *this; }
+};
+
+struct Z1
+{
+    Z1() = default;
+    Z1(Z1&&) = default;
+    Z1(const Z1&) = default;
+    Z1& operator=(Z1&&) = default;
+    Z1& operator=(const Z1&) = delete;
+};
+
+struct Z2
+{
+    Z2() = default;
+    Z2(Z2&&) = default;
+    Z2(const Z2&) = delete;
+    Z2& operator=(Z2&&) = default;
+    Z2& operator=(const Z2&) = default;
+};
+
+#if __cplusplus >= 201402
+template <class T>
+constexpr bool
+test()
+{
+    optional<T> opt;
+    optional<T> opt2;
+    opt = opt2;
+    return true;
+}
+#endif
+
+int main()
+{
+    {
+        using T = int;
+        static_assert((std::is_trivially_copy_assignable<optional<T>>::value), "");
+#if __cplusplus >= 201402
+        static_assert(test<T>(), "");
+#endif
+    }
+    {
+        using T = X;
+        static_assert((std::is_trivially_copy_assignable<optional<T>>::value), "");
+#if __cplusplus >= 201402
+        static_assert(test<T>(), "");
+#endif
+    }
+    static_assert(!(std::is_trivially_copy_assignable<optional<Y>>::value), "");
+    static_assert(!(std::is_trivially_copy_assignable<optional<std::string>>::value), "");
+
+    static_assert(!(std::is_copy_assignable<optional<Z1>>::value), "");
+    static_assert(!(std::is_copy_assignable<optional<Z2>>::value), "");
+}

test/libcxx/utilities/optional/optional.object/optional.object.assign/move.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+// XFAIL: libcpp-no-exceptions
+// <optional>
+
+// optional<T>& operator=(optional<T>&& rhs);
+
+#include <optional>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+using std::optional;
+
+struct X {};
+
+struct Y
+{
+    Y() = default;
+    Y& operator=(Y&&) { return *this; }
+};
+
+struct Z1
+{
+    Z1() = default;
+    Z1(Z1&&) = default;
+    Z1& operator=(Z1&&) = delete;
+};
+
+struct Z2
+{
+    Z2() = default;
+    Z2(Z2&&) = delete;
+    Z2& operator=(Z2&&) = default;
+};
+
+#if __cplusplus >= 201402
+template <class T>
+constexpr bool
+test()
+{
+    optional<T> opt;
+    optional<T> opt2;
+    opt = std::move(opt2);
+    return true;
+}
+#endif
+
+int main()
+{
+    {
+        using T = int;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+#if __cplusplus >= 201402
+        static_assert(test<T>(), "");
+#endif
+    }
+    {
+        using T = X;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+#if __cplusplus >= 201402
+        static_assert(test<T>(), "");
+#endif
+    }
+    static_assert(!(std::is_trivially_move_assignable<optional<Y>>::value), "");
+    static_assert(!(std::is_trivially_move_assignable<optional<std::string>>::value), "");
+
+    static_assert(!(std::is_move_assignable<optional<Z1>>::value), "");
+    static_assert(!(std::is_move_assignable<optional<Z2>>::value), "");
+}

test/libcxx/utilities/optional/optional.object/optional.object.ctor/copy.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+// XFAIL: libcpp-no-exceptions
+// <optional>
+
+// optional(const optional<T>& rhs);
+
+#include <optional>
+#include <string>
+#include <type_traits>
+
+using std::optional;
+
+struct X {};
+
+struct Y
+{
+    Y() = default;
+    Y(const Y&) {}
+};
+
+struct Z
+{
+    Z() = default;
+    Z(Z&&) = delete;
+    Z(const Z&) = delete;
+    Z& operator=(Z&&) = delete;
+    Z& operator=(const Z&) = delete;
+};
+
+int main()
+{
+    {
+        using T = int;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+        constexpr optional<T> opt;
+        constexpr optional<T> opt2 = opt;
+        (void)opt2;
+    }
+    {
+        using T = X;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+        constexpr optional<T> opt;
+        constexpr optional<T> opt2 = opt;
+        (void)opt2;
+    }
+    static_assert(!(std::is_trivially_copy_constructible<optional<Y>>::value), "");
+    static_assert(!(std::is_trivially_copy_constructible<optional<std::string>>::value), "");
+
+    static_assert(!(std::is_copy_constructible<optional<Z>>::value), "");
+}

test/libcxx/utilities/optional/optional.object/optional.object.ctor/move.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+// XFAIL: libcpp-no-exceptions
+// <optional>
+
+// optional(optional<T>&& rhs);
+
+#include <optional>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+using std::optional;
+
+struct X {};
+
+struct Y
+{
+    Y() = default;
+    Y(Y&&) {}
+};
+
+struct Z
+{
+    Z() = default;
+    Z(Z&&) = delete;
+    Z(const Z&) = delete;
+    Z& operator=(Z&&) = delete;
+    Z& operator=(const Z&) = delete;
+};
+
+int main()
+{
+    {
+        using T = int;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+        constexpr optional<T> opt;
+        constexpr optional<T> opt2 = std::move(opt);
+        (void)opt2;
+    }
+    {
+        using T = X;
+        static_assert((std::is_trivially_copy_constructible<optional<T>>::value), "");
+        constexpr optional<T> opt;
+        constexpr optional<T> opt2 = std::move(opt);
+        (void)opt2;
+    }
+    static_assert(!(std::is_trivially_move_constructible<optional<Y>>::value), "");
+    static_assert(!(std::is_trivially_move_constructible<optional<std::string>>::value), "");
+
+    static_assert(!(std::is_move_constructible<optional<Z>>::value), "");
+}

test/libcxx/utilities/optional/optional.object/special_member_gen.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "archetypes.hpp"
+
+template <class T>
+struct SpecialMemberTest {
+    using O = std::optional<T>;
+
+    template <template <class> class TestMF>
+    static constexpr bool check_same() {
+        return TestMF<O>::value == TestMF<T>::value;
+    }
+
+    // Test that optional inherits the correct trivial/non-trivial members
+    static_assert(check_same<std::is_trivially_destructible>(), "");
+    static_assert(check_same<std::is_trivially_copyable>(), "");
+};
+
+template <class ...Args> static void sink(Args&&...) {}
+
+template <class ...TestTypes>
+struct DoTestsMetafunction {
+    DoTestsMetafunction() { sink(SpecialMemberTest<TestTypes>{}...); }
+};
+
+struct TrivialMoveNonTrivialCopy {
+    TrivialMoveNonTrivialCopy() = default;
+    TrivialMoveNonTrivialCopy(const TrivialMoveNonTrivialCopy&) {}
+    TrivialMoveNonTrivialCopy(TrivialMoveNonTrivialCopy&&) = default;
+    TrivialMoveNonTrivialCopy& operator=(const TrivialMoveNonTrivialCopy&) { return *this; }
+    TrivialMoveNonTrivialCopy& operator=(TrivialMoveNonTrivialCopy&&) = default;
+};
+
+struct TrivialCopyNonTrivialMove {
+    TrivialCopyNonTrivialMove() = default;
+    TrivialCopyNonTrivialMove(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove(TrivialCopyNonTrivialMove&&) {}
+    TrivialCopyNonTrivialMove& operator=(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove& operator=(TrivialCopyNonTrivialMove&&) { return *this; }
+};
+
+int main()
+{
+    sink(
+        ImplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        ExplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonLiteralTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonTrivialTypes::ApplyTypes<DoTestsMetafunction>{},
+        DoTestsMetafunction<TrivialMoveNonTrivialCopy, TrivialCopyNonTrivialMove>{}
+    );
+}

test/libcxx/utilities/optional/version.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <optional>
+
+#include <optional>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main()
+{
+}

test/std/utilities/meta/meta.unary/meta.unary.prop/is_nothrow_swappable_with.pass.cpp

using namespace MyNS;
         // to the type. Instead it is up to the user.
         static_assert(!std::is_nothrow_swappable_with<int, int>::value, "");
         static_assert(std::is_nothrow_swappable_with<int&, int&>::value, "");
         static_assert(std::is_nothrow_swappable_with<M, M>::value, "");
         static_assert(std::is_swappable_with<A&, A&>::value &&
                       !std::is_nothrow_swappable_with<A&, A&>::value, "");
     }
     {
-        // test that hetrogenius swap is allowed only if both 'swap(A, B)' and
+        // test that heterogeneous swap is allowed only if both 'swap(A, B)' and
         // 'swap(B, A)' are valid.
         static_assert(std::is_nothrow_swappable_with<A&, B&>::value, "");
         static_assert(!std::is_nothrow_swappable_with<A&, C&>::value &&
                       std::is_swappable_with<A&, C&>::value, "");
         static_assert(!std::is_nothrow_swappable_with<D&, C&>::value, "");
     }
     {
         // test we guard against cv void inputs as required.

test/std/utilities/optional/optional.hash/hash.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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> struct hash<optional<T>>;
+
+#include <optional>
+#include <string>
+#include <memory>
+#include <cassert>
+
+
+int main()
+{
+    using std::optional;
+    const std::size_t nullopt_hash =
+        std::hash<optional<double>>{}(optional<double>{});
+
+    {
+        typedef int T;
+        optional<T> opt;
+        assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
+        opt = 2;
+        assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));
+    }
+    {
+        typedef std::string T;
+        optional<T> opt;
+        assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
+        opt = std::string("123");
+        assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));
+    }
+    {
+        typedef std::unique_ptr<int> T;
+        optional<T> opt;
+        assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
+        opt = std::unique_ptr<int>(new int(3));
+        assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));
+    }
+}

test/std/utilities/optional/optional.bad_optional_access/default.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// class bad_optional_access is default constructible
+
+#include <optional>
+#include <type_traits>
+
+int main()
+{
+    using std::bad_optional_access;
+    bad_optional_access ex;
+}

test/std/utilities/optional/optional.bad_optional_access/derive.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// class bad_optional_access : public logic_error
+
+#include <optional>
+#include <type_traits>
+
+int main()
+{
+    using std::bad_optional_access;
+
+    static_assert(std::is_base_of<std::logic_error, bad_optional_access>::value, "");
+    static_assert(std::is_convertible<bad_optional_access*, std::logic_error*>::value, "");
+}

test/std/utilities/optional/optional.comp_with_t/equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator==(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator == ( const X &lhs, const X &rhs )
+    { return lhs.i_ == rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert ( !(o1 == T(1)), "" );
+    static_assert (  (o2 == T(1)), "" );
+    static_assert ( !(o3 == T(1)), "" );
+    static_assert (  (o3 == T(2)), "" );
+    static_assert (  (o3 == val),  "" );
+
+    static_assert ( !(T(1) == o1), "" );
+    static_assert (  (T(1) == o2), "" );
+    static_assert ( !(T(1) == o3), "" );
+    static_assert (  (T(2) == o3), "" );
+    static_assert (  (val  == o3), "" );
+    }
+}

test/std/utilities/optional/optional.comp_with_t/greater.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator>(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator > ( const X &lhs, const X &rhs )
+    { return lhs.i_ > rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert ( !(o1 > T(1)), "" );
+    static_assert ( !(o2 > T(1)), "" );  // equal
+    static_assert (  (o3 > T(1)), "" );
+    static_assert ( !(o2 >  val), "" );
+    static_assert ( !(o3 >  val), "" );  // equal
+    static_assert ( !(o3 > T(3)), "" );
+
+    static_assert (   (T(1) > o1), "" );
+    static_assert (  !(T(1) > o2), "" ); // equal
+    static_assert (  !(T(1) > o3), "" );
+    static_assert (   (val  > o2), "" );
+    static_assert (  !(val  > o3), "" ); // equal
+    static_assert (   (T(3) > o3), "" );
+    }
+}

test/std/utilities/optional/optional.comp_with_t/greater_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator>=(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator >= ( const X &lhs, const X &rhs )
+    { return lhs.i_ >= rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert ( !(o1 >= T(1)), "" );
+    static_assert (  (o2 >= T(1)), "" );  // equal
+    static_assert (  (o3 >= T(1)), "" );
+    static_assert ( !(o2 >=  val), "" );
+    static_assert (  (o3 >=  val), "" );  // equal
+    static_assert ( !(o3 >= T(3)), "" );
+
+    static_assert (   (T(1) >= o1), "" );
+    static_assert (   (T(1) >= o2), "" ); // equal
+    static_assert (  !(T(1) >= o3), "" );
+    static_assert (   (val  >= o2), "" );
+    static_assert (   (val  >= o3), "" ); // equal
+    static_assert (   (T(3) >= o3), "" );
+    }
+}

test/std/utilities/optional/optional.comp_with_t/less_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator<=(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator <= ( const X &lhs, const X &rhs )
+    { return lhs.i_ <= rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert (  (o1 <= T(1)), "" );
+    static_assert (  (o2 <= T(1)), "" );  // equal
+    static_assert ( !(o3 <= T(1)), "" );
+    static_assert (  (o2 <=  val), "" );
+    static_assert (  (o3 <=  val), "" );  // equal
+    static_assert (  (o3 <= T(3)), "" );
+
+    static_assert (  !(T(1) <= o1), "" );
+    static_assert (   (T(1) <= o2), "" ); // equal
+    static_assert (   (T(1) <= o3), "" );
+    static_assert (  !(val  <= o2), "" );
+    static_assert (   (val  <= o3), "" ); // equal
+    static_assert (  !(T(3) <= o3), "" );
+    }
+}

test/std/utilities/optional/optional.comp_with_t/less_than.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator<(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator < ( const X &lhs, const X &rhs )
+    { return lhs.i_ < rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert (  (o1 < T(1)), "" );
+    static_assert ( !(o2 < T(1)), "" );  // equal
+    static_assert ( !(o3 < T(1)), "" );
+    static_assert (  (o2 <  val), "" );
+    static_assert ( !(o3 <  val), "" );  // equal
+    static_assert (  (o3 < T(3)), "" );
+
+    static_assert (  !(T(1) < o1), "" );
+    static_assert (  !(T(1) < o2), "" ); // equal
+    static_assert (   (T(1) < o3), "" );
+    static_assert (  !(val  < o2), "" );
+    static_assert (  !(val  < o3), "" ); // equal
+    static_assert (  !(T(3) < o3), "" );
+    }
+}

test/std/utilities/optional/optional.comp_with_t/not_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const T& v);
+// template <class T> constexpr bool operator!=(const T& v, const optional<T>& x);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator != ( const X &lhs, const X &rhs )
+    { return lhs.i_ != rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr T val(2);
+    constexpr O o1;       // disengaged
+    constexpr O o2{1};    // engaged
+    constexpr O o3{val};  // engaged
+
+    static_assert (  (o1 != T(1)), "" );
+    static_assert ( !(o2 != T(1)), "" );
+    static_assert (  (o3 != T(1)), "" );
+    static_assert ( !(o3 != T(2)), "" );
+    static_assert ( !(o3 != val),  "" );
+
+    static_assert (  (T(1) != o1), "" );
+    static_assert ( !(T(1) != o2), "" );
+    static_assert (  (T(1) != o3), "" );
+    static_assert ( !(T(2) != o3), "" );
+    static_assert ( !(val  != o3), "" );
+    }
+}

