Look-ahead for arrow function expressions too permissive when encountering "()"

When encountering code like

```
().toString();
```

We make a strange assumption, which is that the `()` belongs to an arrow function like the following:

```
() => x
```

This is weird because it bubbles up to nothing better than the error

```
Cannot find name 'toString'.
```

In this case, we should check to see if the next token is an arrow (`=>`).
