From fd5f48e465ab011c64e989c4e1f656a8e4b6ebf1 Mon Sep 17 00:00:00 2001
From: Antonio Sanchez <cantonios@google.com>
Date: Wed, 29 Sep 2021 20:34:03 -0700
Subject: [PATCH] Fix tuple compilation for VS2017.

VS2017 doesn't like deducing alias types, leading to a bunch of compile
errors for functions involving the `tuple` alias.  Replacing with
`TupleImpl` seems to solve this, allowing the test to compile/pass.
---
 Eigen/src/Core/arch/GPU/Tuple.h | 26 +++++++++++++-------------
 test/tuple_test.cpp             |  2 +-
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/Eigen/src/Core/arch/GPU/Tuple.h b/Eigen/src/Core/arch/GPU/Tuple.h
index d381cd886..bbcdf64ff 100644
--- a/Eigen/src/Core/arch/GPU/Tuple.h
+++ b/Eigen/src/Core/arch/GPU/Tuple.h
@@ -217,12 +217,6 @@ struct unwrap_decay {
   using type = typename unwrap_reference_wrapper<typename std::decay<T>::type>::type;
 };
 
-/**
- * Alternative to std::tuple that can be used on device.
- */
-template<typename... Types>
-using tuple = TupleImpl<sizeof...(Types), Types...>;
-
 /**
  * Utility for determining a tuple's size.
  */
@@ -230,7 +224,7 @@ template<typename Tuple>
 struct tuple_size;
 
 template<typename... Types >
-struct tuple_size< tuple<Types...> > : std::integral_constant<size_t, sizeof...(Types)> {};
+struct tuple_size< TupleImpl<sizeof...(Types), Types...> > : std::integral_constant<size_t, sizeof...(Types)> {};
 
 /**
  * Gets an element of a tuple.
@@ -242,14 +236,14 @@ struct tuple_size< tuple<Types...> > : std::integral_constant<size_t, sizeof...(
 template<size_t Idx, typename... Types>
 EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 const typename tuple_get_impl<Idx, Types...>::ReturnType&
-get(const tuple<Types...>& tuple) {
+get(const TupleImpl<sizeof...(Types), Types...>& tuple) {
   return tuple_get_impl<Idx, Types...>::run(tuple);
 }
 
 template<size_t Idx, typename... Types>
 EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 typename tuple_get_impl<Idx, Types...>::ReturnType&
-get(tuple<Types...>& tuple) {
+get(TupleImpl<sizeof...(Types), Types...>& tuple) {
   return tuple_get_impl<Idx, Types...>::run(tuple);
 }
 
@@ -271,7 +265,7 @@ tuple_cat(Tuples&&... tuples) {
 /**
  * Tie arguments together into a tuple.
  */
-template <typename... Args, typename ReturnType = tuple<Args&...> >
+template <typename... Args, typename ReturnType = TupleImpl<sizeof...(Args), Args&...> >
 EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 ReturnType tie(Args&... args) EIGEN_NOEXCEPT {
     return ReturnType{args...};
@@ -280,7 +274,7 @@ ReturnType tie(Args&... args) EIGEN_NOEXCEPT {
 /**
  * Create a tuple of l-values with the supplied arguments.
  */
-template <typename... Args, typename ReturnType = tuple<typename unwrap_decay<Args>::type...> >
+template <typename... Args, typename ReturnType = TupleImpl<sizeof...(Args), typename unwrap_decay<Args>::type...> >
 EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 ReturnType make_tuple(Args&&... args) {
   return ReturnType{std::forward<Args>(args)...};
@@ -291,10 +285,16 @@ ReturnType make_tuple(Args&&... args) {
  */
 template <typename... Args>
 EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
-tuple<Args...> forward_as_tuple(Args&&... args) {
-  return tuple<Args...>(std::forward<Args>(args)...);
+TupleImpl<sizeof...(Args), Args...> forward_as_tuple(Args&&... args) {
+  return TupleImpl<sizeof...(Args), Args...>(std::forward<Args>(args)...);
 }
 
+/**
+ * Alternative to std::tuple that can be used on device.
+ */
+template<typename... Types>
+using tuple = TupleImpl<sizeof...(Types), Types...>;
+
 }  // namespace tuple_impl
 }  // namespace internal
 }  // namespace Eigen
diff --git a/test/tuple_test.cpp b/test/tuple_test.cpp
index 8d8a5aacc..c3bbe37b7 100644
--- a/test/tuple_test.cpp
+++ b/test/tuple_test.cpp
@@ -99,7 +99,7 @@ void basic_tuple_test() {
   VERIFY_IS_EQUAL(x, tuple_impl::get<0>(tuple3));
   VERIFY_IS_EQUAL(y, tuple_impl::get<1>(tuple3));
   VERIFY_IS_EQUAL(z, tuple_impl::get<2>(tuple3));
-  tuple<int, float, double> tuple3c(-2, -2, -2);
+  tuple<int, float, double> tuple3c(-2, -2.0f, -2.0);
   tuple3c = std::move(tuple3b);
   VERIFY_IS_EQUAL(tuple_impl::get<0>(tuple3c), tuple_impl::get<0>(tuple3));
   VERIFY_IS_EQUAL(tuple_impl::get<1>(tuple3c), tuple_impl::get<1>(tuple3));