test/std/utilities/optional/optional.nullops/equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullops/greater.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullops/greater_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullops/less_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullops/less_than.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullops/not_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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), "");
+    }
+}

test/std/utilities/optional/optional.nullopt/not_brace_initializable.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 = {};
+}

test/std/utilities/optional/optional.nullopt/nullopt_t.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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};
+// constexpr nullopt_t nullopt(unspecified);
+
+#include <optional>
+#include <type_traits>
+
+using std::optional;
+using std::nullopt_t;
+using std::nullopt;
+
+constexpr
+int
+test(const nullopt_t&)
+{
+    return 3;
+}
+
+int main()
+{
+    static_assert((std::is_class<nullopt_t>::value), "");
+    static_assert((std::is_empty<nullopt_t>::value), "");
+    static_assert((std::is_literal_type<nullopt_t>::value), "");
+    static_assert((!std::is_default_constructible<nullopt_t>::value), "");
+
+    static_assert(test(nullopt) == 3, "");
+}

test/std/utilities/optional/optional.object/optional.object.assign/assign_value.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U> optional<T>& operator=(U&& v);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+#include <memory>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+struct ThrowAssign {
+  static int dtor_called;
+  ThrowAssign() = default;
+  ThrowAssign(int) { TEST_THROW(42); }
+  ThrowAssign& operator=(int) {
+      TEST_THROW(42);
+  }
+  ~ThrowAssign() { ++dtor_called; }
+};
+int ThrowAssign::dtor_called = 0;
+
+template <class T, class Arg = T, bool Expect = true>
+void assert_assignable() {
+    static_assert(std::is_assignable<optional<T>&, Arg>::value == Expect, "");
+    static_assert(!std::is_assignable<const optional<T>&, Arg>::value, "");
+}
+
+struct MismatchType {
+  explicit MismatchType(int) {}
+  explicit MismatchType(char*) {}
+  explicit MismatchType(int*) = delete;
+  MismatchType& operator=(int) { return *this; }
+  MismatchType& operator=(int*) { return *this; }
+  MismatchType& operator=(char*) = delete;
+};
+
+void test_sfinae() {
+    using I = TestTypes::TestType;
+    using E = ExplicitTestTypes::TestType;
+    assert_assignable<int>();
+    assert_assignable<int, int&>();
+    assert_assignable<int, int const&>();
+    // Implicit test type
+    assert_assignable<I, I const&>();
+    assert_assignable<I, I&&>();
+    assert_assignable<I, int>();
+    assert_assignable<I, void*, false>();
+    // Explicit test type
+    assert_assignable<E, E const&>();
+    assert_assignable<E, E &&>();
+    assert_assignable<E, int>();
+    assert_assignable<E, void*, false>();
+    // Mismatch type
+    assert_assignable<MismatchType, int>();
+    assert_assignable<MismatchType, int*, false>();
+    assert_assignable<MismatchType, char*, false>();
+}
+
+void test_with_test_type()
+{
+    using T = TestTypes::TestType;
+    T::reset();
+    { // to empty
+        optional<T> opt;
+        opt = 3;
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(3));
+    }
+    { // to existing
+        optional<T> opt(42);
+        T::reset_constructors();
+        opt = 3;
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 1);
+        assert(T::value_assigned == 1);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(3));
+    }
+    { // test default argument
+        optional<T> opt;
+        T::reset_constructors();
+        opt = {1, 2};
+        assert(T::alive == 1);
+        assert(T::constructed == 2);
+        assert(T::value_constructed == 1);
+        assert(T::move_constructed == 1);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1, 2));
+    }
+    { // test default argument
+        optional<T> opt(42);
+        T::reset_constructors();
+        opt = {1, 2};
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::assigned == 1);
+        assert(T::move_assigned == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1, 2));
+    }
+    { // test default argument
+        optional<T> opt;
+        T::reset_constructors();
+        opt = {1};
+        assert(T::alive == 1);
+        assert(T::constructed == 2);
+        assert(T::value_constructed == 1);
+        assert(T::move_constructed == 1);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1));
+    }
+    { // test default argument
+        optional<T> opt(42);
+        T::reset_constructors();
+        opt = {};
+        assert(static_cast<bool>(opt) == false);
+        assert(T::alive == 0);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 1);
+    }
+}
+
+template <class T, class Value = int>
+void test_with_type() {
+    { // to empty
+        optional<T> opt;
+        opt = Value(3);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(3));
+    }
+    { // to existing
+        optional<T> opt(Value(42));
+        opt = Value(3);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(3));
+    }
+    { // test const
+        optional<T> opt(Value(42));
+        const T t(Value(3));
+        opt = t;
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(3));
+    }
+    { // test default argument
+        optional<T> opt;
+        opt = {Value(1)};
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1));
+    }
+    { // test default argument
+        optional<T> opt(Value(42));
+        opt = {};
+        assert(static_cast<bool>(opt) == false);
+    }
+}
+
+template <class T>
+void test_with_type_multi() {
+    test_with_type<T>();
+    { // test default argument
+        optional<T> opt;
+        opt = {1, 2};
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1, 2));
+    }
+    { // test default argument
+        optional<T> opt(42);
+        opt = {1, 2};
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1, 2));
+    }
+}
+
+void test_throws()
+{
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    using T = ThrowAssign;
+    {
+        using T = ThrowAssign;
+        optional<T> opt;
+        try {
+            opt = 42;
+            assert(false);
+        } catch (int) {}
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(T::dtor_called == 0);
+    {
+        T::dtor_called = 0;
+        optional<T> opt(std::in_place);
+        try {
+            opt = 42;
+            assert(false);
+        } catch (int) {}
+        assert(static_cast<bool>(opt) == true);
+        assert(T::dtor_called == 0);
+    }
+    assert(T::dtor_called == 1);
+#endif
+}
+
+enum MyEnum { Zero, One, Two, Three, FortyTwo = 42 };
+
+using Fn = void(*)();
+
+int main()
+{
+    test_sfinae();
+    // Test with instrumented type
+    test_with_test_type();
+    // Test with various scalar types
+    test_with_type<int>();
+    test_with_type<MyEnum, MyEnum>();
+    test_with_type<int, MyEnum>();
+    test_with_type<Fn, Fn>();
+    // Test types with multi argument constructors
+    test_with_type_multi<ConstexprTestTypes::TestType>();
+    test_with_type_multi<TrivialTestTypes::TestType>();
+    // Test move only types
+    {
+        optional<std::unique_ptr<int>> opt;
+        opt = std::unique_ptr<int>(new int(3));
+        assert(static_cast<bool>(opt) == true);
+        assert(**opt == 3);
+    }
+    {
+        optional<std::unique_ptr<int>> opt(std::unique_ptr<int>(new int(2)));
+        opt = std::unique_ptr<int>(new int(3));
+        assert(static_cast<bool>(opt) == true);
+        assert(**opt == 3);
+    }
+    test_throws();
+}

test/std/utilities/optional/optional.object/optional.object.assign/const_optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// From LWG2451:
+// template<class U>
+//   optional<T>& operator=(const optional<U>& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+struct X
+{
+    static bool throw_now;
+
+    X() = default;
+    X(int)
+    {
+        if (throw_now)
+            TEST_THROW(6);
+    }
+};
+
+bool X::throw_now = false;
+
+struct Y1
+{
+    Y1() = default;
+    Y1(const int&) {}
+    Y1& operator=(const Y1&) = delete;
+};
+
+struct Y2
+{
+    Y2() = default;
+    Y2(const int&) = delete;
+    Y2& operator=(const int&) { return *this; }
+};
+
+template <class T>
+struct AssignableFrom {
+  static int type_constructed;
+  static int type_assigned;
+static int int_constructed;
+  static int int_assigned;
+
+  static void reset() {
+      type_constructed = int_constructed = 0;
+      type_assigned = int_assigned = 0;
+  }
+
+  AssignableFrom() = default;
+
+  explicit AssignableFrom(T) { ++type_constructed; }
+  AssignableFrom& operator=(T) { ++type_assigned; return *this; }
+
+  AssignableFrom(int) { ++int_constructed; }
+  AssignableFrom& operator=(int) { ++int_assigned; return *this; }
+private:
+  AssignableFrom(AssignableFrom const&) = delete;
+  AssignableFrom& operator=(AssignableFrom const&) = delete;
+};
+
+template <class T> int AssignableFrom<T>::type_constructed = 0;
+template <class T> int AssignableFrom<T>::type_assigned = 0;
+template <class T> int AssignableFrom<T>::int_constructed = 0;
+template <class T> int AssignableFrom<T>::int_assigned = 0;
+
+
+void test_with_test_type() {
+    using T = TestTypes::TestType;
+    T::reset();
+    { // non-empty to empty
+        T::reset_constructors();
+        optional<T> opt;
+        const optional<int> other(42);
+        opt = other;
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == true);
+        assert(*other == 42);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(42));
+    }
+    assert(T::alive == 0);
+    { // non-empty to non-empty
+        optional<T> opt(101);
+        const optional<int> other(42);
+        T::reset_constructors();
+        opt = other;
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 1);
+        assert(T::value_assigned == 1);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == true);
+        assert(*other == 42);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(42));
+    }
+    assert(T::alive == 0);
+    { // empty to non-empty
+        optional<T> opt(101);
+        const optional<int> other;
+        T::reset_constructors();
+        opt = other;
+        assert(T::alive == 0);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(other) == false);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(T::alive == 0);
+    { // empty to empty
+        optional<T> opt;
+        const optional<int> other;
+        T::reset_constructors();
+        opt = other;
+        assert(T::alive == 0);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == false);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(T::alive == 0);
+}
+
+void test_ambigious_assign() {
+    using OptInt = std::optional<int>;
+    {
+        using T = AssignableFrom<OptInt const&>;
+        const OptInt a(42);
+        T::reset();
+        {
+            std::optional<T> t;
+            t = a;
+            assert(T::type_constructed == 1);
+            assert(T::type_assigned == 0);
+            assert(T::int_constructed == 0);
+            assert(T::int_assigned == 0);
+        }
+        T::reset();
+        {
+            std::optional<T> t(42);
+            t = a;
+            assert(T::type_constructed == 0);
+            assert(T::type_assigned == 1);
+            assert(T::int_constructed == 1);
+            assert(T::int_assigned == 0);
+        }
+        T::reset();
+        {
+            std::optional<T> t(42);
+            t = std::move(a);
+            assert(T::type_constructed == 0);
+            assert(T::type_assigned == 1);
+            assert(T::int_constructed == 1);
+            assert(T::int_assigned == 0);
+        }
+    }
+    {
+        using T = AssignableFrom<OptInt&>;
+        OptInt a(42);
+        T::reset();
+        {
+            std::optional<T> t;
+            t = a;
+            assert(T::type_constructed == 1);
+            assert(T::type_assigned == 0);
+            assert(T::int_constructed == 0);
+            assert(T::int_assigned == 0);
+        }
+        {
+            using Opt = std::optional<T>;
+            static_assert(!std::is_assignable_v<Opt&, OptInt const&>, "");
+        }
+    }
+}
+
+
+int main()
+{
+    test_with_test_type();
+    test_ambigious_assign();
+    {
+        optional<int> opt;
+        constexpr optional<short> opt2;
+        opt = opt2;
+        static_assert(static_cast<bool>(opt2) == false, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt;
+        constexpr optional<short> opt2(short{2});
+        opt = 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<short> opt2;
+        opt = opt2;
+        static_assert(static_cast<bool>(opt2) == false, "");
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt(3);
+        constexpr optional<short> opt2(short{2});
+        opt = 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
+    {
+        optional<X> opt;
+        optional<int> opt2(42);
+        assert(static_cast<bool>(opt2) == true);
+        try
+        {
+            X::throw_now = true;
+            opt = opt2;
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+            assert(static_cast<bool>(opt) == false);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.assign/copy.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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=(const optional<T>& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+struct X
+{
+    static bool throw_now;
+
+    X() = default;
+    X(const X&)
+    {
+        if (throw_now)
+            TEST_THROW(6);
+    }
+};
+
+bool X::throw_now = false;
+
+template <class Tp>
+constexpr bool assign_empty(optional<Tp>&& lhs) {
+    const optional<Tp> rhs;
+    lhs = rhs;
+    return !lhs.has_value() && !rhs.has_value();
+}
+
+template <class Tp>
+constexpr bool assign_value(optional<Tp>&& lhs) {
+    const optional<Tp> rhs(101);
+    lhs = rhs;
+    return lhs.has_value() && rhs.has_value() && *lhs == *rhs;
+}
+
+int main()
+{
+    {
+        using O = optional<int>;
+        LIBCPP_STATIC_ASSERT(assign_empty(O{42}), "");
+        LIBCPP_STATIC_ASSERT(assign_value(O{42}), "");
+        assert(assign_empty(O{42}));
+        assert(assign_value(O{42}));
+    }
+    {
+        using O = optional<TrivialTestTypes::TestType>;
+        LIBCPP_STATIC_ASSERT(assign_empty(O{42}), "");
+        LIBCPP_STATIC_ASSERT(assign_value(O{42}), "");
+        assert(assign_empty(O{42}));
+        assert(assign_value(O{42}));
+    }
+    {
+        using O = optional<TestTypes::TestType>;
+        assert(assign_empty(O{42}));
+        assert(assign_value(O{42}));
+    }
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        optional<T> opt(3);
+        const optional<T> opt2;
+        assert(T::alive == 1);
+        opt = opt2;
+        assert(T::alive == 0);
+        assert(!opt2.has_value());
+        assert(!opt.has_value());
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        optional<X> opt;
+        optional<X> opt2(X{});
+        assert(static_cast<bool>(opt2) == true);
+        try
+        {
+            X::throw_now = true;
+            opt = opt2;
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+            assert(static_cast<bool>(opt) == false);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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... Args> void optional<T>::emplace(Args&&... args);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+#include <memory>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+class X
+{
+    int i_;
+    int j_ = 0;
+public:
+    X() : i_(0) {}
+    X(int i) : i_(i) {}
+    X(int i, int j) : i_(i), j_(j) {}
+
+    friend bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Y
+{
+public:
+    static bool dtor_called;
+    Y() = default;
+    Y(int) { TEST_THROW(6);}
+    ~Y() {dtor_called = true;}
+};
+
+bool Y::dtor_called = false;
+
+template <class T>
+void test_one_arg() {
+    using Opt = std::optional<T>;
+    {
+        Opt opt;
+        opt.emplace();
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(0));
+    }
+    {
+        Opt opt;
+        opt.emplace(1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1));
+    }
+    {
+        Opt opt(2);
+        opt.emplace();
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(0));
+    }
+    {
+        Opt opt(2);
+        opt.emplace(1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(1));
+    }
+}
+
+
+template <class T>
+void test_multi_arg()
+{
+    test_one_arg<T>();
+    using Opt = std::optional<T>;
+    Opt opt;
+    {
+        opt.emplace(101, 41);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(101, 41));
+    }
+    {
+        Opt opt;
+        opt.emplace({1, 2, 3, 4});
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(4)); // T sets its value to the size of the init list
+    }
+    {
+        Opt opt;
+        opt.emplace({1, 2, 3, 4, 5}, 6);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(5)); // T sets its value to the size of the init list
+    }
+}
+
+template <class T>
+void test_on_test_type() {
+
+    T::reset();
+    optional<T> opt;
+    assert(T::alive == 0);
+    {
+        T::reset_constructors();
+        opt.emplace();
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::default_constructed == 1);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T());
+    }
+    {
+        T::reset_constructors();
+        opt.emplace();
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::default_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T());
+    }
+    {
+        T::reset_constructors();
+        opt.emplace(101);
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(101));
+    }
+    {
+        T::reset_constructors();
+        opt.emplace(-10, 99);
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(-10, 99));
+    }
+    {
+        T::reset_constructors();
+        opt.emplace(-10, 99);
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(-10, 99));
+    }
+    {
+        T::reset_constructors();
+        opt.emplace({-10, 99, 42, 1});
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(4)); // size of the initializer list
+    }
+    {
+        T::reset_constructors();
+        opt.emplace({-10, 99, 42, 1}, 42);
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(4)); // size of the initializer list
+    }
+}
+
+
+
+int main()
+{
+    {
+        test_on_test_type<TestTypes::TestType>();
+        test_on_test_type<ExplicitTestTypes::TestType>();
+    }
+    {
+        using T = int;
+        test_one_arg<T>();
+        test_one_arg<const T>();
+    }
+    {
+        using T = ConstexprTestTypes::TestType;
+        test_multi_arg<T>();
+    }
+    {
+        using T = ExplicitConstexprTestTypes::TestType;
+        test_multi_arg<T>();
+    }
+    {
+        using T = TrivialTestTypes::TestType;
+        test_multi_arg<T>();
+    }
+    {
+        using T = ExplicitTrivialTestTypes::TestType;
+        test_multi_arg<T>();
+    }
+    {
+        optional<const int> opt;
+        opt.emplace(42);
+        assert(*opt == 42);
+        opt.emplace();
+        assert(*opt == 0);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    Y::dtor_called = false;
+    {
+        Y y;
+        optional<Y> opt(y);
+        try
+        {
+            assert(static_cast<bool>(opt) == true);
+            assert(Y::dtor_called == false);
+            opt.emplace(1);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+            assert(static_cast<bool>(opt) == false);
+            assert(Y::dtor_called == true);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U, class... Args>
+//   void optional<T>::emplace(initializer_list<U> il, Args&&... args);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+#include <vector>
+
+#include "test_macros.h"
+
+using std::optional;
+
+class X
+{
+    int i_;
+    int j_ = 0;
+public:
+    static bool dtor_called;
+    constexpr X() : i_(0) {}
+    constexpr X(int i) : i_(i) {}
+    constexpr X(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1]) {}
+    ~X() {dtor_called = true;}
+
+    friend constexpr bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+bool X::dtor_called = false;
+
+class Y
+{
+    int i_;
+    int j_ = 0;
+public:
+    constexpr Y() : i_(0) {}
+    constexpr Y(int i) : i_(i) {}
+    constexpr Y(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1]) {}
+
+    friend constexpr bool operator==(const Y& x, const Y& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Z
+{
+    int i_;
+    int j_ = 0;
+public:
+    static bool dtor_called;
+    Z() : i_(0) {}
+    Z(int i) : i_(i) {}
+    Z(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1])
+        { TEST_THROW(6);}
+    ~Z() {dtor_called = true;}
+
+    friend bool operator==(const Z& x, const Z& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+bool Z::dtor_called = false;
+
+int main()
+{
+    {
+        X x;
+        optional<X> opt(x);
+        assert(X::dtor_called == false);
+        opt.emplace({1, 2});
+        assert(X::dtor_called == true);
+        assert(*opt == X({1, 2}));
+    }
+    {
+        optional<std::vector<int>> opt;
+        opt.emplace({1, 2, 3}, std::allocator<int>());
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == std::vector<int>({1, 2, 3}));
+    }
+    {
+        optional<Y> opt;
+        opt.emplace({1, 2});
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == Y({1, 2}));
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        Z z;
+        optional<Z> opt(z);
+        try
+        {
+            assert(static_cast<bool>(opt) == true);
+            assert(Z::dtor_called == false);
+            opt.emplace({1, 2});
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+            assert(static_cast<bool>(opt) == false);
+            assert(Z::dtor_called == true);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.assign/move.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, "");
+    }
+}

