pub fn get_toplevel_constant(&self, class_name: &str) -> Value {
        let id = IdentId::get_id(class_name);
        let mut object = BuiltinClass::object();
        match object.get_const_noautoload(id) {
            Some(val) => val,
            _ => unreachable!("{} is not defined in Object.", class_name),
        }
    }
Get object bound to the constant `name` of the root object.
ruruby/src/globals/constants.rs