Enforce allocator::value_type consistency for containers in C++2a

diff --git a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
index 8a17747e3bd..4b0336931f4 100644
--- a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
+++ b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
@@ -951,6 +951,21 @@  Feature-testing recommendations for C++</link>.
       <entry align="center"> 9.1 </entry>
       <entry />
     </row>
+
+    <row>
+      <entry>
+        Mandating the Standard Library:
+        Clause 21 - Containers library
+      </entry>
+      <entry>
+        <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1463r1.pdf">
+        P1463R1
+	</link>
+      </entry>
+      <entry align="center"> 10 </entry>
+      <entry/>
+    </row>
+
   </tbody>
 </tgroup>
 </table>
diff --git a/libstdc++-v3/include/bits/forward_list.h b/libstdc++-v3/include/bits/forward_list.h
index 4c277845a51..e686283a432 100644
--- a/libstdc++-v3/include/bits/forward_list.h
+++ b/libstdc++-v3/include/bits/forward_list.h
@@ -421,7 +421,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     {
       static_assert(is_same<typename remove_cv<_Tp>::type, _Tp>::value,
 	  "std::forward_list must have a non-const, non-volatile value_type");
-#ifdef __STRICT_ANSI__
+#if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
 	  "std::forward_list must have the same value_type as its allocator");
 #endif
diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index ab24b5bb537..384e39877f2 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -188,7 +188,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       static_assert(is_same<typename remove_cv<_Value>::type, _Value>::value,
 	  "unordered container must have a non-const, non-volatile value_type");
-#ifdef __STRICT_ANSI__
+#if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Value>{},
 	  "unordered container must have the same value_type as its allocator");
 #endif
diff --git a/libstdc++-v3/include/bits/stl_deque.h b/libstdc++-v3/include/bits/stl_deque.h
index 7dcb53823c4..ac76d681ff0 100644
--- a/libstdc++-v3/include/bits/stl_deque.h
+++ b/libstdc++-v3/include/bits/stl_deque.h
@@ -824,7 +824,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #if __cplusplus >= 201103L
       static_assert(is_same<typename remove_cv<_Tp>::type, _Tp>::value,
 	  "std::deque must have a non-const, non-volatile value_type");
-# ifdef __STRICT_ANSI__
+# if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
 	  "std::deque must have the same value_type as its allocator");
 # endif
diff --git a/libstdc++-v3/include/bits/stl_list.h b/libstdc++-v3/include/bits/stl_list.h
index 68bab94af1e..701982538df 100644
--- a/libstdc++-v3/include/bits/stl_list.h
+++ b/libstdc++-v3/include/bits/stl_list.h
@@ -563,7 +563,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #if __cplusplus >= 201103L
       static_assert(is_same<typename remove_cv<_Tp>::type, _Tp>::value,
 	  "std::list must have a non-const, non-volatile value_type");
-# ifdef __STRICT_ANSI__
+# if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
 	  "std::list must have the same value_type as its allocator");
 # endif
diff --git a/libstdc++-v3/include/bits/stl_map.h b/libstdc++-v3/include/bits/stl_map.h
index 322d0a8290a..b1083d572d6 100644
--- a/libstdc++-v3/include/bits/stl_map.h
+++ b/libstdc++-v3/include/bits/stl_map.h
@@ -118,7 +118,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       __glibcxx_class_requires2(value_type, _Alloc_value_type, _SameTypeConcept)
 #endif
 
-#if __cplusplus >= 201103L && defined(__STRICT_ANSI__)
+#if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, value_type>::value,
 	  "std::map must have the same value_type as its allocator");
 #endif
diff --git a/libstdc++-v3/include/bits/stl_multimap.h b/libstdc++-v3/include/bits/stl_multimap.h
index 4c4ccad3ac0..bb4aece96bf 100644
--- a/libstdc++-v3/include/bits/stl_multimap.h
+++ b/libstdc++-v3/include/bits/stl_multimap.h
@@ -117,7 +117,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       __glibcxx_class_requires2(value_type, _Alloc_value_type, _SameTypeConcept)
 #endif
 
