Bug: compiler error on arrow function implicit return in server functions - Invariant failed: createServerFn must be called with a function that is marked with the 'use server' pragma.

[SeyyedKhandon]

Which project does this relate to?

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Describe the bug

This issue is a follow up for #2434 discussion:

This server function:

const getHashId = createServerFn("GET", () => storage.hashId);

results in :

Invariant failed: createServerFn must be called with a function that is marked with the 'use server' pragma. Are you using the @tanstack/router-plugin/vite ?

while it works for:

const getHashId = createServerFn("GET", () => {
  return storage.hashId;
});

Your Example Website or App

#2434

Steps to Reproduce the Bug or Issue

1. just use an arrow function with implicit return

Expected behavior

As a user I expect it to support javascript syntax correctly, which means it should support any variant of functions that we pass to be considered a fully javascript compatible.

Screenshots or Videos

Platform

• OS: Macos 15 sequia
• Browser: Chrome 129.0.6668.60

Additional context

No response