libstdc++: Fix constructor constraints for std::any (PR 90415)

This removes a non-standard extension to std::any which causes errors
for valid code, due to recursive instantiation of a trait that isn't
supposed to be in the constraints.

It also removes some incorrect constraints on the in_place_type<T>
constructors and emplace members, which were preventing creating a
std::any object with another std::any as the contained value.

2020-04-24  Kamlesh Kumar  <kamleshbhalui@gmail.com>
	    Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/90415
	PR libstdc++/92156
	* include/std/any (any): Rename template parameters for consistency
	with the standard.
	(any::_Decay): Rename to _Decay_if_not_any.
	(any::any(T&&):: Remove is_constructible from constraints. Remove
	non-standard overload.
	(any::any(in_place_type_t<T>, Args&&...))
	(any::any(in_place_type_t<T>, initializer_list<U>, Args&&...))
	(any::emplace(Args&&...))
	(any::emplace(initializer_list<U>, Args&&...)):
	Use decay_t instead of _Decay.
	* testsuite/20_util/any/cons/90415.cc: New test.
	* testsuite/20_util/any/cons/92156.cc: New Test.
	* testsuite/20_util/any/misc/any_cast_neg.cc: Make dg-error directives
	more robust.
	* testsuite/20_util/any/modifiers/92156.cc: New test.

4 files changed, 183 insertions, 7 deletions

diff --git a/libstdc++-v3/testsuite/20_util/any/cons/90415.cc b/libstdc++-v3/testsuite/20_util/any/cons/90415.cc
new file mode 100644
index 00000000000..122262386d3
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/any/cons/90415.cc
@@ -0,0 +1,64 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+// 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 <any>
+#include <utility>
+#include <tuple>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  // PR libstdc++/90415
+  static_assert( std::is_copy_constructible<std::tuple<std::any>>::value );
+}
+
+struct wrapper
+{
+  wrapper() = default;
+
+  wrapper(const std::any& t);
+
+  wrapper(const wrapper& w);
+
+  auto& operator=(const std::any& t);
+
+  auto& operator=(const wrapper& w)
+  {
+    value = w.value;
+    return *this;
+  }
+
+  std::any value;
+};
+
+void
+test02()
+{
+  // PR libstdc++/91630
+  wrapper a, b;
+  a = b;
+}
+
+int main()
+{
+  test01();
+  test02();
+}
diff --git a/libstdc++-v3/testsuite/20_util/any/cons/92156.cc b/libstdc++-v3/testsuite/20_util/any/cons/92156.cc
new file mode 100644
index 00000000000..d797473716d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/any/cons/92156.cc
@@ -0,0 +1,53 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+// 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 <any>
+#include <utility>
+#include <tuple>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto a = std::any(std::in_place_type<std::any>, 5);
+  VERIFY( std::any_cast<int>(std::any_cast<std::any>(a)) == 5 );
+
+  auto b = std::any(std::in_place_type<std::any>, {1});
+  (void) std::any_cast<std::initializer_list<int>>(std::any_cast<std::any>(b));
+}
+
+void
+test02()
+{
+  std::any p = std::pair<std::any, std::any>(1, 1);
+  auto pt = std::any_cast<std::pair<std::any, std::any>>(p);
+  VERIFY( std::any_cast<int>(pt.first) == 1 );
+  VERIFY( std::any_cast<int>(pt.second) == 1 );
+
+  std::any t = std::tuple<std::any>(1);
+  auto tt = std::any_cast<std::tuple<std::any>>(t);
+  VERIFY( std::any_cast<int>(std::get<0>(tt)) == 1 );
+}
+
+int main()
+{
+  test01();
+  test02();
+}
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 6a271e8faab..049815a0c1f 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
@@ -1,5 +1,5 @@
 // { dg-options "-std=gnu++17" }
-// { dg-do compile }
+// { dg-do compile { target c++17 } }
 
 // Copyright (C) 2014-2020 Free Software Foundation, Inc.
 //
@@ -26,20 +26,22 @@ using std::any_cast;
 void test01()
 {
   const any y(1);
-  any_cast<int&>(y); // { dg-error "invalid 'static_cast'" "" { target { *-*-* } } 461 }
-  // { dg-error "Template argument must be constructible from a const value" "" { target { *-*-* } } 457 }
+  any_cast<int&>(y); // { dg-error "here" }
+  // { dg-error "Template argument must be constructible from a const value" "" { target { *-*-* } } 0 }
 }
 
 void test02()
 {
   any y(1);
-  any_cast<int&&>(y);
-  // { dg-error "Template argument must be constructible from an lvalue" "" { target { *-*-* } } 483 }
+  any_cast<int&&>(y); // { dg-error "here" }
+  // { dg-error "Template argument must be constructible from an lvalue" "" { target { *-*-* } } 0 }
 }
 
 void test03()
 {
   any y(1);
-  any_cast<int&>(std::move(y));  // { dg-error "invalid 'static_cast'" "" { target { *-*-* } } 501 }
-  // { dg-error "Template argument must be constructible from an rvalue" "" { target { *-*-* } } 497 }
+  any_cast<int&>(std::move(y)); // { dg-error "here" }
+  // { dg-error "Template argument must be constructible from an rvalue" "" { target { *-*-* } } 0 }
 }
+
+// { dg-prune-output "invalid 'static_cast'" }
diff --git a/libstdc++-v3/testsuite/20_util/any/modifiers/92156.cc b/libstdc++-v3/testsuite/20_util/any/modifiers/92156.cc
new file mode 100644
index 00000000000..4a7bc97bb83
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/any/modifiers/92156.cc
@@ -0,0 +1,57 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+// 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 <any>
+#include <utility>
+#include <tuple>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::any a;
+  a.emplace<std::any>(5);
+  VERIFY( std::any_cast<int>(std::any_cast<std::any>(a)) == 5 );
+
+  std::any b;
+  b.emplace<std::any>({1});
+  (void) std::any_cast<std::initializer_list<int>>(std::any_cast<std::any>(b));
+}
+
+void
+test02()
+{
+  std::any p;
+  p.emplace<std::pair<std::any, std::any>>(1, 1);
+  auto pt = std::any_cast<std::pair<std::any, std::any>>(p);
+  VERIFY( std::any_cast<int>(pt.first) == 1 );
+  VERIFY( std::any_cast<int>(pt.second) == 1 );
+
+  std::any t;
+  t.emplace<std::tuple<std::any>>(1);
+  auto tt = std::any_cast<std::tuple<std::any>>(t);
+  VERIFY( std::any_cast<int>(std::get<0>(tt)) == 1 );
+}
+
+int main()
+{
+  test01();
+  test02();
+}