Recommit r276548 - Make pair/tuples assignment operators SFINAE properly.

I think I've solved issues with is_assignable and references to incomplete
types. The updated patch adds tests for this case.

llvm-svn: 276603

2 files changed, 52 insertions, 12 deletions

diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index 31613d2b94f..a68f115b68c 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -647,6 +647,9 @@ public:
     _LIBCPP_CONSTEXPR tuple()
         _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
 
+    tuple(tuple const&) = default;
+    tuple(tuple&&) = default;
+
     template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = typename enable_if<
         __lazy_and<
             is_same<allocator_arg_t, _AllocArgT>,
@@ -885,6 +888,25 @@ public:
         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
             : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
 
+    using _CanCopyAssign = __all<is_copy_assignable<_Tp>::value...>;
+    using _CanMoveAssign = __all<is_move_assignable<_Tp>::value...>;
+
+    _LIBCPP_INLINE_VISIBILITY
+    tuple& operator=(typename conditional<_CanCopyAssign::value, tuple, __nat>::type const& __t)
+        _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
+    {
+        base_.operator=(__t.base_);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    tuple& operator=(typename conditional<_CanMoveAssign::value, tuple, __nat>::type&& __t)
+        _NOEXCEPT_((__all<is_nothrow_move_assignable<_Tp>::value...>::value))
+    {
+        base_.operator=(static_cast<base&&>(__t.base_));
+        return *this;
+    }
+
     template <class _Tuple,
               class = typename enable_if
                       <
diff --git a/libcxx/include/utility b/libcxx/include/utility
index 022a641d6e8..456a5f7fa42 100644
--- a/libcxx/include/utility
+++ b/libcxx/include/utility
@@ -348,8 +348,23 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
   // Use the implicitly declared copy constructor in C++03
 #endif
 
+#if !defined(_LIBCPP_CXX03_LANG)
+    typedef typename conditional<
+           is_copy_assignable<_T1>::value
+        && is_copy_assignable<_T2>::value,
+        pair, __nat
+    >::type _CopyAssignT;
+    typedef typename conditional<
+           is_move_assignable<_T1>::value
+        && is_move_assignable<_T2>::value,
+        pair, __nat
+    >::type _MoveAssignT;
+#else
+    typedef pair _CopyAssignT;
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
-    pair& operator=(const pair& __p)
+    pair& operator=(_CopyAssignT const& __p)
         _NOEXCEPT_(is_nothrow_copy_assignable<first_type>::value &&
                    is_nothrow_copy_assignable<second_type>::value)
     {
@@ -358,6 +373,18 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
         return *this;
     }
 
+#ifndef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(_MoveAssignT&& __p)
+        _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
+                   is_nothrow_move_assignable<second_type>::value)
+    {
+        first = _VSTD::forward<first_type>(__p.first);
+        second = _VSTD::forward<second_type>(__p.second);
+        return *this;
+    }
+#endif
+
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
     template <class _U1, class _U2,
@@ -377,18 +404,9 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
             : first(_VSTD::forward<_U1>(__p.first)),
               second(_VSTD::forward<_U2>(__p.second)) {}
 
-    _LIBCPP_INLINE_VISIBILITY
-    pair&
-    operator=(pair&& __p) _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
-                                     is_nothrow_move_assignable<second_type>::value)
-    {
-        first = _VSTD::forward<first_type>(__p.first);
-        second = _VSTD::forward<second_type>(__p.second);
-        return *this;
-    }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
 
+#ifndef _LIBCPP_HAS_NO_VARIADICS
     template<class _Tuple,
              class = typename enable_if<__tuple_convertible<_Tuple, pair>::value>::type>
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -411,7 +429,7 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
             {}
 
     template <class _Tuple,
-              class = typename enable_if<__tuple_assignable<_Tuple, pair>::value>::type>
+              class = typename enable_if<!is_same<typename decay<_Tuple>::type, pair>::value && __tuple_assignable<_Tuple, pair>::value>::type>
         _LIBCPP_INLINE_VISIBILITY
         pair&
         operator=(_Tuple&& __p)