Never return type is a special one in Swift, and tells the compiler that execution will never return when this function is called. It’s used by Swift’s
preconditionFailure() functions, both of which cause your app to crash if they are called.
Never return type is useful because it lets Swift waive other requirements. For example, if you’re in a function that must return a value, calling a
Never function means you don’t need to return anything – Swift knows you can’t return a value any more.
Available from iOS 8.0 – learn more in my book Pro Swift
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