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
- This wouldn't be a breaking change in existing TypeScript/JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- 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:
Basically, I often find myself using the satisfies operator to define mutable tuples inline:
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.
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:
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:
💻 Use Cases
- What do you want to use this for?
Adding free semantics
- What shortcomings exist with current approaches?
Requires a layer of indirection + introduces the possibility of drift
- What workarounds are you using in the meantime?
Outlined in the example I shared
貢獻指南
從這裡開始
- 先讀完整個 Issue,再讀專案的貢獻指南。
- 在 Issue 下留言說明你要接手 —— 這能避免兩個人做同樣的事。
- Fork 儲存庫,在一個分支上完成修改。
- 送出 Pull Request,並在描述裡引用這個 Issue 編號。
研究方向
從連結的 TypeScript Playground 開始,重現涉及 satisfies、as const 和 labeled tuples 的範例。該 issue 未指定原始檔案或測試;完成表示透過 satisfies 提供的標籤會參與推論,同時保留所示範的 tuple 元素型別。
由索引模型根據 Issue 內容生成。
評估
- 技術堆疊
- typescript
- 領域
- compilers
- Issue 類型
- 功能
- 難度
- 5/5
- 預估耗時
- 一週以上
- 活躍度
- 停滯
- 描述清晰度
- 基本清楚
- 新手友好度
- 38/100