foo.rs

fn try<T: Send>(f: ~fn(~fn(~str) -> !) -> T) -> Result<T, ~str> {
    let (wr, rd) = task::stream();
    let result: Result<T, ()> = do tasks::try |move wr| {
        let fail_: fn~(~str) -> ! = fn~(x: ~str) -> ! { wr.send(x); fail; };
        f(fail_)
    };
    return match move result {
        Ok(move v)  => Ok(move v),
        Err(_)      => match rd.try_recv() {
            Some(move s) => Err(move s),
            None         => Err(~"fail")
        }
    }
}

fn main() {
   let result: Result<int, ~str> = do try |fail_| {
       fail_(~"This didn't work at all!");
   };

   io::println(fmt!("%?", result));
}

gistfile1.txt

foo.rs:4:56: 4:58 error: copying a noncopyable value
foo.rs:4         let fail_: fn~(~str) -> ! = fn~(x: ~str) -> ! { wr.send(x); fail; };
                                                                 ^~
foo.rs:4:56: 4:58 note: non-copyable value cannot be copied into a ~fn closure
foo.rs:4         let fail_: fn~(~str) -> ! = fn~(x: ~str) -> ! { wr.send(x); fail; };