More tests to validate the const-correctness of the tensor code.

Eigen/src/Core/GenericPacketMath.h

diff --git a/Eigen/src/Core/GenericPacketMath.h b/Eigen/src/Core/GenericPacketMath.h
index 6ec29d0..e6fea5b 100644
--- a/Eigen/src/Core/GenericPacketMath.h
+++ b/Eigen/src/Core/GenericPacketMath.h
@@ -95,6 +95,8 @@
   };
 };
 
+template<typename T> struct packet_traits<const T> : packet_traits<T> { };
+
 /** \internal \returns a + b (coeff-wise) */
 template<typename Packet> EIGEN_DEVICE_FUNC inline Packet
 padd(const Packet& a,

Eigen/src/Core/util/XprHelper.h

diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 7c77b22..67ca497 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -415,6 +415,14 @@
 {
   typedef A ret;
 };
+template <typename A> struct promote_storage_type<A, const A>
+{
+  typedef A ret;
+};
+template <typename A> struct promote_storage_type<const A, A>
+{
+  typedef A ret;
+};
 
 /** \internal gives the plain matrix or array type to store a row/column/diagonal of a matrix type.
   * \param Scalar optional parameter allowing to pass a different scalar type than the one of the MatrixType.

unsupported/test/CMakeLists.txt

diff --git a/unsupported/test/CMakeLists.txt b/unsupported/test/CMakeLists.txt
index e83d8b5..a47c7bc 100644
--- a/unsupported/test/CMakeLists.txt
+++ b/unsupported/test/CMakeLists.txt
@@ -106,7 +106,8 @@
   ei_add_test(cxx11_tensor_convolution "-std=c++0x")
   ei_add_test(cxx11_tensor_expr "-std=c++0x")
 #  ei_add_test(cxx11_tensor_fixed_size "-std=c++0x")
-#  ei_add_test(cxx11_tensor_of_const_values "-std=c++0x")
+  ei_add_test(cxx11_tensor_const "-std=c++0x")
+  ei_add_test(cxx11_tensor_of_const_values "-std=c++0x")
   ei_add_test(cxx11_tensor_of_strings "-std=c++0x")
   ei_add_test(cxx11_tensor_intdiv "-std=c++0x")
   ei_add_test(cxx11_tensor_lvalue "-std=c++0x")

unsupported/test/cxx11_tensor_const.cpp

diff --git a/unsupported/test/cxx11_tensor_const.cpp b/unsupported/test/cxx11_tensor_const.cpp
new file mode 100644
index 0000000..0ffb02a
--- /dev/null
+++ b/unsupported/test/cxx11_tensor_const.cpp
@@ -0,0 +1,39 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include "main.h"
+
+#include <Eigen/CXX11/Tensor>
+using Eigen::Tensor;
+
+
+
+
+static void test_simple_assign()
+{
+  Tensor<int, 3> random(2,3,7);
+  random.setRandom();
+
+  TensorMap<Tensor<const int, 3> > constant(random.data(), 2, 3, 7);
+  Tensor<int, 3> result(2,3,7);
+  result = constant;
+
+  for (int i = 0; i < 2; ++i) {
+    for (int j = 0; j < 3; ++j) {
+      for (int k = 0; k < 7; ++k) {
+        VERIFY_IS_EQUAL((result(i,j,k)), random(i,j,k));
+      }
+    }
+  }
+}
+
+void test_cxx11_tensor_const()
+{
+  CALL_SUBTEST(test_simple_assign());
+}