test/std/utilities/optional/optional.object/optional.object.assign/nullopt_t.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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();
+}

test/std/utilities/optional/optional.object/optional.object.assign/optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// From LWG2451:
+// template <class U>
+// optional<T>& operator=(optional<U>&& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <memory>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+struct X
+{
+    static bool throw_now;
+
+    X() = default;
+    X(int &&)
+    {
+        if (throw_now)
+            TEST_THROW(6);
+    }
+};
+
+bool X::throw_now = false;
+
+struct Y1
+{
+    Y1() = default;
+    Y1(const int&) {}
+    Y1& operator=(const Y1&) = delete;
+};
+
+struct Y2
+{
+    Y2() = default;
+    Y2(const int&) = delete;
+    Y2& operator=(const int&) { return *this; }
+};
+
+class B {};
+class D : public B {};
+
+
+template <class T>
+struct AssignableFrom {
+  static int type_constructed;
+  static int type_assigned;
+static int int_constructed;
+  static int int_assigned;
+
+  static void reset() {
+      type_constructed = int_constructed = 0;
+      type_assigned = int_assigned = 0;
+  }
+
+  AssignableFrom() = default;
+
+  explicit AssignableFrom(T) { ++type_constructed; }
+  AssignableFrom& operator=(T) { ++type_assigned; return *this; }
+
+  AssignableFrom(int) { ++int_constructed; }
+  AssignableFrom& operator=(int) { ++int_assigned; return *this; }
+private:
+  AssignableFrom(AssignableFrom const&) = delete;
+  AssignableFrom& operator=(AssignableFrom const&) = delete;
+};
+
+template <class T> int AssignableFrom<T>::type_constructed = 0;
+template <class T> int AssignableFrom<T>::type_assigned = 0;
+template <class T> int AssignableFrom<T>::int_constructed = 0;
+template <class T> int AssignableFrom<T>::int_assigned = 0;
+
+void test_with_test_type() {
+    using T = TestTypes::TestType;
+    T::reset();
+    { // non-empty to empty
+        T::reset_constructors();
+        optional<T> opt;
+        optional<int> other(42);
+        opt = std::move(other);
+        assert(T::alive == 1);
+        assert(T::constructed == 1);
+        assert(T::value_constructed == 1);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == true);
+        assert(*other == 42);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(42));
+    }
+    assert(T::alive == 0);
+    { // non-empty to non-empty
+        optional<T> opt(101);
+        optional<int> other(42);
+        T::reset_constructors();
+        opt = std::move(other);
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 1);
+        assert(T::value_assigned == 1);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == true);
+        assert(*other == 42);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == T(42));
+    }
+    assert(T::alive == 0);
+    { // empty to non-empty
+        optional<T> opt(101);
+        optional<int> other;
+        T::reset_constructors();
+        opt = std::move(other);
+        assert(T::alive == 0);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 1);
+        assert(static_cast<bool>(other) == false);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(T::alive == 0);
+    { // empty to empty
+        optional<T> opt;
+        optional<int> other;
+        T::reset_constructors();
+        opt = std::move(other);
+        assert(T::alive == 0);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+        assert(static_cast<bool>(other) == false);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(T::alive == 0);
+}
+
+
+void test_ambigious_assign() {
+    using OptInt = std::optional<int>;
+    {
+        using T = AssignableFrom<OptInt&&>;
+        T::reset();
+        {
+            OptInt a(42);
+            std::optional<T> t;
+            t = std::move(a);
+            assert(T::type_constructed == 1);
+            assert(T::type_assigned == 0);
+            assert(T::int_constructed == 0);
+            assert(T::int_assigned == 0);
+        }
+        {
+            using Opt = std::optional<T>;
+            static_assert(!std::is_assignable<Opt&, const OptInt&&>::value, "");
+            static_assert(!std::is_assignable<Opt&, const OptInt&>::value, "");
+            static_assert(!std::is_assignable<Opt&, OptInt&>::value, "");
+        }
+    }
+    {
+        using T = AssignableFrom<OptInt const&&>;
+        T::reset();
+        {
+            const OptInt a(42);
+            std::optional<T> t;
+            t = std::move(a);
+            assert(T::type_constructed == 1);
+            assert(T::type_assigned == 0);
+            assert(T::int_constructed == 0);
+            assert(T::int_assigned == 0);
+        }
+        T::reset();
+        {
+            OptInt a(42);
+            std::optional<T> t;
+            t = std::move(a);
+            assert(T::type_constructed == 1);
+            assert(T::type_assigned == 0);
+            assert(T::int_constructed == 0);
+            assert(T::int_assigned == 0);
+        }
+        {
+            using Opt = std::optional<T>;
+            static_assert(std::is_assignable<Opt&, OptInt&&>::value, "");
+            static_assert(!std::is_assignable<Opt&, const OptInt&>::value, "");
+            static_assert(!std::is_assignable<Opt&, OptInt&>::value, "");
+        }
+    }
+}
+
+
+int main()
+{
+    test_with_test_type();
+    test_ambigious_assign();
+    {
+        optional<int> opt;
+        optional<short> opt2;
+        opt = std::move(opt2);
+        assert(static_cast<bool>(opt2) == false);
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt;
+        optional<short> opt2(short{2});
+        opt = std::move(opt2);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+        assert(*opt == *opt2);
+    }
+    {
+        optional<int> opt(3);
+        optional<short> opt2;
+        opt = std::move(opt2);
+        assert(static_cast<bool>(opt2) == false);
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+    }
+    {
+        optional<int> opt(3);
+        optional<short> opt2(short{2});
+        opt = std::move(opt2);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        assert(static_cast<bool>(opt) == static_cast<bool>(opt2));
+        assert(*opt == *opt2);
+    }
+    {
+        optional<std::unique_ptr<B>> opt;
+        optional<std::unique_ptr<D>> other(new D());
+        opt = std::move(other);
+        assert(static_cast<bool>(opt) == true);
+        assert(static_cast<bool>(other) == true);
+        assert(opt->get() != nullptr);
+        assert(other->get() == nullptr);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        optional<X> opt;
+        optional<int> opt2(42);
+        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);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.ctor/U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U>
+//   constexpr EXPLICIT optional(U&& u);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+#include "test_convertible.hpp"
+
+
+using std::optional;
+
+struct ImplicitThrow
+{
+    constexpr ImplicitThrow(int x) { if (x != -1) TEST_THROW(6);}
+};
+
+struct ExplicitThrow
+{
+    constexpr explicit ExplicitThrow(int x) { if (x != -1) TEST_THROW(6);}
+};
+
+
+template <class To, class From>
+constexpr bool implicit_conversion(optional<To>&& opt, const From& v)
+{
+    using O = optional<To>;
+    static_assert(test_convertible<O, From>(), "");
+    static_assert(!test_convertible<O, void*>(), "");
+    static_assert(!test_convertible<O, From, int>(), "");
+    return opt && *opt == static_cast<To>(v);
+}
+
+template <class To, class Input, class Expect>
+constexpr bool explicit_conversion(Input&& in, const Expect& v)
+{
+    using O = optional<To>;
+    static_assert(std::is_constructible<O, Input>::value, "");
+    static_assert(!std::is_convertible<Input, O>::value, "");
+    static_assert(!std::is_constructible<O, void*>::value, "");
+    static_assert(!std::is_constructible<O, Input, int>::value, "");
+    optional<To> opt(std::forward<Input>(in));
+    return opt && *opt == static_cast<To>(v);
+}
+
+void test_implicit()
+{
+    {
+        using T = long long;
+        static_assert(implicit_conversion<long long>(42, 42), "");
+    }
+    {
+        using T = long double;
+        static_assert(implicit_conversion<long double>(3.14, 3.14), "");
+    }
+    {
+        using T = TrivialTestTypes::TestType;
+        static_assert(implicit_conversion<T>(42, 42), "");
+    }
+    {
+        using T = TestTypes::TestType;
+        assert(implicit_conversion<T>(3, T(3)));
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        try {
+            using T = ImplicitThrow;
+            optional<T> t = 42;
+            assert(false);
+        } catch (int) {
+        }
+    }
+#endif
+}
+
+void test_explicit() {
+    {
+        using T = ExplicitTrivialTestTypes::TestType;
+        using O = optional<T>;
+        static_assert(explicit_conversion<T>(42, 42), "");
+    }
+    {
+        using T = ExplicitConstexprTestTypes::TestType;
+        using O = optional<T>;
+        static_assert(explicit_conversion<T>(42, 42), "");
+        static_assert(!std::is_convertible<int, T>::value, "");
+    }
+    {
+        using T = ExplicitTestTypes::TestType;
+        using O = optional<T>;
+        T::reset();
+        {
+            assert(explicit_conversion<T>(42, 42));
+            assert(T::alive == 0);
+        }
+        T::reset();
+        {
+            optional<T> t(42);
+            assert(T::alive == 1);
+            assert(T::value_constructed == 1);
+            assert(T::move_constructed == 0);
+            assert(T::copy_constructed == 0);
+            assert(t.value().value == 42);
+        }
+        assert(T::alive == 0);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        try {
+            using T = ExplicitThrow;
+            optional<T> t(42);
+            assert(false);
+        } catch (int) {
+        }
+    }
+#endif
+}
+
+int main() {
+    test_implicit();
+    test_explicit();
+}

