1 files changed, 13 insertions, 51 deletions
diff --git a/libcxx/include/__tuple b/libcxx/include/__tuple
index 8e6d2bd5915..775d7340b54 100644
--- a/libcxx/include/__tuple
+++ b/libcxx/include/__tuple
@@ -453,57 +453,19 @@ using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
 #ifndef _LIBCPP_CXX03_LANG
-
-template <class _Tp, size_t _TSize, bool _Good = true>
-struct __lookup_result {
-  using type = _Tp;
-  static constexpr bool _Success = _Good;
-  static constexpr size_t _Size = _TSize;
-};
-using __lookup_failure = __lookup_result<void, (size_t)-1, false>;
-
-template <class ..._Args>
-auto __deduce_tuple_type_ovl(tuple<_Args...>&)
-    -> __lookup_result<tuple<_Args...>, sizeof...(_Args)>;
-
-template <class _T1, class _T2>
-auto __deduce_tuple_type_ovl(pair<_T1, _T2>&)
-    -> __lookup_result<pair<_T1, _T2>, 2>;
-
-template <class _Tp, size_t _Size>
-auto __deduce_tuple_type_ovl(array<_Tp, _Size>&)
-  -> __lookup_result<array<_Tp, _Size>, _Size>;
-
-template <class _Tp>
-auto __deduce_tuple_type_imp(int)
-  -> decltype(__deduce_tuple_type_ovl(_VSTD::declval<__uncvref_t<_Tp>&>()));
-template <class> __lookup_failure __deduce_tuple_type_imp(...);
-
-// __deduce_tuple_like - Given a type determine if it is, or is derived from,
-//   a tuple-like type. This trait is used to support constructing and assigning
-//   to std::tuple from user-types derived from a tuple-like type.
-template <class _TupleLike,
-    class _Result = decltype(__deduce_tuple_type_imp<_TupleLike>(0)),
-    bool _Good = _Result::_Success>
-struct __deduce_tuple_like {
-  static_assert(_Good, "incorrect specialization choosen");
-  static constexpr bool _Success = true;
-  static constexpr size_t _Size = _Result::_Size;
-  using _RawType = typename _Result::type;
-  using _QualType =
-    typename __propagate_value_category<_TupleLike>::template __apply<_RawType>;
-};
-
-template <class _TupleLike, class _Result>
-struct __deduce_tuple_like<_TupleLike, _Result, /*_Good=*/false> {
-  static constexpr bool _Success = false;
-  static constexpr size_t _Size = (size_t)-1;
-};
-
-template <class _TupleLike, size_t _ExpectedSize,
-          class _Deduced = __deduce_tuple_like<_TupleLike>>
-using __tuple_like_with_size = integral_constant<bool,
-    _Deduced::_Success && _Deduced::_Size == _ExpectedSize>;
+template <bool _IsTuple, class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp : false_type {};
+
+template <class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp<true, _SizeTrait, _Expected>
+    : integral_constant<bool, _SizeTrait::value == _Expected> {};
+
+template <class _Tuple, size_t _ExpectedSize,
+          class _RawTuple = typename __uncvref<_Tuple>::type>
+using __tuple_like_with_size = __tuple_like_with_size_imp<
+                                   __tuple_like<_RawTuple>::value,
+                                   tuple_size<_RawTuple>, _ExpectedSize
+                              >;
 
 struct _LIBCPP_TYPE_VIS __check_tuple_constructor_fail {
     template <class ...>