register_fn_constraints3.rs

use std::any::Any;

#[derive(Debug)]
struct Engine {
    x: i32
}

trait FnRegister<RetVal, Args> {
    fn register<T: Fn(Args)->RetVal>(&mut self, name: &str, f: T);
}

impl FnRegister<i32, (i32, i32)> for Engine {
    fn register<T: Fn(i32, i32)->i32>(&mut self, name: &str, f: T) {
        self.x += 2;
    }
}

fn add(x:i32, y: i32) -> i32 { 
    x + 10
}

fn main() {
    let mut engine = Engine { x: 0 };

    engine.register("bar", add);

    println!("Engine: {:?}", engine);
}