[c++0x] tuple rework

[Pedro LamarÃo <pedro dot lamarao at mndfck dot org>]

Attached is a patch to the <tuple> header.

The reason they fail is discussed in another messge I sent today.

I'm not sending this patch to gcc-patches with a Changelog entry because 
of it provokes new test case failures and because I feel I'm stepping in 
the limits of my C++0x knowledge.

This patch changes basically these things:

*) all __add_c_ref and remove_references uses were removed and replaced 
with simple const& and && variations;
*) all tuple constructors taking a tuple argument convert the argument 
explicitly to it's corresponding _Tuple_base in order to pick the 
correct base constructor;
*) all template constructors taking a tuple&& argument std::forward the 
tuple elements instead of std::move'ing them when initializing the 
contained element.

I believe the remove_reference and __add_c_ref machinery was put in 
place to deal with the case where the tuple element type is a T& .
Properly std::forward'ing elements in initialization solves this difficulty.

This patch makes the attached test case PASS.
Four other tests FAIL, on the other hand.

FAIL: 20_util/tuple/comparison_operators/comparisons.cc (test for excess 
errors)
WARNING: 20_util/tuple/comparison_operators/comparisons.cc compilation 
failed to produce executable
FAIL: 20_util/tuple/cons/assignment.cc (test for excess errors)
WARNING: 20_util/tuple/cons/assignment.cc compilation failed to produce 
executable
FAIL: 20_util/tuple/cons/big_tuples.cc (test for excess errors)
WARNING: 20_util/tuple/cons/big_tuples.cc compilation failed to produce 
executable
FAIL: 20_util/tuple/cons/constructor.cc (test for excess errors)
WARNING: 20_util/tuple/cons/constructor.cc compilation failed to produce 
executable

All these failures are similar to the problem I describe in another 
email: when passing a tuple object to initialize another tuple object 
the wrong constructor is being selected.

--
 P.

// { dg-options "-std=gnu++0x" }

// Copyright (C) 2007 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

#include <tuple>
#include <utility>
#include <testsuite_hooks.h>

class MoveOnly {
public:
  
  MoveOnly () { }
  
  MoveOnly (MoveOnly&&) { }
  
  MoveOnly& operator= (MoveOnly&&) { return *this; }
  
private:
  MoveOnly (MoveOnly const&); // = delete
  MoveOnly& operator= (MoveOnly const&); // = delete
};

MoveOnly
make_move_only () { return MoveOnly(); }

int main()
{
  bool test __attribute__((unused)) = true;

  std::tuple<MoveOnly> t1(make_move_only());
  std::tuple<MoveOnly> t2(std::move(t1));
  std::tuple<MoveOnly> t3 = std::move(t2);
  t1 = std::move(t3);
  
  return 0;
}

Index: /home/pedro.lamarao/Projetos/gcc/mainline/libstdc++-v3/include/std/tuple
===================================================================
--- /home/pedro.lamarao/Projetos/gcc/mainline/libstdc++-v3/include/std/tuple	(revisão 132322)
+++ /home/pedro.lamarao/Projetos/gcc/mainline/libstdc++-v3/include/std/tuple	(cópia de trabalho)
@@ -72,11 +72,12 @@
       _Head_base()
       : _Head() { }
 
-      _Head_base(typename __add_c_ref<_Head>::type __h)
+      _Head_base(const _Head& __h)
       : _Head(__h) { }
 
-      _Head_base(typename std::remove_reference<_Head>::type&& __h)
-      : _Head(std::forward<_Head>(__h)) { }
+      template <typename _UHead>
+      _Head_base(_UHead&& __h)
+      : _Head(std::forward<_UHead>(__h)) { }
 
       _Head&       _M_head()       { return *this; }
       const _Head& _M_head() const { return *this; }
@@ -88,11 +89,12 @@
       _Head_base()
       : _M_head_impl() { }
 
-      _Head_base(typename __add_c_ref<_Head>::type __h)
+      _Head_base(const _Head& __h)
       : _M_head_impl(__h) { }
 
-      _Head_base(typename std::remove_reference<_Head>::type&& __h)
-      : _M_head_impl(std::move(__h)) { }
+      template <typename _UHead>
+      _Head_base(_UHead&& __h)
+      : _M_head_impl(std::forward<_UHead>(__h)) { }
 
