internal compiler error: Explicit deref of non-derefable type

``` rust
fn main() {
    let &ref a = [0u].as_slice();
}
```

```
test.rs:2:9: 2:15 error: internal compiler error: Explicit deref of non-derefable type: &[uint]
test.rs:2     let &ref a = [0u].as_slice();
                  ^~~~~~
```
