`never` as keyof tuples/arrays behaves the same as `number`

🔎 Search Terms

tuple keyof never, tuple[never], array keyof never

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about this issue

Versions I tried:

• 5.2.2
• nightly (playground)

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.0-dev.20230923#code/C4TwDgpgBAglC8UDeBfA2gOwgNwgJwF0oB6YqQUHIotc8AoUSKAIQWSgEMAuKAZ2DwCWGAOZR01fEVIUqOfPXDQAwqzQFMcwiTKUJdBtAAiqvoJHq9UsoBlyXvyHCFjAKKtTDtRppWot9yKdoADFWAAp-UQAfKgBXAFsAI3wASk9LKG1fOzMo2MT8IA

💻 Code

type A = {}[never] // ✅ never
type B = { a: string }[never] // ✅ never
type C = [][never] // ✅ never
type D = [string][never] // ❌ string
type E = string[][never] // ❌ string
type F = (string | number)[][never]  // ❌ string | number

🙁 Actual behavior

After using a never key on tuples/arrays you get back the entirety of the tuple/array elements type.

🙂 Expected behavior

After using a never key on tuples/arrays you get back never, as when dealing with objects.

Additional information about the issue

Not sure if this has historical reasons to behave like it does, but couldn't find any specific info about it.

Inizia riproducendo il comportamento nel TypeScript Playground collegato, confrontando gli esempi di oggetto, tupla e array che usano never. Traccia la gestione degli accessi indicizzati da parte del compilatore per le chiavi di tuple e array; il lavoro è completato quando questi esempi vengono valutati come never in modo coerente con l'indicizzazione degli oggetti, con un'adeguata copertura di regressione.