Function Updater

packages/react-reconciler/src/__tests__/ReactAsyncActions-test.js:1257–1265

()

    async () => {
      let startTransition;
      function Updater() {
        const [isPending, _start] = useTransition();
        startTransition = _start;
        return (
          <span>
            <Text text={'Pending: ' + isPending} />
          </span>
        );
      }

      let setText;
      let setOptimisticText;