PR libstdc++/95915

	PR libstdc++/95915
	* include/std/type_traits (is_literal_type, is_literal_type_v):
	Deprecate in C++17.
	* include/std/variant (_Uninitialized):
	Adjust the condition and the comment.
	* testsuite/20_util/is_literal_type/deprecated-1z.cc: New.
	* testsuite/20_util/is_literal_type/requirements/explicit_instantiation.cc:
	Adjust.
	* testsuite/20_util/is_literal_type/requirements/typedefs.cc: Likewise.
	* testsuite/20_util/is_literal_type/value.cc: Likewise.
	* testsuite/20_util/optional/constexpr/nullopt.cc:
	Use __is_literal_type directly.
	* testsuite/20_util/optional/nullopt.cc: Likewise.
	* testsuite/20_util/variable_templates_for_traits.cc: Adjust.
	* testsuite/20_util/variant/95915.cc: New.
	* testsuite/20_util/variant/compile.cc: Add new test.
	* testsuite/experimental/optional/constexpr/nullopt.cc:
	Use __is_literal_type directly.
	* testsuite/experimental/optional/nullopt.cc: Likewise.
	* testsuite/experimental/type_traits/value.cc: Adjust.
	* testsuite/util/testsuite_common_types.h:
	Use __is_literal_type directly.

15 files changed, 92 insertions, 18 deletions

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index bc9a45b..9cd3a2d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -703,7 +703,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   /// is_literal_type
   template<typename _Tp>
-    struct is_literal_type
+    struct
+    _GLIBCXX17_DEPRECATED
+    is_literal_type
     : public integral_constant<bool, __is_literal_type(_Tp)>
     {
       static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
@@ -3085,10 +3087,11 @@ template <typename _Tp>
 template <typename _Tp>
   _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
   inline constexpr bool is_pod_v = is_pod<_Tp>::value;
-#pragma GCC diagnostic pop
 template <typename _Tp>
+  _GLIBCXX17_DEPRECATED
   inline constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
-template <typename _Tp>
+#pragma GCC diagnostic pop
+ template <typename _Tp>
   inline constexpr bool is_empty_v = is_empty<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_polymorphic_v = is_polymorphic<_Tp>::value;
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 6eeb3c8..c950491 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -202,15 +202,9 @@ namespace __variant
 	  std::forward<_Variants>(__variants)...);
     }
 
-  // _Uninitialized<T> is guaranteed to be a literal type, even if T is not.
-  // We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented
-  // yet. When it's implemented, _Uninitialized<T> can be changed to the alias
-  // to T, therefore equivalent to being removed entirely.
-  //
-  // Another reason we may not want to remove _Uninitialzied<T> may be that, we
-  // want _Uninitialized<T> to be trivially destructible, no matter whether T
-  // is; but we will see.
-  template<typename _Type, bool = std::is_literal_type_v<_Type>>
+  // _Uninitialized<T> is guaranteed to be a trivially destructible type,
+  // even if T is not.
+  template<typename _Type, bool = std::is_trivially_destructible_v<_Type>>
     struct _Uninitialized;
 
   template<typename _Type>
diff --git a/libstdc++-v3/testsuite/20_util/is_literal_type/deprecated-1z.cc b/libstdc++-v3/testsuite/20_util/is_literal_type/deprecated-1z.cc
new file mode 100644
index 0000000..a91ff56
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_literal_type/deprecated-1z.cc
@@ -0,0 +1,26 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <type_traits>
+
+static_assert(std::is_literal_type<int>::value); // { dg-warning "is deprecated" }
+static_assert(std::is_literal_type_v<int>); // { dg-warning "is deprecated" }
+
+// { dg-prune-output "declared here" }
diff --git a/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/explicit_instantiation.cc b/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/explicit_instantiation.cc
index d0a20f3..aa2a80e 100644
--- a/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/explicit_instantiation.cc
+++ b/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/explicit_instantiation.cc
@@ -1,3 +1,4 @@
+// { dg-additional-options "-Wno-deprecated" { target c++17 } }
 // { dg-do compile { target c++11 } }
 // 2010-02-21  Paolo Carlini  <paolo.carlini@oracle.com>
 
diff --git a/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/typedefs.cc b/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/typedefs.cc
index 9b7ae89..2bb7554 100644
--- a/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/typedefs.cc
+++ b/libstdc++-v3/testsuite/20_util/is_literal_type/requirements/typedefs.cc
@@ -1,3 +1,4 @@
+// { dg-additional-options "-Wno-deprecated" { target c++17 } }
 // { dg-do compile { target c++11 } }
 
