Microsoft/TypeScript

`typeChecker.getTypeArguments` returns unexpected extra type argument

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#38,391 创建于 2020年5月7日

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 (1 评论) (0 反应) (0 负责人)TypeScript (48,455 star) (6,726 fork)batch import
BugDomain: APIHelp Wanted

描述

TypeScript Version: 3.8.3

Search Terms: getTypeArguments

Code

Given input like

class X extends Y<string> {}

Call typeChecker.getTypeArguments(typeChecker.getTypeAtLocation(...)) on the Y<string> node.

Expected behavior: You get back one type argument (string).

Actual behavior: You get back two, string and X.

I imagine this is maybe something around how TS handles this typing internally, but as a user of the API I'm not sure I can predict when this function returns these or not.

Playground Link:

Related Issues: https://github.com/microsoft/TypeScript/issues/33693 suggests this API changed recently

贡献者指南

技术栈
typescript
领域
apitooling
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
4
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
3-5 days
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
TypeScript type systemType checker API basics
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
15
研究方向
Investigate the `getTypeArguments` implementation in TypeScript's checker.ts. The bug is likely in how type arguments are computed for class heritage expressions, possibly related to 'this' type handling. Refer to the related issue #33693 which may indicate a recent change. Check if similar behavior occurs for other constructs.