register_fn_constraints.rs

use std::any::Any;

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

trait FnRegisterTest {
    fn register(self, engine: &mut Engine, name: &str);
}

impl<A: Any+Clone, B: Any+Clone, T: Fn(A)->B> FnRegisterTest for T {
    fn register(self, engine: &mut Engine, name: &str) {
        engine.x += 1;
    }
}

fn id(x: i32) -> i32 {
    x
}

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

    id.register(&mut engine, "foo");

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