cp:
	PR c++/12698, c++/12699, c++/12700, c++/12566
	* cp-tree.h (THUNK_ALIAS_P, THUNK_ALIAS): New.
	(debug_class, debug_thunks): New.
	* class.c (dump_class_hierarchy_1): New break out from ...
	(dump_class_hierarchy): ... here.
	(dump_thunk, debug_thunks, debug_class): New.
	(update_vtable_entry_for_fn): Add ssizetype casts. Correct
	continued search for primary binfo via virtual.
	(build_vtbl_initializer): Follow covariant thunk alias.
	* method.c (make_thunk): Clear DECL_THUNKS of the thunk.
	(finish_thunk): Look for an alias of the covariant thunk and point
	to it.
	(use_thunk): We should never use an alias.
	* semantics.c (emit_associated_thunks): Do not emit aliases.

	PR c++/12566
	* cp-tree.h (cp_fname_init): Add TYPE pointer param.
	* decl.c (cp_fname_init): Add TYPE pointer param. Set it. Don't
	create an ad-hoc ERROR_MARK.
	(cp_make_fname_decl): Adjust.
	* pt.c (tsubst_expr): Adjust.
testsuite:
	PR c++/12698, c++/12699, c++/12700, c++/12566
	* g++.dg/inherit/covariant9.C: New test.
	* g++.dg/inherit/covariant10.C: New test.
	* g++.dg/inherit/covariant11.C: New test.

From-SVN: r72882