test/std/utilities/optional/optional.object/optional.object.ctor/const_T.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr optional(const T& v);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+int main()
+{
+    {
+        typedef int T;
+        constexpr T t(5);
+        constexpr optional<T> opt(t);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == 5, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+
+    }
+    {
+        typedef double T;
+        constexpr T t(3);
+        constexpr optional<T> opt(t);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+
+    }
+    {
+        typedef TestTypes::TestType T;
+        T::reset();
+        const T t(3);
+        optional<T> opt = t;
+        assert(T::alive == 2);
+        assert(T::copy_constructed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(opt.value().value == 3);
+    }
+    {
+        typedef ExplicitTestTypes::TestType T;
+        static_assert(!std::is_convertible<T const&, optional<T>>::value, "");
+        T::reset();
+        const T t(3);
+        optional<T> opt(t);
+        assert(T::alive == 2);
+        assert(T::copy_constructed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(opt.value().value == 3);
+    }
+    {
+        typedef ConstexprTestTypes::TestType T;
+        constexpr T t(3);
+        constexpr optional<T> opt = {t};
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(opt.value().value == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+    }
+    {
+        typedef ExplicitConstexprTestTypes::TestType T;
+        static_assert(!std::is_convertible<const T&, optional<T>>::value, "");
+        constexpr T t(3);
+        constexpr optional<T> opt(t);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(opt.value().value == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        struct Z {
+            Z(int) {}
+            Z(const Z&) {throw 6;}
+        };
+        typedef Z T;
+        try
+        {
+            const T t(3);
+            optional<T> opt(t);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.ctor/const_optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U>
+//   optional(const optional<U>& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+template <class T, class U>
+void
+test(const optional<U>& rhs, bool is_going_to_throw = false)
+{
+    bool rhs_engaged = static_cast<bool>(rhs);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try
+    {
+        optional<T> lhs = rhs;
+        assert(is_going_to_throw == false);
+        assert(static_cast<bool>(lhs) == rhs_engaged);
+        if (rhs_engaged)
+            assert(*lhs == *rhs);
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#else
+    if (is_going_to_throw) return;
+    optional<T> lhs = rhs;
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(*lhs == *rhs);
+#endif
+}
+
+class X
+{
+    int i_;
+public:
+    X(int i) : i_(i) {}
+    X(const X& x) : i_(x.i_) {}
+    ~X() {i_ = 0;}
+    friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
+};
+
+class Y
+{
+    int i_;
+public:
+    Y(int i) : i_(i) {}
+
+    friend constexpr bool operator==(const Y& x, const Y& y) {return x.i_ == y.i_;}
+};
+
+int count = 0;
+
+class Z
+{
+    int i_;
+public:
+    Z(int i) : i_(i) {TEST_THROW(6);}
+
+    friend constexpr bool operator==(const Z& x, const Z& y) {return x.i_ == y.i_;}
+};
+
+
+int main()
+{
+    {
+        typedef short U;
+        typedef int T;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef short U;
+        typedef int T;
+        optional<U> rhs(U{3});
+        test<T>(rhs);
+    }
+    {
+        typedef X T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef X T;
+        typedef int U;
+        optional<U> rhs(U{3});
+        test<T>(rhs);
+    }
+    {
+        typedef Y T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef Y T;
+        typedef int U;
+        optional<U> rhs(U{3});
+        test<T>(rhs);
+    }
+    {
+        typedef Z T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef Z T;
+        typedef int U;
+        optional<U> rhs(U{3});
+        test<T>(rhs, true);
+    }
+
+    static_assert(!(std::is_constructible<optional<X>, const optional<Y>&>::value), "");
+}

test/std/utilities/optional/optional.object/optional.object.ctor/copy.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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(const optional<T>& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+template <class T, class ...InitArgs>
+void test(InitArgs&&... args)
+{
+    const optional<T> rhs(std::forward<InitArgs>(args)...);
+    bool rhs_engaged = static_cast<bool>(rhs);
+    optional<T> lhs = rhs;
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(*lhs == *rhs);
+}
+
+void test_throwing_ctor() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    struct Z {
+      Z() : count(0) {}
+      Z(Z const& o) : count(o.count + 1)
+      { if (count == 2) throw 6; }
+      int count;
+    };
+    const Z z;
+    const optional<Z> rhs(z);
+    try
+    {
+        optional<Z> lhs(rhs);
+        assert(false);
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#endif
+}
+
+template <class T, class ...InitArgs>
+void test_ref(InitArgs&&... args)
+{
+    const optional<T> rhs(std::forward<InitArgs>(args)...);
+    bool rhs_engaged = static_cast<bool>(rhs);
+    optional<T> lhs = rhs;
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(&(*lhs) == &(*rhs));
+}
+
+
+void test_reference_extension()
+{
+#if defined(_LIBCPP_VERSION) && 0 // FIXME these extensions are currently disabled.
+    using T = TestTypes::TestType;
+    T::reset();
+    {
+        T t;
+        T::reset_constructors();
+        test_ref<T&>();
+        test_ref<T&>(t);
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::destroyed == 1);
+    assert(T::alive == 0);
+    {
+        T t;
+        const T& ct = t;
+        T::reset_constructors();
+        test_ref<T const&>();
+        test_ref<T const&>(t);
+        test_ref<T const&>(ct);
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::alive == 0);
+    assert(T::destroyed == 1);
+    {
+        static_assert(!std::is_copy_constructible<std::optional<T&&>>::value, "");
+        static_assert(!std::is_copy_constructible<std::optional<T const&&>>::value, "");
+    }
+#endif
+}
+
+int main()
+{
+    test<int>();
+    test<int>(3);
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        const optional<T> rhs;
+        assert(T::alive == 0);
+        const optional<T> lhs(rhs);
+        assert(lhs.has_value() == false);
+        assert(T::alive == 0);
+    }
+    TestTypes::TestType::reset();
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        const optional<T> rhs(42);
+        assert(T::alive == 1);
+        assert(T::value_constructed == 1);
+        assert(T::copy_constructed == 0);
+        const optional<T> lhs(rhs);
+        assert(lhs.has_value());
+        assert(T::copy_constructed == 1);
+        assert(T::alive == 2);
+    }
+    TestTypes::TestType::reset();
+    {
+        using namespace ConstexprTestTypes;
+        test<TestType>();
+        test<TestType>(42);
+    }
+    {
+        using namespace TrivialTestTypes;
+        test<TestType>();
+        test<TestType>(42);
+    }
+    {
+        test_throwing_ctor();
+    }
+    {
+        test_reference_extension();
+    }
+}

test/std/utilities/optional/optional.object/optional.object.ctor/default.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr optional() noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+template <class Opt>
+void
+test_constexpr()
+{
+    static_assert(std::is_nothrow_default_constructible<Opt>::value, "");
+    static_assert(std::is_trivially_destructible<Opt>::value, "");
+    static_assert(std::is_trivially_destructible<typename Opt::value_type>::value, "");
+
+    constexpr Opt opt;
+    static_assert(static_cast<bool>(opt) == false, "");
+
+    struct test_constexpr_ctor
+        : public Opt
+    {
+        constexpr test_constexpr_ctor() {}
+    };
+}
+
+template <class Opt>
+void
+test()
+{
+    static_assert(std::is_nothrow_default_constructible<Opt>::value, "");
+    static_assert(!std::is_trivially_destructible<Opt>::value, "");
+    static_assert(!std::is_trivially_destructible<typename Opt::value_type>::value, "");
+    {
+        Opt opt;
+        assert(static_cast<bool>(opt) == false);
+    }
+    {
+        const Opt opt;
+        assert(static_cast<bool>(opt) == false);
+    }
+
+    struct test_constexpr_ctor
+        : public Opt
+    {
+        constexpr test_constexpr_ctor() {}
+    };
+}
+
+int main()
+{
+    test_constexpr<optional<int>>();
+    test_constexpr<optional<int*>>();
+    test_constexpr<optional<ImplicitTypes::NoCtors>>();
+    test_constexpr<optional<NonTrivialTypes::NoCtors>>();
+    test_constexpr<optional<NonConstexprTypes::NoCtors>>();
+    test<optional<NonLiteralTypes::NoCtors>>();
+    // EXTENSIONS
+#if defined(_LIBCPP_VERSION) && 0 // FIXME these extensions are currently disabled.
+    test_constexpr<optional<int&>>();
+    test_constexpr<optional<const int&>>();
+    test_constexpr<optional<int&>>();
+    test_constexpr<optional<NonLiteralTypes::NoCtors&>>();
+    test_constexpr<optional<NonLiteralTypes::NoCtors&&>>();
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.ctor/explicit_const_optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U>
+//   explicit optional(const optional<U>& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+template <class T, class U>
+void
+test(const optional<U>& rhs, bool is_going_to_throw = false)
+{
+    static_assert(!(std::is_convertible<const optional<U>&, optional<T>>::value), "");
+    bool rhs_engaged = static_cast<bool>(rhs);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try
+    {
+        optional<T> lhs(rhs);
+        assert(is_going_to_throw == false);
+        assert(static_cast<bool>(lhs) == rhs_engaged);
+        if (rhs_engaged)
+            assert(*lhs == T(*rhs));
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#else
+    if (is_going_to_throw) return;
+    optional<T> lhs(rhs);
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(*lhs == T(*rhs));
+#endif
+}
+
+class X
+{
+    int i_;
+public:
+    explicit X(int i) : i_(i) {}
+    X(const X& x) : i_(x.i_) {}
+    ~X() {i_ = 0;}
+    friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
+};
+
+class Y
+{
+    int i_;
+public:
+    explicit Y(int i) : i_(i) {}
+
+    friend constexpr bool operator==(const Y& x, const Y& y) {return x.i_ == y.i_;}
+};
+
+int count = 0;
+
+class Z
+{
+    int i_;
+public:
+    explicit Z(int i) : i_(i) { TEST_THROW(6);}
+
+    friend constexpr bool operator==(const Z& x, const Z& y) {return x.i_ == y.i_;}
+};
+
+
+int main()
+{
+    {
+        typedef X T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef X T;
+        typedef int U;
+        optional<U> rhs(3);
+        test<T>(rhs);
+    }
+    {
+        typedef Y T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef Y T;
+        typedef int U;
+        optional<U> rhs(3);
+        test<T>(rhs);
+    }
+    {
+        typedef Z T;
+        typedef int U;
+        optional<U> rhs;
+        test<T>(rhs);
+    }
+    {
+        typedef Z T;
+        typedef int U;
+        optional<U> rhs(3);
+        test<T>(rhs, true);
+    }
+}

test/std/utilities/optional/optional.object/optional.object.ctor/explicit_optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U>
+//   explicit optional(optional<U>&& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+template <class T, class U>
+void
+test(optional<U>&& rhs, bool is_going_to_throw = false)
+{
+    static_assert(!(std::is_convertible<optional<U>&&, optional<T>>::value), "");
+    bool rhs_engaged = static_cast<bool>(rhs);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try
+    {
+        optional<T> lhs(std::move(rhs));
+        assert(is_going_to_throw == false);
+        assert(static_cast<bool>(lhs) == rhs_engaged);
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#else
+    if (is_going_to_throw) return;
+    optional<T> lhs(std::move(rhs));
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+#endif
+}
+
+class X
+{
+    int i_;
+public:
+    explicit X(int i) : i_(i) {}
+    X(X&& x) : i_(std::exchange(x.i_, 0)) {}
+    ~X() {i_ = 0;}
+    friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
+};
+
+int count = 0;
+
+class Z
+{
+public:
+    explicit Z(int) { TEST_THROW(6); }
+};
+
+int main()
+{
+    {
+        optional<int> rhs;
+        test<X>(std::move(rhs));
+    }
+    {
+        optional<int> rhs(3);
+        test<X>(std::move(rhs));
+    }
+    {
+        optional<int> rhs;
+        test<Z>(std::move(rhs));
+    }
+    {
+        optional<int> rhs(3);
+        test<Z>(std::move(rhs), true);
+    }
+}

test/std/utilities/optional/optional.object/optional.object.ctor/in_place_t.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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... Args>
+//   constexpr explicit optional(in_place_t, Args&&... args);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::in_place_t;
+using std::in_place;
+
+class X
+{
+    int i_;
+    int j_ = 0;
+public:
+    X() : i_(0) {}
+    X(int i) : i_(i) {}
+    X(int i, int j) : i_(i), j_(j) {}
+
+    ~X() {}
+
+    friend bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Y
+{
+    int i_;
+    int j_ = 0;
+public:
+    constexpr Y() : i_(0) {}
+    constexpr Y(int i) : i_(i) {}
+    constexpr Y(int i, int j) : i_(i), j_(j) {}
+
+    friend constexpr bool operator==(const Y& x, const Y& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Z
+{
+public:
+    Z(int i) {TEST_THROW(6);}
+};
+
+
+int main()
+{
+    {
+        constexpr optional<int> opt(in_place, 5);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == 5, "");
+
+        struct test_constexpr_ctor
+            : public optional<int>
+        {
+            constexpr test_constexpr_ctor(in_place_t, int i)
+                : optional<int>(in_place, i) {}
+        };
+
+    }
+    {
+        const optional<X> opt(in_place);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == X());
+    }
+    {
+        const optional<X> opt(in_place, 5);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == X(5));
+    }
+    {
+        const optional<X> opt(in_place, 5, 4);
+        assert(static_cast<bool>(opt) == true);
+        assert(*opt == X(5, 4));
+    }
+    {
+        constexpr optional<Y> opt(in_place);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == Y(), "");
+
+        struct test_constexpr_ctor
+            : public optional<Y>
+        {
+            constexpr test_constexpr_ctor(in_place_t)
+                : optional<Y>(in_place) {}
+        };
+
+    }
+    {
+        constexpr optional<Y> opt(in_place, 5);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == Y(5), "");
+
+        struct test_constexpr_ctor
+            : public optional<Y>
+        {
+            constexpr test_constexpr_ctor(in_place_t, int i)
+                : optional<Y>(in_place, i) {}
+        };
+
+    }
+    {
+        constexpr optional<Y> opt(in_place, 5, 4);
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == Y(5, 4), "");
+
+        struct test_constexpr_ctor
+            : public optional<Y>
+        {
+            constexpr test_constexpr_ctor(in_place_t, int i, int j)
+                : optional<Y>(in_place, i, j) {}
+        };
+
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        try
+        {
+            const optional<Z> opt(in_place, 1);
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.ctor/initializer_list.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U, class... Args>
+//     constexpr
+//     explicit optional(in_place_t, initializer_list<U> il, Args&&... args);
+
+#include <optional>
+#include <type_traits>
+#include <vector>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::in_place_t;
+using std::in_place;
+
+class X
+{
+    int i_;
+    int j_ = 0;
+public:
+    X() : i_(0) {}
+    X(int i) : i_(i) {}
+    X(int i, int j) : i_(i), j_(j) {}
+
+    ~X() {}
+
+    friend bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Y
+{
+    int i_;
+    int j_ = 0;
+public:
+    constexpr Y() : i_(0) {}
+    constexpr Y(int i) : i_(i) {}
+    constexpr Y(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1]) {}
+
+    friend constexpr bool operator==(const Y& x, const Y& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+class Z
+{
+    int i_;
+    int j_ = 0;
+public:
+    Z() : i_(0) {}
+    Z(int i) : i_(i) {}
+    Z(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1])
+        {TEST_THROW(6);}
+
+    friend bool operator==(const Z& x, const Z& y)
+        {return x.i_ == y.i_ && x.j_ == y.j_;}
+};
+
+int main()
+{
+    {
+        static_assert(!std::is_constructible<X, std::initializer_list<int>&>::value, "");
+        static_assert(!std::is_constructible<optional<X>, std::initializer_list<int>&>::value, "");
+    }
+    {
+        optional<std::vector<int>> opt(in_place, {3, 1});
+        assert(static_cast<bool>(opt) == true);
+        assert((*opt == std::vector<int>{3, 1}));
+        assert(opt->size() == 2);
+    }
+    {
+        optional<std::vector<int>> opt(in_place, {3, 1}, std::allocator<int>());
+        assert(static_cast<bool>(opt) == true);
+        assert((*opt == std::vector<int>{3, 1}));
+        assert(opt->size() == 2);
+    }
+    {
+        static_assert(std::is_constructible<optional<Y>, std::initializer_list<int>&>::value, "");
+        constexpr optional<Y> opt(in_place, {3, 1});
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == Y{3, 1}, "");
+
+        struct test_constexpr_ctor
+            : public optional<Y>
+        {
+            constexpr test_constexpr_ctor(in_place_t, std::initializer_list<int> i)
+                : optional<Y>(in_place, i) {}
+        };
+
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        static_assert(std::is_constructible<optional<Z>, std::initializer_list<int>&>::value, "");
+        try
+        {
+            optional<Z> opt(in_place, {3, 1});
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.ctor/move.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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(optional<T>&& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+using std::optional;
+
+template <class T, class ...InitArgs>
+void test(InitArgs&&... args)
+{
+    const optional<T> orig(std::forward<InitArgs>(args)...);
+    optional<T> rhs(orig);
+    bool rhs_engaged = static_cast<bool>(rhs);
+    optional<T> lhs = std::move(rhs);
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(*lhs == *orig);
+}
+
+void test_throwing_ctor() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    struct Z {
+      Z() : count(0) {}
+      Z(Z&& o) : count(o.count + 1)
+      { if (count == 2) throw 6; }
+      int count;
+    };
+    Z z;
+    optional<Z> rhs(std::move(z));
+    try
+    {
+        optional<Z> lhs(std::move(rhs));
+        assert(false);
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#endif
+}
+
+
+template <class T, class ...InitArgs>
+void test_ref(InitArgs&&... args)
+{
+    optional<T> rhs(std::forward<InitArgs>(args)...);
+    bool rhs_engaged = static_cast<bool>(rhs);
+    optional<T> lhs = std::move(rhs);
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+    if (rhs_engaged)
+        assert(&(*lhs) == &(*rhs));
+}
+
+void test_reference_extension()
+{
+#if defined(_LIBCPP_VERSION) && 0 // FIXME these extensions are currently disabled.
+    using T = TestTypes::TestType;
+    T::reset();
+    {
+        T t;
+        T::reset_constructors();
+        test_ref<T&>();
+        test_ref<T&>(t);
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::destroyed == 1);
+    assert(T::alive == 0);
+    {
+        T t;
+        const T& ct = t;
+        T::reset_constructors();
+        test_ref<T const&>();
+        test_ref<T const&>(t);
+        test_ref<T const&>(ct);
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::alive == 0);
+    assert(T::destroyed == 1);
+    {
+        T t;
+        T::reset_constructors();
+        test_ref<T&&>();
+        test_ref<T&&>(std::move(t));
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::alive == 0);
+    assert(T::destroyed == 1);
+    {
+        T t;
+        const T& ct = t;
+        T::reset_constructors();
+        test_ref<T const&&>();
+        test_ref<T const&&>(std::move(t));
+        test_ref<T const&&>(std::move(ct));
+        assert(T::alive == 1);
+        assert(T::constructed == 0);
+        assert(T::assigned == 0);
+        assert(T::destroyed == 0);
+    }
+    assert(T::alive == 0);
+    assert(T::destroyed == 1);
+    {
+        static_assert(!std::is_copy_constructible<std::optional<T&&>>::value, "");
+        static_assert(!std::is_copy_constructible<std::optional<T const&&>>::value, "");
+    }
+#endif
+}
+
+
+int main()
+{
+    test<int>();
+    test<int>(3);
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        optional<T> rhs;
+        assert(T::alive == 0);
+        const optional<T> lhs(std::move(rhs));
+        assert(lhs.has_value() == false);
+        assert(rhs.has_value() == false);
+        assert(T::alive == 0);
+    }
+    TestTypes::TestType::reset();
+    {
+        using T = TestTypes::TestType;
+        T::reset();
+        optional<T> rhs(42);
+        assert(T::alive == 1);
+        assert(T::value_constructed == 1);
+        assert(T::move_constructed == 0);
+        const optional<T> lhs(std::move(rhs));
+        assert(lhs.has_value());
+        assert(rhs.has_value());
+        assert(lhs.value().value == 42);
+        assert(rhs.value().value == -1);
+        assert(T::move_constructed == 1);
+        assert(T::alive == 2);
+    }
+    TestTypes::TestType::reset();
+    {
+        using namespace ConstexprTestTypes;
+        test<TestType>();
+        test<TestType>(42);
+    }
+    {
+        using namespace TrivialTestTypes;
+        test<TestType>();
+        test<TestType>(42);
+    }
+    {
+        test_throwing_ctor();
+    }
+    {
+        struct ThrowsMove {
+          ThrowsMove() noexcept(false) {}
+          ThrowsMove(ThrowsMove const&) noexcept(false) {}
+          ThrowsMove(ThrowsMove &&) noexcept(false) {}
+        };
+        static_assert(!std::is_nothrow_move_constructible<optional<ThrowsMove>>::value, "");
+        struct NoThrowMove {
+          NoThrowMove() noexcept(false) {}
+          NoThrowMove(NoThrowMove const&) noexcept(false) {}
+          NoThrowMove(NoThrowMove &&) noexcept(true) {}
+        };
+        static_assert(std::is_nothrow_move_constructible<optional<NoThrowMove>>::value, "");
+    }
+    {
+        test_reference_extension();
+    }
+}

