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

**What is the current behavior?**
In normal rendering, you can memoize a class-based component: https://jsfiddle.net/586ea3cx/

With the shallow renderer, it seems like you can't: https://jsfiddle.net/odj217Lv/1/

This might be blocking https://github.com/airbnb/enzyme/pull/1914, in which tests are failing with `Cannot call a class as a function`. (it's tough to repro stuff with the shallow renderer)
return <div />;
      }
    }
    const shallowRenderer = createRenderer();
    shallowRenderer.render(<SomeComponent foo={1} />);
    
    
    expect(logs).toEqual(['componentWillMount']);
    logs.splice(0);
    const instance = shallowRenderer.getMountedInstance();
    instance.setState({});
    expect(logs).toEqual(['shouldComponentUpdate', 'componentWillUpdate']);
    logs.splice(0);
    shallowRenderer.render(<SomeComponent foo={2} />);
    
    expect(logs).toEqual([
      'componentWillReceiveProps',
      'shouldComponentUpdate',
      'componentWillUpdate',
    ]);
  });
  it('should call all of the new lifecycle hooks', () => {
    const logs = [];
    const logger = message => () => logs.push(message) || true;
    class SomeComponent extends React.Component {