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

@@ -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>
 {

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);
+}