ReadonlyMapClass.ts

interface ReadonlyMapConstructor {
  new <K, V>(entries?: IterableIterator<[K, V]> | null): ReadonlyMap<K, V>;
}

class ReadonlyMapClass<K, V> extends Map<K, V> {}

export const ReadonlyMap: ReadonlyMapConstructor = ReadonlyMapClass;

//

const readonlyMap = new ReadonlyMap<string, number>();
readonlyMap.get("foo");
readonlyMap.set("foo", 1); // type error