test/std/utilities/optional/optional.object/optional.object.ctor/nullopt_t.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr optional(nullopt_t) noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "archetypes.hpp"
+
+using std::optional;
+using std::nullopt_t;
+using std::nullopt;
+
+template <class Opt>
+void
+test_constexpr()
+{
+    static_assert(std::is_nothrow_constructible<Opt, nullopt_t&>::value, "");
+    static_assert(std::is_trivially_destructible<Opt>::value, "");
+    static_assert(std::is_trivially_destructible<typename Opt::value_type>::value, "");
+
+    constexpr Opt opt(nullopt);
+    static_assert(static_cast<bool>(opt) == false, "");
+
+    struct test_constexpr_ctor
+        : public Opt
+    {
+        constexpr test_constexpr_ctor() {}
+    };
+}
+
+template <class Opt>
+void
+test()
+{
+    static_assert(std::is_nothrow_constructible<Opt, nullopt_t&>::value, "");
+    static_assert(!std::is_trivially_destructible<Opt>::value, "");
+    static_assert(!std::is_trivially_destructible<typename Opt::value_type>::value, "");
+    {
+    Opt opt(nullopt);
+    assert(static_cast<bool>(opt) == false);
+    }
+    {
+    const Opt opt(nullopt);
+    assert(static_cast<bool>(opt) == false);
+    }
+    struct test_constexpr_ctor
+        : public Opt
+    {
+        constexpr test_constexpr_ctor() {}
+    };
+}
+
+int main()
+{
+    test_constexpr<optional<int>>();
+    test_constexpr<optional<int*>>();
+    test_constexpr<optional<ImplicitTypes::NoCtors>>();
+    test_constexpr<optional<NonTrivialTypes::NoCtors>>();
+    test_constexpr<optional<NonConstexprTypes::NoCtors>>();
+    test<optional<NonLiteralTypes::NoCtors>>();
+}

test/std/utilities/optional/optional.object/optional.object.ctor/optional_U.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U>
+//   optional(optional<U>&& rhs);
+
+#include <optional>
+#include <type_traits>
+#include <memory>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+template <class T, class U>
+void
+test(optional<U>&& rhs, bool is_going_to_throw = false)
+{
+    bool rhs_engaged = static_cast<bool>(rhs);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try
+    {
+        optional<T> lhs = std::move(rhs);
+        assert(is_going_to_throw == false);
+        assert(static_cast<bool>(lhs) == rhs_engaged);
+    }
+    catch (int i)
+    {
+        assert(i == 6);
+    }
+#else
+    if (is_going_to_throw) return;
+    optional<T> lhs = std::move(rhs);
+    assert(static_cast<bool>(lhs) == rhs_engaged);
+#endif
+}
+
+class X
+{
+    int i_;
+public:
+    X(int i) : i_(i) {}
+    X(X&& x) : i_(std::exchange(x.i_, 0)) {}
+    ~X() {i_ = 0;}
+    friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
+};
+
+int count = 0;
+
+struct Z
+{
+    Z(int) { TEST_THROW(6); }
+};
+
+int main()
+{
+    {
+        optional<short> rhs;
+        test<int>(std::move(rhs));
+    }
+    {
+        optional<short> rhs(short{3});
+        test<int>(std::move(rhs));
+    }
+    {
+        optional<int> rhs;
+        test<X>(std::move(rhs));
+    }
+    {
+        optional<int> rhs(3);
+        test<X>(std::move(rhs));
+    }
+    {
+        optional<int> rhs;
+        test<Z>(std::move(rhs));
+    }
+    {
+        optional<int> rhs(3);
+        test<Z>(std::move(rhs), true);
+    }
+
+    static_assert(!(std::is_constructible<optional<X>, optional<Z>>::value), "");
+}

test/std/utilities/optional/optional.object/optional.object.ctor/rvalue_T.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr optional(T&& v);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "archetypes.hpp"
+
+
+using std::optional;
+
+
+class Z
+{
+public:
+    Z(int) {}
+    Z(Z&&) {TEST_THROW(6);}
+};
+
+
+int main()
+{
+    {
+        typedef int T;
+        constexpr optional<T> opt(T(5));
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == 5, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(T&&) {}
+        };
+    }
+    {
+        typedef double T;
+        constexpr optional<T> opt(T(3));
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(*opt == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(T&&) {}
+        };
+    }
+    {
+        typedef TestTypes::TestType T;
+        T::reset();
+        optional<T> opt = T{3};
+        assert(T::alive == 1);
+        assert(T::move_constructed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(opt.value().value == 3);
+    }
+    {
+        typedef ExplicitTestTypes::TestType T;
+        static_assert(!std::is_convertible<T&&, optional<T>>::value, "");
+        T::reset();
+        optional<T> opt(T{3});
+        assert(T::alive == 1);
+        assert(T::move_constructed == 1);
+        assert(static_cast<bool>(opt) == true);
+        assert(opt.value().value == 3);
+    }
+    {
+        typedef TestTypes::TestType T;
+        T::reset();
+        optional<T> opt = {3};
+        assert(T::alive == 1);
+        assert(T::value_constructed == 1);
+        assert(T::copy_constructed == 0);
+        assert(T::move_constructed == 0);
+        assert(static_cast<bool>(opt) == true);
+        assert(opt.value().value == 3);
+    }
+    {
+        typedef ConstexprTestTypes::TestType T;
+        constexpr optional<T> opt = {T(3)};
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(opt.value().value == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+    }
+    {
+        typedef ConstexprTestTypes::TestType T;
+        constexpr optional<T> opt = {3};
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(opt.value().value == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(const T&) {}
+        };
+    }
+    {
+        typedef ExplicitConstexprTestTypes::TestType T;
+        static_assert(!std::is_convertible<T&&, optional<T>>::value, "");
+        constexpr optional<T> opt(T{3});
+        static_assert(static_cast<bool>(opt) == true, "");
+        static_assert(opt.value().value == 3, "");
+
+        struct test_constexpr_ctor
+            : public optional<T>
+        {
+            constexpr test_constexpr_ctor(T&&) {}
+        };
+
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        struct Z {
+            Z(int) {}
+            Z(Z&&) {throw 6;}
+        };
+        typedef Z T;
+        try
+        {
+            T t(3);
+            optional<T> opt(std::move(t));
+            assert(false);
+        }
+        catch (int i)
+        {
+            assert(i == 6);
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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();
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct PODType {
+  int value;
+  int value2;
+};
+
+class X
+{
+public:
+    static bool dtor_called;
+    X() = default;
+    ~X() {dtor_called = true;}
+};
+
+bool X::dtor_called = false;
+
+int main()
+{
+    {
+        typedef int T;
+        static_assert(std::is_trivially_destructible<T>::value, "");
+        static_assert(std::is_trivially_destructible<optional<T>>::value, "");
+        static_assert(std::is_literal_type<optional<T>>::value, "");
+    }
+    {
+        typedef double T;
+        static_assert(std::is_trivially_destructible<T>::value, "");
+        static_assert(std::is_trivially_destructible<optional<T>>::value, "");
+        static_assert(std::is_literal_type<optional<T>>::value, "");
+    }
+    {
+        typedef PODType T;
+        static_assert(std::is_trivially_destructible<T>::value, "");
+        static_assert(std::is_trivially_destructible<optional<T>>::value, "");
+        static_assert(std::is_literal_type<optional<T>>::value, "");
+    }
+    {
+        typedef X T;
+        static_assert(!std::is_trivially_destructible<T>::value, "");
+        static_assert(!std::is_trivially_destructible<optional<T>>::value, "");
+        static_assert(!std::is_literal_type<optional<T>>::value, "");
+        {
+            X x;
+            optional<X> opt{x};
+            assert(X::dtor_called == false);
+        }
+        assert(X::dtor_called == true);
+    }
+}

test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// void reset() noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct X
+{
+    static bool dtor_called;
+    ~X() {dtor_called = true;}
+};
+
+bool X::dtor_called = false;
+
+int main()
+{
+    {
+        optional<int> opt;
+        static_assert(noexcept(opt.reset()) == true, "");
+        opt.reset();
+        assert(static_cast<bool>(opt) == false);
+    }
+    {
+        optional<int> opt(3);
+        opt.reset();
+        assert(static_cast<bool>(opt) == false);
+    }
+    {
+        optional<X> opt;
+        static_assert(noexcept(opt.reset()) == true, "");
+        assert(X::dtor_called == false);
+        opt.reset();
+        assert(X::dtor_called == false);
+        assert(static_cast<bool>(opt) == false);
+    }
+    assert(X::dtor_called == false); // TRANSITION, Clang/C2 VSO#239997
+    {
+        optional<X> opt(X{});
+        X::dtor_called = false;
+        opt.reset();
+        assert(X::dtor_called == true);
+        assert(static_cast<bool>(opt) == false);
+        X::dtor_called = false;
+    }
+    assert(X::dtor_called == false); // TRANSITION, Clang/C2 VSO#239997
+}

test/std/utilities/optional/optional.object/optional.object.observe/bool.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr explicit optional<T>::operator bool() const noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using std::optional;
+    {
+        const optional<int> opt; ((void)opt);
+        ASSERT_NOEXCEPT(bool(opt));
+        static_assert(!std::is_convertible<optional<int>, bool>::value, "");
+    }
+    {
+        constexpr optional<int> opt;
+        static_assert(!opt, "");
+    }
+    {
+        constexpr optional<int> opt(0);
+        static_assert(opt, "");
+    }
+}

