Function useFiber

docs/index.js:6288–6293

(fiber, pendingProps)

    return existingChildren;
  }
  function useFiber(fiber, pendingProps) {
    fiber = createWorkInProgress(fiber, pendingProps);
    fiber.index = 0;
    fiber.sibling = null;
    return fiber;
  }
  function placeChild(newFiber, lastPlacedIndex, newIndex) {
    newFiber.index = newIndex;
    if (!shouldTrackSideEffects)