From bd5f7828683cd4306c7709a4183d0f84a789401e Mon Sep 17 00:00:00 2001
From: Marshall Clow <mclow.lists@gmail.com>
Date: Mon, 10 Apr 2017 22:51:07 +0000
Subject: [PATCH] Fix PR#32606: std::decay mishandles abominable function types

llvm-svn: 299894
---
 libcxx/include/type_traits                          | 21 ++++++++++++++++-----
 .../meta/meta.trans/meta.trans.other/decay.pass.cpp |  6 ++++++
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
index 277a9fb..ec158fc 100644
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -1272,11 +1272,13 @@ template <class _Tp> using remove_all_extents_t = typename remove_all_extents<_T
 
 // decay
 
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS decay
-{
-private:
-    typedef typename remove_reference<_Tp>::type _Up;
+template <class _Up, bool>
+struct __decay {
+    typedef typename remove_cv<_Up>::type type;
+};
+
+template <class _Up>
+struct __decay<_Up, true> {
 public:
     typedef typename conditional
                      <
@@ -1291,6 +1293,15 @@ public:
                      >::type type;
 };
 
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS decay
+{
+private:
+    typedef typename remove_reference<_Tp>::type _Up;
+public:
+    typedef typename __decay<_Up, __is_referenceable<_Up>::value>::type type;
+};
+
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using decay_t = typename decay<_Tp>::type;
 #endif
diff --git a/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp b/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
index bcd8398..4f45a03 100644
--- a/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
+++ b/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
@@ -33,4 +33,10 @@ int main()
     test_decay<int[3], int*>();
     test_decay<const int[3], const int*>();
     test_decay<void(), void (*)()>();
+#if TEST_STD_VER > 11
+	test_decay<int(int) const, int(int) const>();
+	test_decay<int(int) volatile, int(int) volatile>();
+	test_decay<int(int)  &, int(int)  &>();
+	test_decay<int(int) &&, int(int) &&>();
+#endif
 }
-- 
2.7.4