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 React.createElement('div');
      }
    };
  });
  it('warns for keys for arrays of elements in rest args', () => {
    const Component = React.createFactory(ComponentClass);
    expect(() => {
      Component(null, [Component(), Component()]);
    }).toWarnDev(
      'Each child in an array or iterator should have a unique "key" prop.',
    );
  });
  it('warns for keys for arrays of elements with owner info', () => {
    const Component = React.createFactory(ComponentClass);
    class InnerClass extends React.Component {