**Please describe what the rule should do:**

**What category of rule is this (place an "X" next to just one item)?**

[ ] Enforces code style
[ ] Warns about a potential error
[ ] Suggests an alternate way of doing something
[ ] Other (please specify:)

**Provide 2-3 code examples that this rule will warn about:**

```js
<!-- put your code examples here -->
```

**Why should this rule be included in ESLint (instead of a plugin)?**