Create an append-only Map in TypeScript

Dictionary.ts

interface Dictionary<K, V> {
  forEach(callbackfn: (value: V, key: K, map: Dictionary<K, V>) => void, thisArg?: any): void;
  set(key: K, value: V): this;
  has<T extends K>(key: T): this is { get(key: T): V } & Dictionary<K, V>;
  has(key: K): boolean;
  get(key: K): V | undefined;
  readonly size: number;
}

interface DictionaryConstructor {
  new<K, V>(entries?: readonly (readonly [K, V])[] | null): Dictionary<K, V>;
}

const Dictionary: DictionaryConstructor = Map;

Usage:

type Fruit = 'orange' | 'apple';

const inventory = new Dictionary<Fruit, number>();

inventory.set('apple', 10);
inventory.set('orange', 20);

inventory.delete('apple'); // Compile-time error
inventory.clear(); // Compile-time error

if (inventory.has('apple')) {
  const count: number = inventory.get('apple');
  
  inventory.set('apple', count + 1);
}

Map version https://gist.github.com/karol-majewski/b7f46141a84c4a2d8d0dead84a06414e