microsoft / microsoft/TypeScript

Allow tuple labels passed to `satisfies` to participate in type inference

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Experience Enhancement Help Wanted Suggestion
Langage dominant
Go
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Forks
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Merge moyen
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PR mergées (30 j)
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Description

### 🔍 Search Terms

tuple, tuples, label, labels, tuple labels, satisfies, as const

### ✅ Viability Checklist

- [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
- [x] This wouldn't change the runtime behavior of existing JavaScript code
- [x] This could be implemented without emitting different JS based on the types of the expressions
- [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- [x] This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- [x] This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

### ⭐ Suggestion

Hey TypeScript team! First of all, _super_ excited to hear about `tsgo`.

I've got a feature request for y'all -- the body of this issue was ported from a playground that I created:

https://tsplay.dev/NljeQW

Basically, I often find myself using the `satisfies` operator to define mutable tuples inline:

```typescript
const base = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] as const satisfies any[]
// ^? const base: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
```

Sometimes when working with tuples of a known length, I use labels, because why not? Free semantics!

But to get the behavior I'm after, I have to add a layer of indirection.

```typescript
const ex = [0, 0] as const
type Example = never | [x: typeof ex[0], y: typeof ex[1]]
const example: Example = [...ex]
// ^? const example: [x: 0, y: 0]
```

This makes the code more confusing to read, which makes the tradeoff basically a wash.

### __Feature Request__

Allow any labels passed to `satisfies` to participate in type inference, like so:

```typescript
const point = [0, 0] as const satisfies [x: any, y: any]
//
// Desired type:
// ^? const point: [x: 0, y: 0]
// ^ ^

```

Let me know if you'd like a more complex example, or if there's anything else I can provide.

### 📃 Motivating Example

Playground:

https://tsplay.dev/NljeQW

### 💻 Use Cases

1. What do you want to use this for?

Adding free semantics

3. What shortcomings exist with current approaches?

Requires a layer of indirection + introduces the possibility of drift

5. What workarounds are you using in the meantime?

Outlined in the example I shared

Guide de contribution

Ouvrir le guide de contribution

Piste de recherche

Commencez par le TypeScript Playground lié et reproduisez les exemples concernant satisfies, as const et labeled tuples. L’issue ne nomme aucun fichier source ni aucun test ; la tâche est terminée lorsque les labels fournis via satisfies participent à l’inférence tout en préservant les types d’éléments de tuple démontrés.

Rédigé par le modèle d'indexation à partir du texte de l'issue.

Évaluation

Stack technique
typescript
Domaine
compilers
Type d'issue
Fonctionnalité
Difficulté
5/5
Temps estimé
Plus d'une semaine
Activité
À l'abandon
Clarté
Plutôt claire
Accessibilité débutants
38/100

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