created.return = returnFiber;
        return created;
      }
      throwOnInvalidObjectType(returnFiber, newChild);
    }
    if (__DEV__) {
      if (typeof newChild === 'function') {
        warnOnFunctionType();
      }
    }
    return null;
  }
  function updateSlot(
    returnFiber: Fiber,
    oldFiber: Fiber | null,
    newChild: any,
    expirationTime: ExpirationTime,
  ): Fiber | null {
    
    const key = oldFiber !== null ? oldFiber.key : null;
    if (typeof newChild === 'string' || typeof newChild === 'number') {
      
      
      
      if (key !== null) {
        return null;
      }
      return updateTextNode(
        returnFiber,
        oldFiber,