class Base { ping(): number { return 1; } }

class Repo {
  load(key: number): number { return key; }
  save(row: number): number { return row; }
}

class Service extends Base {
  repo: Repo;
  constructor(repo: Repo) { super(); this.repo = repo; }
  run(key: number): number {
    const row = this.repo.load(key);
    return this.repo.save(row);
  }
}
