microsoft / microsoft/TypeScript

Incorrect type resolution with nested constructors

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还没有人认领这个 Issue。

Bug Domain: classes
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描述

### 🔎 Search Terms

nested constructors type resolution anti-pattern

### 🕗 Version & Regression Information

- This changed between versions ______ and _______
- This changed in commit or PR _______
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
- I was unable to test this on prior versions because I only report bugs to be helpful, but I don't have time to dive deeper myself.

### ⏯ Playground Link

https://www.typescriptlang.org/play/?#code/KYDwDg9gTgLgBAE2AYwDYEMrDsiA7AZ3gCF0DgAuOAbwCgBIPYAdwAoBKKu++gawEs8CKgHIAgiIaMWHLnAFDRxEXAC+DdetyF4YuAF44TZjgwECcUDGBCLpcjTW1tROMQNGWpshas2EFnrUTsQAdAoIQA

### 💻 Code

```ts
export declare const Base: {
new(): {
kind: 'A'
new(): { kind: 'B' }
}
}
const A = new class extends Base { }
const B = new class extends A { }
B.kind // shows 'A', but should be 'B'
```

### 🙁 Actual behavior

If a ctor returns another ctor, it repeats the first level. In the above example, B.kind is 'A', but since we extended and instantiated twice, it should be 'B'.

### 🙂 Expected behavior

After extending twice, it should reach the inner class, instead of repeating the outer one.

### Additional information about the issue

I can only reproduce this bug with this weird experimental anti-pattern - so on its own probably not a priority at all, but types should probably reflect the runtime state as much as possible, even in weird edge cases such as this, and it might indicate a deeper underlying issue.

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  3. Fork 仓库,在一个分支上完成修改。
  4. 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 复现开始,跟踪两个嵌套的 `new class extends ...` 表达式的类型解析过程。在两次扩展和实例化之后,当示例将 `B.kind` 报告为 `'B'` 而不是 `'A'` 时,工作就完成了。

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评估

技术栈
typescript
领域
compilers
Issue 类型
缺陷
难度
4/5
预计耗时
3-5 天
活跃度
冷清
描述清晰度
基本清楚
新手友好度
48/100

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