mod final_impl {
    #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
    #[repr(transparent)]
    pub struct Final<T>(T);

    impl<T> Final<T> {
        pub fn new(val: T) -> Self {
            Self(val)
        }
    }

    impl<T> std::ops::Deref for Final<T> {
        type Target = T;
        fn deref(&self) -> &T {
            &self.0
        }
    }
}

use final_impl::Final;

struct MyStruct {
    vec: Final<Vec<u8>>,
}

impl MyStruct {
    fn new() -> Self {
        Self {
            vec: Final::new(vec![0, 1, 2, 3]),
        }
    }
}

fn main() {
    let mut s = MyStruct::new();
    s.vec.push(4);
}