From 2c462f4201365d1ac4872245e81066746f09ac47 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Mon, 6 Jun 2016 23:11:38 +0200
Subject: [PATCH] Clean handling for void type in
 EIGEN_CHECK_BINARY_COMPATIBILIY

---
 Eigen/src/Core/util/Meta.h      | 24 ++++++++++++++++++++++++
 Eigen/src/Core/util/XprHelper.h |  8 +-------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index af661c313..efb9961ce 100644
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -430,6 +430,30 @@ struct ScalarBinaryOpTraits<T,T,BinaryOp>
   typedef T ReturnType;
 };
 
+// For Matrix * Permutation
+template<typename T, typename BinaryOp>
+struct ScalarBinaryOpTraits<T,void,BinaryOp>
+{
+  enum { Defined = 1 };
+  typedef T ReturnType;
+};
+
+// For Permutation * Matrix
+template<typename T, typename BinaryOp>
+struct ScalarBinaryOpTraits<void,T,BinaryOp>
+{
+  enum { Defined = 1 };
+  typedef T ReturnType;
+};
+
+// for Permutation*Permutation
+template<typename BinaryOp>
+struct ScalarBinaryOpTraits<void,void,BinaryOp>
+{
+  enum { Defined = 1 };
+  typedef void ReturnType;
+};
+
 template<typename T, typename BinaryOp>
 struct ScalarBinaryOpTraits<T,std::complex<T>,BinaryOp>
 {
diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 4fd4a9b0d..828813161 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -610,11 +610,6 @@ bool is_same_dense(const T1 &, const T2 &, typename enable_if<!(has_direct_acces
   return false;
 }
 
-template<typename T, typename U> struct is_same_or_void { enum { value = is_same<T,U>::value }; };
-template<typename T> struct is_same_or_void<void,T>     { enum { value = 1 }; };
-template<typename T> struct is_same_or_void<T,void>     { enum { value = 1 }; };
-template<>           struct is_same_or_void<void,void>  { enum { value = 1 }; };
-
 #ifdef EIGEN_DEBUG_ASSIGN
 std::string demangle_traversal(int t)
 {
@@ -653,9 +648,8 @@ std::string demangle_flags(int f)
 // It is tempting to always allow mixing different types but remember that this is often impossible in the vectorized paths.
 // So allowing mixing different types gives very unexpected errors when enabling vectorization, when the user tries to
 // add together a float matrix and a double matrix.
-// Treat "void" as a special case. Needed for permutation products. TODO: this should be handled by ScalarBinaryOpTraits
 #define EIGEN_CHECK_BINARY_COMPATIBILIY(BINOP,LHS,RHS) \
-  EIGEN_STATIC_ASSERT(int(internal::is_same_or_void<LHS, RHS>::value) || int(ScalarBinaryOpTraits<LHS, RHS,BINOP>::Defined), \
+  EIGEN_STATIC_ASSERT(int(ScalarBinaryOpTraits<LHS, RHS,BINOP>::Defined), \
     YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
     
 } // end namespace Eigen