Implement LWG 2769, Redundant const in the return type of any_cast(const any&).

Implement LWG 2769, Redundant const in the return type of
any_cast(const any&).
* include/std/any (_AnyCast): New.
(any_cast(const any&)): Use it and add an explicit cast for return.
(any_cast(any&)): Likewise.
(any_cast(any&&)): Likewise.
* testsuite/20_util/any/misc/any_cast.cc: Add a test for a type
that has an explicit copy constructor.
*testsuite/20_util/any/misc/any_cast_neg.cc: Adjust.

From-SVN: r243739

2 files changed, 14 insertions, 1 deletions

diff --git a/libstdc++-v3/testsuite/20_util/any/misc/any_cast.cc b/libstdc++-v3/testsuite/20_util/any/misc/any_cast.cc
index 96f9419e070..f3ae5927904 100644
--- a/libstdc++-v3/testsuite/20_util/any/misc/any_cast.cc
+++ b/libstdc++-v3/testsuite/20_util/any/misc/any_cast.cc
@@ -106,9 +106,22 @@ void test03()
   MoveDeleted&& md3 = any_cast<MoveDeleted&&>(any(std::move(md)));
 }
 
+void test04()
+{
+  struct ExplicitCopy
+  {
+    ExplicitCopy() = default;
+    explicit ExplicitCopy(const ExplicitCopy&) = default;
+  };
+  any x = ExplicitCopy();
+  ExplicitCopy ec{any_cast<ExplicitCopy>(x)};
+  ExplicitCopy ec2{any_cast<ExplicitCopy>(std::move(x))};
+}
+
 int main()
 {
   test01();
   test02();
   test03();
+  test04();
 }
diff --git a/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc b/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
index 4de400d717e..a8a1ca9fd0a 100644
--- a/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
@@ -26,5 +26,5 @@ void test01()
   using std::any_cast;
 
   const any y(1);
-  any_cast<int&>(y); // { dg-error "qualifiers" "" { target { *-*-* } } 453 }
+  any_cast<int&>(y); // { dg-error "invalid static_cast" "" { target { *-*-* } } 455 }
 }