Microsoft/TypeScript

Distributed keyof over union leads to erroneous indexed access

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#49,000 创建于 2022年5月6日

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 (11 评论) (1 反应) (0 负责人)TypeScript (6,726 fork)batch import
BugDomain: Indexed Access TypesHelp Wanted

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描述

Bug Report

🕗 Version & Regression Information

This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 Code

type KeyOf<T> = T extends unknown ? keyof T : never

type Wrong<T> = { [K in KeyOf<T>]: T[K] }

🙁 Actual behavior

It is accepted by the type checker, but it shouldn't be allowed because T could be a union of objects with unrelated properties. The computed type doesn't even have any sense:

type test= Wrong<{ prop0: string } | { prop1: number; prop2: boolean } | { prop3: string[] }>
//   { prop0: unknown; prop1: unknown; prop2: unknown; prop3: unknown; }

🙂 Expected behavior

K shouldn't be allowed to index type T.

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