let _definetly_none = ConstOption::<String, false>::new();
let definetly_some = ConstOption::<String, true>::new("hello, world".to_string());

// When there is definitely some value, the deref trait can be used.
println!("{}", &*definitely_some);

// Obtain the string inside.
let contained_string = definitely_some.into_inner();


struct Container<T, const IS_UNIQUE: bool> {
    data: ConstEither<Vec<T>, HashSet<T>, UNIQUE>,
}

impl<T> Container<T, false> {
    fn insert(&mut self, val: T) {
        /* ... */
    }
}

impl<T: Eq + Hash> Container<T, true> {
    fn insert(&mut self, val: T) -> Result<(), T> {
        /* ... */
    }
}