I am trying to create a mock object for testing in my Rust project, the mock object implements the trait ‘Dao’.

Here is the trait:

pub trait Dao<T: Identifiable + Serialize + DeserializeOwned + FileDescriptor> {

    fn new_id(&self) -> Result<u64, DaoError>;

    fn get(&self, id: u64) -> Result<Option<T>, DaoError>;

    fn get_some(&self, ids: &Vec<u64>) -> Result<Vec<T>, DaoError>;

    fn get_all(&self) -> Result<Vec<T>, DaoError>;

    fn save(&mut self, to_save: &T) -> Result<(), DaoError>;

    fn update(&self, to_update: &T) -> Result<(), DaoError>;

    fn delete(&self, to_delete: &T) -> Result<(), DaoError>;
}

I then try to create my mock which implements this trait:

#[derive(Serialize, Deserialize, Clone)]
    pub struct MockComponent {}

    impl MockComponent {

        pub fn new() -> MockComponent {

            return MockComponent {};
        }
    }

    impl Identifiable for MockComponent {

        fn id(&self) -> u64 {
            
            return 0;
        }
    }

    impl FileDescriptor for MockComponent {

        fn file_descriptor() -> String {
            
            return String::new();
        }
    }


    pub struct MockDao;

    impl<MockComponent> Dao<MockComponent> for MockDao {

        fn new_id(&self) -> Result<u64, DaoError> {
            
            return Ok(0);
        }
        // other implemented methods
    }

For some reason I have an error on Dao<MockComponent> telling me that:

the trait bound `MockComponent: components::component_access::FileDescriptor` is not satisfied
`Dao` is a "sealed trait", because to implement it you also need to implement `components::component_access::FileDescriptor`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it

I dont quite understand what is meant by a sealed trait, the trait Dao is public in my crate, and my MockComponent implements both Identifiable and FileDescriptor. Does it matter where in my folder structure these traits are defined even if they are public and available to the module in which im defining my mock component?