[eslint-plugin-react-hooks] New Rule Proposal: `no-unnecessary-setstate `

Hi there! First of all, again want to extend thanks for your tireless work on creating this amazing library and supporting the ecosystem! Really big up to everyone involved! 💯 🙌 I wanted to see if the `eslint-plugin-react-hooks` project would accept a new rule: `no-unnecessary-setstate`. I have the feeling that this may be too opinionated for the plugin, but I was sent here by ljharb from `eslint-plugin-react` after proposing it over there: https://github.com/yannickcr/eslint-plugin-react/issues/2997 --- Anyway, here goes: **Rule proposal:** `no-unnecessary-setstate` - forbid setting state to the value of the existing state variable I've seen this pattern also a bunch from beginners learning React. And regardless of whether you're a beginner or not, this is probably not what you want to do (even if it's an object / array). Example of **incorrect** code: ```jsx function Input (props) { const [name, setName] = useState(''); return ( <input value={name} onChange={(event) => { setName(event.currentTarget.value); setName(name); // ESLint problem reported }} /> ); } ``` Examples of **correct** code: ```jsx function Input (props) { const [name, setName] = useState(''); return ( <input value={name} onChange={(event) => { setName(event.currentTarget.value); }} /> ); } ``` ```jsx function Input (props) { const [name, setName] = useState(''); return ( <input value={name} onChange={(event) => { const name = event.currentTarget.value; // Shadowing setName(name); }} /> ); } ``` --- cc @gaearon