yew rust framework: mount component to dom macro

mount.rs

pub enum MountError {
    QuerySelectorError,
    ElementNotFound(String)
}

impl From<TODO> for MountError {
    fn from(_: TODO) -> Self {
        MountError::QuerySelectorError
    }
}

macro_rules! mount {
    ($element:expr, $model:ty) => {{
        |()| -> Result<(),MountError> {
            if let Some(element) = document().query_selector($element)? {
            App::<$model>::new().mount(element);
                Ok(())
            } else {
            Err(MountError::ElementNotFound(format!("Could not find the element {} in the DOM.", $element)))
            }
        }
    }};
}

pub fn mount_app() -> () {
    mount!("#banner", Banner);
}