call.c (convert_class_to_reference): Binding an lvalue to an rvalue reference is bad.

	* call.c (convert_class_to_reference): Binding an lvalue to an
	rvalue reference is bad.  If the user-defined conversion is bad,
	set bad_p before merging conversions.
	(maybe_handle_ref_bind): Don't push down bad_p.
	(reference_binding): Binding an lvalue to an rvalue reference is bad.
	(convert_like_real): Give a helpful error about binding lvalue
	to rvalue reference.
	(reference_related_p): No longer static.
	* typeck.c (build_typed_address): New.
	(build_static_cast_1): Add static_cast from lvalue to &&.
	* cp-tree.h: Adjust.

	* include/bits/move.h (forward): Implement as in N2835.
	(move): Implement as in N2831.
	* include/std/istream (rvalue stream operator>>): New.
	* include/std/ostream (rvalue stream operator<<): New.

Co-Authored-By: Douglas Gregor <doug.gregor@gmail.com>

From-SVN: r150327

5 files changed, 117 insertions, 4 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index eb8b0e727fe..19f3dd1e7f2 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,4 +1,13 @@
 2009-07-31  Jason Merrill  <jason@redhat.com>
+	    Douglas Gregor  <doug.gregor@gmail.com>
+
+	* include/bits/move.h (forward): Implement as in N2835.
+	(move): Implement as in N2831.
+	* include/std/istream (rvalue stream operator>>): New.
+	* include/std/ostream (rvalue stream operator<<): New.
+	* testsuite/27_io/rvalue_streams.cc: New.
+
+2009-07-31  Jason Merrill  <jason@redhat.com>
 
 	* include/bits/forward_list.h (splice_after): Use forward.
 	(merge): Likewise.
diff --git a/libstdc++-v3/include/bits/move.h b/libstdc++-v3/include/bits/move.h
index 25773e13c48..d1da1e40ddf 100644
--- a/libstdc++-v3/include/bits/move.h
+++ b/libstdc++-v3/include/bits/move.h
@@ -46,12 +46,31 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       typedef _Tp type;
     };
 
-  /// forward
-  template<typename _Tp>
-    inline _Tp&&
+  /// forward (as per N2835)
+  /// Forward lvalues as rvalues.
+  template <class _Tp>
+    inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
+    forward(typename std::identity<_Tp>::type& __t)
+    { return static_cast<_Tp&&>(__t); }
+
+  /// Forward rvalues as rvalues.
+  template <class _Tp>
+    inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
     forward(typename std::identity<_Tp>::type&& __t)
+    { return static_cast<_Tp&&>(__t); }
+
+  // Forward lvalues as lvalues.
+  template <class _Tp>
+    inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
+    forward(typename std::identity<_Tp>::type __t)
     { return __t; }
 
+  // Prevent forwarding rvalues as const lvalues.
+  template <class _Tp>
+    inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
+    forward(typename std::remove_reference<_Tp>::type&& __t)
+    = delete;
+
   /**
    *  @brief Move a value.
    *  @ingroup mutating_algorithms
@@ -61,7 +80,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
   template<typename _Tp>
     inline typename std::remove_reference<_Tp>::type&&
     move(_Tp&& __t)
-    { return __t; }
+    { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
 
 _GLIBCXX_END_NAMESPACE
 
diff --git a/libstdc++-v3/include/std/istream b/libstdc++-v3/include/std/istream
index 1979a51327f..f20b8962539 100644
--- a/libstdc++-v3/include/std/istream
+++ b/libstdc++-v3/include/std/istream
@@ -827,6 +827,27 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     basic_istream<_CharT, _Traits>& 
     ws(basic_istream<_CharT, _Traits>& __is);
 
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+  // [27.7.1.6] Rvalue stream extraction
+  /**
+   *  @brief  Generic extractor for rvalue stream
+   *  @param  is  An input stream.
+   *  @param  x  A reference to the extraction target.
+   *  @return  is
+   *
+   *  This is just a forwarding function to allow extraction from
+   *  rvalue streams since they won't bind to the extractor functions
+   *  that take an lvalue reference.
+  */
+  template<typename _CharT, typename _Traits, typename _Tp>
+  basic_istream<_CharT, _Traits>&
+  operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
+  {
+    __is >> __x;
+    return __is;
+  }
+#endif // __GXX_EXPERIMENTAL_CXX0X__
+
 _GLIBCXX_END_NAMESPACE
 
 #ifndef _GLIBCXX_EXPORT_TEMPLATE
diff --git a/libstdc++-v3/include/std/ostream b/libstdc++-v3/include/std/ostream
index b9ea4a8ce19..136c3d62fba 100644
--- a/libstdc++-v3/include/std/ostream
+++ b/libstdc++-v3/include/std/ostream
@@ -562,6 +562,27 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     flush(basic_ostream<_CharT, _Traits>& __os)
     { return __os.flush(); }
 
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+  // [27.7.2.9] Rvalue stream insertion
+  /**
+   *  @brief  Generic inserter for rvalue stream
+   *  @param  os  An input stream.
+   *  @param  x  A reference to the object being inserted.
+   *  @return  os
+   *
+   *  This is just a forwarding function to allow insertion to
+   *  rvalue streams since they won't bind to the inserter functions
+   *  that take an lvalue reference.
+  */
+  template<typename _CharT, typename _Traits, typename _Tp>
+  basic_ostream<_CharT, _Traits>&
+  operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
+  {
+    __os << __x;
+    return __os;
+  }
+#endif // __GXX_EXPERIMENTAL_CXX0X__
+
 _GLIBCXX_END_NAMESPACE
 
 #ifndef _GLIBCXX_EXPORT_TEMPLATE
diff --git a/libstdc++-v3/testsuite/27_io/rvalue_streams.cc b/libstdc++-v3/testsuite/27_io/rvalue_streams.cc
new file mode 100644
index 00000000000..b3cc630edc0
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/rvalue_streams.cc
@@ -0,0 +1,43 @@
+// Copyright (C) 2008 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+// { dg-do run }
+
+#include <sstream>
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  int i = 1742;
+  // This usage isn't supported by the current draft.
+  // std::string result = (std::ostringstream() << i).str();
+  std::ostringstream() << i;
+  std::string result ("1742");
+  int i2;
+  std::istringstream(result) >> i2;
+  VERIFY (i == i2);
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}