#![feature(optin_builtin_traits)]

trait Encode {
    fn encode() -> Vec<u8>;
}

auto trait GeneralVecEncode {}
impl !GeneralVecEncode for u8 {}

impl Encode for u8 {
    fn encode() -> Vec<u8> { vec![0x2; 1] }
}

impl<T> Encode for Vec<T>
where
    T: Encode + GeneralVecEncode
{
    fn encode() -> Vec<u8> { vec![0x0; 1] }
}

impl Encode for Vec<u8> {
    fn encode() -> Vec<u8> { vec![0x1; 1] }
}

fn main() {

}