Fails to compile with "rustc --opt-level 3 macro_test.rs" but compiles fine with just "rustc macro_test.rs"

macro_test.rs

#![feature(macro_rules)]

macro_rules! early_return(
    ($inp:expr, $($sp:ident),+) => (
        match $inp {
            $(
                $sp(x) => { return x; }
            )+
            _ => {}
        }
    );
)

fn main() {
    let n : Result<uint, ()> = Err(());
    early_return!(n, Err);
    println!("Got {}!", n.unwrap());
}