cp/
	PR c++/30818
	* typeck.c (structural_comptypes): No need to check
	resolve_typename_type return value here.
	* cp-tree.h (TYPENAME_IS_RESOLVING_P): New.
	* pt.c (resolve_typename_type): Follow typename typedefs.  Return
	original type rather than error_mark_node in case of failure.
	* parser.c (cp_parser_nested_name_specifier_opt): Adjust
	resolve_typename_type result check.
	(cp_parser_direct_declarator, cp_parser_head,
	cp_parser_constructor_declarator_p): Likewise.

testsuite/
	PR c++/30818
	* g++.dg/template/crash47.C: Adjust errors.
	* g++.dg/template/crash48.C: Adjust errors.
	* g++.dg/template/typename12.C: New.
	* g++.dg/template/typename13.C: New.
	* g++.dg/template/typename14.C: New.
	* g++.dg/template/typedef6.C: Adjust errors.

From-SVN: r126825