字面量和类型拓宽

const specifiedStr: 'this is string' = 'this is string';
const specifiedNum: 1 = 1;
const specifiedBoolean: true = true;

type prefix = `#${string}`
const a: prefix = 'aaa' // error
const b: prefix = '#aaa' // ok

type Direction = 'up' | 'down'

let s1 = 'a' // 类型：string
const s2 = 'a' // 类型：'a'

// name 类型为 string
interface Props {
  	name: 'musi'
}
// name 类型为 'musi'
interface Props {
  	name: 'musi' as const
}

// 断言多个
interface Props {
  	name: 'musi',
  	id: 1
} as const

// 元祖断言
['musi' as const]