**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?).
this._enqueueCallback(callback, publicInstance);
    this._renderer._newState = completeState;
    this._renderer.render(this._renderer._element, this._renderer._context);
  }
  enqueueSetState(publicInstance, partialState, callback, callerName) {
    this._enqueueCallback(callback, publicInstance);
    const currentState = this._renderer._newState || publicInstance.state;
    if (typeof partialState === 'function') {
      partialState = partialState.call(
        publicInstance,
        currentState,
        publicInstance.props,
      );
    }
    
    if (partialState === null || partialState === undefined) {
      return;
    }
    this._renderer._newState = {
      ...currentState,
      ...partialState,
    };
    this._renderer.render(this._renderer._element, this._renderer._context);
  }
}
let currentlyValidatingElement = null;
function getDisplayName(element) {