[libcxx] LWG2485: get() should be overloaded for const tuple&&. Patch from K-Ballo.

Review: http://reviews.llvm.org/D14839

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@255941 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/tuple/tuple.tuple/tuple.elem/get_const_rv.pass.cpp

@@ -0,0 +1,80 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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>
+//   const typename tuple_element<I, tuple<Types...> >::type&&
+//   get(const tuple<Types...>&& t);
+
+// UNSUPPORTED: c++98, c++03
+
+#include <tuple>
+#include <utility>
+#include <string>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::tuple<int> T;
+    const T t(3);
+    static_assert(std::is_same<const int&&, decltype(std::get<0>(std::move(t)))>::value, "");
+    static_assert(noexcept(std::get<0>(std::move(t))), "");
+    const int&& i = std::get<0>(std::move(t));
+    assert(i == 3);
+    }
+
+    {
+    typedef std::tuple<std::string, int> T;
+    const T t("high", 5);
+    static_assert(std::is_same<const std::string&&, decltype(std::get<0>(std::move(t)))>::value, "");
+    static_assert(noexcept(std::get<0>(std::move(t))), "");
+    static_assert(std::is_same<const int&&, decltype(std::get<1>(std::move(t)))>::value, "");
+    static_assert(noexcept(std::get<1>(std::move(t))), "");
+    const std::string&& s = std::get<0>(std::move(t));
+    const int&& i = std::get<1>(std::move(t));
+    assert(s == "high");
+    assert(i == 5);
+    }
+
+    {
+    int x = 42;
+    int const y = 43;
+    std::tuple<int&, int const&> const p(x, y);
+    static_assert(std::is_same<int&, decltype(std::get<0>(std::move(p)))>::value, "");
+    static_assert(noexcept(std::get<0>(std::move(p))), "");
+    static_assert(std::is_same<int const&, decltype(std::get<1>(std::move(p)))>::value, "");
+    static_assert(noexcept(std::get<1>(std::move(p))), "");
+    }
+
+    {
+    int x = 42;
+    int const y = 43;
+    std::tuple<int&&, int const&&> const p(std::move(x), std::move(y));
+    static_assert(std::is_same<int&&, decltype(std::get<0>(std::move(p)))>::value, "");
+    static_assert(noexcept(std::get<0>(std::move(p))), "");
+    static_assert(std::is_same<int const&&, decltype(std::get<1>(std::move(p)))>::value, "");
+    static_assert(noexcept(std::get<1>(std::move(p))), "");
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::tuple<double, int> T;
+    constexpr const T t(2.718, 5);
+    static_assert(std::get<0>(std::move(t)) == 2.718, "");
+    static_assert(std::get<1>(std::move(t)) == 5, "");
+    }
+#endif
+}