**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>{this.context.name}</div>;
      }
    }
    const shallowRenderer = createRenderer();
    expect(() => shallowRenderer.render(<SimpleComponent />)).toWarnDev(
      'Warning: Failed context type: The context `name` is marked as ' +
        'required in `SimpleComponent`, but its value is `undefined`.\n' +
        '    in SimpleComponent (at **)',
    );
  });
  it('should warn about propTypes (but only once)', () => {
    class SimpleComponent extends React.Component {
      render() {
        return React.createElement('div', null, this.props.name);
      }
    }
    SimpleComponent.propTypes = {
      name: PropTypes.string.isRequired,
    };
    const shallowRenderer = createRenderer();
    expect(() =>
      shallowRenderer.render(React.createElement(SimpleComponent, {name: 123})),
    ).toWarnDev(
      'Warning: Failed prop type: Invalid prop `name` of type `number` ' +
        'supplied to `SimpleComponent`, expected `string`.\n' +
        '    in SimpleComponent',
    );
  });
  it('should enable rendering of cloned element', () => {
    class SimpleComponent extends React.Component {