unbind

static VALUE
method_unbind(VALUE obj)
{
    VALUE method;
    struct METHOD *orig, *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, orig);
    method = TypedData_Make_Struct(rb_cUnboundMethod, struct METHOD,
                                   &method_data_type, data);
    data->recv = Qundef;
    data->id = orig->id;
    data->me = ALLOC(rb_method_entry_t);
    *data->me = *orig->me;
    if (orig->me->def) orig->me->def->alias_count++;
    data->rclass = orig->rclass;
    data->ume = ALLOC(struct unlinked_method_entry_list_entry);
    OBJ_INFECT(method, obj);

    return method;
}