re PR libstdc++/84601 (std::optional<std::pair<int, int>> is not assignment copyable)

PR libstdc++/84601
* include/std/optional (_Optional_payload): Split into multiple
specializations that can handle different cases of trivial or
non-trivial assignment operators.
* testsuite/20_util/optional/84601.cc: New.
* testsuite/20_util/optional/cons/value_neg.cc: Adjust.

From-SVN: r258304

libstdc++-v3/ChangeLog

+2018-03-06  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR libstdc++/84601
+	* include/std/optional (_Optional_payload): Split into multiple
+	specializations that can handle different cases of trivial or
+	non-trivial assignment operators.
+	* testsuite/20_util/optional/84601.cc: New.
+	* testsuite/20_util/optional/cons/value_neg.cc: Adjust.
+
 2018-03-02  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/84671

libstdc++-v3/testsuite/20_util/optional/84601.cc

+// { dg-options "-std=gnu++17" }
+// { dg-do compile }
+
+#include <optional>
+
+using pair_t = std::pair<int, int>;
+using opt_t = std::optional<pair_t>;
+
+static_assert(std::is_copy_constructible_v<opt_t::value_type>);
+static_assert(std::is_copy_assignable_v<opt_t::value_type>);
+
+static_assert(std::is_copy_assignable_v<opt_t>); // assertion fails.
+
+class A
+{
+  void f(const opt_t& opt)
+  {
+    _opt = opt;
+  }
+
+  opt_t _opt;
+};

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 { *-*-* } } 647 }
-    // { dg-error "no type" "" { target { *-*-* } } 657 }
-    // { dg-error "no type" "" { target { *-*-* } } 714 }
+    // { dg-error "no type" "" { target { *-*-* } } 1015 }
+    // { dg-error "no type" "" { target { *-*-* } } 1025 }
+    // { dg-error "no type" "" { target { *-*-* } } 1082 }
   }
 }