Microsoft/TypeScript

Services for non-homomorphic mapped type

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#25,607 创建于 2018年7月12日

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 (0 评论) (3 反应) (0 负责人)TypeScript (48,455 star) (6,726 fork)batch import
Domain: LS: Symbol NavigationDomain: Mapped TypesExperience EnhancementHelp WantedSuggestion

描述

TypeScript Version: 3.0.0-dev.20180712

Code

interface I {
 a: number;
 b: number;
}
type J = { [K in "b"]: I[K] };
declare const j: J;
j.b; // Go-to-definition does not work

Expected behavior:

Since the type we're getting is I[K], the mapped property symbol should have a reference back to the corresponding property in I.

Actual behavior:

The mapped type creates an unrelated property symbol and services don't work.

贡献者指南

技术栈
typescript
领域
developer experiencetooling
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。
3
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。
1-3 hours
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。
clear
前置要求
TypeScript mapped typesTypeScript compiler internalsSymbol resolution
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。
25
研究方向
Investigate how the TypeScript compiler creates property symbols for mapped types, particularly in the checker.ts file. Focus on the handling of non homomorphic mapped types (e.g., `type J = { [K in "b"]: I[K] }`) where the property symbol should reference the original property in the base type. Review the code that builds mapped type symbols and ensure that the go to definition service correctly resolves to the source property.
Services for non-homomorphic mapped type · Microsoft/TypeScript#25607 | Good First Issue