字面量推断

Literal Inference

当变量初始化一个字面量对象时，对象的类型会被推断出来

Preview

解决：

type Method = 'GET' | 'POST'
declare function handleRequest(url: string, method: Method): void

const req = { url: 'https://example.com', method: 'GET' }

handleRequest(req.url, req.method as Method)