Update status for std::optional LWG issues and fix an optional SFINAE bug

llvm-svn: 284323

5 files changed, 35 insertions, 14 deletions

diff --git a/libcxx/include/experimental/optional b/libcxx/include/experimental/optional
index 966c889e99d..ebe11e6b934 100644
--- a/libcxx/include/experimental/optional
+++ b/libcxx/include/experimental/optional
@@ -487,7 +487,11 @@ public:
     operator->() const
     {
         _LIBCPP_ASSERT(this->__engaged_, "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return _VSTD::addressof(this->__val_);
+#else
         return __operator_arrow(__has_operator_addressof<value_type>{});
+#endif
     }
 
     _LIBCPP_INLINE_VISIBILITY
diff --git a/libcxx/include/optional b/libcxx/include/optional
index 46252c7e0e0..c64aa8f7f72 100644
--- a/libcxx/include/optional
+++ b/libcxx/include/optional
@@ -681,12 +681,14 @@ public:
     // 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>
-                      >
+                      <__lazy_and<
+                          integral_constant<bool,
+                              !is_same_v<decay_t<_Up>, optional> &&
+                              !(is_same_v<_Up, value_type> && is_scalar_v<value_type>)
+                          >,
+                          is_constructible<value_type, _Up>,
+                          is_assignable<value_type&, _Up>
+                      >::value>
              >
     _LIBCPP_INLINE_VISIBILITY
     optional&
diff --git a/libcxx/test/std/experimental/optional/optional.object/optional.object.observe/op_arrow_const.pass.cpp b/libcxx/test/std/experimental/optional/optional.object/optional.object.observe/op_arrow_const.pass.cpp
index cf900d7029e..46586c65a6e 100644
--- a/libcxx/test/std/experimental/optional/optional.object/optional.object.observe/op_arrow_const.pass.cpp
+++ b/libcxx/test/std/experimental/optional/optional.object/optional.object.observe/op_arrow_const.pass.cpp
@@ -51,6 +51,9 @@ int main()
     {
         constexpr optional<Z> opt(Z{});
         assert(opt->test() == 1);
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        static_assert(opt->test() == 1, "");
+#endif
     }
 #ifdef _LIBCPP_DEBUG
     {
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/assign_value.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/assign_value.pass.cpp
index 6abdd0db63c..1207e24150f 100644
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/assign_value.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/assign_value.pass.cpp
@@ -48,6 +48,16 @@ struct MismatchType {
   MismatchType& operator=(char*) = delete;
 };
 
+struct FromOptionalType {
+  using Opt = std::optional<FromOptionalType>;
+  FromOptionalType() = default;
+  FromOptionalType(FromOptionalType const&) = delete;
+  template <class Dummy = void>
+  constexpr FromOptionalType(Opt&) { Dummy::BARK; }
+  template <class Dummy = void>
+  constexpr FromOptionalType& operator=(Opt&) { Dummy::BARK; return *this; }
+};
+
 void test_sfinae() {
     using I = TestTypes::TestType;
     using E = ExplicitTestTypes::TestType;
@@ -68,6 +78,8 @@ void test_sfinae() {
     assert_assignable<MismatchType, int>();
     assert_assignable<MismatchType, int*, false>();
     assert_assignable<MismatchType, char*, false>();
+    // Type constructible from optional
+    assert_assignable<FromOptionalType, std::optional<FromOptionalType>&, false>();
 }
 
