This:

```js
createElement(<div />)
```

doesn't currently give a distinguishable message.

https://stackoverflow.com/questions/51110436/wrapping-provider-in-same-component-throws-element-type-is-invalid-expected-a-s

But we can easily detect it by checking for `$$typeof` and in that case suggest something more concrete (e.g. "Did you accidentally export JSX instead of a component?").
return <div />;
    }
    Object.defineProperty(Anonymous, 'name', {value: undefined});
    const divs = [<div />, <div />];
    expect(() => {
      ReactTestUtils.renderIntoDocument(<Anonymous>{divs}</Anonymous>);
    }).toWarnDev(
      'Warning: Each child in an array or iterator should have a unique ' +
        '"key" prop. See https://fb.me/react-warning-keys for more information.\n' +
        '    in div (at **)',
    );
  });
  it('warns for keys for arrays of elements with no owner info', () => {
    const divs = [<div />, <div />];
    expect(() => {
      ReactTestUtils.renderIntoDocument(<div>{divs}</div>);
    }).toWarnDev(
      'Warning: Each child in an array or iterator should have a unique ' +
        '"key" prop.\n\nCheck the top-level render call using <div>. See ' +
        'https://fb.me/react-warning-keys for more information.\n' +
        '    in div (at **)',
    );
  });
  it('warns for keys with component stack info', () => {
    function Component() {