Proposed resolution (September, 2013):

Change 7.6.1.9 [expr.static.cast] paragraph 3 as follows:

A glvalue, class prvalue, or array prvalue of type “cv1 T1” can be cast to type “rvalue reference to cv2 T2” if “cv2 T2” is reference-compatible with “cv1 T1” (9.5.4 [dcl.init.ref]). If the glvalue value is not a bit-field, the result refers to the object or the specified base class subobject thereof; otherwise, the lvalue-to-rvalue conversion (7.3.2 [conv.lval]) is applied to the bit-field and the resulting prvalue is used as the expression of the static_cast for the remainder of this section. If T2 is an inaccessible (11.8 [class.access]) or ambiguous (6.5.2 [class.member.lookup]) base class of T1, a program that necessitates such a cast is ill-formed.