Change  from a  to a . Fixes PR#39871.

llvm-svn: 350972
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: e49576014077d4080f51a56799fca0bdf9dbb522
diff --git a/include/__tuple b/include/__tuple
index 69d6ee9..3b23d78 100644
--- a/include/__tuple
+++ b/include/__tuple
@@ -22,36 +22,36 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size;
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size;
 
 #if !defined(_LIBCPP_CXX03_LANG)
 template <class _Tp, class...>
 using __enable_if_tuple_size_imp = _Tp;
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     const _Tp,
     typename enable_if<!is_volatile<_Tp>::value>::type,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     volatile _Tp,
     typename enable_if<!is_const<_Tp>::value>::type,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     const volatile _Tp,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 #else
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const _Tp> : public tuple_size<_Tp> {};
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<volatile _Tp> : public tuple_size<_Tp> {};
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const volatile _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<const _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<volatile _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<const volatile _Tp> : public tuple_size<_Tp> {};
 #endif
 
 template <size_t _Ip, class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_element;
@@ -165,7 +165,7 @@
 template <class... _Tp> struct __tuple_like<tuple<_Tp...> > : true_type {};
 
 template <class ..._Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<tuple<_Tp...> >
+struct _LIBCPP_TEMPLATE_VIS tuple_size<tuple<_Tp...> >
     : public integral_constant<size_t, sizeof...(_Tp)>
 {
 };
@@ -291,7 +291,7 @@
 
 
 template <class ..._Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__tuple_types<_Tp...> >
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__tuple_types<_Tp...> >
     : public integral_constant<size_t, sizeof...(_Tp)>
 {
 };