fallback export in +server.js not recognized

[karimfromjordan]

Describe the bug

SvelteKit 1.25.0 added support for a fallback export in +server.js files sveltejs/kit#9755. Writing such a fallback export currently produces the following warning:

Invalid export 'fallback' (valid exports are prerender, trailingSlash, config, entries, GET, POST, PUT, PATCH, DELETE, OPTIONS, HEAD, or anything with a '_' prefix)

Reproduction

// +server.js
/** @type {import('./$types').RequestHandler} */
export async function fallback(event) {

}

Expected behaviour

No warning should be shown.

System Info

• OS: Linux (Fedora 38)
• IDE: VSCode

Which package is the issue about?

No response

Additional Information, eg. Screenshots

No response