enum Error {
    InvalidLoginOrPassword,
    Other,
}

struct Status {
    code: i32
}

impl Status {
    fn ok() -> Status {
        Status {
            code: 200,
        }
    }
}

struct LoginForm(Status);
struct UpdateUserForm(Status);
// etc...

fn login<'a>(_username: &'a str, _password: &'a str) -> Result<LoginForm, Error> {
    Ok(LoginForm(Status::ok()))
}

fn main() {
    login("Username", "Password");
}