class UnreachableError extends Error {
constructor(_nvr: never, message: string) {
super(message)
}
}
class Car {
drive() {
console.log("vroom")
}
}
class Truck {
tow() {
console.log("dragging something")
}
}
class Boat {
isFloating() {
return true
}
}
type Vehicle = Truck | Car | Boat
let myVehicle: Vehicle = obtainRandomVehicle()
// The exhaustive conditional
if (myVehicle instanceof Truck) {
myVehicle.tow() // Truck
} else if (myVehicle instanceof Car) {
myVehicle.drive() // Car
} else {
// NEITHER!
// Argument of type 'Boat' is not assignable to parameter of type 'never'
throw new UnreachableError(myVehicle, `There is a unreacheable code for ${myVehicle}`)
}
原创文章，作者：bd101bd101，如若转载，请注明出处：https://blog.ytso.com/tech/pnotes/278575.html