TypeScriptで幽霊型を使う

metadataをもう少し加える

実装

{unique symbol: never}

確実に被らなくなる

{unique symbol: string}

Tagにuniqueな文字列を入れる必要がある

type Branded<T, Tag> = T & {[key in Tag]: never}

code:def1.ts

code:def2.ts

declare const tag: unique symbol;

複数のBranded typesを組み合わせられるようにしてある

code:ts

declare const brand: unique symbol;

code:a@0.1.0.ts

declare const tag: unique symbol;

code:a@0.2.0.ts

declare const tag: unique symbol;

code:main-1.ts

import type { Branded } from "./a@0.1.0.ts";

import type { Branded as Branded2 } from "./a@0.2.0.ts";

const a = 34 as Branded<number, "pointer">;

// @ts-expect-error

const b: Branded2<number, "pointer"> = a;