[libc++] fix array<T, 0> under USE_WRAP_ITER (#101156)

`array<T, 0>::iterator` was always a pointer even when
`_LIBCXX_ABI_USE_WRAP_ITER_IN_STD_ARRAY` was defined. This patch fixes
that minor bug.

Discovered as part of [#100603][].

Drive-by: switch from `typedef` to `using` in `<array>`

[#100603]: #100603

Author: strega-nil

libcxx/include/array

@@ -19,17 +19,17 @@ template <class T, size_t N >
 struct array
 {
     // types:
-    typedef T & reference;
-    typedef const T & const_reference;
-    typedef implementation defined iterator;
-    typedef implementation defined const_iterator;
-    typedef size_t size_type;
-    typedef ptrdiff_t difference_type;
-    typedef T value_type;
-    typedef T* pointer;
-    typedef const T* const_pointer;
-    typedef std::reverse_iterator<iterator> reverse_iterator;
-    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+    using value_type             = T;
+    using pointer                = T*;
+    using const_pointer          = const T*;
+    using reference              = T&;
+    using const_reference        = const T&;
+    using size_type              = size_t;
+    using difference_type        = ptrdiff_t;
+    using iterator               = implementation-defined;
+    using const_iterator         = implementation-defined;
+    using reverse_iterator       = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
     // No explicit construct/copy/destroy for aggregate type
     void fill(const T& u);                                      // constexpr in C++20
@@ -270,20 +270,25 @@ struct _LIBCPP_TEMPLATE_VIS array {
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS array<_Tp, 0> {
   // types:
-  typedef array __self;
-  typedef _Tp value_type;
-  typedef value_type& reference;
-  typedef const value_type& const_reference;
-  typedef value_type* iterator;
-  typedef const value_type* const_iterator;
-  typedef value_type* pointer;
-  typedef const value_type* const_pointer;
-  typedef size_t size_type;
-  typedef ptrdiff_t difference_type;
-  typedef std::reverse_iterator<iterator> reverse_iterator;
-  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
-
-  typedef __conditional_t<is_const<_Tp>::value, const __empty, __empty> _EmptyType;
+  using __self          = array;
+  using value_type      = _Tp;
+  using reference       = value_type&;
+  using const_reference = const value_type&;
+  using pointer         = value_type*;
+  using const_pointer   = const value_type*;
+#if defined(_LIBCPP_ABI_USE_WRAP_ITER_IN_STD_ARRAY)
+  using iterator       = __wrap_iter<pointer>;
+  using const_iterator = __wrap_iter<const_pointer>;
+#else
+  using iterator       = pointer;
+  using const_iterator = const_pointer;
+#endif
+  using size_type              = size_t;
+  using difference_type        = ptrdiff_t;
+  using reverse_iterator       = std::reverse_iterator<iterator>;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+  using _EmptyType = __conditional_t<is_const<_Tp>::value, const __empty, __empty>;
 
   struct _ArrayInStructT {
     _Tp __data_[1];
@@ -440,7 +445,7 @@ struct _LIBCPP_TEMPLATE_VIS tuple_size<array<_Tp, _Size> > : public integral_con
 template <size_t _Ip, class _Tp, size_t _Size>
 struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, array<_Tp, _Size> > {
   static_assert(_Ip < _Size, "Index out of bounds in std::tuple_element<> (std::array)");
-  typedef _Tp type;
+  using type = _Tp;
 };
 
 template <size_t _Ip, class _Tp, size_t _Size>