https://jsfiddle.net/3apqnhmw/

```jsx
class Foo extends React.Component {
  render() {
     return <div>Foo</div>
  }
}

class App extends React.Component {
  render() {
    return Foo
  }
}
```

When `App` returns `Foo` instead of `<Foo />` accidentally, Fiber does not catch this.
getTitle = () => {
        return this.props.title;
      };
      render() {
        return this.props.getContent();
      }
    }
    var mounted = false;
    class Component extends React.Component {
      getInner = () => {
        
        
        return <div className="inner" ref={c => (this.innerRef = c)} />;
      };
      render() {
        return (
          <Wrapper
            title="wrapper"
            ref={c => (this.wrapperRef = c)}
            getContent={this.getInner}
          />
        );
      }
      componentDidMount() {