Dart - How to force map key to be contained in a list strings

If I understood it correctly (I don't know TypeScript)

Dart doesn't have key constraints so will have to extend the Map and implement those constraints. Here is code for that.

import 'dart:collection';class InvalidKeyError<K> extends Error {  final Object key;  final Set<K> keys;  InvalidKeyError(this.key, this.keys);  @override  String toString() => "InvalidKeyError: $key not found in $keys";}class SpecialMap<K, V> extends MapMixin<K, V> {  final Set<K> availableKeys;  final Map<K, V> _map = {};  SpecialMap(this.availableKeys) : assert(availableKeys != null);  @override  Iterable<K> get keys => _map.keys;  @override  void clear() => _map.clear();  @override  V remove(Object key) => _map.remove(key);  @override  V operator [](Object key) => availableKeys.contains(key)      ? _map[key]      : throw InvalidKeyError(key, availableKeys);  @override  operator []=(K key, V value) => availableKeys.contains(key)      ? _map[key] = value      : throw InvalidKeyError(key, availableKeys);}void main() {  final availableKeys = {"cat", "dog"};  final map = SpecialMap<String, bool>(availableKeys);  map["cat"] = true;  map["dog"] = true;  map["anything else"] = false; //will throw InvalidKeyError at runtime}

Although you can simply constrain through type if you want. Something like this.

enum Keys {cat, dog}void main(){  final Map<Keys, bool> map = {};  map[Keys.cat] = true;  map[Keys.dog] = true;  map["any other type"] = false; //complie time error}