[TypeScript] aggregationFn cannot be set to one of the built-in string identifiers when using legacyCreateColumnHelper

[markpfeifle]

TanStack Table version

9.0.0

Framework/Library version

React 19.1.0

Describe the bug and the steps to reproduce it

I'm trying to do the quick-and-dirty migration to v9 using useLegacyTable & legacyCreateColumnHelper. One of my column definitions has an accessor column with aggregationFn set to "mean". This leads to a Typescript error, because stockFeatures (which is used implicitly when using the legacy helpers) does not have any aggregation functions registered. See codesandbox for a minimal example

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

https://codesandbox.io/p/devbox/4dsjf6

Screenshots or Videos (Optional)

No response

Do you intend to try to help solve this bug with your own PR?

No, because I do not have time to dig into it

Terms & Code of Conduct

• I agree to follow this project's Code of Conduct
• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.