This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
return <div>{props.name}</div>;
    }
    FunctionComponentWithChildContext.childContextTypes = {
      foo: PropTypes.string,
    };
    const container = document.createElement('div');
    expect(() =>
      ReactDOM.render(
        <FunctionComponentWithChildContext name="A" />,
        container,
      ),
    ).toErrorDev(
      'FunctionComponentWithChildContext(...): childContextTypes cannot ' +
        'be defined on a function component.',
    );
  });
  it('should throw when stateless component returns undefined', () => {
    function NotAComponent() {}