从返回类型推断窄字符串文字类型

Question

const createFruit = <T extends string[]>(fruits: T): typeof fruits[0] => fruits[0]

const fruit = createFruit(['apple', 'orange']) // fruit is of type `string`

我希望将 的类型fruit推断为字符串文字apple。难道就没有办法了吗？

Answer 1

对参数使用可变参数元组语法fruits将提示编译器推断文字类型。

const createFruit = <T extends string[]>(
  fruits: [...T]
): typeof fruits[0] => fruits[0]

const fruit = createFruit(['apple', 'orange'])
//    ^? fruit: "apple"

操场