test/std/utilities/optional/optional.object/optional.object.observe/dereference.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T& optional<T>::operator*() &;
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const& {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const&& {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    constexpr int test() {return 7;}
+};
+
+constexpr int
+test()
+{
+    optional<Y> opt{Y{}};
+    return (*opt).test();
+}
+
+int main()
+{
+    {
+        optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(*opt), X&);
+        // ASSERT_NOT_NOEXCEPT(*opt);
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator*() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        optional<X> opt(X{});
+        assert((*opt).test() == 4);
+    }
+    static_assert(test() == 7, "");
+#ifdef _LIBCPP_DEBUG
+    {
+        optional<X> opt;
+        assert((*opt).test() == 3);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/dereference_const.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr const T& optional<T>::operator*() const &;
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const& {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const&& {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    int test() const {return 2;}
+};
+
+int main()
+{
+    {
+        const optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(*opt), X const&);
+        // ASSERT_NOT_NOEXCEPT(*opt);
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator*() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        constexpr optional<X> opt(X{});
+        static_assert((*opt).test() == 3, "");
+    }
+    {
+        constexpr optional<Y> opt(Y{});
+        assert((*opt).test() == 2);
+    }
+#ifdef _LIBCPP_DEBUG
+    {
+        const optional<X> opt;
+        assert((*opt).test() == 3);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/dereference_const_rvalue.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T&& optional<T>::operator*() const &&;
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const& {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const&& {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    int test() const && {return 2;}
+};
+
+int main()
+{
+    {
+        const optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(*std::move(opt)), X const &&);
+        // ASSERT_NOT_NOEXCEPT(*std::move(opt));
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator*() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        constexpr optional<X> opt(X{});
+        static_assert((*std::move(opt)).test() == 5, "");
+    }
+    {
+        constexpr optional<Y> opt(Y{});
+        assert((*std::move(opt)).test() == 2);
+    }
+#ifdef _LIBCPP_DEBUG
+    {
+        optional<X> opt;
+        assert((*std::move(opt)).test() == 5);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/dereference_rvalue.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T&& optional<T>::operator*() &&;
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const& {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const&& {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    constexpr int test() && {return 7;}
+};
+
+constexpr int
+test()
+{
+    optional<Y> opt{Y{}};
+    return (*std::move(opt)).test();
+}
+
+int main()
+{
+    {
+        optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(*std::move(opt)), X&&);
+        // ASSERT_NOT_NOEXCEPT(*std::move(opt));
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator*() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        optional<X> opt(X{});
+        assert((*std::move(opt)).test() == 6);
+    }
+    static_assert(test() == 7, "");
+#ifdef _LIBCPP_DEBUG
+    {
+        optional<X> opt;
+        assert((*std::move(opt)).test() == 3);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/has_value.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr bool optional<T>::has_value() const noexcept;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using std::optional;
+    {
+        const optional<int> opt; ((void)opt);
+        ASSERT_NOEXCEPT(opt.has_value());
+        ASSERT_SAME_TYPE(decltype(opt.has_value()), bool);
+    }
+    {
+        constexpr optional<int> opt;
+        static_assert(!opt.has_value(), "");
+    }
+    {
+        constexpr optional<int> opt(0);
+        static_assert(opt.has_value(), "");
+    }
+}

test/std/utilities/optional/optional.object/optional.object.observe/op_arrow.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T* optional<T>::operator->();
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    int test() noexcept {return 3;}
+};
+
+struct Y
+{
+    constexpr int test() {return 3;}
+};
+
+constexpr int
+test()
+{
+    optional<Y> opt{Y{}};
+    return opt->test();
+}
+
+int main()
+{
+    {
+        std::optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(opt.operator->()), X*);
+        // ASSERT_NOT_NOEXCEPT(opt.operator->());
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator->() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        optional<X> opt(X{});
+        assert(opt->test() == 3);
+    }
+    {
+        static_assert(test() == 3, "");
+    }
+#ifdef _LIBCPP_DEBUG
+    {
+        optional<X> opt;
+        assert(opt->test() == 3);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/op_arrow_const.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr const T* optional<T>::operator->() const;
+
+#ifdef _LIBCPP_DEBUG
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+#endif
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const {return 3;}
+};
+
+struct Y
+{
+    int test() const noexcept {return 2;}
+};
+
+struct Z
+{
+    const Z* operator&() const;
+    constexpr int test() const {return 1;}
+};
+
+int main()
+{
+    {
+        const std::optional<X> opt; ((void)opt);
+        ASSERT_SAME_TYPE(decltype(opt.operator->()), X const*);
+        // ASSERT_NOT_NOEXCEPT(opt.operator->());
+        // FIXME: This assertion fails with GCC because it can see that
+        // (A) operator->() is constexpr, and
+        // (B) there is no path through the function that throws.
+        // It's arguable if this is the correct behavior for the noexcept
+        // operator.
+        // Regardless this function should still be noexcept(false) because
+        // it has a narrow contract.
+    }
+    {
+        constexpr optional<X> opt(X{});
+        static_assert(opt->test() == 3, "");
+    }
+    {
+        constexpr optional<Y> opt(Y{});
+        assert(opt->test() == 2);
+    }
+    {
+        constexpr optional<Z> opt(Z{});
+        static_assert(opt->test() == 1, "");
+    }
+#ifdef _LIBCPP_DEBUG
+    {
+        const optional<X> opt;
+        assert(opt->test() == 3);
+        assert(false);
+    }
+#endif  // _LIBCPP_DEBUG
+}

test/std/utilities/optional/optional.object/optional.object.observe/value.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T& optional<T>::value() &;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::bad_optional_access;
+
+struct X
+{
+    X() = default;
+    X(const X&) = delete;
+    constexpr int test() const & {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const && {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    constexpr int test() & {return 7;}
+};
+
+constexpr int
+test()
+{
+    optional<Y> opt{Y{}};
+    return opt.value().test();
+}
+
+
+int main()
+{
+    {
+        optional<X> opt; ((void)opt);
+        ASSERT_NOT_NOEXCEPT(opt.value());
+        ASSERT_SAME_TYPE(decltype(opt.value()), X&);
+    }
+    {
+        optional<X> opt;
+        opt.emplace();
+        assert(opt.value().test() == 4);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        optional<X> opt;
+        try
+        {
+            opt.value();
+            assert(false);
+        }
+        catch (const bad_optional_access&)
+        {
+        }
+    }
+#endif
+    static_assert(test() == 7, "");
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_const.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr const T& optional<T>::value() const &;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct X
+{
+    constexpr int test() const {return 3;}
+    int test() {return 4;}
+};
+
+int main()
+{
+    {
+        constexpr optional<X> opt;
+        static_assert(opt.value().test() == 3, "");
+    }
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_const.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr const T& optional<T>::value() const &;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::in_place_t;
+using std::in_place;
+using std::bad_optional_access;
+
+struct X
+{
+    X() = default;
+    X(const X&) = delete;
+    constexpr int test() const & {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const && {return 5;}
+    int test() && {return 6;}
+};
+
+int main()
+{
+    {
+        const optional<X> opt; ((void)opt);
+        ASSERT_NOT_NOEXCEPT(opt.value());
+        ASSERT_SAME_TYPE(decltype(opt.value()), X const&);
+    }
+    {
+        constexpr optional<X> opt(in_place);
+        static_assert(opt.value().test() == 3, "");
+    }
+    {
+        const optional<X> opt(in_place);
+        assert(opt.value().test() == 3);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        const optional<X> opt;
+        try
+        {
+            opt.value();
+            assert(false);
+        }
+        catch (const bad_optional_access&)
+        {
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_const_rvalue.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr const T& optional<T>::value() const &&;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::in_place_t;
+using std::in_place;
+using std::bad_optional_access;
+
+struct X
+{
+    X() = default;
+    X(const X&) = delete;
+    constexpr int test() const & {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const && {return 5;}
+    int test() && {return 6;}
+};
+
+int main()
+{
+    {
+        const optional<X> opt; ((void)opt);
+        ASSERT_NOT_NOEXCEPT(std::move(opt).value());
+        ASSERT_SAME_TYPE(decltype(std::move(opt).value()), X const&&);
+    }
+    {
+        constexpr optional<X> opt(in_place);
+        static_assert(std::move(opt).value().test() == 5, "");
+    }
+    {
+        const optional<X> opt(in_place);
+        assert(std::move(opt).value().test() == 5);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        const optional<X> opt;
+        try
+        {
+            std::move(opt).value();
+            assert(false);
+        }
+        catch (const bad_optional_access&)
+        {
+        }
+    }
+#endif
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_or.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U> T optional<T>::value_or(U&& v) &&;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::in_place_t;
+using std::in_place;
+
+struct Y
+{
+    int i_;
+
+    Y(int i) : i_(i) {}
+};
+
+struct X
+{
+    int i_;
+
+    X(int i) : i_(i) {}
+    X(X&& x) : i_(x.i_) {x.i_ = 0;}
+    X(const Y& y) : i_(y.i_) {}
+    X(Y&& y) : i_(y.i_+1) {}
+    friend constexpr bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_;}
+};
+
+int main()
+{
+    {
+        optional<X> opt(in_place, 2);
+        Y y(3);
+        assert(std::move(opt).value_or(y) == 2);
+        assert(*opt == 0);
+    }
+    {
+        optional<X> opt(in_place, 2);
+        assert(std::move(opt).value_or(Y(3)) == 2);
+        assert(*opt == 0);
+    }
+    {
+        optional<X> opt;
+        Y y(3);
+        assert(std::move(opt).value_or(y) == 3);
+        assert(!opt);
+    }
+    {
+        optional<X> opt;
+        assert(std::move(opt).value_or(Y(3)) == 4);
+        assert(!opt);
+    }
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_or_const.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 U> constexpr T optional<T>::value_or(U&& v) const&;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct Y
+{
+    int i_;
+
+    constexpr Y(int i) : i_(i) {}
+};
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+    constexpr X(const Y& y) : i_(y.i_) {}
+    constexpr X(Y&& y) : i_(y.i_+1) {}
+    friend constexpr bool operator==(const X& x, const X& y)
+        {return x.i_ == y.i_;}
+};
+
+int main()
+{
+    {
+        constexpr optional<X> opt(2);
+        constexpr Y y(3);
+        static_assert(opt.value_or(y) == 2, "");
+    }
+    {
+        constexpr optional<X> opt(2);
+        static_assert(opt.value_or(Y(3)) == 2, "");
+    }
+    {
+        constexpr optional<X> opt;
+        constexpr Y y(3);
+        static_assert(opt.value_or(y) == 3, "");
+    }
+    {
+        constexpr optional<X> opt;
+        static_assert(opt.value_or(Y(3)) == 4, "");
+    }
+    {
+        const optional<X> opt(2);
+        const Y y(3);
+        assert(opt.value_or(y) == 2);
+    }
+    {
+        const optional<X> opt(2);
+        assert(opt.value_or(Y(3)) == 2);
+    }
+    {
+        const optional<X> opt;
+        const Y y(3);
+        assert(opt.value_or(y) == 3);
+    }
+    {
+        const optional<X> opt;
+        assert(opt.value_or(Y(3)) == 4);
+    }
+}

test/std/utilities/optional/optional.object/optional.object.observe/value_rvalue.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// constexpr T& optional<T>::value() &&;
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+using std::optional;
+using std::bad_optional_access;
+
+struct X
+{
+    X() = default;
+    X(const X&) = delete;
+    constexpr int test() const & {return 3;}
+    int test() & {return 4;}
+    constexpr int test() const && {return 5;}
+    int test() && {return 6;}
+};
+
+struct Y
+{
+    constexpr int test() && {return 7;}
+};
+
+constexpr int
+test()
+{
+    optional<Y> opt{Y{}};
+    return std::move(opt).value().test();
+}
+
+int main()
+{
+    {
+        optional<X> opt; ((void)opt);
+        ASSERT_NOT_NOEXCEPT(std::move(opt).value());
+        ASSERT_SAME_TYPE(decltype(std::move(opt).value()), X&&);
+    }
+    {
+        optional<X> opt;
+        opt.emplace();
+        assert(std::move(opt).value().test() == 6);
+    }
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        optional<X> opt;
+        try
+        {
+            std::move(opt).value();
+            assert(false);
+        }
+        catch (const bad_optional_access&)
+        {
+        }
+    }
+#endif
+    static_assert(test() == 7, "");
+}

test/std/utilities/optional/optional.object/optional.object.swap/swap.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// void swap(optional&)
+//     noexcept(is_nothrow_move_constructible<T>::value &&
+//              is_nothrow_swappable<T>::value)
+
+#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);}
+};
+
+
+int main()
+{
+    {
+        optional<int> opt1;
+        optional<int> opt2;
+        static_assert(noexcept(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        opt1.swap(opt2);
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+    }
+    {
+        optional<int> opt1(1);
+        optional<int> opt2;
+        static_assert(noexcept(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        X::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        X::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == true, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        X::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        Y::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        Y::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        Y::dtor_called = 0;
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == false);
+        opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == false);
+        try
+        {
+            opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == false);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        try
+        {
+            opt1.swap(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(opt1.swap(opt2)) == false, "");
+        assert(static_cast<bool>(opt1) == true);
+        assert(*opt1 == 1);
+        assert(static_cast<bool>(opt2) == true);
+        assert(*opt2 == 2);
+        try
+        {
+            opt1.swap(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/std/utilities/optional/optional.object/optional_requires_destructible_object.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// T shall be an object type and shall satisfy the requirements of Destructible
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+private:
+    ~X() {}
+};
+
+int main()
+{
+    using std::optional;
+    {
+        // expected-error@optional:* 2 {{static_assert failed "instantiation of optional with a reference type is ill-formed}}
+        optional<int&> opt1;
+        optional<int&&> opt2;
+    }
+    {
+        // expected-error@optional:* {{static_assert failed "instantiation of optional with a non-destructible type is ill-formed"}}
+        optional<X> opt3;
+    }
+    {
+        // expected-error@optional:* {{static_assert failed "instantiation of optional with a non-object type is undefined behavior"}}
+        // expected-error@optional:* {{static_assert failed "instantiation of optional with a non-destructible type is ill-formed}}
+        optional<void()> opt4;
+    }
+    {
+        // expected-error@optional:* {{static_assert failed "instantiation of optional with a non-object type is undefined behavior"}}
+        // expected-error@optional:* {{static_assert failed "instantiation of optional with a non-destructible type is ill-formed}}
+        // expected-error@optional:* 1+ {{cannot form a reference to 'void'}}
+        optional<const void> opt4;
+    }
+    // FIXME these are garbage diagnostics that Clang should not produce
+    // expected-error@optional:* 0+ {{is not a base class}}
+}

test/std/utilities/optional/optional.object/special_member_gen.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "archetypes.hpp"
+
+template <class T>
+struct SpecialMemberTest {
+    using O = std::optional<T>;
+
+    static_assert(std::is_default_constructible_v<O>,
+        "optional is always default constructible.");
+    static_assert(std::is_copy_constructible_v<O> == std::is_copy_constructible_v<T>,
+        "optional<T> is copy constructible if and only if T is copy constructible.");
+    static_assert(std::is_move_constructible_v<O> ==
+        (std::is_copy_constructible_v<T> || std::is_move_constructible_v<T>),
+        "optional<T> is move constructible if and only if T is copy or move constructible.");
+    static_assert(std::is_copy_assignable_v<O> ==
+        (std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>),
+        "optional<T> is copy assignable if and only if T is both copy "
+        "constructible and copy assignable.");
+    static_assert(std::is_move_assignable_v<O> ==
+        ((std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>) ||
+         (std::is_move_constructible_v<T> && std::is_move_assignable_v<T>)),
+        "optional<T> is move assignable if and only if T is both move assignable and "
+        "move constructible, or both copy constructible and copy assignable.");
+};
+
+template <class ...Args> static void sink(Args&&...) {}
+
+template <class ...TestTypes>
+struct DoTestsMetafunction {
+    DoTestsMetafunction() { sink(SpecialMemberTest<TestTypes>{}...); }
+};
+
+struct TrivialMoveNonTrivialCopy {
+    TrivialMoveNonTrivialCopy() = default;
+    TrivialMoveNonTrivialCopy(const TrivialMoveNonTrivialCopy&) {}
+    TrivialMoveNonTrivialCopy(TrivialMoveNonTrivialCopy&&) = default;
+    TrivialMoveNonTrivialCopy& operator=(const TrivialMoveNonTrivialCopy&) { return *this; }
+    TrivialMoveNonTrivialCopy& operator=(TrivialMoveNonTrivialCopy&&) = default;
+};
+
+struct TrivialCopyNonTrivialMove {
+    TrivialCopyNonTrivialMove() = default;
+    TrivialCopyNonTrivialMove(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove(TrivialCopyNonTrivialMove&&) {}
+    TrivialCopyNonTrivialMove& operator=(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove& operator=(TrivialCopyNonTrivialMove&&) { return *this; }
+};
+
+int main()
+{
+    sink(
+        ImplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        ExplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonLiteralTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonTrivialTypes::ApplyTypes<DoTestsMetafunction>{},
+        DoTestsMetafunction<TrivialMoveNonTrivialCopy, TrivialCopyNonTrivialMove>{}
+    );
+}

