[NFC] Remove non-variadic overloads of allocator_traits::construct.

[zoecarver]

Summary

Libcxx only supports compilers with variadics. We can safely remove all "fake" variadic overloads of allocator_traits::construct.

This also provides the correct behavior if anything other than exactly one argument is supplied to allocator_traits::construct in C++03 mode.

[ldionne]

libcxx/include/memory

1421

Is there any reason why this can't be shared with the non-C++03 implementation above?

[zoecarver]

libcxx/include/memory

1421

No reason. I'll replace the current implementation with this one.

[zoecarver]

• Rebase off master
• Unify __has_construct implementation

[ldionne]

LGTM if this passes in both pre and post C++11.

libcxx/include/memory

 template <class _Alloc, class _SizeType, class _ConstVoidPtr>
 struct __has_allocate_hint
     : true_type
 {
 };
 
 #endif  // _LIBCPP_CXX03_LANG
 
-#if !defined(_LIBCPP_CXX03_LANG)
+template <class _Alloc, class ..._Args,
+    class = decltype(_VSTD::declval<_Alloc>().construct(_VSTD::declval<_Args>()...))>
+static true_type __test_has_construct(int);
+template <class _Alloc, class...>
+static false_type __test_has_construct(...);
 
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-template <class _Alloc, class _Tp, class... _Args>
-auto
-__has_construct_test(_Alloc&& __a, _Tp* __p, _Args&&... __args)
-    -> decltype(__a.construct(__p, _VSTD::forward<_Args>(__args)...), true_type());
-_LIBCPP_SUPPRESS_DEPRECATED_POP
+template <class _Alloc, class ..._Args>
+struct __has_construct : decltype(__test_has_construct<_Alloc, _Args...>(0)) {};
 
-template <class _Alloc, class _Pointer, class ..._Args>
-auto
-__has_construct_test(const _Alloc& __a, _Pointer&& __p, _Args&& ...__args)
-    -> false_type;
-
-template <class _Alloc, class _Pointer, class ..._Args>
-struct __has_construct
-    : decltype(_VSTD::__has_construct_test(declval<_Alloc>(),
-                                           declval<_Pointer>(),
-                                           declval<_Args>()...))
-{
-};
+#if !defined(_LIBCPP_CXX03_LANG)
 
 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
 template <class _Alloc, class _Pointer>
 auto
 __has_destroy_test(_Alloc&& __a, _Pointer&& __p)
     -> decltype(__a.destroy(__p), true_type());
 _LIBCPP_SUPPRESS_DEPRECATED_POP
 

 template <class _Alloc>
 struct __has_select_on_container_copy_construction
     : decltype(_VSTD::__has_select_on_container_copy_construction_test(declval<_Alloc&>()))
 {
 };
 
 #else  // _LIBCPP_CXX03_LANG
 
-template <class _Alloc, class _Pointer, class _Tp, class = void>
-struct __has_construct : std::false_type {};
-
-template <class _Alloc, class _Pointer, class _Tp>
-struct __has_construct<_Alloc, _Pointer, _Tp, typename __void_t<
-    decltype(_VSTD::declval<_Alloc>().construct(_VSTD::declval<_Pointer>(), _VSTD::declval<_Tp>()))
->::type> : std::true_type {};
-
 template <class _Alloc, class _Pointer, class = void>
 struct __has_destroy : false_type {};
 
 template <class _Alloc, class _Pointer>
 struct __has_destroy<_Alloc, _Pointer, typename __void_t<
     decltype(_VSTD::declval<_Alloc>().destroy(_VSTD::declval<_Pointer>()))
 >::type> : std::true_type {};
 
 template <class _Alloc>
#endif  // _LIBCPP_CXX03_LANG
     static pointer allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
         {return __allocate(__a, __n, __hint,
             __has_allocate_hint<allocator_type, size_type, const_void_pointer>());}
 
     _LIBCPP_INLINE_VISIBILITY
     static void deallocate(allocator_type& __a, pointer __p, size_type __n) _NOEXCEPT
         {__a.deallocate(__p, __n);}
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
     template <class _Tp, class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         static void construct(allocator_type& __a, _Tp* __p, _Args&&... __args)
             {__construct(__has_construct<allocator_type, _Tp*, _Args...>(),
                          __a, __p, _VSTD::forward<_Args>(__args)...);}
-#else  // _LIBCPP_HAS_NO_VARIADICS
-    template <class _Tp>
-        _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type&, _Tp* __p)
-            {
-                ::new ((void*)__p) _Tp();
-            }
-    template <class _Tp, class _A0>
-        _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0)
-            {
-                __construct(__has_construct<allocator_type, _Tp*, const _A0&>(),
-                            __a, __p, __a0);
-            }
-    template <class _Tp, class _A0, class _A1>
-        _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type&, _Tp* __p, const _A0& __a0,
-                              const _A1& __a1)
-            {
-                ::new ((void*)__p) _Tp(__a0, __a1);
-            }
-    template <class _Tp, class _A0, class _A1, class _A2>
-        _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type&, _Tp* __p, const _A0& __a0,
-                              const _A1& __a1, const _A2& __a2)
-            {
-                ::new ((void*)__p) _Tp(__a0, __a1, __a2);
-            }
-#endif  // _LIBCPP_HAS_NO_VARIADICS
 
     template <class _Tp>
         _LIBCPP_INLINE_VISIBILITY
         static void destroy(allocator_type& __a, _Tp* __p)
             {__destroy(__has_destroy<allocator_type, _Tp*>(), __a, __p);}
 
     _LIBCPP_INLINE_VISIBILITY
     static size_type max_size(const allocator_type& __a) _NOEXCEPT
static pointer __allocate(allocator_type& __a, size_type __n,
             return __a.allocate(__n, __hint);
             _LIBCPP_SUPPRESS_DEPRECATED_POP
         }
     _LIBCPP_INLINE_VISIBILITY
     static pointer __allocate(allocator_type& __a, size_type __n,
         const_void_pointer, false_type)
         {return __a.allocate(__n);}
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
     template <class _Tp, class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         static void __construct(true_type, allocator_type& __a, _Tp* __p, _Args&&... __args)
             {
                 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
                 __a.construct(__p, _VSTD::forward<_Args>(__args)...);
                 _LIBCPP_SUPPRESS_DEPRECATED_POP
             }
 
     template <class _Tp, class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         static void __construct(false_type, allocator_type&, _Tp* __p, _Args&&... __args)
             {
                 ::new ((void*)__p) _Tp(_VSTD::forward<_Args>(__args)...);
             }
-#else  // _LIBCPP_HAS_NO_VARIADICS
-    template <class _Tp, class _A0>
-        _LIBCPP_INLINE_VISIBILITY
-        static void __construct(true_type, allocator_type& __a, _Tp* __p,
-                                const _A0& __a0)
-            {__a.construct(__p, __a0);}
-    template <class _Tp, class _A0>
-        _LIBCPP_INLINE_VISIBILITY
-        static void __construct(false_type, allocator_type&, _Tp* __p,
-                                const _A0& __a0)
-            {
-                ::new ((void*)__p) _Tp(__a0);
-            }
-#endif  // _LIBCPP_HAS_NO_VARIADICS
 
     template <class _Tp>
         _LIBCPP_INLINE_VISIBILITY
         static void __destroy(true_type, allocator_type& __a, _Tp* __p)
             {
                 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
                 __a.destroy(__p);
                 _LIBCPP_SUPPRESS_DEPRECATED_POP