https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60440
--- Comment #9 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- I think it would be appropriate for the front end to generate something for return <error_mark>; that avoids this warning. I don't know whether that should be a literal return of error_mark_node, or a return of a dummy value, or something marked with TREE_NO_WARNING, or a call to __builtin_unreachable or __builtin_trap.
