libstdc++: Avoid errors in allocator's noexcept-specifier (PR 89510)

This fixes a regression due to the conditional noexcept-specifier on
std::allocator::construct and std::allocator::destroy, as well as the
corresponding members of new_allocator, malloc_allocator, and
allocator_traits. Those noexcept-specifiers were using expressions which
might be ill-formed, which caused errors outside the immediate context
when checking for the presence of construct and destroy in SFINAE
contexts.

The fix is to use the is_nothrow_constructible and
is_nothrow_destructible type traits instead, because those traits are
safe to use even when the construction/destruction itself is not valid.

The is_nothrow_constructible trait will be false for a type that is not
also nothrow-destructible, even if the new-expression used in the
construct function body is actually noexcept. That's not the correct
answer, but isn't a problem because providing a noexcept-specifier on
these functions is not required by the standard anyway. If the answer is
false when it should be true, that's suboptimal but OK (unlike giving
errors for valid code, or giving a true answer when it should be false).

	PR libstdc++/89510
	* include/bits/alloc_traits.h (allocator_traits::_S_construct)
	(allocator_traits::_S_destroy)
	(allocator_traits<allocator<T>>::construct): Use traits in
	noexcept-specifiers.
	* include/bits/allocator.h (allocator<void>::construct)
	(allocator<void>::destroy): Likewise.
	* include/ext/malloc_allocator.h (malloc_allocator::construct)
	(malloc_allocator::destroy): Likewise.
	* include/ext/new_allocator.h (new_allocator::construct)
	(new_allocator::destroy): Likewise.
	* testsuite/20_util/allocator/89510.cc: New test.
	* testsuite/ext/malloc_allocator/89510.cc: New test.
	* testsuite/ext/new_allocator/89510.cc: New test.

8 files changed, 471 insertions, 13 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 2032e90abeb..b21c44fc0b8 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,20 @@
+2020-04-30  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/89510
+	* include/bits/alloc_traits.h (allocator_traits::_S_construct)
+	(allocator_traits::_S_destroy)
+	(allocator_traits<allocator<T>>::construct): Use traits in
+	noexcept-specifiers.
+	* include/bits/allocator.h (allocator<void>::construct)
+	(allocator<void>::destroy): Likewise.
+	* include/ext/malloc_allocator.h (malloc_allocator::construct)
+	(malloc_allocator::destroy): Likewise.
+	* include/ext/new_allocator.h (new_allocator::construct)
+	(new_allocator::destroy): Likewise.
+	* testsuite/20_util/allocator/89510.cc: New test.
+	* testsuite/ext/malloc_allocator/89510.cc: New test.
+	* testsuite/ext/new_allocator/89510.cc: New test.
+
 2020-04-29  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/94854
diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h
index 6066f48d24c..86d8ed221ff 100644
--- a/libstdc++-v3/include/bits/alloc_traits.h
+++ b/libstdc++-v3/include/bits/alloc_traits.h
@@ -251,8 +251,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
 			       is_constructible<_Tp, _Args...>>>
 	_S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
-	noexcept(noexcept(::new((void*)__p)
-			  _Tp(std::forward<_Args>(__args)...)))
+	noexcept(std::is_nothrow_constructible<_Tp, _Args...>::value)
 	{
 #if __cplusplus <= 201703L
 	  ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
@@ -271,7 +270,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Alloc2, typename _Tp>
 	static _GLIBCXX14_CONSTEXPR void
 	_S_destroy(_Alloc2&, _Tp* __p, ...)
-	noexcept(noexcept(__p->~_Tp()))
+	noexcept(std::is_nothrow_destructible<_Tp>::value)
 	{ std::_Destroy(__p); }
 
