From 66f056776f1220ede1aa5cbfe058b88d6df3e359 Mon Sep 17 00:00:00 2001
From: Eugene Zhulenev <ezhulenev@google.com>
Date: Sat, 15 Sep 2018 15:17:38 -0700
Subject: [PATCH] Add DSizes index type promotion

---
 .../Eigen/CXX11/src/Tensor/TensorDimensions.h | 19 ++++++++++++++++++-
 unsupported/test/cxx11_tensor_dimension.cpp   | 18 ++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
index 94871ef43..5de0d0de7 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
@@ -290,10 +290,27 @@ struct DSizes : array<DenseIndex, NumDims> {
     }
   }
 
+#ifdef EIGEN_HAS_CXX11
+  // Enable DSizes index type promotion only if we are promoting to the
+  // larger type, e.g. allow to promote dimensions of type int to long.
+  template<typename OtherIndex,
+           typename std::enable_if<
+               std::is_same<
+                 DenseIndex,
+                 typename internal::promote_index_type<DenseIndex, OtherIndex>::type
+               >::value, int>::type = 0>
+  EIGEN_DEVICE_FUNC
+  explicit DSizes(const array<OtherIndex, NumDims>& other) {
+    for (int i = 0; i < NumDims; ++i) {
+      (*this)[i] = static_cast<DenseIndex>(other[i]);
+    }
+  }
+#endif  // EIGEN_HAS_CXX11
+
 #ifdef EIGEN_HAS_INDEX_LIST
   template <typename FirstType, typename... OtherTypes>
   EIGEN_DEVICE_FUNC
-  DSizes(const Eigen::IndexList<FirstType, OtherTypes...>& dimensions) {
+  explicit DSizes(const Eigen::IndexList<FirstType, OtherTypes...>& dimensions) {
     for (int i = 0; i < dimensions.count; ++i) {
       (*this)[i] = dimensions[i];
     }
diff --git a/unsupported/test/cxx11_tensor_dimension.cpp b/unsupported/test/cxx11_tensor_dimension.cpp
index 10364d4b4..26f8edd8a 100644
--- a/unsupported/test/cxx11_tensor_dimension.cpp
+++ b/unsupported/test/cxx11_tensor_dimension.cpp
@@ -60,10 +60,28 @@ static void test_rank_zero()
   VERIFY_IS_EQUAL((int)dscalar.rank(), 0);
 }
 
+static void test_index_type_promotion() {
+#ifdef EIGEN_HAS_CXX11
+  Eigen::DSizes<int, 3> src0(1, 2, 3);
+  Eigen::array<int, 3> src1 = {4, 5, 6};
+
+  Eigen::DSizes<long, 3> dst0(src0);
+  Eigen::DSizes<long, 3> dst1(src1);
+
+  VERIFY_IS_EQUAL(dst0[0], 1L);
+  VERIFY_IS_EQUAL(dst0[1], 2L);
+  VERIFY_IS_EQUAL(dst0[2], 3L);
+  VERIFY_IS_EQUAL(dst1[0], 4L);
+  VERIFY_IS_EQUAL(dst1[1], 5L);
+  VERIFY_IS_EQUAL(dst1[2], 6L);
+#endif  // EIGEN_HAS_CXX11
+}
+
 EIGEN_DECLARE_TEST(cxx11_tensor_dimension)
 {
   CALL_SUBTEST(test_dynamic_size());
   CALL_SUBTEST(test_fixed_size());
   CALL_SUBTEST(test_match());
   CALL_SUBTEST(test_rank_zero());
+  CALL_SUBTEST(test_index_type_promotion());
 }