### What it does Checks for looping over the range of `0..len` of some collection just to get the values by index. ### Why is this bad? Just iterating the collection itself makes the intent more clear and is probably faster. ### Example ``` let vec = vec!['a', 'b', 'c']; for i in 0..vec.len() { println!("{}", vec[i]); } ``` Use instead: ``` let vec = vec!['a', 'b', 'c']; for i in vec { println!("{}", i); } ```