Rust code shared from the playground

playground.rs

use std::io::{self};
use std::result;

type KKResults <T> = Result <T, KKError>;

#[derive(Debug)]
enum KKError {
    Io(io::Error),
}

impl From<io::Error> for KKError {
    fn from(err: io::Error) -> KKError {
        KKError::Io(err)
    }
}


trait knightknave {
    type Output;
    fn is_knight_or_knave (&self) -> KKResults <Self::Output>;
}

struct Knight; 
struct Knave;
struct visitor;

impl knightknave for visitor {
    type Output = bool;

    fn is_knight_or_knave(&self) -> KKResults<Self::Output> {
        Ok(true)
    }
} 

fn main() {
    println!("{:?}", visitor.is_knight_or_knave());
}