**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)
owner && getComponentName(owner.type),
    );
  }
  return stack;
}
function getName(type, instance) {
  const constructor = instance && instance.constructor;
  return (
    type.displayName ||
    (constructor && constructor.displayName) ||
    type.name ||
    (constructor && constructor.name) ||
    null
  );
}
function shouldConstruct(Component) {
  return !!(Component.prototype && Component.prototype.isReactComponent);
}
function getMaskedContext(contextTypes, unmaskedContext) {
  if (!contextTypes || !unmaskedContext) {
    return emptyObject;
  }
  const context = {};
  for (let key in contextTypes) {
    context[key] = unmaskedContext[key];
  }
  return context;
}
export default ReactShallowRenderer;