### What it does
Checks for `for` loops over `Option` or `Result` values.

### Why is this bad?
Readability. This is more clearly expressed as an `if
let`.

### Example
```
for x in opt {
    // ..
}

for x in &res {
    // ..
}

for x in res.iter() {
    // ..
}
```

Use instead:
```
if let Some(x) = opt {
    // ..
}

if let Ok(x) = res {
    // ..
}
```