ICE: only string and byte strings supported in compare_values

``` Rust
fn main() {
    let x = (0,2);
    match x {
        (0, ref y) => { /* use y */}
        (y, 0) => { /* use y */ }
        _ => ()
    }
}
```

I had this error on [play.rust-lang](https://play.rust-lang.org/) on release, beta and nightly.
