c++: Fix ICEs with OBJ_TYPE_REF pretty printing [PR101597]

c++: Fix ICEs with OBJ_TYPE_REF pretty printing [PR101597]

The following testcase ICEs, because middle-end uses the C++ FE pretty
printing code through langhooks in the diagnostics.
The FE expects OBJ_TYPE_REF_OBJECT's type to be useful (pointer to the
class type it is called on), but in the middle-end conversions between
pointer types are useless, so the actual type can be some random
unrelated pointer type (in the testcase void * pointer).  The pretty
printing code then ICEs on it.

The following patch fixes that by sticking the original
OBJ_TYPE_REF_OBJECT's also as type of OBJ_TYPE_REF_TOKEN operand.
That one must be an INTEGER_CST, all the current uses of
OBJ_TYPE_REF_TOKEN just use tree_to_uhwi or tree_to_shwi on it,
and because it is constant, there is no risk of the middle-end propagating
into it some other pointer type.  So, approach similar to how MEM_REF
treats its second operand or a couple of internal functions (e.g.
IFN_VA_ARG) some of its parameters.

2022-01-11  Jakub Jelinek  <jakub@redhat.com>

	PR c++/101597
gcc/
	* tree.def (OBJ_TYPE_REF): Document type of OBJ_TYPE_REF_TOKEN.
gcc/cp/
	* class.c (build_vfn_ref): Build OBJ_TYPE_REF with INTEGER_CST
	OBJ_TYPE_REF_TOKEN with type equal to OBJ_TYPE_REF_OBJECT type.
	* error.c (resolve_virtual_fun_from_obj_type_ref): Use type of
	OBJ_TYPE_REF_TOKEN rather than type of OBJ_TYPE_REF_OBJECT as
	obj_type.
gcc/objc/
	* objc-act.c (objc_rewrite_function_call): Build OBJ_TYPE_REF
	with INTEGER_CST OBJ_TYPE_REF_TOKEN with type equal to
	OBJ_TYPE_REF_OBJECT type.
	* objc-next-runtime-abi-01.c (build_objc_method_call): Likewise.
	* objc-gnu-runtime-abi-01.c (build_objc_method_call): Likewise.
	* objc-next-runtime-abi-02.c (build_v2_objc_method_fixup_call,
	build_v2_build_objc_method_call): Likewise.
gcc/testsuite/
	* g++.dg/opt/pr101597.C: New test.