Function constructor

packages/react-dom/src/__tests__/ReactDOMFiber-test.js:432–438

(props)

    let instance;
    class Wrapper extends React.Component {
      constructor(props) {
        super(props);
        instance = this;
        this.state = {
          show: true,
        };
      }
      render() {
        return (
          <div>