Typing useState and useEffect

A line as ordinary as useState([]) creates a state that can hold nothing. Try to store a value in it:

import { useState } from "react";

const PostTitles = () => {
  const [titles, setTitles] = useState([]);

  return <button onClick={() => setTitles(["Hello"])}>{titles.length}</button>;
};

error TS2322: Type 'string' is not assignable to type 'never'.

The compiler infers the type of a state from its initial value. An empty array gives it no information about the items, so the state becomes never[], an array that can contain no items