Got this debugging another error. Filing here for reference. Original code: https://phabricator.intern.facebook.com/P59317705
return next;
        }
        if (
          returnFiber !== null &&
          
          (returnFiber.effectTag & Incomplete) === NoEffect
        ) {
          
          
          
          if (returnFiber.firstEffect === null) {
            returnFiber.firstEffect = workInProgress.firstEffect;
          }
          if (workInProgress.lastEffect !== null) {
            if (returnFiber.lastEffect !== null) {
              returnFiber.lastEffect.nextEffect = workInProgress.firstEffect;
            }
            returnFiber.lastEffect = workInProgress.lastEffect;
          }
          
          
          
          
          
          
          const effectTag = workInProgress.effectTag;
          
          
          if (effectTag > PerformedWork) {