Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
function mountClassInstance(
    workInProgress: Fiber,
    renderExpirationTime: ExpirationTime,
  ): void {
    const current = workInProgress.alternate;
    if (__DEV__) {
      checkClassInstance(workInProgress);
    }
    const instance = workInProgress.stateNode;
    const state = instance.state || null;
    let props = workInProgress.pendingProps;
    invariant(
      props,
      'There must be pending props for an initial mount. This error is ' +
        'likely caused by a bug in React. Please file an issue.',
    );
    const unmaskedContext = getUnmaskedContext(workInProgress);
    instance.props = props;
    instance.state = workInProgress.memoizedState = state;
    instance.refs = emptyObject;
    instance.context = getMaskedContext(workInProgress, unmaskedContext);
    if (
      enableAsyncSubtreeAPI &&
      workInProgress.type != null &&
      workInProgress.type.prototype != null &&
      workInProgress.type.prototype.unstable_isAsyncReactComponent === true
    ) {
      workInProgress.internalContextTag |= AsyncUpdates;
    }