**Do you want to request a *feature* or report a *bug*?**
bug.

**What is the current behavior?**
This addresses a bug in `enzyme`, https://github.com/airbnb/enzyme/issues/1683.

On [this line](https://github.com/facebook/react/blob/master/packages/react-test-renderer/src/ReactShallowRenderer.js#L110) `element.type()` invokes the SFC with `element` as the `this` value. I believe that this is needed for create-react-class components, but that there needs to be a separate branch for SFCs.

**What is the expected behavior?**
`this` inside a strict-mode SFC will be `undefined`, not the element.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
In all of React 0.13, 0.14, 15, and 16, this bug exists.

While the bug ideally will be fixed, I understand that it's highly unlikely that it would be backported to the 14/15 lines - but I can wrap around it if there's a reliable way, in those versions, to distinguish SFCs from create-react-class components (is there?).
getSnapshotBeforeUpdate() {
        throw Error('unexpected');
      }
      componentDidUpdate() {
        throw Error('unexpected');
      }
      render() {
        return null;
      }
    }
    const shallowRenderer = createRenderer();
    shallowRenderer.render(<Component value={1} />);
    shallowRenderer.render(<Component value={2} />);
  });
  it('should only render 1 level deep', () => {
    function Parent() {
      return (
        <div>
          <Child />
        </div>
      );
    }
    function Child() {
      throw Error('This component should not render');
    }
    const shallowRenderer = createRenderer();
    shallowRenderer.render(React.createElement(Parent));
  });
  it('should have shallow rendering', () => {
    class SomeComponent extends React.Component {