newChild.props.children,
              expirationTime,
              newChild.key,
            );
          }
          return updateElement(
            returnFiber,
            matchedFiber,
            newChild,
            expirationTime,
          );
        }
        case REACT_PORTAL_TYPE: {
          const matchedFiber =
            existingChildren.get(
              newChild.key === null ? newIdx : newChild.key,
            ) || null;
          return updatePortal(
            returnFiber,
            matchedFiber,
            newChild,
            expirationTime,
          );
        }
      }
      if (isArray(newChild) || getIteratorFn(newChild)) {
        const matchedFiber = existingChildren.get(newIdx) || null;
        return updateFragment(
          returnFiber,
          matchedFiber,