microsoft / microsoft/TypeScript

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

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Experience Enhancement Help Wanted Suggestion
Linguagem predominante
Go
Estrelas
111k
Forks
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Merge médio
2d 4h
PRs com merge (30d)
132

Descrição

### 🔍 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

Guia de contribuição

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  1. Leia a issue inteira e depois o guia de contribuição do projeto.
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  4. Abra um pull request que referencie o número da issue.

Direção de pesquisa

Comece pelo TypeScript Playground vinculado e reproduza os exemplos envolvendo satisfies, as const e labeled tuples. A issue não nomeia arquivos-fonte nem testes; a conclusão significa que os labels fornecidos por meio de satisfies participem da inferência, preservando os tipos demonstrados dos elementos da tupla.

Escrita pelo modelo de indexação a partir do texto da issue.

Avaliação

Stack de tecnologia
typescript
Domínio
compilers
Tipo de issue
Funcionalidade
Dificuldade
5/5
Tempo estimado
Mais de uma semana
Status de atividade
Estagnada
Clareza
Razoavelmente clara
Facilidade para iniciantes
38/100

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