test/std/utilities/optional/optional.object/types.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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 optional
+// {
+// public:
+//     typedef T value_type;
+//     ...
+
+#include <optional>
+#include <type_traits>
+
+using std::optional;
+
+template <class Opt, class T>
+void
+test()
+{
+    static_assert(std::is_same<typename Opt::value_type, T>::value, "");
+}
+
+int main()
+{
+    test<optional<int>, int>();
+    test<optional<const int>, const int>();
+    test<optional<double>, double>();
+    test<optional<const double>, const double>();
+}

test/std/utilities/optional/optional.relops/equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator == ( const X &lhs, const X &rhs )
+    { return lhs.i_ == rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert (   o1 == o1 , "" );
+    static_assert (   o1 == o2 , "" );
+    static_assert ( !(o1 == o3), "" );
+    static_assert ( !(o1 == o4), "" );
+    static_assert ( !(o1 == o5), "" );
+
+    static_assert (   o2 == o1 , "" );
+    static_assert (   o2 == o2 , "" );
+    static_assert ( !(o2 == o3), "" );
+    static_assert ( !(o2 == o4), "" );
+    static_assert ( !(o2 == o5), "" );
+
+    static_assert ( !(o3 == o1), "" );
+    static_assert ( !(o3 == o2), "" );
+    static_assert (   o3 == o3 , "" );
+    static_assert ( !(o3 == o4), "" );
+    static_assert (   o3 == o5 , "" );
+
+    static_assert ( !(o4 == o1), "" );
+    static_assert ( !(o4 == o2), "" );
+    static_assert ( !(o4 == o3), "" );
+    static_assert (   o4 == o4 , "" );
+    static_assert ( !(o4 == o5), "" );
+
+    static_assert ( !(o5 == o1), "" );
+    static_assert ( !(o5 == o2), "" );
+    static_assert (   o5 == o3 , "" );
+    static_assert ( !(o5 == o4), "" );
+    static_assert (   o5 == o5 , "" );
+
+    }
+}

test/std/utilities/optional/optional.relops/greater_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator >= ( const X &lhs, const X &rhs )
+    { return lhs.i_ >= rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef optional<X> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert (  (o1 >= o1), "" );
+    static_assert (  (o1 >= o2), "" );
+    static_assert ( !(o1 >= o3), "" );
+    static_assert ( !(o1 >= o4), "" );
+    static_assert ( !(o1 >= o5), "" );
+
+    static_assert (  (o2 >= o1), "" );
+    static_assert (  (o2 >= o2), "" );
+    static_assert ( !(o2 >= o3), "" );
+    static_assert ( !(o2 >= o4), "" );
+    static_assert ( !(o2 >= o5), "" );
+
+    static_assert (  (o3 >= o1), "" );
+    static_assert (  (o3 >= o2), "" );
+    static_assert (  (o3 >= o3), "" );
+    static_assert ( !(o3 >= o4), "" );
+    static_assert (  (o3 >= o5), "" );
+
+    static_assert (  (o4 >= o1), "" );
+    static_assert (  (o4 >= o2), "" );
+    static_assert (  (o4 >= o3), "" );
+    static_assert (  (o4 >= o4), "" );
+    static_assert (  (o4 >= o5), "" );
+
+    static_assert (  (o5 >= o1), "" );
+    static_assert (  (o5 >= o2), "" );
+    static_assert (  (o5 >= o3), "" );
+    static_assert ( !(o5 >= o4), "" );
+    static_assert (  (o5 >= o5), "" );
+    }
+}

test/std/utilities/optional/optional.relops/greater_than.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator > ( const X &lhs, const X &rhs )
+    { return lhs.i_ > rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef optional<X> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert ( !(o1 > o1), "" );
+    static_assert ( !(o1 > o2), "" );
+    static_assert ( !(o1 > o3), "" );
+    static_assert ( !(o1 > o4), "" );
+    static_assert ( !(o1 > o5), "" );
+
+    static_assert ( !(o2 > o1), "" );
+    static_assert ( !(o2 > o2), "" );
+    static_assert ( !(o2 > o3), "" );
+    static_assert ( !(o2 > o4), "" );
+    static_assert ( !(o2 > o5), "" );
+
+    static_assert (  (o3 > o1), "" );
+    static_assert (  (o3 > o2), "" );
+    static_assert ( !(o3 > o3), "" );
+    static_assert ( !(o3 > o4), "" );
+    static_assert ( !(o3 > o5), "" );
+
+    static_assert (  (o4 > o1), "" );
+    static_assert (  (o4 > o2), "" );
+    static_assert (  (o4 > o3), "" );
+    static_assert ( !(o4 > o4), "" );
+    static_assert (  (o4 > o5), "" );
+
+    static_assert (  (o5 > o1), "" );
+    static_assert (  (o5 > o2), "" );
+    static_assert ( !(o5 > o3), "" );
+    static_assert ( !(o5 > o4), "" );
+    static_assert ( !(o5 > o5), "" );
+    }
+}

test/std/utilities/optional/optional.relops/less_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator <= ( const X &lhs, const X &rhs )
+    { return lhs.i_ <= rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef optional<X> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert (  (o1 <= o1), "" );
+    static_assert (  (o1 <= o2), "" );
+    static_assert (  (o1 <= o3), "" );
+    static_assert (  (o1 <= o4), "" );
+    static_assert (  (o1 <= o5), "" );
+
+    static_assert (  (o2 <= o1), "" );
+    static_assert (  (o2 <= o2), "" );
+    static_assert (  (o2 <= o3), "" );
+    static_assert (  (o2 <= o4), "" );
+    static_assert (  (o2 <= o5), "" );
+
+    static_assert ( !(o3 <= o1), "" );
+    static_assert ( !(o3 <= o2), "" );
+    static_assert (  (o3 <= o3), "" );
+    static_assert (  (o3 <= o4), "" );
+    static_assert (  (o3 <= o5), "" );
+
+    static_assert ( !(o4 <= o1), "" );
+    static_assert ( !(o4 <= o2), "" );
+    static_assert ( !(o4 <= o3), "" );
+    static_assert (  (o4 <= o4), "" );
+    static_assert ( !(o4 <= o5), "" );
+
+    static_assert ( !(o5 <= o1), "" );
+    static_assert ( !(o5 <= o2), "" );
+    static_assert (  (o5 <= o3), "" );
+    static_assert (  (o5 <= o4), "" );
+    static_assert (  (o5 <= o5), "" );
+    }
+}

test/std/utilities/optional/optional.relops/less_than.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator < ( const X &lhs, const X &rhs )
+    { return lhs.i_ < rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef optional<X> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert ( !(o1 < o1), "" );
+    static_assert ( !(o1 < o2), "" );
+    static_assert (  (o1 < o3), "" );
+    static_assert (  (o1 < o4), "" );
+    static_assert (  (o1 < o5), "" );
+
+    static_assert ( !(o2 < o1), "" );
+    static_assert ( !(o2 < o2), "" );
+    static_assert (  (o2 < o3), "" );
+    static_assert (  (o2 < o4), "" );
+    static_assert (  (o2 < o5), "" );
+
+    static_assert ( !(o3 < o1), "" );
+    static_assert ( !(o3 < o2), "" );
+    static_assert ( !(o3 < o3), "" );
+    static_assert (  (o3 < o4), "" );
+    static_assert ( !(o3 < o5), "" );
+
+    static_assert ( !(o4 < o1), "" );
+    static_assert ( !(o4 < o2), "" );
+    static_assert ( !(o4 < o3), "" );
+    static_assert ( !(o4 < o4), "" );
+    static_assert ( !(o4 < o5), "" );
+
+    static_assert ( !(o5 < o1), "" );
+    static_assert ( !(o5 < o2), "" );
+    static_assert ( !(o5 < o3), "" );
+    static_assert (  (o5 < o4), "" );
+    static_assert ( !(o5 < o5), "" );
+    }
+}

test/std/utilities/optional/optional.relops/not_equal.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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, const optional<T>& y);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+using std::optional;
+
+struct X
+{
+    int i_;
+
+    constexpr X(int i) : i_(i) {}
+};
+
+constexpr bool operator != ( const X &lhs, const X &rhs )
+    { return lhs.i_ != rhs.i_ ; }
+
+int main()
+{
+    {
+    typedef X T;
+    typedef optional<T> O;
+
+    constexpr O o1;     // disengaged
+    constexpr O o2;     // disengaged
+    constexpr O o3{1};  // engaged
+    constexpr O o4{2};  // engaged
+    constexpr O o5{1};  // engaged
+
+    static_assert ( !(o1 != o1), "" );
+    static_assert ( !(o1 != o2), "" );
+    static_assert (  (o1 != o3), "" );
+    static_assert (  (o1 != o4), "" );
+    static_assert (  (o1 != o5), "" );
+
+    static_assert ( !(o2 != o1), "" );
+    static_assert ( !(o2 != o2), "" );
+    static_assert (  (o2 != o3), "" );
+    static_assert (  (o2 != o4), "" );
+    static_assert (  (o2 != o5), "" );
+
+    static_assert (  (o3 != o1), "" );
+    static_assert (  (o3 != o2), "" );
+    static_assert ( !(o3 != o3), "" );
+    static_assert (  (o3 != o4), "" );
+    static_assert ( !(o3 != o5), "" );
+
+    static_assert (  (o4 != o1), "" );
+    static_assert (  (o4 != o2), "" );
+    static_assert (  (o4 != o3), "" );
+    static_assert ( !(o4 != o4), "" );
+    static_assert (  (o4 != o5), "" );
+
+    static_assert (  (o5 != o1), "" );
+    static_assert (  (o5 != o2), "" );
+    static_assert ( !(o5 != o3), "" );
+    static_assert (  (o5 != o4), "" );
+    static_assert ( !(o5 != o5), "" );
+
+    }
+}

test/std/utilities/optional/optional.specalg/make_optional.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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);
+    }
+}

test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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");
+    }
+}

test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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");
+    }
+}

test/std/utilities/optional/optional.specalg/swap.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+}

test/std/utilities/optional/optional.syn/optional_in_place_t.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// A program that necessitates the instantiation of template optional for
+// (possibly cv-qualified) in_place_t is ill-formed.
+
+#include <optional>
+
+int main()
+{
+    using std::optional;
+    using std::in_place_t;
+    using std::in_place;
+
+    optional<in_place_t> opt; // expected-note {{requested here}}
+    // expected-error@optional:* {{"instantiation of optional with in_place_t is ill-formed"}}
+}

test/std/utilities/optional/optional.syn/optional_includes_initializer_list.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// #include <initializer_list>
+
+#include <optional>
+
+int main()
+{
+    using std::optional;
+
+    std::initializer_list<int> list;
+}

test/std/utilities/optional/optional.syn/optional_nullopt_t.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// A program that necessitates the instantiation of template optional for
+// (possibly cv-qualified) nullopt_t is ill-formed.
+
+#include <optional>
+
+int main()
+{
+    using std::optional;
+    using std::nullopt_t;
+    using std::nullopt;
+
+    optional<nullopt_t> opt; // expected-note 1 {{requested here}}
+    optional<const nullopt_t> opt1; // expected-note 1 {{requested here}}
+    optional<nullopt_t &> opt2; // expected-note 1 {{requested here}}
+    optional<nullopt_t &&> opt3; // expected-note 1 {{requested here}}
+    // expected-error@optional:* 4 {{instantiation of optional with nullopt_t is ill-formed}}
+}

test/support/archetypes.hpp

 #ifndef TEST_SUPPORT_ARCHETYPES_HPP
 #define TEST_SUPPORT_ARCHETYPES_HPP
 
+#include <type_traits>
+#include <cassert>
+
 #include "test_macros.h"
 
