(Useless) code that handles unsized values can be written

``` Rust
pub fn take_unsized(ref _v: [u8])  { }

pub trait ReturnUnsized {
    fn returns_unsized(&self) -> [u8];
}

pub fn create_unsized(v: &ReturnUnsized) {
    let ref _v = v.returns_unsized();
}

fn main() {}
```

I don't think this should compile.
