ts-i18n-example.ts

// forked from https://github.com/ahejlsberg/tsconf2020-demos/blob/master/template/main.ts
type SubKeys<T, K extends string> = K extends keyof T ? `${K}.${PathKeys<T[K]>}` : never

type PathKeys<T> = object extends T
  ? string
  : T extends readonly any[]
  ? Extract<keyof T, `${number}`> | SubKeys<T, Extract<keyof T, `${number}`>>
  : T extends object
  ? Extract<keyof T, string> | SubKeys<T, Extract<keyof T, string>>
  : never

type PropType<T, Path extends string> = Path extends keyof T
  ? T[Path]
  : Path extends `${infer K}.${infer R}`
  ? K extends keyof T
    ? PropType<T[K], R>
    : unknown
  : unknown

// i18n example
declare function useI18n<T>(i18n: T): <P extends PathKeys<T>>(path: P) => PropType<T, P>

interface HomeI18n {
  setting: string
  menu: {
    close: string
    expand: string
  }
}

const t = useI18n({} as HomeI18n)

t("menu.close")