types.union only supports up to 9 arguments for correct typing result

[limbosounds]

Here is an example:

and when we stripping out 10th model, it is starting to work normally:

The only way I can see to workaround this is to use union of unions, but it sounds like schizophrenia :)

Am I missing something?

[coolsoftwaretyler]

Hey @limbosounds - this sounds like it might be a typescript issue on our end. I'm not sure exactly what's going on there (hopefully someone else does). I'm sorry I don't have a better answer for you, but I'd be happy to move this to the issue tracker if you like!

We are slowly working through a lot of the existing issues, including our overall TypeScript challenges, so hopefully we can figure this out for you in the coming months.

[limbosounds]

Hello and thank you for your response!
This issue has a workaround:

types.union(
    types.union(
        // ...up to 9 types
    ),
    types.union(
        // ...up to 9 types
    ),
    // ...up to 9 unions
)

This workaround supports up to 81 types in total and resulting type is just the same as if it was a plain union.
So, it's kinda suitable for me despite looking schizophrenic 🤣

I tried to discover the source of this issue, and seems like it is in types.union definition
It has 33 overloads, and each next has more generic types than previous
Simplified example

declare function union<T1>(model1: T1)
declare function union<T1, T2>(model1: T1, model2: T2)
declare function union<T1, T2, T3>(model1: T1, model2: T2, model3: T3)
// and so on
// but in original types there are more additional helper generics

My bet is there are just not enough overloads for unions with 10+ models

Hope this can help you in future)

[coolsoftwaretyler]

Thanks @limbosounds! I appreciate the follow up. Very helpful. I'm going to mark that as the answer for now, and hopefully we can improve this for folks in the future.