Assign to union with over 25 items gives error

[cevek]

Bug Report

🔎 Search Terms

union 25

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 Code

type A = { kind: 'AA' | 'AB' | 'AC' | 'AD' | 'AE' | 'AF' | 'AG' | 'AH' | 'AK' };
type B = { kind: 'BA' | 'BB' | 'BC' | 'BD' | 'BE' | 'BF' | 'BG' | 'BH' | 'BK' };
type C = { kind: 'CA' | 'CB' | 'CC' | 'CD' | 'CE' | 'CF' | 'CG' | 'CH' | 'CK' }; // if remove 2 last items then ok
type ABC = A | B | C;

declare const kind: ABC['kind'];
const x: ABC = { kind }; // error

🙁 Actual behavior

Types of property 'kind' are incompatible.

🙂 Expected behavior

no error

[MartinJohns]

Duplicate of #40803. Used search terms: union 25. I also found this issue using your search terms: big union.

This is a hard coded intentional limit.

[MrNovado]

@MartinJohns Thanks! Is there any known and accepted workaround for this? And are there any plans to up the limit in the near future?

[MartinJohns]

I don't know of any workaround, and I'm not aware of any plans to increase this limit. But that would be up to the TypeScript team, of course.

A good idea is to subscribe to the existing issue, so you get notified if something is changing.

[RyanCavanaugh]

We don't plan to change this. There are a decent number of cases where we try this structural expansion but it doesn't work, so limiting the cost of that happening is important.

[cevek]

It will be good if there will be right error about this limit, not incompatible error

[RyanCavanaugh]

It will be good if there will be right error about this limit, not incompatible error

It's not clear how to do this. "It's possible that a finite expansion of all possible inhabitants of each type may result in a subset" is going to be true a decent amount of time yet would be very confusing.

[jogibear9988]

Wouldn't it be desiarable to add a tsconfig parameter for the limit?

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.