impl_on_fns.rs

fn simple_fn(x: i32) -> i32 {
    x + 100
}

trait FooFn {
    fn foo(&self);
}

impl FooFn for Fn(i32)->i32 {
    fn foo(&self) {
        println!("Function foo!");
    }
}

fn main() {
    //Works
    //let f : fn(i32)->i32 = simple_fn;
    //f.foo();
    
    //error: no method named `foo` found for type `fn(i32) -> i32 {simple_fn}` in the current scope
    simple_fn.foo();
}