From c05e98660f673191b13ae2fee8f6b823e515d4a2 Mon Sep 17 00:00:00 2001
From: Howard Hinnant <hhinnant@apple.com>
Date: Sun, 30 Jun 2013 19:48:15 +0000
Subject: [PATCH] Fix bind by making _is_valid_bind_return more robust.  It
 should return false instead of give a compile time error, always.  The
 problem was down in ____mu_return, the version that handles nested bind
 objects.  This fixes http://llvm.org/bugs/show_bug.cgi?id=16343

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@185289 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/functional                            | 14 ++++-
 .../func.bind/func.bind.bind/nested.pass.cpp  | 51 +++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 test/utilities/function.objects/bind/func.bind/func.bind.bind/nested.pass.cpp

diff --git a/include/functional b/include/functional
index 995db564c..d9e6ee94b 100644
--- a/include/functional
+++ b/include/functional
@@ -1594,12 +1594,24 @@ template <class _Ti, bool IsReferenceWrapper, bool IsBindEx, bool IsPh,
           class _TupleUj>
 struct ____mu_return;
 
+template <bool _Invokable, class _Ti, class ..._Uj>
+struct ____mu_return_invokable  // false
+{
+    typedef __nat type;
+};
+
 template <class _Ti, class ..._Uj>
-struct ____mu_return<_Ti, false, true, false, tuple<_Uj...> >
+struct ____mu_return_invokable<true, _Ti, _Uj...>
 {
     typedef typename __invoke_of<_Ti&, _Uj...>::type type;
 };
 
+template <class _Ti, class ..._Uj>
+struct ____mu_return<_Ti, false, true, false, tuple<_Uj...> >
+    : public ____mu_return_invokable<__invokable<_Ti&, _Uj...>::value, _Ti, _Uj...>
+{
+};
+
 template <class _Ti, class _TupleUj>
 struct ____mu_return<_Ti, false, false, true, _TupleUj>
 {
diff --git a/test/utilities/function.objects/bind/func.bind/func.bind.bind/nested.pass.cpp b/test/utilities/function.objects/bind/func.bind/func.bind.bind/nested.pass.cpp
new file mode 100644
index 000000000..12720f7b5
--- /dev/null
+++ b/test/utilities/function.objects/bind/func.bind/func.bind.bind/nested.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// template<CopyConstructible Fn, CopyConstructible... Types>
+//   unspecified bind(Fn, Types...);
+// template<Returnable R, CopyConstructible Fn, CopyConstructible... Types>
+//   unspecified bind(Fn, Types...);
+
+// http://llvm.org/bugs/show_bug.cgi?id=16343
+
+#include <cmath>
+#include <functional>
+#include <cassert>
+
+struct power
+{
+  template <typename T>
+  T
+  operator()(T a, T b)
+  {
+    return std::pow(a, b);
+  }
+};
+
+struct plus_one
+{
+  template <typename T>
+  T
+  operator()(T a)
+  {
+    return a + 1;
+  }
+};
+
+int
+main()
+{
+    using std::placeholders::_1;
+
+    auto g = std::bind(power(), 2, _1);
+    assert(g(5) == 32);
+    assert(std::bind(plus_one(), g)(5) == 33);
+}