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Mutable Keys

提出詳細

type MutableKeys<T, K extends keyof T = keyof T> =
  K extends K
  ? Equal<Readonly<Pick<T, K>>, Pick<T, K>> extends true
  ? never
  : K
  : never
提出日時2024-09-12 15:14:54
問題Mutable Keys
ユーザーookkoouu
ステータスAccepted
テストケース
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<MutableKeys<{ a: number; readonly b: string }>, 'a'>>,
  Expect<Equal<MutableKeys<{ a: undefined; readonly b: undefined }>, 'a'>>,
  Expect<Equal<MutableKeys<{ a: undefined; readonly b?: undefined; c: string; d: null }>, 'a' | 'c' | 'd'>>,
  Expect<Equal<MutableKeys<{}>, never>>,
]