Bug: useState with class as initial state throws an error

Using a JavaScript class as initial state in useState throws an error. This is because mountState check if the initial state is a function by typeof initialState === 'function' and classes are technically functions. However since ES6+, I feel like most developers don't consider classes functions because of the less prototype-inheritance feel since ES6 and the class keyword.

React version: 17.0.2

Steps To Reproduce

1. Define an ES6 class
2. Use the class as initialState argument to useState

Code example:

import { useState } from "react";
import ReactDOM from "react-dom";

class A {}

function App() {
  const [cls, setCls] = useState(A);
  return <h2>{cls.name}</h2>;
}

ReactDOM.render(<App />, document.body);

The current behavior

TypeError: Cannot call a class as a function
    at _classCallCheck (eval at z (eval.js:42), <anonymous>:3:11)
    at A (VM302 index.js:19)
    at mountState (react-dom.development.js:10436)
    at Object.useState (react-dom.development.js:10919)
    at useState (react.development.js:954)
    at App (VM302 index.js:25)

Alternatively, the error can be TypeError: Class constructor X cannot be invoked without 'new'.

The expected behavior

As mentioned in the description above, I would

• either expect classes to work
• or mention this caveat in the docs.

I guess checking, if the initial state is actually a non-class function, could cause instances of subclasses of functions not to work (depending how the check is done).