Y combinator in Rust

y.rs

/* Y combinator for Rust. 
   Implemented by Vitaly "_Vi" Shukela.
   
   $ rustc --version
   rustc 0.6 (5f13e9c 2013-04-02 13:36:51 -0700)
   host: i686-unknown-linux-gnu
*/

type Yfunc<T> = @fn(x:T) -> T;
type Yfunc2<T> = @fn(f: Yfunc<T>, x:T) -> T;

fn fix<T>(f:Yfunc2<T>) -> Yfunc<T> {
    let closure1 : @mut Yfunc<T> = @mut |_| { fail!() };
    let closure2 : @fn(ff : Yfunc2<T> , xx : T)->T = |ff : Yfunc2<T> , xx : T| {
        ff(*closure1, xx)
    };
    *closure1 = |x| {
        let result = closure2(f, x);
        *closure1 = |_| { fail!() }; // Fix memory leak
        result
    };
    *closure1
}

fn main() {
    let fac : Yfunc2<int> = |f:Yfunc<int>, x:int| {
        if (x==0) { 1 } else { f(x-1) * x } 
    };
    io::println( fmt!("%d", fix(fac) (5)  ));
    
    
    let fib : Yfunc2<int> = |f:Yfunc<int>, x:int| {
        if (x<2) { 1 } else { f(x-1) + f(x-2)  } 
    };
    io::println( fmt!("%d", fix(fib) (10)  ));
}