#![feature(unboxed_closures, fn_traits)]

struct S {
    capture: i32,
}

impl Fn<(i32,)> for S {
    extern "rust-call" fn call(&self, (x,): (i32,)) -> i32 {
        println!("call fn");
        self.capture * x
    }
}
impl FnMut<(i32,)> for S {
    extern "rust-call" fn call_mut(&mut self, args: (i32,)) -> i32 {
        println!("call mut");
        self.call(args)
    }
}
impl FnOnce<(i32,)> for S {
    type Output = i32;
    extern "rust-call" fn call_once(self, args: (i32,)) -> i32 {
        println!("call once");
        self.call(args)
    }
}
fn call_it<F: Fn(i32) -> i32>(f: &F, x: i32) -> i32 {
    f(x)
}
fn call_it_mut<F: FnMut(i32) -> i32>(f: &mut F, x: i32) -> i32 {
    f(x)
}
fn call_it_once<F: FnOnce(i32) -> i32>(f: F, x: i32) -> i32 {
    f(x)
}
fn main() {
    let mut s = S { capture: 5 };
    {
        let x = call_it(&s, 22);
    }
    {
        let y = call_it_mut(&mut s, 22);
    }
    let z = call_it_once(s, 22);
    // assert_eq!(x, y);
    // assert_eq!(y, z);
}