Swift downcast initializer code#

This change fulfills a long-standing prophecy in Hashable's documentation: In particular, random seeding enables better protection against (accidental or deliberate) hash-flooding attacks. “Random seeding” varies the result of hashValue on each execution of a Swift program, improving the reliability of the standard library's hashed collections such as Set and Dictionary. The standard library now uses a high-quality, randomly seeded, universal hash function, represented by the new public Hasher struct. Please see this blog post for more information.

Swift downcast initializer code#

In some cases this change will cause code that previously compiled to need to be adjusted. If an expression involving one of these values will not compile successfully with the type Optional, it is implicitly unwrapped, producing a value of type T. Declarations annotated with ! have the type Optional. ImplicitlyUnwrappedOptional is now an unavailable typealias of Optional. An #if compiler block can be used to conditionalize code between 4.2 and 5.0, for example: #if compiler( Int ) įinally, due to Decodable having an init requirement, it is not possible to conform to Decodable in an extension of a non-final class: such a class needs to have any inits from protocols be required, which means they need to be in the class definition. Note that the old _ExpressibleByStringInterpolation protocol has been removed any code making use of this protocol will need to be updated for the new design. String interpolation has been overhauled to improve its performance, clarity, and efficiency. Supported values for the -swift-version flag are 4, 4.2, and 5.