trait MyTrait {
    type ReturnValue;

    fn next(&self) -> Self::ReturnValue;
}

struct Something {
    data: [u8; 16],
}

impl MyTrait for Something {
    type ReturnValue = &'a [u8; 16];

    fn next(&self) -> Self::ReturnValue {
        unimplemented!();
    }
}



fn main() {
    println!("Hello, world!");
}