This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 111d. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
[Voted into WP at March, 2010 meeting as document N3055.]
A cast to an rvalue reference type produces an rvalue, and rvalues must have complete types (7.2.1 [basic.lval] paragraph 9). However, none of the sections dealing with cast operators in 7.6.1 [expr.post] require that the referred-to type must be complete in an rvalue reference cast.(Note that the approach described for issue 690, in which an rvalue reference type would be essentially an lvalue instead of an rvalue, would address this issue as well, since lvalues can have incomplete types.)
Proposed resolution (February, 2010):
See paper N3030.