From a382bc9364b5d5a049678f8cc138670ca1c7a4fa Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Fri, 18 May 2018 17:02:27 +0200
Subject: [PATCH] is_convertible<T,Index> does not seems to work well with MSVC
 2013, so let's rather use __is_enum(T) for old MSVC versions

---
 Eigen/src/Core/util/XprHelper.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 1217404d6..9ffb0474b 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -39,10 +39,12 @@ template<typename T> struct is_valid_index_type
 {
   enum { value =
 #if EIGEN_HAS_TYPE_TRAITS
-   internal::is_integral<T>::value || std::is_enum<T>::value
+    internal::is_integral<T>::value || std::is_enum<T>::value
+#else if EIGEN_COMP_MSVC >= 1500
+    internal::is_integral<T>::value || __is_enum(T)
 #else
-  // without C++11, we use is_convertible to Index instead of is_integral in order to treat enums as Index.
-  internal::is_convertible<T,Index>::value
+    // without C++11, we use is_convertible to Index instead of is_integral in order to treat enums as Index.
+    internal::is_convertible<T,Index>::value
 #endif
   };
 };