[React 19] Export SuspenseException

## Problem Statement Currently, in React's `use(promise)` mechanism, there is no straightforward way to determine whether an exception originates from a promise suspended within the `use` hook. This makes it challenging for developers to: - Accurately catch and handle errors related to suspended promises. - Differentiate between errors caused by `use(promise)` and other unrelated errors, complicating error handling logic. ## Proposal React should export either: 1. A `SuspenseException` class that can be used to identify errors originating from a promise suspension, or 2. A utility function to check whether a given error is caused by a suspended promise in `use(promise)`. ### Example Usage 1. **SuspenseException Class:** ```jsx import { SuspenseException } from 'react'; try { use(fetchData()); } catch (error) { if (error === SuspenseException) { // Handle Suspense-related logic } else { // Handle other types of errors } } ``` 2. **Utility Function:** ```jsx import { isSuspenseException } from 'react'; try { use(fetchData()); } catch (error) { if (isSuspenseException(error)) { // Handle Suspense-related logic } else { // Handle other types of errors } } ``` ## Benefits - **Error differentiation:** Clear distinction between promise suspensions and other errors. - **Enhanced debugging:** Easier diagnosis of Suspense-related issues in both development and production. - **Safer error handling:** Prevents unintended catches of non-Suspense errors during Suspense management. ## Conclusion By exporting either a `SuspenseException` or a utility function, React would offer developers more control over managing Suspense-related errors, improving both error handling and debugging in applications.