microsoft / microsoft/TypeScript
Allow tuple labels passed to `satisfies` to participate in type inference
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描述
### 🔍 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
贡献指南
从这里开始
- 先读完整个 Issue,再读项目的贡献指南。
- 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
- Fork 仓库,在一个分支上完成修改。
- 提交 Pull Request,并在描述里引用这个 Issue 编号。
调研方向
从链接的 TypeScript Playground 开始,重现涉及 satisfies、as const 和 labeled tuples 的示例。该 issue 未指定源文件或测试;完成意味着通过 satisfies 提供的标签参与推断,同时保留所演示的元组元素类型。
由索引模型根据 Issue 内容生成。
评估
- 技术栈
- typescript
- 领域
- compilers
- Issue 类型
- 功能
- 难度
- 5/5
- 预计耗时
- 一周以上
- 活跃度
- 停滞
- 描述清晰度
- 基本清楚
- 新手友好度
- 38/100