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.
import shallowEqual from 'fbjs/lib/shallowEqual';
import invariant from 'fbjs/lib/invariant';
import warning from 'fbjs/lib/warning';
import {startPhaseTimer, stopPhaseTimer} from './ReactDebugFiberPerf';
import {AsyncUpdates} from './ReactTypeOfInternalContext';
import {
  cacheContext,
  getMaskedContext,
  getUnmaskedContext,
  isContextConsumer,
} from './ReactFiberContext';
import {
  insertUpdateIntoFiber,
  processUpdateQueue,
} from './ReactFiberUpdateQueue';
import {hasContextChanged} from './ReactFiberContext';
const fakeInternalInstance = {};
const isArray = Array.isArray;
if (__DEV__) {
  var didWarnAboutStateAssignmentForComponent = {};
  var warnOnInvalidCallback = function(callback: mixed, callerName: string) {
    warning(
      callback === null || typeof callback === 'function',
      '%s(...): Expected the last optional `callback` argument to be a ' +
        'function. Instead received: %s.',
      callerName,
      callback,
    );
  };