Implement LWG 2900, The copy and move constructors of optional are not constexpr.

Implement LWG 2900, The copy and move constructors
of optional are not constexpr.
* include/std/optional (_Optional_payload): New.
(_Optional_base): Remove the bool parameter.
(_Optional_base<_Tp, false>): Remove.
(_Optional_base()): Adjust.
(_Optional_base(nullopt_t)): Likewise.
(_Optional_base(in_place_t, _Args&&...)): Likewise.
(_Optional_base(in_place_t, initializer_list<_Up>, _Args&&...)):
Likewise.
(_Optional_base(const _Optional_base&)): Likewise.
(_Optional_base(_Optional_base&&)): Likewise.
(operator=(const _Optional_base&)): Likewise.
(operator=(_Optional_base&&)): Likewise.
(~_Optional_base()): Remove.
(_M_is_engaged()): Adjust.
(_M_get()): Likewise.
(_M_construct(_Args&&...)): Likewise.
(_M_destruct()): Likewise.
(_M_reset()): Likewise.
(_Optional_base::_Empty_byte): Remove.
(_Optional_base::_M_empty): Remove.
(_Optional_base::_M_payload): Adjust.
* testsuite/20_util/optional/cons/value_neg.cc: Adjust.
* testsuite/20_util/optional/constexpr/cons/value.cc: Add tests.

From-SVN: r246556

libstdc++-v3/ChangeLog

+2017-03-29  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	Implement LWG 2900, The copy and move constructors
+	of optional are not constexpr.
+	* include/std/optional (_Optional_payload): New.
+	(_Optional_base): Remove the bool parameter.
+	(_Optional_base<_Tp, false>): Remove.
+	(_Optional_base()): Adjust.
+	(_Optional_base(nullopt_t)): Likewise.
+	(_Optional_base(in_place_t, _Args&&...)): Likewise.
+	(_Optional_base(in_place_t, initializer_list<_Up>, _Args&&...)):
+	Likewise.
+	(_Optional_base(const _Optional_base&)): Likewise.
+	(_Optional_base(_Optional_base&&)): Likewise.
+	(operator=(const _Optional_base&)): Likewise.
+	(operator=(_Optional_base&&)): Likewise.
+	(~_Optional_base()): Remove.
+	(_M_is_engaged()): Adjust.
+	(_M_get()): Likewise.
+	(_M_construct(_Args&&...)): Likewise.
+	(_M_destruct()): Likewise.
+	(_M_reset()): Likewise.
+	(_Optional_base::_Empty_byte): Remove.
+	(_Optional_base::_M_empty): Remove.
+	(_Optional_base::_M_payload): Adjust.
+	* testsuite/20_util/optional/cons/value_neg.cc: Adjust.
+	* testsuite/20_util/optional/constexpr/cons/value.cc: Add tests.
+
 2017-03-28  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/80137

libstdc++-v3/testsuite/20_util/optional/cons/value_neg.cc

@@ -37,8 +37,8 @@ int main()
     std::optional<std::unique_ptr<int>> oup2 = new int;  // { dg-error "conversion" }
     struct U { explicit U(std::in_place_t); };
     std::optional<U> ou(std::in_place); // { dg-error "no matching" }
-    // { dg-error "no type" "" { target { *-*-* } } 437 }
-    // { dg-error "no type" "" { target { *-*-* } } 447 }
-    // { dg-error "no type" "" { target { *-*-* } } 504 }
+    // { dg-error "no type" "" { target { *-*-* } } 488 }
+    // { dg-error "no type" "" { target { *-*-* } } 498 }
+    // { dg-error "no type" "" { target { *-*-* } } 555 }
   }
 }

libstdc++-v3/testsuite/20_util/optional/constexpr/cons/value.cc

@@ -66,4 +66,21 @@ int main()
     static_assert( o, "" );
     static_assert( *o == 0x1234ABCD, "" );
   }
+  {
+    constexpr std::optional<long> o = 42;
+    constexpr std::optional<long> o2{o};
+    constexpr std::optional<long> o3(o);
+    constexpr std::optional<long> o4 = o;
+    constexpr std::optional<long> o5;
+    constexpr std::optional<long> o6{o5};
+    constexpr std::optional<long> o7(o5);
+    constexpr std::optional<long> o8 = o5;
+    constexpr std::optional<long> o9{std::move(o)};
+    constexpr std::optional<long> o10(std::move(o));
+    constexpr std::optional<long> o11 = std::move(o);
+    constexpr std::optional<long> o12;
+    constexpr std::optional<long> o13{std::move(o5)};
+    constexpr std::optional<long> o14(std::move(o5));
+    constexpr std::optional<long> o15 = std::move(o5);
+  }
 }