Proposed resolution (July, 2009):

Change 7.6.2.5 [expr.sizeof] paragraph 1 as follows:

...The sizeof operator shall not be applied to an expression that has function or incomplete type, or to an enumeration type whose underlying type is not fixed before all its enumerators have been declared, or to the parenthesized name of such types, or to an lvalue that designates a bit-field...