 #if TEST_STD_VER >= 11
 
+namespace ArchetypeBases {
+
+template <bool, class T>
+struct DepType : T {};
+
+struct NullBase {};
+
+template <class Derived, bool Explicit = false>
+struct TestBase {
+    static int alive;
+    static int constructed;
+    static int value_constructed;
+    static int default_constructed;
+    static int copy_constructed;
+    static int move_constructed;
+    static int assigned;
+    static int value_assigned;
+    static int copy_assigned;
+    static int move_assigned;
+    static int destroyed;
+
+    static void reset() {
+        assert(alive == 0);
+        alive = 0;
+        reset_constructors();
+    }
+
+    static void reset_constructors() {
+      constructed = value_constructed = default_constructed =
+        copy_constructed = move_constructed = 0;
+      assigned = value_assigned = copy_assigned = move_assigned = destroyed = 0;
+    }
+
+    TestBase() noexcept : value(0) {
+        ++alive; ++constructed; ++default_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit TestBase(int x) noexcept : value(x) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    TestBase(int x) noexcept : value(x) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit TestBase(int x, int y) noexcept : value(y) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    TestBase(int x, int y) noexcept : value(y) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit TestBase(std::initializer_list<int>& il, int y = 0) noexcept
+      : value(il.size()) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    TestBase(std::initializer_list<int>& il, int y = 0) noexcept : value(il.size()) {
+        ++alive; ++constructed; ++value_constructed;
+    }
+    TestBase& operator=(int xvalue) noexcept {
+      value = xvalue;
+      ++assigned; ++value_assigned;
+      return *this;
+    }
+protected:
+    ~TestBase() {
+      assert(value != -999); assert(alive > 0);
+      --alive; ++destroyed; value = -999;
+    }
+    TestBase(TestBase const& o) noexcept : value(o.value) {
+        assert(o.value != -1); assert(o.value != -999);
+        ++alive; ++constructed; ++copy_constructed;
+    }
+    TestBase(TestBase && o) noexcept : value(o.value) {
+        assert(o.value != -1); assert(o.value != -999);
+        ++alive; ++constructed; ++move_constructed;
+        o.value = -1;
+    }
+    TestBase& operator=(TestBase const& o) noexcept {
+      assert(o.value != -1); assert(o.value != -999);
+      ++assigned; ++copy_assigned;
+      value = o.value;
+      return *this;
+    }
+    TestBase& operator=(TestBase&& o) noexcept {
+        assert(o.value != -1); assert(o.value != -999);
+        ++assigned; ++move_assigned;
+        value = o.value;
+        o.value = -1;
+        return *this;
+    }
+public:
+    int value;
+};
+
+template <class D, bool E> int TestBase<D, E>::alive = 0;
+template <class D, bool E> int TestBase<D, E>::constructed = 0;
+template <class D, bool E> int TestBase<D, E>::value_constructed = 0;
+template <class D, bool E> int TestBase<D, E>::default_constructed = 0;
+template <class D, bool E> int TestBase<D, E>::copy_constructed = 0;
+template <class D, bool E> int TestBase<D, E>::move_constructed = 0;
+template <class D, bool E> int TestBase<D, E>::assigned = 0;
+template <class D, bool E> int TestBase<D, E>::value_assigned = 0;
+template <class D, bool E> int TestBase<D, E>::copy_assigned = 0;
+template <class D, bool E> int TestBase<D, E>::move_assigned = 0;
+template <class D, bool E> int TestBase<D, E>::destroyed = 0;
+
+template <bool Explicit = false>
+struct ValueBase {
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr ValueBase(int x) : value(x) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr ValueBase(int x) : value(x) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr ValueBase(int x, int y) : value(y) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr ValueBase(int x, int y) : value(y) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr ValueBase(std::initializer_list<int>& il, int y = 0) : value(il.size()) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr ValueBase(std::initializer_list<int>& il, int y = 0) : value(il.size()) {}
+    constexpr ValueBase& operator=(int xvalue) noexcept {
+        value = xvalue;
+        return *this;
+    }
+    //~ValueBase() { assert(value != -999); value = -999; }
+    int value;
+protected:
+  constexpr ValueBase() noexcept : value(0) {}
+    constexpr ValueBase(ValueBase const& o) noexcept : value(o.value) {
+        assert(o.value != -1); assert(o.value != -999);
+    }
+    constexpr ValueBase(ValueBase && o) noexcept : value(o.value) {
+        assert(o.value != -1); assert(o.value != -999);
+        o.value = -1;
+    }
+    constexpr ValueBase& operator=(ValueBase const& o) noexcept {
+        assert(o.value != -1); assert(o.value != -999);
+        value = o.value;
+        return *this;
+    }
+    constexpr ValueBase& operator=(ValueBase&& o) noexcept {
+        assert(o.value != -1); assert(o.value != -999);
+        value = o.value;
+        o.value = -1;
+        return *this;
+    }
+};
+
+
+template <bool Explicit = false>
+struct TrivialValueBase {
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr TrivialValueBase(int x) : value(x) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr TrivialValueBase(int x) : value(x) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr TrivialValueBase(int x, int y) : value(y) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr TrivialValueBase(int x, int y) : value(y) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && Explicit, bool>::type = true>
+    explicit constexpr TrivialValueBase(std::initializer_list<int>& il, int y = 0) : value(il.size()) {}
+    template <bool Dummy = true, typename std::enable_if<Dummy && !Explicit, bool>::type = true>
+    constexpr TrivialValueBase(std::initializer_list<int>& il, int y = 0) : value(il.size()) {};
+    int value;
+protected:
+    constexpr TrivialValueBase() noexcept : value(0) {}
+};
+
+}
+
 //============================================================================//
 // Trivial Implicit Test Types
 namespace ImplicitTypes {
 #include "archetypes.ipp"
 }
 
 //============================================================================//
 // Trivial Explicit Test Types
 namespace ExplicitTypes {
 #define DEFINE_EXPLICIT explicit
 #include "archetypes.ipp"
 }
 
+
 //============================================================================//
-// Non-Trivial Implicit Test Types
+//
+namespace NonConstexprTypes {
+#define DEFINE_CONSTEXPR
+#include "archetypes.ipp"
+}
+
+//============================================================================//
+// Non-literal implicit test types
 namespace NonLiteralTypes {
+#define DEFINE_ASSIGN_CONSTEXPR
 #define DEFINE_DTOR(Name) ~Name() {}
 #include "archetypes.ipp"
 }
 
 //============================================================================//
 // Non-Trivially Copyable Implicit Test Types
 namespace NonTrivialTypes {
 #define DEFINE_CTOR {}
+#define DEFINE_ASSIGN { return *this; }
+#define DEFINE_DEFAULT_CTOR = default
+#include "archetypes.ipp"
+}
+
+//============================================================================//
+// Implicit counting types
+namespace TestTypes {
+#define DEFINE_CONSTEXPR
+#define DEFINE_BASE(Name) ::ArchetypeBases::TestBase<Name>
+#include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
+}
+
+}
+
+//============================================================================//
+// Implicit counting types
+namespace ExplicitTestTypes {
+#define DEFINE_CONSTEXPR
+#define DEFINE_EXPLICIT explicit
+#define DEFINE_BASE(Name) ::ArchetypeBases::TestBase<Name, true>
+#include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
+}
+
+}
+
+//============================================================================//
+// Implicit value types
+namespace ConstexprTestTypes {
+#define DEFINE_BASE(Name) ::ArchetypeBases::ValueBase<>
+#include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
+}
+
+} // end namespace ValueTypes
+
+
+//============================================================================//
+//
+namespace ExplicitConstexprTestTypes {
+#define DEFINE_EXPLICIT explicit
+#define DEFINE_BASE(Name) ::ArchetypeBases::ValueBase<true>
 #include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
 }
 
+} // end namespace ValueTypes
+
+
+//============================================================================//
+//
+namespace TrivialTestTypes {
+#define DEFINE_BASE(Name) ::ArchetypeBases::TrivialValueBase<false>
+#include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
+}
+
+} // end namespace TrivialValueTypes
+
+//============================================================================//
+//
+namespace ExplicitTrivialTestTypes {
+#define DEFINE_EXPLICIT explicit
+#define DEFINE_BASE(Name) ::ArchetypeBases::TrivialValueBase<true>
+#include "archetypes.ipp"
+
+using TestType = AllCtors;
+
+// Add equality operators
+template <class Tp>
+constexpr bool operator==(Tp const& L, Tp const& R) noexcept {
+  return L.value == R.value;
+}
+
+template <class Tp>
+constexpr bool operator!=(Tp const& L, Tp const& R) noexcept {
+  return L.value != R.value;
+}
+
+} // end namespace ExplicitTrivialTestTypes
+
 #endif // TEST_STD_VER >= 11
 
 #endif // TEST_SUPPORT_ARCHETYPES_HPP

test/support/archetypes.ipp

 
+#ifndef DEFINE_BASE
+#define DEFINE_BASE(Name) ::ArchetypeBases::NullBase
+#endif
 #ifndef DEFINE_EXPLICIT
 #define DEFINE_EXPLICIT
 #endif
+#ifndef DEFINE_CONSTEXPR
+#define DEFINE_CONSTEXPR constexpr
+#endif
+#ifndef DEFINE_ASSIGN_CONSTEXPR
+#define DEFINE_ASSIGN_CONSTEXPR DEFINE_CONSTEXPR
+#endif
 #ifndef DEFINE_CTOR
 #define DEFINE_CTOR = default
 #endif
+#ifndef DEFINE_DEFAULT_CTOR
+#define DEFINE_DEFAULT_CTOR DEFINE_CTOR
+#endif
 #ifndef DEFINE_ASSIGN
 #define DEFINE_ASSIGN = default
 #endif
 #ifndef DEFINE_DTOR
 #define DEFINE_DTOR(Name)
 #endif
 
-struct NoDefault {
-  DEFINE_EXPLICIT NoDefault() = delete;
+struct AllCtors : DEFINE_BASE(AllCtors) {
+  using Base = DEFINE_BASE(AllCtors);
+  using Base::Base;
+  using Base::operator=;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR AllCtors() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR AllCtors(AllCtors const&) DEFINE_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR AllCtors(AllCtors &&) DEFINE_CTOR;
+  DEFINE_ASSIGN_CONSTEXPR AllCtors& operator=(AllCtors const&) DEFINE_ASSIGN;
+  DEFINE_ASSIGN_CONSTEXPR AllCtors& operator=(AllCtors &&) DEFINE_ASSIGN;
+  DEFINE_DTOR(AllCtors)
+};
+
+struct NoCtors : DEFINE_BASE(NoCtors) {
+  using Base = DEFINE_BASE(NoCtors);
+  using Base::Base;
+  DEFINE_EXPLICIT NoCtors() = delete;
+  DEFINE_EXPLICIT NoCtors(NoCtors const&) = delete;
+  NoCtors& operator=(NoCtors const&) = delete;
+  DEFINE_DTOR(NoCtors)
+};
+
+struct NoDefault : DEFINE_BASE(NoDefault) {
+  using Base = DEFINE_BASE(NoDefault);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR NoDefault() = delete;
   DEFINE_DTOR(NoDefault)
 };
 
-struct AllCtors {
-  DEFINE_EXPLICIT AllCtors() DEFINE_CTOR;
-  DEFINE_EXPLICIT AllCtors(AllCtors const&) DEFINE_CTOR;
-  DEFINE_EXPLICIT AllCtors(AllCtors &&) DEFINE_CTOR;
-  AllCtors& operator=(AllCtors const&) DEFINE_ASSIGN;
-  AllCtors& operator=(AllCtors &&) DEFINE_ASSIGN;
-  DEFINE_DTOR(AllCtors)
+struct DefaultOnly : DEFINE_BASE(DefaultOnly) {
+  using Base = DEFINE_BASE(DefaultOnly);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR DefaultOnly() DEFINE_DEFAULT_CTOR;
+  DefaultOnly(DefaultOnly const&) = delete;
+  DefaultOnly& operator=(DefaultOnly const&) = delete;
+  DEFINE_DTOR(DefaultOnly)
 };
 
-struct Copyable {
-  DEFINE_EXPLICIT Copyable() DEFINE_CTOR;
-  DEFINE_EXPLICIT Copyable(Copyable const &) DEFINE_CTOR;
+struct Copyable : DEFINE_BASE(Copyable) {
+  using Base = DEFINE_BASE(Copyable);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR Copyable() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR Copyable(Copyable const &) DEFINE_CTOR;
   Copyable &operator=(Copyable const &) DEFINE_ASSIGN;
   DEFINE_DTOR(Copyable)
 };
 
-struct CopyOnly {
-  DEFINE_EXPLICIT CopyOnly() DEFINE_CTOR;
-  DEFINE_EXPLICIT CopyOnly(CopyOnly const &) DEFINE_CTOR;
-  DEFINE_EXPLICIT CopyOnly(CopyOnly &&) = delete;
+struct CopyOnly : DEFINE_BASE(CopyOnly) {
+  using Base = DEFINE_BASE(CopyOnly);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR CopyOnly() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR CopyOnly(CopyOnly const &) DEFINE_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR CopyOnly(CopyOnly &&) = delete;
   CopyOnly &operator=(CopyOnly const &) DEFINE_ASSIGN;
   CopyOnly &operator=(CopyOnly &&) = delete;
   DEFINE_DTOR(CopyOnly)
 };
 
-struct NonCopyable {
-  DEFINE_EXPLICIT NonCopyable() DEFINE_CTOR;
-  DEFINE_EXPLICIT NonCopyable(NonCopyable const &) = delete;
+struct NonCopyable : DEFINE_BASE(NonCopyable) {
+  using Base = DEFINE_BASE(NonCopyable);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR NonCopyable() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR NonCopyable(NonCopyable const &) = delete;
   NonCopyable &operator=(NonCopyable const &) = delete;
   DEFINE_DTOR(NonCopyable)
 };
 
-struct MoveOnly {
-  DEFINE_EXPLICIT MoveOnly() DEFINE_CTOR;
-  DEFINE_EXPLICIT MoveOnly(MoveOnly &&) DEFINE_CTOR;
+struct MoveOnly : DEFINE_BASE(MoveOnly) {
+  using Base = DEFINE_BASE(MoveOnly);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR MoveOnly() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR MoveOnly(MoveOnly &&) DEFINE_CTOR;
   MoveOnly &operator=(MoveOnly &&) DEFINE_ASSIGN;
   DEFINE_DTOR(MoveOnly)
 };
 
-struct CopyAssignable {
-    DEFINE_EXPLICIT CopyAssignable() = delete;
-    CopyAssignable& operator=(CopyAssignable const&) DEFINE_ASSIGN;
-    DEFINE_DTOR(CopyAssignable)
+struct CopyAssignable : DEFINE_BASE(CopyAssignable) {
+  using Base = DEFINE_BASE(CopyAssignable);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR CopyAssignable() = delete;
 };
 
-struct CopyAssignOnly {
-    DEFINE_EXPLICIT CopyAssignOnly() = delete;
-    CopyAssignOnly& operator=(CopyAssignOnly const&) DEFINE_ASSIGN;
-    CopyAssignOnly& operator=(CopyAssignOnly &&) = delete;
-    DEFINE_DTOR(CopyAssignOnly)
+struct CopyAssignOnly : DEFINE_BASE(CopyAssignOnly) {
+  using Base = DEFINE_BASE(CopyAssignOnly);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR CopyAssignOnly() = delete;
 };
 
-struct MoveAssignOnly {
-    DEFINE_EXPLICIT MoveAssignOnly() = delete;
-    MoveAssignOnly& operator=(MoveAssignOnly const&) = delete;
-    MoveAssignOnly& operator=(MoveAssignOnly &&) DEFINE_ASSIGN;
-    DEFINE_DTOR(MoveAssignOnly)
+struct MoveAssignOnly : DEFINE_BASE(MoveAssignOnly) {
+  using Base = DEFINE_BASE(MoveAssignOnly);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR MoveAssignOnly() = delete;
 };
 
-struct ConvertingType {
-  DEFINE_EXPLICIT ConvertingType() DEFINE_CTOR;
-  DEFINE_EXPLICIT ConvertingType(ConvertingType const&) DEFINE_CTOR;
-  DEFINE_EXPLICIT ConvertingType(ConvertingType &&) DEFINE_CTOR;
+struct ConvertingType : DEFINE_BASE(ConvertingType) {
+  using Base = DEFINE_BASE(ConvertingType);
+  using Base::Base;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR ConvertingType() DEFINE_DEFAULT_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR ConvertingType(ConvertingType const&) DEFINE_CTOR;
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR ConvertingType(ConvertingType &&) DEFINE_CTOR;
   ConvertingType& operator=(ConvertingType const&) DEFINE_ASSIGN;
   ConvertingType& operator=(ConvertingType &&) DEFINE_ASSIGN;
   template <class ...Args>
-  DEFINE_EXPLICIT ConvertingType(Args&&...) {}
+  DEFINE_EXPLICIT DEFINE_CONSTEXPR ConvertingType(Args&&...) {}
   template <class Arg>
   ConvertingType& operator=(Arg&&) { return *this; }
   DEFINE_DTOR(ConvertingType)
 };
 
 template <template <class...> class List>
 using ApplyTypes = List<
-    NoDefault,
     AllCtors,
+    NoCtors,
+    NoDefault,
+    DefaultOnly,
     Copyable,
     CopyOnly,
     NonCopyable,
     MoveOnly,
     CopyAssignable,
     CopyAssignOnly,
     MoveAssignOnly,
     ConvertingType
   >;
 
+#undef DEFINE_BASE
 #undef DEFINE_EXPLICIT
+#undef DEFINE_CONSTEXPR
+#undef DEFINE_ASSIGN_CONSTEXPR
 #undef DEFINE_CTOR
+#undef DEFINE_DEFAULT_CTOR
 #undef DEFINE_ASSIGN
 #undef DEFINE_DTOR