io.c:2907
static VALUE
rb_io_s_new(argc, argv, klass)
    int argc;
    VALUE *argv;
    VALUE klass;
{
    if (rb_block_given_p()) {
	char *cname = rb_class2name(klass);

	rb_warn("%s::new() does not take block; use %s::open() instead",
		cname, cname);
    }
    return rb_class_new_instance(argc, argv, klass);
}
