Flatten the tuple_element and __make_tuple_types implementations.

This patch attempts to improve the QoI of std::tuples tuple_element and
__make_tuple_types helpers. Previously they required O(N) instantiations,
one for every element in the tuple

The new implementations are O(1) after __tuple_indices<Id...> is created.

llvm-svn: 274330

1 files changed, 34 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.fail.cpp b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.fail.cpp
new file mode 100644
index 00000000000..4cb73573e7c
--- /dev/null
+++ b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_element.fail.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <tuple>
+
+// template <class... Types> class tuple;
+
+// template <size_t I, class... Types>
+// class tuple_element<I, tuple<Types...> >
+// {
+// public:
+//     typedef Ti type;
+// };
+
+// UNSUPPORTED: c++98, c++03
+
+#include <tuple>
+#include <type_traits>
+
+int main()
+{
+    using T =  std::tuple<int, long, void*>;
+    using E1 = typename std::tuple_element<1, T &>::type; // expected-error{{undefined template}}
+    using E2 = typename std::tuple_element<3, T>::type;
+    using E3 = typename std::tuple_element<4, T const>::type;
+        // expected-error@__tuple:* 2 {{static_assert failed}}
+
+}