       template<typename _Alloc2>
@@ -507,7 +506,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	static _GLIBCXX20_CONSTEXPR void
 	construct(allocator_type& __a __attribute__((__unused__)), _Up* __p,
 		  _Args&&... __args)
-	noexcept(noexcept(::new((void*)__p) _Up(std::declval<_Args>()...)))
+	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
 	{
 #if __cplusplus <= 201703L
 	  __a.construct(__p, std::forward<_Args>(__args)...);
diff --git a/libstdc++-v3/include/bits/allocator.h b/libstdc++-v3/include/bits/allocator.h
index dcca769938c..d224aa3ec5e 100644
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -93,14 +93,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
 	void
 	construct(_Up* __p, _Args&&... __args)
-	noexcept(noexcept(::new((void *)__p)
-			    _Up(std::forward<_Args>(__args)...)))
+	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
 	{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
 	void
 	destroy(_Up* __p)
-	noexcept(noexcept(__p->~_Up()))
+	noexcept(std::is_nothrow_destructible<_Up>::value)
 	{ __p->~_Up(); }
 #endif // C++11 to C++17
     };
diff --git a/libstdc++-v3/include/ext/malloc_allocator.h b/libstdc++-v3/include/ext/malloc_allocator.h
index 1f41660fac7..366c766f25b 100644
--- a/libstdc++-v3/include/ext/malloc_allocator.h
+++ b/libstdc++-v3/include/ext/malloc_allocator.h
@@ -147,14 +147,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
         void
         construct(_Up* __p, _Args&&... __args)
-	noexcept(noexcept(::new((void *)__p)
-			  _Up(std::forward<_Args>(__args)...)))
+	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
 	{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
         void 
         destroy(_Up* __p)
-	noexcept(noexcept(__p->~_Up()))
+	noexcept(std::is_nothrow_destructible<_Up>::value)
 	{ __p->~_Up(); }
 #else
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h
index 959d6880276..131718b8b2f 100644
--- a/libstdc++-v3/include/ext/new_allocator.h
+++ b/libstdc++-v3/include/ext/new_allocator.h
@@ -146,14 +146,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
 	void
 	construct(_Up* __p, _Args&&... __args)
-	noexcept(noexcept(::new((void *)__p)
-			    _Up(std::forward<_Args>(__args)...)))
+	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
 	{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
 	void
 	destroy(_Up* __p)
-	noexcept(noexcept( __p->~_Up()))
+	noexcept(std::is_nothrow_destructible<_Up>::value)
 	{ __p->~_Up(); }
 #else
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
diff --git a/libstdc++-v3/testsuite/20_util/allocator/89510.cc b/libstdc++-v3/testsuite/20_util/allocator/89510.cc
new file mode 100644
index 00000000000..a3100a2b062
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/allocator/89510.cc
@@ -0,0 +1,147 @@
+// 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-do compile { target c++11 } }
+
+#include <memory>
+
+using AT = std::allocator_traits<std::allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, this should not give an error:
+constexpr bool c = has_construct<std::allocator<NoDefault>, NoDefault>::value;
+constexpr bool cv = has_construct<std::allocator<void>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<std::allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<std::allocator<NoDest>, NoDest>::value;
+constexpr bool d2 = has_traits_destroy<std::allocator<int>, NoDest>::value;
+
+std::allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );
diff --git a/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc b/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc
new file mode 100644
index 00000000000..f2ab25adb74
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc
@@ -0,0 +1,149 @@
+// 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-do compile { target c++11 } }
+
+#include <ext/malloc_allocator.h>
+#include <memory>
+#include <type_traits>
+
+using __gnu_cxx::malloc_allocator;
+using AT = std::allocator_traits<malloc_allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, these should not give errors:
+constexpr bool c = has_construct<malloc_allocator<NoDefault>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<malloc_allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<malloc_allocator<NoDest>, NoDest>::value;
+constexpr bool b2 = has_traits_destroy<malloc_allocator<int>, NoDest>::value;
+
+malloc_allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );
diff --git a/libstdc++-v3/testsuite/ext/new_allocator/89510.cc b/libstdc++-v3/testsuite/ext/new_allocator/89510.cc
new file mode 100644
index 00000000000..f684a9c157d
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/new_allocator/89510.cc
@@ -0,0 +1,149 @@
+// 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-do compile { target c++11 } }
+
+#include <ext/new_allocator.h>
+#include <memory>
+#include <type_traits>
+
+using __gnu_cxx::new_allocator;
+using AT = std::allocator_traits<new_allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, these should not give errors:
+constexpr bool c = has_construct<new_allocator<NoDefault>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<new_allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<new_allocator<NoDest>, NoDest>::value;
+constexpr bool d2 = has_traits_destroy<new_allocator<int>, NoDest>::value;
+
+new_allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );