Infinities as number literal types

🔎 Search Terms

infinity number literal

🕗 Version & Regression Information

• This changed in PR https://github.com/microsoft/TypeScript/pull/55268

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.0-dev.20231031#code/C4TwDgpgBACg9gZwJbCQNwgSQHYDMnYohQC8UAjBAJw0DcAUAPSNSsB6A-PaJFAHIQA5gENUGHPkKhSUALSUaVBs1ZRO9IA

💻 Code

type PositiveInfinity = 1e999;
//   ^?
type NegativeInfinity = -1e999;
//   ^?

🙁 Actual behavior

In TS 5.2 we get NumberLiteralTypes with Infinity and -Infinity values.

In the upcoming TS 5.3 we get a number type in the of the PositiveInfinity

🙂 Expected behavior

I don't know. I created this issue to discuss exactly that.

Should this part of the change be reverted and should Infinity be allowed as a literal number value? Or should -Infinity be aligned with Infinity and should it be converted~ to a number type as well?

Additional information about the issue

I didn't see an Infinity as a literal type so I made this change while working in this area. @rbuckton commented here:

I really hope no one is relying on this.

but it turns out that some try to rely on this. We can see it in this issue, cc @Max10240

Inizia con l’esempio Playground collegato e confronta il comportamento di TypeScript 5.2 con il comportamento imminente di 5.3 introdotto da PR 55268. Esamina la discussione in quella pull request e nell’issue 56270, quindi stabilisci il trattamento previsto dell’infinito positivo e negativo prima di modificare il comportamento del compilatore e la relativa copertura delle regressioni.