2 Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
5 Readability, this can be written more concisely as
6 `_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
10 let vec = vec![vec![1]];
13 vec.iter().map(|x| x.iter()).flatten();
14 opt.map(|x| Some(x * 2)).flatten();
19 vec.iter().flat_map(|x| x.iter());
20 opt.and_then(|x| Some(x * 2));