268. If

<题目描述>

::: playground#ts 268. If

@file index.ts

// ============= Test Cases =============
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<If<true, 'a', 'b'>, 'a'>>,
  Expect<Equal<If<false, 'a', 2>, 2>>,
]

// @ts-expect-error
type error = If<null, 'a', 'b'>

// ============= Your Code Here =============
type If<C, T, F> = any

:::

点击查看答案

type If<C extends true | false, T, F> = C extends true ? T : F