CopyWith isn't working

copyWith.dart

import 'package:flutter/foundation.dart';
  
void main() {
  final newWord = Word('123','hello','greet');
  newWord.copyWith(id: '345',word:"edited word");
  print(newWord.id); // `123` instead of `345`
  print(newWord.word); // `hello` instead of `edited word`
}


class Word {
  final String id;
  String word;
  String meaning;
  List<String>? synonyms;
  List<String>? examples;
  List<String>? mnemonics;
  DateTime? created_at;

  Word(this.id, this.word, this.meaning,
      {this.synonyms = const [],
      this.mnemonics = const [],
      this.created_at,
      this.examples = const []});

  /// TODO: Doesn't seem to work for iterables
  Word copyWith(
      {String? id,
      String? word,
      String? meaning,
      List<String>? synonyms = const [],
      List<String>? examples = const [],
      List<String>? mnemonics = const [],
      DateTime? created_at}) {
    return Word(
      id ?? this.id,
      word ?? this.word,
      meaning ?? this.meaning,
      examples: examples!.isEmpty ? this.examples : examples,
      synonyms: synonyms!.isEmpty ? this.synonyms : synonyms,
      mnemonics: mnemonics!.isEmpty ? this.mnemonics : mnemonics,
      created_at: created_at ?? this.created_at,
    );
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Word &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          word == other.word &&
          meaning == other.meaning &&
          listEquals(synonyms, other.synonyms) &&
          listEquals(examples, other.examples) &&
          listEquals(mnemonics, other.mnemonics) &&
          created_at == other.created_at;

  @override
  int get hashCode => id.hashCode ^ word.hashCode;

}