Bugs parsing the try!() macro

This code from serde causes red underlining in VS Code even though rustc is fine with it:

```rust
        match try!(self.next_key_seed(kseed)) {
            Some(key) => {
                let value = try!(self.next_value_seed(vseed));
                Ok(Some((key, value)))
            }
            None => Ok(None),
        }
```

As of 5c3ccc55082838524f695ffe40138fd8e805db70.