Shared via Rust Playground

playground.rs

pub trait Ast<'a> {
    fn evaluate(self: Box<Self>) -> Option<Box<Ast<'a> + 'a>>;
}

pub struct Assignment<'a> {
    lhs: Option<Box<Ast<'a> + 'a>>,
    rhs: Option<Box<Ast<'a> + 'a>>
}

impl<'a> Ast<'a> for Assignment<'a> {
    fn evaluate(mut self: Box<Self>) -> Option<Box<Ast<'a> + 'a>>{
        println!("Eval assignment");
        let evaluated = self.lhs.take().unwrap().evaluate();
        self.lhs = evaluated;
        Some(self)
    }
}


fn main() {
    println!("Foo");
    
    //let var = Var{var_id: "X"};
   // let ass = Assignment{lhs: Some(Box::new(var)), rhs: None};
    //let maybe = ass.evaluate();
}

pub trait Ast {
fn evaluate(&mut self) -> Option<Box>;
}

pub struct Assignment<'a> {
lhs: Option<Box<Ast + 'a>>,
rhs: Option<Box<Ast + 'a>>
}

impl<'a> Ast for Assignment<'a> {

fn evaluate(&mut self) -> Option<Box<Ast>>{

    println!("Eval assignment");
    let evaluated = self.lhs.take().unwrap().evaluate();
    self.lhs = evaluated;
    //Some(Box::new(self))
    None
}

}

fn main() {
println!("Foo");

//let var = Var{var_id: "X"};

// let ass = Assignment{lhs: Some(Box::new(var)), rhs: None};
//let maybe = ass.evaluate();
}