Implement LWG Paper n3887: Consistent Metafunction Aliases. This adds std::tuple_element_t<> as an alias for tuple_element<>::type. Clean up the synopsis for tuple_element in <utility> as well.
llvm-svn: 202673
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 05c8dad23000f344763694d346e978ccaea07713
diff --git a/include/tuple b/include/tuple
index 30a958a..3a1752e 100644
--- a/include/tuple
+++ b/include/tuple
@@ -82,13 +82,15 @@
template <class... T> class tuple_size<tuple<T...>>;
template <intsize_t I, class T> class tuple_element; // undefined
template <intsize_t I, class... T> class tuple_element<I, tuple<T...>>;
+template <size_t _Ip, class ..._Tp>
+ using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type; // C++14
// 20.4.1.5, element access:
template <intsize_t I, class... T>
typename tuple_element<I, tuple<T...>>::type&
get(tuple<T...>&) noexcept; // constexpr in C++14
template <intsize_t I, class... T>
- typename tuple_element<I, tuple<T...>>::type const&
+ typename const tuple_element<I, tuple<T...>>::type &
get(const tuple<T...>&) noexcept; // constexpr in C++14
template <intsize_t I, class... T>
typename tuple_element<I, tuple<T...>>::type&&
@@ -152,6 +154,11 @@
typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
};
+#if _LIBCPP_STD_VER > 11
+template <size_t _Ip, class ..._Tp>
+using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
+#endif
+
// __tuple_leaf
template <size_t _Ip, class _Hp, bool=is_empty<_Hp>::value
diff --git a/include/utility b/include/utility
index 0a1a7f1..8a7e1dc 100644
--- a/include/utility
+++ b/include/utility
@@ -101,30 +101,30 @@
template <class T> class tuple_size;
template <size_t I, class T> class tuple_element;
-template <class T1, class T2> struct tuple_size<std::pair<T1, T2> >;
-template <class T1, class T2> struct tuple_element<0, std::pair<T1, T2> >;
-template <class T1, class T2> struct tuple_element<1, std::pair<T1, T2> >;
+template <class T1, class T2> struct tuple_size<pair<T1, T2> >;
+template <class T1, class T2> struct tuple_element<0, pair<T1, T2> >;
+template <class T1, class T2> struct tuple_element<1, pair<T1, T2> >;
template<size_t I, class T1, class T2>
- typename tuple_element<I, std::pair<T1, T2> >::type&
- get(std::pair<T1, T2>&) noexcept; // constexpr in C++14
+ typename tuple_element<I, pair<T1, T2> >::type&
+ get(pair<T1, T2>&) noexcept; // constexpr in C++14
template<size_t I, class T1, class T2>
- const typename const tuple_element<I, std::pair<T1, T2> >::type&
- get(const std::pair<T1, T2>&) noexcept; // constexpr in C++14
+ const typename const tuple_element<I, pair<T1, T2> >::type&
+ get(const pair<T1, T2>&) noexcept; // constexpr in C++14
template<size_t I, class T1, class T2>
- typename tuple_element<I, std::pair<T1, T2> >::type&&
- get(std::pair<T1, T2>&&) noexcept; // constexpr in C++14
+ typename tuple_element<I, pair<T1, T2> >::type&&
+ get(pair<T1, T2>&&) noexcept; // constexpr in C++14
template<class T1, class T2>
- constexpr T1& get(std::pair<T1, T2>&) noexcept; // C++14
+ constexpr T1& get(pair<T1, T2>&) noexcept; // C++14
template<size_t I, class T1, class T2>
- constexpr T1 const& get(std::pair<T1, T2> const &) noexcept; // C++14
+ constexpr T1 const& get(pair<T1, T2> const &) noexcept; // C++14
template<size_t I, class T1, class T2>
- constexpr T1&& get(std::pair<T1, T2>&&) noexcept; // C++14
+ constexpr T1&& get(pair<T1, T2>&&) noexcept; // C++14
// C++14
diff --git a/test/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.pass.cpp b/test/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.pass.cpp
index 7b1ff8b..f3f8f2b 100644
--- a/test/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.pass.cpp
+++ b/test/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.pass.cpp
@@ -28,7 +28,14 @@
static_assert((std::is_same<typename std::tuple_element<N, const T>::type, const U>::value), "");
static_assert((std::is_same<typename std::tuple_element<N, volatile T>::type, volatile U>::value), "");
static_assert((std::is_same<typename std::tuple_element<N, const volatile T>::type, const volatile U>::value), "");
+#if _LIBCPP_STD_VER > 11
+ static_assert((std::is_same<typename std::tuple_element_t<N, T>, U>::value), "");
+ static_assert((std::is_same<typename std::tuple_element_t<N, const T>, const U>::value), "");
+ static_assert((std::is_same<typename std::tuple_element_t<N, volatile T>, volatile U>::value), "");
+ static_assert((std::is_same<typename std::tuple_element_t<N, const volatile T>, const volatile U>::value), "");
+#endif
}
+
int main()
{
test<std::tuple<int>, 0, int>();
diff --git a/www/cxx1y_status.html b/www/cxx1y_status.html
index c698463..d1632c5 100644
--- a/www/cxx1y_status.html
+++ b/www/cxx1y_status.html
@@ -100,7 +100,7 @@
<tr><td></td><td></td><td></td><td></td><td></td><td></td></tr>
<tr><td><a href="http://wiki.edg.com/twiki/pub/Wg21issaquah/FormalMotions/N3924_rand-note-v2.pdf">3924</a></td><td>LWG</td><td>Discouraging rand() in C++14</td><td>Issaquah</td><td></td><td></td></tr>
- <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3887">3887</a></td><td>LWG</td><td>Consistent Metafunction Aliases</td><td>Issaquah</td><td></td><td></td></tr>
+ <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3887">3887</a></td><td>LWG</td><td>Consistent Metafunction Aliases</td><td>Issaquah</td><td></td><td>Complete</td></tr>
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