This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
workInProgress.memoizedState = nextState;
      workInProgress.updateQueue = null;
      
      
      pushRenderLanes(workInProgress, nextBaseLanes);
      if (enableLazyContextPropagation && current !== null) {
        
        
        
        propagateParentContextChangesToDeferredTree(
          current,
          workInProgress,
          renderLanes,
        );
      }
      return null;
    } else {
      
      
      if (enableCache && prevState !== null) {
        
        
        
        const prevCachePool = prevState.cachePool;
        if (prevCachePool !== null) {
          spawnedCachePool = restoreSpawnedCachePool(
            workInProgress,
            prevCachePool,
          );
        }