#![feature(unboxed_closures, fn_traits)]

struct SelfFunc {
    sum: i32,
}

impl FnOnce<(i32, i32)> for SelfFunc {
    type Output = SelfFunc;

    extern "rust-call" fn call_once(mut self, args: (i32, i32)) -> Self::Output {
        println!("Adding {}", args.0);
        self.sum += args.0;
        self
    }
}

impl FnOnce<()> for SelfFunc {
    type Output = i32;

    extern "rust-call" fn call_once(self, _args: ()) -> Self::Output {
        println!("Finished adding");
        self.sum
    }
}

fn main() {
    let f = SelfFunc { sum: 0 };
    let a = (1, 2);
    let sum = f(1, 0)(2, 0)(3, 0)();
    println!("Sum = {}", sum)
}