Rationale (July, 2009):

The CWG reaffirmed the previous decisions not to have attributes apply to types and did not believe that the benefits were sufficient for this case to make an exception to the general rule.

The [[noreturn]] attribute, as specified in 9.12.11 [dcl.attr.noreturn], applies to function declarations and is not integrated with the type system. This is incompatible with existing practice (as in gcc) and should be reconsidered.