2 Checks for occurrences where one vector gets extended instead of append
5 Using `append` instead of `extend` is more concise and faster
9 let mut a = vec![1, 2, 3];
10 let mut b = vec![4, 5, 6];
12 a.extend(b.drain(..));
17 let mut a = vec![1, 2, 3];
18 let mut b = vec![4, 5, 6];