car.ts

class Car {
  label: string = 'Generic Car'
  numWheels: Number = 4
  horn() {
    return "beep beep!"
  }
}

class Truck extends Car {
  label = 'Truck'
  numWheels = 18
}

class Vespa extends Car {
  label = 'Vespa'
  numWheels = 2
}

function washCar <T extends Car> (car: T) : T {
  console.log(`Received a ${car.label} in the car wash.`)
  console.log(`Cleaning all ${car.numWheels} tires.`)
  console.log('Beeping horn -', car.horn())
  console.log('Returning your car now')
  return car
}

const myVespa = new Vespa()
washCar<Vespa>(myVespa)

const myTruck = new Truck()
washCar<Truck>(myTruck)