variable.c:1690
static int
cv_i(key, value, ary)
    ID key;
    VALUE value;
    VALUE ary;
{
    if (rb_is_class_id(key)) {
	VALUE kval = rb_str_new2(rb_id2name(key));
	if (!rb_ary_includes(ary, kval)) {
	    rb_ary_push(ary, kval);
	}
    }
    return ST_CONTINUE;
}
