This resolves another small but potentially annoying inconsistency in Swift where downcasting a collection – e.g. casting an array of ClassA to an array of another type that inherits from ClassA – would not be allowed in some circumstances.
For example, this code is now valid in Swift 5.8, whereas it would not have worked previously:
class Pet { }
class Dog: Pet {
func bark() { print("Woof!") }
}
func bark(using pets: [Pet]) {
switch pets {
case let pets as [Dog]:
for pet in pets {
pet.bark()
}
default:
print("No barking today.")
}
}Before Swift 5.8 that would have led to the error message, “Collection downcast in cast pattern is not implemented; use an explicit downcast to '[Dog]' instead.” In practice, syntax such as if let dogs = pets as? [Dog] { worked just fine, so I would imagine that error was rarely seen. However, this change does mean another language inconsistency is resolved, which is always welcome.
SPONSORED Take the pain out of configuring and testing your paywalls. RevenueCat's Paywalls allow you to remotely configure your entire paywall view without any code changes or app updates.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Other changes in Swift 5.8…
- Lift all limitations on variables in result builders
- Function back deployment
- Allow implicit self for weak self captures, after self is unwrapped
- Concise magic file names
- Opening existential arguments to optional parameters
Download all Swift 5.8 changes as a playground Link to Swift 5.8 changes
