using Keyword for Automatic Resource Disposal

Resources like database connections, file handles, and timers require manual cleanup. Try/finally blocks are verbose and easy to forget, leading to resource leaks.

Implement the Disposable interface and use the 'using' keyword for automatic cleanup at block exit.

// Implement Symbol.dispose
class DatabaseConnection implements Disposable {
  constructor(private conn: Connection) {}

  query(sql: string) { return this.conn.query(sql); }

  [Symbol.dispose]() {
    this.conn.close();
    console.log('Connection closed');
  }
}

// 'using' ensures disposal at end of block (even on throw)
function processData() {
  using db = new DatabaseConnection(createConnection());
  const rows = db.query('SELECT * FROM users');
  return rows; // db[Symbol.dispose]() called here automatically
}

// Async version
class AsyncResource implements AsyncDisposable {
  async [Symbol.asyncDispose]() {
    await this.cleanup();
  }
}

async function run() {
  await using res = new AsyncResource();
  // res disposed async at end of block
}

The 'using' declaration is based on the TC39 Explicit Resource Management proposal. TypeScript 5.2 implements it using Symbol.dispose/Symbol.asyncDispose, modeled after C# 'using' and Python 'with'.