Final return statements versus implicit return

Exhibit A

``` rust
fn i_am_the_walrus(foo: u32) -> u64 {
    ((foo as u64) << 32) + (foo as u64)
}
```

Exhibit B

``` rust
fn i_am_the_walrus(foo: u32) -> u64 {
    return ((foo as u64) << 32) + (foo as u64);
}
```

Given that the Book refers to B as “poor style”, is it within rustfmt's bailiwick (being that it is a tool for resolving stylistic disagreements) to replace it with A?
