Index: include/functional
===================================================================
--- include/functional
+++ include/functional
@@ -1446,18 +1446,86 @@
     template <class _R2, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(_R2 (*__p)(_Ap...)) {return __p;}
+    template <class _R2, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (*__p)(_Ap..., ...)) { return __p; }
     template <class _R2, class _Cp, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(_R2 (_Cp::*__p)(_Ap...)) {return __p;}
     template <class _R2, class _Cp, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...)) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const) {return __p;}
     template <class _R2, class _Cp, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(_R2 (_Cp::*__p)(_Ap...) volatile) {return __p;}
     template <class _R2, class _Cp, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) volatile) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const volatile) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const volatile) {return __p;}
+
+#if __has_feature(cxx_reference_qualified_functions)
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) volatile &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) volatile &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const volatile &) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const volatile &) {return __p;}
+
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) volatile &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) volatile &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap...) const volatile &&) {return __p;}
+    template <class _R2, class _Cp, class ..._Ap>
+        _LIBCPP_INLINE_VISIBILITY
+        static bool __not_null(_R2 (_Cp::*__p)(_Ap..., ...) const volatile &&) {return __p;}
+#endif // __has_feature(cxx_reference_qualified_functions)
+
     template <class _R2, class ..._Ap>
         _LIBCPP_INLINE_VISIBILITY
         static bool __not_null(const function<_R2(_Ap...)>& __p) {return !!__p;}
Index: test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/F.pass.cpp
===================================================================
--- test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/F.pass.cpp
+++ test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/F.pass.cpp
@@ -11,7 +11,7 @@
 
 // class function<R(ArgTypes...)>
 
-// function(nullptr_t);
+// function(Fp);
 
 #include <functional>
 #include <cassert>
Index: test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/F_nullptr.pass.cpp
===================================================================
--- /dev/null
+++ test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/F_nullptr.pass.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <functional>
+
+// class function<R(ArgTypes...)>
+
+// function(Fp);
+
+// Ensure that __not_null works for all function types.
+// See https://llvm.org/bugs/show_bug.cgi?id=23589
+
+#include <functional>
+#include <cassert>
+
+struct A {};
+
+#define NULL_CV_TYPE
+
+#define TEST_CV_TYPE(CV) \
+    test<void(A::*)() CV, void(A CV &), A CV &>(); \
+    test<void(A::*)(...) CV, void(A CV &), A CV &>(); \
+    test<void(A::*)() CV &, void(A CV &), A CV &>(); \
+    test<void(A::*)(...) CV &, void(A CV &), A CV &>(); \
+    test<void(A::*)() CV &&, void(A CV &&), A CV &&>(); \
+    test<void(A::*)(...) CV &&, void(A CV &&), A CV &&>()
+
+template <class MemFn, class Fn, class CVA>
+void test() {
+    MemFn mf = nullptr;
+    std::function<Fn> f = mf;
+    A a;
+    try { f(static_cast<CVA>(a)); assert(false); }
+    catch (std::bad_function_call&) {}
+}
+
+int main() {
+    {
+        void (*p)() = nullptr;
+        std::function< void() > f = p;
+        try { f(); }
+        catch ( std::bad_function_call & ) {}
+    }
+    {
+        void (*p)(...) = nullptr;
+        std::function< void() > f = p;
+        try { f(); }
+        catch ( std::bad_function_call & ) {}
+    }
+    {
+        TEST_CV_TYPE( NULL_CV_TYPE );
+        TEST_CV_TYPE( const );
+        TEST_CV_TYPE( volatile );
+        TEST_CV_TYPE( const volatile );
+    }
+}
\ No newline at end of file