[ Peter provided wording. ]

[ Pete and Peter will provide wording. ]

In 20.5.4 [lib.func.ret] ([tr.func.ret]) p3 add the following bullet after bullet 2:

1. […]
2. […]
3. If F is a member data pointer type R T::*, type shall be cv R& when T1 is cv U1&, R otherwise.

In the original proposal for binders, the return type of bind() when called with a pointer to member data as it's callable object was defined to be mem_fn(ptr); when Peter Dimov and I unified the descriptions of the TR1 function objects we hoisted the descriptions of return types into the INVOKE pseudo-function and into result_of. Unfortunately, we left pointer to member data out of result_of, so bind doesn't have any specified behavior when called with a pointer to member data.