Float repr fail in nested tuple access error message

This code

``` rust
(1, (2, 3)).1.1
```

produces this error message

```
expr.rs:5:14: 5:17 error: unexpected token: `1.1`
expr.rs:5 {(1, (2, 3)).1.1}
                       ^~~
expr.rs:5:14: 5:17 help: try parenthesizing the first index; e.g., `(foo.1).10000000000000009`
```

It should suggest `(foo.1).1` of course, but floats gotta be floats.
