1042 - IsNever

1042 - IsNever

by hiroya iizuka (@hiroyaiizuka) #中等 #union #utils

题目

Implement a type IsNever, which takes input type T.
If the type of resolves to never, return true, otherwise false.

For example:

type A = IsNever<never> // expected to be true
type B = IsNever<undefined> // expected to be false
type C = IsNever<null> // expected to be false
type D = IsNever<[]> // expected to be false
type E = IsNever<number> // expected to be false

在 Github 上查看：https://tsch.js.org/1042/zh-CN

代码

/* _____________ 你的代码 _____________ */

type IsNever<T> = [T] extends [never] ? true : false

测试用例

/* _____________ 测试用例 _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<IsNever<never>, true>>,
  Expect<Equal<IsNever<never | string>, false>>,
  Expect<Equal<IsNever<''>, false>>,
  Expect<Equal<IsNever<undefined>, false>>,
  Expect<Equal<IsNever<null>, false>>,
  Expect<Equal<IsNever<[]>, false>>,
  Expect<Equal<IsNever<{}>, false>>,
]

相关链接

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