       _Head&       _M_head()       { return _M_head_impl; }
       const _Head& _M_head() const { return _M_head_impl; }        
@@ -141,23 +143,23 @@
       : _Inherited(), _Base() { }
 
       explicit 
-      _Tuple_impl(typename __add_c_ref<_Head>::type __head,
-		  typename __add_c_ref<_Tail>::type... __tail)
+      _Tuple_impl(const _Head& __head,
+		  const _Tail&... __tail)
       : _Inherited(__tail...), _Base(__head) { }
 
       template<typename _UHead, typename... _UTail> 
         explicit
-        _Tuple_impl(typename std::remove_reference<_UHead>::type&& __head,
-		    typename std::remove_reference<_UTail>::type&&... __tail)
-	: _Inherited(std::forward<_Inherited>(__tail)...),
-	  _Base(std::forward<_Base>(__head)) { }
+        _Tuple_impl(_UHead&& __head,
+		    _UTail&&... __tail)
+	: _Inherited(std::forward<_UTail>(__tail)...),
+	  _Base(std::forward<_UHead>(__head)) { }
 
       _Tuple_impl(const _Tuple_impl& __in)
       : _Inherited(__in._M_tail()), _Base(__in._M_head()) { }
 
       _Tuple_impl(_Tuple_impl&& __in)
-      : _Inherited(std::forward<_Inherited>(__in._M_tail())),
-	_Base(std::forward<_Base>(__in._M_head())) { }
+      : _Inherited(std::move<_Inherited&&>(__in._M_tail())),
+	_Base(std::forward<_Head>(__in._M_head())) { }
 
       template<typename... _UElements>
         _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
@@ -165,8 +167,8 @@
 
       template<typename... _UElements>
         _Tuple_impl(_Tuple_impl<_Idx, _UElements...>&& __in)
-	: _Inherited(std::forward<_Inherited>(__in._M_tail())),
-	  _Base(std::forward<_Base>(__in._M_head())) { }
+	: _Inherited(std::move<typename _Tuple_impl<_Idx, _UElements...>::_Inherited&&>(__in._M_tail())),
+	  _Base(std::forward<typename _Tuple_impl<_Idx, _UElements...>::_Base>(__in._M_head())) { }
 
       _Tuple_impl&
       operator=(const _Tuple_impl& __in)
@@ -219,21 +221,21 @@
       template<typename... _UElements>
         explicit
         tuple(_UElements&&... __elements)
-	: _Inherited(std::forward<_UElements>(__elements)...) { }
+	: _Inherited(std::forward<_UElements>(__elements)...) {	}
 
       tuple(const tuple& __in)
-      : _Inherited(__in) { }
+      : _Inherited(static_cast<const _Inherited&>(__in)) { }
 
       tuple(tuple&& __in)
-      : _Inherited(std::move(__in)) { }
+      : _Inherited(std::move<_Inherited>(__in)) { }
 
       template<typename... _UElements>
         tuple(const tuple<_UElements...>& __in)
-	: _Inherited(__in) { }
+	: _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in)) { }
 
       template<typename... _UElements>
         tuple(tuple<_UElements...>&& __in)
-	: _Inherited(std::move(__in)) { }
+	: _Inherited(std::move<_Tuple_impl<0, _UElements...> >(__in)) { }
 
       tuple&
       operator=(const tuple& __in)
@@ -288,33 +290,27 @@
 	: _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 
       tuple(const tuple& __in)
-      : _Inherited(__in) { }
+      : _Inherited(static_cast<const _Inherited&>(__in)) { }
 
       tuple(tuple&& __in)
-      : _Inherited(std::move(__in)) { }
+      : _Inherited(std::move<_Inherited>(__in)) { }
 
       template<typename _U1, typename _U2>
         tuple(const tuple<_U1, _U2>& __in)
-	: _Inherited(__in) { }
+	: _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 
       template<typename _U1, typename _U2>
         tuple(tuple<_U1, _U2>&& __in)
-	: _Inherited(std::move(__in)) { }
+	: _Inherited(std::move<_Tuple_impl<0, _U1, _U2> >(__in)) { }
 
       template<typename _U1, typename _U2>
         tuple(const pair<_U1, _U2>& __in)
-	: _Inherited(_Tuple_impl<0, 
-		     typename __add_c_ref<_U1>::type,
-		     typename __add_c_ref<_U2>::type>(__in.first, 
-						      __in.second))
+	: _Inherited(__in.first, __in.second)
         { }
 
       template<typename _U1, typename _U2>
         tuple(pair<_U1, _U2>&& __in)
-	: _Inherited(_Tuple_impl<0, 
-		     typename std::remove_reference<_U1>::type&&,
-		     typename std::remove_reference<_U2>::type&&>
-		     (std::move(__in.first), std::move(__in.second)))
+	: _Inherited(std::forward<_U1>(__in.first), std::forward<_U2>(__in.second))
         { }
 
       tuple&