Proposed resolution:

1. Edit Table 28 as indicated:

   Table 28 — Allocator requirements (continued)

   Expression	Return type	Assertion/note pre-/post-condition	Default
   …
   static_cast<X::const_pointer>(z)	X::const_pointer	static_cast<X::const_pointer>(z) == q
   pointer_traits<X::pointer>::pointer_to(r)	X::pointer
   …

[ 2016-11-12, Issaquah ]

This is related to 1521.

Sat PM: Restore original P/R and move to tentatively ready.

[ 2015-07 Telecon ]

Marshall to ping Pablo for proposed wording and disable current wording.

1. Edit Table 28 as indicated:

   Table 28 — Allocator requirements (continued)

   Expression	Return type	Assertion/note pre-/post-condition	Default
   …
   static_cast<X::const_pointer>(z)	X::const_pointer	static_cast<X::const_pointer>(z) == q
   pointer_traits<X::pointer>::pointer_to(r)	X::pointer
   …

[ 2013-09 Chicago ]

Pablo to come back with proposed wording

For an allocator A<T> which defines A<T>::pointer to a class type, i.e. not T*, I see no requirement that A<T>::pointer is convertible to A<U>::pointer, even if T* is convertible to U*. Such conversions are needed in containers to convert from e.g. ListNodeBase* to ListNode<T>*.

The obvious way to do such conversions appears to be pointer_traits::pointer_to(), but that's ill-formed if the static member function A<T>::pointer::pointer_to() doesn't exist and the allocator requirements don't mention that function, so you need to cast A<T>::pointer to A<T>::void_pointer then cast that to A<U>::pointer.

Is converting via void_pointer really intended, or are we missing a requirement that pointer_traits<A<T>::pointer>::pointer_to() be well-formed?

Proposed resolution:

Add to the Allocator requirements table the following requirement:

The expression pointer_traits<XX::pointer>::pointer_to(r) is well-defined.