The <T as U> syntax generates parsing errors

Example: (http://is.gd/zRXt7J)

``` rust
trait Foo {
    type T;
    fn test(&self) -> Vec<<Self as Foo>::T>;
}
```

Generates:

```
<anon>:5:26: 5:28 error: expected `;` or `{`, found `<<`
<anon>:5     fn test(&self) -> Vec<<Self as Foo>::T>;
```

Adding a space between `Vec<` and `<Self as Foo>` fixes the error.