 // 2010-02-21  Paolo Carlini  <paolo.carlini@oracle.com>
diff --git a/libstdc++-v3/testsuite/20_util/is_literal_type/value.cc b/libstdc++-v3/testsuite/20_util/is_literal_type/value.cc
index a662477..56c5b8d 100644
--- a/libstdc++-v3/testsuite/20_util/is_literal_type/value.cc
+++ b/libstdc++-v3/testsuite/20_util/is_literal_type/value.cc
@@ -1,3 +1,4 @@
+// { dg-additional-options "-Wno-deprecated" { target c++17 } }
 // { dg-do compile { target c++11 } }
 
 // 2010-03-23  Paolo Carlini  <paolo.carlini@oracle.com>
diff --git a/libstdc++-v3/testsuite/20_util/optional/constexpr/nullopt.cc b/libstdc++-v3/testsuite/20_util/optional/constexpr/nullopt.cc
index 62b6681..d66728e 100644
--- a/libstdc++-v3/testsuite/20_util/optional/constexpr/nullopt.cc
+++ b/libstdc++-v3/testsuite/20_util/optional/constexpr/nullopt.cc
@@ -26,7 +26,7 @@ int main()
   // [20.5.6] Disengaged state indicator
   static_assert( std::is_same<decltype(std::nullopt), const std::nullopt_t>(), "" );
   static_assert( std::is_empty<std::nullopt_t>(), "" );
-  static_assert( std::is_literal_type<std::nullopt_t>(), "" );
+  static_assert( __is_literal_type(std::nullopt_t), "" );
   static_assert( !std::is_default_constructible<std::nullopt_t>(), "" );
 
   {
diff --git a/libstdc++-v3/testsuite/20_util/optional/nullopt.cc b/libstdc++-v3/testsuite/20_util/optional/nullopt.cc
index c0b2184..325e528 100644
--- a/libstdc++-v3/testsuite/20_util/optional/nullopt.cc
+++ b/libstdc++-v3/testsuite/20_util/optional/nullopt.cc
@@ -26,7 +26,7 @@ int main()
   // [20.5.6] Disengaged state indicator
   static_assert( std::is_same<decltype(std::nullopt), const std::nullopt_t>(), "" );
   static_assert( std::is_empty<std::nullopt_t>(), "" );
-  static_assert( std::is_literal_type<std::nullopt_t>(), "" );
+  static_assert( __is_literal_type(std::nullopt_t), "" );
   static_assert( !std::is_default_constructible<std::nullopt_t>(), "" );
 
   {
diff --git a/libstdc++-v3/testsuite/20_util/variable_templates_for_traits.cc b/libstdc++-v3/testsuite/20_util/variable_templates_for_traits.cc
index 40a3f41..0f1625a 100644
--- a/libstdc++-v3/testsuite/20_util/variable_templates_for_traits.cc
+++ b/libstdc++-v3/testsuite/20_util/variable_templates_for_traits.cc
@@ -147,10 +147,13 @@ static_assert(is_pod_v<int>
 static_assert(!is_pod_v<NType>
 	      && !is_pod<NType>::value, "");
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 static_assert(is_literal_type_v<int>
 	      && is_literal_type<int>::value, "");
 static_assert(!is_literal_type_v<NType>
 	      && !is_literal_type<NType>::value, "");
+#pragma GCC diagnostic pop
 
 static_assert(is_empty_v<EmptyFinal>
 	      && is_empty<EmptyFinal>::value, "");
diff --git a/libstdc++-v3/testsuite/20_util/variant/95915.cc b/libstdc++-v3/testsuite/20_util/variant/95915.cc
new file mode 100644
index 0000000..411ff2d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/variant/95915.cc
@@ -0,0 +1,35 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <variant>
+
+using namespace std;
+
+struct virtual_default_dtor {
+   virtual ~virtual_default_dtor() = default;
+};
+
+void default_ctor()
+{
+  {
+    variant<virtual_default_dtor> a;
+  }
+}
+
diff --git a/libstdc++-v3/testsuite/20_util/variant/compile.cc b/libstdc++-v3/testsuite/20_util/variant/compile.cc
index b2b60d1..5f68175 100644
--- a/libstdc++-v3/testsuite/20_util/variant/compile.cc
+++ b/libstdc++-v3/testsuite/20_util/variant/compile.cc
@@ -84,6 +84,10 @@ struct nonliteral
   bool operator>(const nonliteral&) const;
 };
 
