Microsoft/TypeScript
Distributed keyof over union leads to erroneous indexed access
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#49.000 geöffnet am 06.05.2022
BugDomain: Indexed Access TypesHelp Wanted
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Beschreibung
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.