Destructuring of references to trait objects is broken

``` rust
fn main() {
    let &f = &(&1 as &::std::fmt::Show);
}
```

```
test.rs:2:9: 2:11 error: mismatched types: expected `&core::fmt::Show` but found an `&`-pointer pattern
test.rs:2     let &f = &(&1 as &::std::fmt::Show);
                  ^~
```

This was introduced in the latest nightly.
