https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63198
--- Comment #2 from Bob Abeles <eightycc at gmail dot com> --- This bug occurs when cp/parser.c:cp_parser_name() while parsing 'decltype(y = y)::t1' is called on 't1'. Earlier, the decltype has been determined to be dependent (it isn't actually in this case, but doing so appears to be a reasonable simplification), so cp_parser_name() defers the look up and returns the result of cp/tree.c:build_qualified_name(). The calling routine, cp/parser.c:cp_parser_class_name() fails to handle this case, returning an error_mark_node.
