From 260bc58f574498791c027b9ad4d4e5ccdcf2d568 Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel@inf.ethz.ch>
Date: Mon, 18 Jan 2016 21:00:25 +0100
Subject: [PATCH] improved SFINAE in type_caster_generic (closes #70)

---
 include/pybind11/cast.h   | 4 ++--
 include/pybind11/common.h | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index bc26e4777..909ce1418 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -209,11 +209,11 @@ public:
     operator type*() { return (type *) value; }
     operator type&() { return *((type *) value); }
 protected:
-    template <typename T = type, typename std::enable_if<std::is_copy_constructible<T>::value, int>::type = 0>
+    template <typename T = type, typename std::enable_if<detail::is_copy_constructible<T>::value, int>::type = 0>
     static void *copy_constructor(const void *arg) {
         return new type(*((const type *) arg));
     }
-    template <typename T = type, typename std::enable_if<!std::is_copy_constructible<T>::value, int>::type = 0>
+    template <typename T = type, typename std::enable_if<!detail::is_copy_constructible<T>::value, int>::type = 0>
     static void *copy_constructor(const void *) { return nullptr; }
 };
 
diff --git a/include/pybind11/common.h b/include/pybind11/common.h
index a0af6787d..7122d80ce 100644
--- a/include/pybind11/common.h
+++ b/include/pybind11/common.h
@@ -240,6 +240,14 @@ template <typename T> struct intrinsic_type<T&&>                  { typedef type
 template <typename T, size_t N> struct intrinsic_type<const T[N]> { typedef typename intrinsic_type<T>::type type; };
 template <typename T, size_t N> struct intrinsic_type<T[N]>       { typedef typename intrinsic_type<T>::type type; };
 
+/** \brief SFINAE helper class to check if a copy constructor is usable (in contrast to 
+ * std::is_copy_constructible, this class also checks if the 'new' operator is accessible */
+template <typename T>  struct is_copy_constructible {
+    template <typename T2> static std::true_type test(decltype(new T2(std::declval<T2>())) *);
+    template <typename T2> static std::false_type test(...);
+    static const bool value = std::is_same<std::true_type, decltype(test<T>(nullptr))>::value;
+};
+
 /// Helper type to replace 'void' in some expressions
 struct void_type { };