ObjectSpace.internal_super_of

static VALUE
objspace_internal_super_of(VALUE self, VALUE obj)
{
    VALUE super;

    if (rb_typeddata_is_kind_of(obj, &iow_data_type)) {
        obj = (VALUE)DATA_PTR(obj);
    }

    switch (OBJ_BUILTIN_TYPE(obj)) {
      case T_MODULE:
      case T_CLASS:
      case T_ICLASS:
        super = RCLASS_SUPER(obj);
        break;
      default:
        rb_raise(rb_eArgError, "class or module is expected");
    }

    return wrap_klass_iow(super);
}