-#if __cplusplus >= 201103L && defined(__STRICT_ANSI__)
+#if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, value_type>::value,
 	  "std::multimap must have the same value_type as its allocator");
 #endif
diff --git a/libstdc++-v3/include/bits/stl_multiset.h b/libstdc++-v3/include/bits/stl_multiset.h
index af733ea34dc..96fa14e2afa 100644
--- a/libstdc++-v3/include/bits/stl_multiset.h
+++ b/libstdc++-v3/include/bits/stl_multiset.h
@@ -109,7 +109,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #if __cplusplus >= 201103L
       static_assert(is_same<typename remove_cv<_Key>::type, _Key>::value,
 	  "std::multiset must have a non-const, non-volatile value_type");
-# ifdef __STRICT_ANSI__
+# if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Key>::value,
 	  "std::multiset must have the same value_type as its allocator");
 # endif
diff --git a/libstdc++-v3/include/bits/stl_set.h b/libstdc++-v3/include/bits/stl_set.h
index 3131a7974b0..279b9705d78 100644
--- a/libstdc++-v3/include/bits/stl_set.h
+++ b/libstdc++-v3/include/bits/stl_set.h
@@ -107,7 +107,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #if __cplusplus >= 201103L
       static_assert(is_same<typename remove_cv<_Key>::type, _Key>::value,
 	  "std::set must have a non-const, non-volatile value_type");
-# ifdef __STRICT_ANSI__
+# if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Key>::value,
 	  "std::set must have the same value_type as its allocator");
 # endif
diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h
index dd9382d254d..d33e589498a 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -397,7 +397,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #if __cplusplus >= 201103L
       static_assert(is_same<typename remove_cv<_Tp>::type, _Tp>::value,
 	  "std::vector must have a non-const, non-volatile value_type");
-# ifdef __STRICT_ANSI__
+# if __cplusplus > 201703L || defined __STRICT_ANSI__
       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
 	  "std::vector must have the same value_type as its allocator");
 # endif
diff --git a/libstdc++-v3/testsuite/23_containers/deque/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/deque/48101-3_neg.cc
new file mode 100644
index 00000000000..724b3de6a03
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/deque/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <deque>
+
+void
+test01()
+{
+  std::deque<int, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/forward_list/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/forward_list/48101-3_neg.cc
new file mode 100644
index 00000000000..d0e56f59494
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/forward_list/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <forward_list>
+
+void
+test01()
+{
+  std::forward_list<int, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/list/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/list/48101-3_neg.cc
new file mode 100644
index 00000000000..ce32e9ced82
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/list/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <list>
+
+void
+test01()
+{
+  std::list<int, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/map/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/map/48101-3_neg.cc
new file mode 100644
index 00000000000..dfce9c2179c
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/map/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <map>
+
+void
+test01()
+{
+  std::map<int, int, std::less<int>, std::allocator<int>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/multimap/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/multimap/48101-3_neg.cc
new file mode 100644
index 00000000000..77769498548
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/multimap/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <map>
+
+void
+test01()
+{
+  std::multimap<int, int, std::less<int>, std::allocator<int>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/multiset/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/multiset/48101-3_neg.cc
new file mode 100644
index 00000000000..209a1d5deeb
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/multiset/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <set>
+
+void
+test01()
+{
+  std::multiset<int, std::less<int>, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/set/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/set/48101-3_neg.cc
new file mode 100644
index 00000000000..75777370a3a
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/set/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <set>
+
+void
+test01()
+{
+  std::set<int, std::less<int>, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/48101-3_neg.cc
new file mode 100644
index 00000000000..98bcd8c755b
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/48101-3_neg.cc
@@ -0,0 +1,30 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <unordered_map>
+
+void
+test01()
+{
+  using namespace std;
+  unordered_map<int, int, hash<int>, equal_to<int>, allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_multimap/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/unordered_multimap/48101-3_neg.cc
new file mode 100644
index 00000000000..3bda27b8354
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_multimap/48101-3_neg.cc
@@ -0,0 +1,30 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <unordered_map>
+
+void
+test01()
+{
+  using namespace std;
+  unordered_multimap<int, int, hash<int>, equal_to<int>, allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_multiset/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/unordered_multiset/48101-3_neg.cc
new file mode 100644
index 00000000000..620c9b703bd
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_multiset/48101-3_neg.cc
@@ -0,0 +1,30 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <unordered_set>
+
+void
+test01()
+{
+  using namespace std;
+  unordered_multiset<int, hash<int>, equal_to<int>, allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_set/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/unordered_set/48101-3_neg.cc
new file mode 100644
index 00000000000..c226c5236f8
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_set/48101-3_neg.cc
@@ -0,0 +1,30 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <unordered_set>
+
+void
+test01()
+{
+  using namespace std;
+  unordered_set<int, hash<int>, equal_to<int>, allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/23_containers/vector/48101-3_neg.cc b/libstdc++-v3/testsuite/23_containers/vector/48101-3_neg.cc
new file mode 100644
index 00000000000..2317efa1516
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/48101-3_neg.cc
@@ -0,0 +1,29 @@ 
+// Copyright (C) 2017-2019 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++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <vector>
+
+void
+test01()
+{
+  std::vector<int, std::allocator<long>> c;
+}
+
+// { dg-error "same value_type as its allocator" "" { target *-*-* } 0 }