+struct virtual_default_dtor {
+   virtual ~virtual_default_dtor() = default;
+};
+
 void default_ctor()
 {
   static_assert(is_default_constructible_v<variant<int, string>>);
@@ -95,6 +99,9 @@ void default_ctor()
   static_assert(noexcept(variant<int>()));
   static_assert(!noexcept(variant<Empty>()));
   static_assert(noexcept(variant<DefaultNoexcept>()));
+  {
+    variant<virtual_default_dtor> a;
+  }
 }
 
 void copy_ctor()
diff --git a/libstdc++-v3/testsuite/experimental/optional/constexpr/nullopt.cc b/libstdc++-v3/testsuite/experimental/optional/constexpr/nullopt.cc
index 3aa9d0c..6fe9a2a 100644
--- a/libstdc++-v3/testsuite/experimental/optional/constexpr/nullopt.cc
+++ b/libstdc++-v3/testsuite/experimental/optional/constexpr/nullopt.cc
@@ -25,7 +25,7 @@ int main()
   // [20.5.6] Disengaged state indicator
   static_assert( std::is_same<decltype(std::experimental::nullopt), const std::experimental::nullopt_t>(), "" );
   static_assert( std::is_empty<std::experimental::nullopt_t>(), "" );
-  static_assert( std::is_literal_type<std::experimental::nullopt_t>(), "" );
+  static_assert( __is_literal_type(std::experimental::nullopt_t), "" );
   static_assert( !std::is_default_constructible<std::experimental::nullopt_t>(), "" );
 
   {
diff --git a/libstdc++-v3/testsuite/experimental/optional/nullopt.cc b/libstdc++-v3/testsuite/experimental/optional/nullopt.cc
index e31fc37..73f6b53 100644
--- a/libstdc++-v3/testsuite/experimental/optional/nullopt.cc
+++ b/libstdc++-v3/testsuite/experimental/optional/nullopt.cc
@@ -25,7 +25,7 @@ int main()
   // [20.5.6] Disengaged state indicator
   static_assert( std::is_same<decltype(std::experimental::nullopt), const std::experimental::nullopt_t>(), "" );
   static_assert( std::is_empty<std::experimental::nullopt_t>(), "" );
-  static_assert( std::is_literal_type<std::experimental::nullopt_t>(), "" );
+  static_assert( __is_literal_type(std::experimental::nullopt_t), "" );
   static_assert( !std::is_default_constructible<std::experimental::nullopt_t>(), "" );
 
   {
diff --git a/libstdc++-v3/testsuite/experimental/type_traits/value.cc b/libstdc++-v3/testsuite/experimental/type_traits/value.cc
index 0e1176d..52a6e69 100644
--- a/libstdc++-v3/testsuite/experimental/type_traits/value.cc
+++ b/libstdc++-v3/testsuite/experimental/type_traits/value.cc
@@ -214,10 +214,13 @@ static_assert(is_pod_v<int>
 static_assert(!is_pod_v<NType>
 	      && !is_pod<NType>::value, "");
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 static_assert(is_literal_type_v<int>
 	      && is_literal_type<int>::value, "");
 static_assert(!is_literal_type_v<NType>
 	      && !is_literal_type<NType>::value, "");
+#pragma GCC diagnostic pop
 
 static_assert(is_empty_v<EmptyFinal>
 	      && is_empty<EmptyFinal>::value, "");
diff --git a/libstdc++-v3/testsuite/util/testsuite_common_types.h b/libstdc++-v3/testsuite/util/testsuite_common_types.h
index 2795df3..92af3af 100644
--- a/libstdc++-v3/testsuite/util/testsuite_common_types.h
+++ b/libstdc++-v3/testsuite/util/testsuite_common_types.h
@@ -749,7 +749,7 @@ namespace __gnu_test
   // Generator to test default constructor.
   struct constexpr_default_constructible
   {
-    template<typename _Tp, bool _IsLitp = std::is_literal_type<_Tp>::value>
+    template<typename _Tp, bool _IsLitp = __is_literal_type(_Tp)>
       struct _Concept;
 
     // NB: _Tp must be a literal type.
@@ -801,7 +801,7 @@ namespace __gnu_test
   struct constexpr_single_value_constructible
   {
     template<typename _Ttesttype, typename _Tvaluetype,
-	     bool _IsLitp = std::is_literal_type<_Ttesttype>::value>
+	     bool _IsLitp = __is_literal_type(_Ttesttype)>
       struct _Concept;
 
     // NB: _Tvaluetype and _Ttesttype must be literal types.