| ### What it does | |
| Checks for iterating a map (`HashMap` or `BTreeMap`) and | |
| ignoring either the keys or values. | |
| ### Why is this bad? | |
| Readability. There are `keys` and `values` methods that | |
| can be used to express that don't need the values or keys. | |
| ### Example | |
| ``` | |
| for (k, _) in &map { | |
| .. | |
| } | |
| ``` | |
| could be replaced by | |
| ``` | |
| for k in map.keys() { | |
| .. | |
| } | |
| ``` |