#[derive(Debug, PartialEq, Clone)]
enum Token {
    Ident(String),
    Int(i64),
}

#[derive(Debug, PartialEq, Clone)]
enum Expression {
    Ident(String),
    Int(i64),
}

impl Expression {
    fn from_token(tok: Token) -> Expression {
        match tok {
            Token::Ident(ident) => Expression::Ident(ident),
            Token::Int(i64)     => Expression::Int(i64),
        }
    }
}

#[derive(Debug, PartialEq, Clone)]
enum Statement {
    Let(Expression, Expression),
}

fn main() {
    let ident = Token::Ident(String::from("aiueo"));
    let ident = Expression::from_token(ident);
    let int   = Token::Int(7i64);
    let int   = Expression::from_token(int);
    let h     = Statement::Let(ident, int);
    println!("{:?}", h);
}