Implement LWG2328. Rvalue stream extraction should perfect forward.

llvm-svn: 276545

3 files changed, 18 insertions, 9 deletions

diff --git a/libcxx/include/istream b/libcxx/include/istream
index ee694003a3d..3a76ba831d3 100644
--- a/libcxx/include/istream
+++ b/libcxx/include/istream
@@ -1481,9 +1481,9 @@ ws(basic_istream<_CharT, _Traits>& __is)
 template <class _CharT, class _Traits, class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_istream<_CharT, _Traits>&
-operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
+operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp&& __x)
 {
-    __is >> __x;
+    __is >> _VSTD::forward<_Tp>(__x);
     return __is;
 }
 
diff --git a/libcxx/test/std/input.output/iostream.format/input.streams/istream.rvalue/rvalue.pass.cpp b/libcxx/test/std/input.output/iostream.format/input.streams/istream.rvalue/rvalue.pass.cpp
index 5b7664e3f55..77c41b09ad7 100644
--- a/libcxx/test/std/input.output/iostream.format/input.streams/istream.rvalue/rvalue.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/input.streams/istream.rvalue/rvalue.pass.cpp
@@ -7,17 +7,18 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
 // <istream>
 
 // template <class charT, class traits, class T>
 //   basic_istream<charT, traits>&
-//   operator>>(basic_istream<charT, traits>&& is, T& x);
+//   operator>>(basic_istream<charT, traits>&& is, T&& x);
 
 #include <istream>
+#include <sstream>
 #include <cassert>
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class CharT>
 struct testbuf
     : public std::basic_streambuf<CharT>
@@ -42,11 +43,13 @@ public:
     CharT* egptr() const {return base::egptr();}
 };
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+struct A{};
+bool called = false;
+void operator>>(std::istream&, A&&){ called = true; }
 
 int main()
 {
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     {
         testbuf<char> sb("   123");
         int i = 0;
@@ -59,5 +62,11 @@ int main()
         std::wistream(&sb) >> i;
         assert(i == 123);
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    { // test perfect forwarding
+        assert(called == false);
+        std::istringstream ss;
+        auto& out = (std::move(ss) >> A{});
+        assert(&out == &ss);
+        assert(called);
+    }
 }
diff --git a/libcxx/www/cxx1z_status.html b/libcxx/www/cxx1z_status.html
index 3af3806172d..db3eb839af1 100644
--- a/libcxx/www/cxx1z_status.html
+++ b/libcxx/www/cxx1z_status.html
@@ -264,7 +264,7 @@
 	<tr><td><a href="http://wg21.link/LWG2309">2309</a></td><td>mutex::lock() should not throw device_or_resource_busy</td><td>Oulu</td><td>Complete</td></tr>
 	<tr><td><a href="http://wg21.link/LWG2310">2310</a></td><td>Public exposition only member in std::array</td><td>Oulu</td><td>Complete</td></tr>
 	<tr><td><a href="http://wg21.link/LWG2312">2312</a></td><td>tuple's constructor constraints need to be phrased more precisely</td><td>Oulu</td><td>Complete</td></tr>
-	<tr><td><a href="http://wg21.link/LWG2328">2328</a></td><td>Rvalue stream extraction should use perfect forwarding</td><td>Oulu</td><td></td></tr>
+	<tr><td><a href="http://wg21.link/LWG2328">2328</a></td><td>Rvalue stream extraction should use perfect forwarding</td><td>Oulu</td><td>Complete</td></tr>
 	<tr><td><a href="http://wg21.link/LWG2393">2393</a></td><td>std::function's Callable definition is broken</td><td>Oulu</td><td></td></tr>
 	<tr><td><a href="http://wg21.link/LWG2422">2422</a></td><td>std::numeric_limits&lt;T&gt;::is_modulo description: "most machines" errata</td><td>Oulu</td><td>Complete</td></tr>
 	<tr><td><a href="http://wg21.link/LWG2426">2426</a></td><td>Issue about compare_exchange</td><td>Oulu</td><td></td></tr>