 void test_with_test_type()
diff --git a/libcxx/www/upcoming_meeting.html b/libcxx/www/upcoming_meeting.html
index 36c9a74272d..1fc56e8e4b0 100644
--- a/libcxx/www/upcoming_meeting.html
+++ b/libcxx/www/upcoming_meeting.html
@@ -109,19 +109,19 @@
 	 <tr><td><a href="http://wg21.link/LWG2736">2736</a></td><td>nullopt_t insufficiently constrained</td><td>Issaquah</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2738">2738</a></td><td>is_constructible with void types</td><td>Issaquah</td><td>We already do this</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2739">2739</a></td><td>Issue with time_point non-member subtraction with an unsigned duration</td><td>Issaquah</td><td>Patch Ready</td></tr>
-	 <tr><td><a href="http://wg21.link/LWG2740">2740</a></td><td>constexpr optional<T>::operator-></td><td>Issaquah</td><td></td></tr>
+	 <tr><td><a href="http://wg21.link/LWG2740">2740</a></td><td>constexpr optional<T>::operator-></td><td>Issaquah</td><td>We already do this</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2742">2742</a></td><td>Inconsistent string interface taking string_view</td><td>Issaquah</td><td>Patch Ready</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2744">2744</a></td><td>any's in_place constructors</td><td>Issaquah</td><td>Implemented in trunk</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2745">2745</a></td><td>[fund.ts.v2] Implementability of LWG 2451</td><td>Issaquah</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2747">2747</a></td><td>Possibly redundant std::move in [alg.foreach]</td><td>Issaquah</td><td>Patch ready</td></tr>
-	 <tr><td><a href="http://wg21.link/LWG2748">2748</a></td><td>swappable traits for optionals</td><td>Issaquah</td><td></td></tr>
+	 <tr><td><a href="http://wg21.link/LWG2748">2748</a></td><td>swappable traits for optionals</td><td>Issaquah</td><td>We already do this</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2749">2749</a></td><td>swappable traits for variants</td><td>Issaquah</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2750">2750</a></td><td>[fund.ts.v2] LWG 2451 conversion constructor constraint</td><td>Issaquah</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2752">2752</a></td><td>"Throws:" clauses of async and packaged_task are unimplementable</td><td>Issaquah</td><td></td></tr>
-	 <tr><td><a href="http://wg21.link/LWG2753">2753</a></td><td>Optional's constructors and assignments need constraints</td><td>Issaquah</td><td></td></tr>
+	 <tr><td><a href="http://wg21.link/LWG2753">2753</a></td><td>Optional's constructors and assignments need constraints</td><td>Issaquah</td><td>We already do this</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2754">2754</a></td><td>The in_place constructors and emplace functions added by P0032R3 don't require CopyConstructible</td><td>Issaquah</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2755">2755</a></td><td>§[string.view.io] uses non-existent basic_string_view::to_string function</td><td>Issaquah</td><td>We already do this</td></tr>
-	 <tr><td><a href="http://wg21.link/LWG2756">2756</a></td><td>C++ WP optional<T> should 'forward' T's implicit conversions</td><td>Issaquah</td><td></td></tr>
+	 <tr><td><a href="http://wg21.link/LWG2756">2756</a></td><td>C++ WP optional<T> should 'forward' T's implicit conversions</td><td>Issaquah</td><td>Implemented in trunk</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2758">2758</a></td><td>std::string{}.assign("ABCDE", 0, 1) is ambiguous</td><td>We already do this</td><td></td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2759">2759</a></td><td>gcd / lcm and bool for the WP</td><td>Issaquah</td><td>Patch ready</td></tr>
 	 <tr><td><a href="http://wg21.link/LWG2760">2760</a></td><td>non-const basic_string::data should not invalidate iterators</td><td>Issaquah</td><td>Nothing to do</td></tr>
@@ -187,19 +187,19 @@
 <li>2736 - </li>
 <li>2738 - We already do this; I added tests for cv-void</li>
 <li>2739 - Patch and tests ready</li>
-<li>2740 - <i>std::optional</i></li>
+<li>2740 - <i>std::optional</i>: The resolution LGTM. </li>
 <li>2742 - Patch and tests ready</li>
 <li>2744 - <i>std::any</i>: We already do this. We also check for a decayed in_place_type_t. </li>
 <li>2745 - <i>std::optional</i> for LFTS -- should be considered for C++17</li>
 <li>2747 - Patch ready, but I can't think of any way to test it.</li>
-<li>2748 - <i>std::optional</i></li>
+<li>2748 - <i>std::optional</i>: LGTM. </li>
 <li>2749 - <i>std::variant</i></li>
 <li>2750 - <i>std::optional</i> for LFTS -- should be considered for C++17</li>
 <li>2752 - </li>
-<li>2753 - <i>std::optional</i></li>
+<li>2753 - <i>std::optional</i>: LGTM. </li>
 <li>2754 - </li>
 <li>2755 - Both string and string_view call a common routine for output; so no code changes needed.</li>
-<li>2756 - <i>std::optional</i></li>
+<li>2756 - <i>std::optional</i>: Very large change. It is fully implemented and tested. </li>
 <li>2758 - We already do this. </li>
 <li>2759 - Patch and tests ready</li>
 <li>2760 - This is just wording cleanup; no code or test changes needed.</li>