Swift provides non-public initializers that default optionals to nil. A design tenet of MemberwiseInit has been to strive to be a pure superset of Swift's memberwise initializer, and this approach has largely served it well.
However, I'm convinced that MemberwiseInit should deviate from Swift 5 and always default _optionalsDefaultNil to false, regardless of access level.
different for Int? and Optional<Int> (defaulted nil and not defaulted, respectively),
hasn't been changeable due to Swift's source compatibility principles, but could be “corrected” in Swift 6. [Update: Swift 6 didn't change this behavior.]
MemberwiseInit can offer a more straightforward approach: Optionals should not default to nil unless explicitly specified by the developer.
Description
Swift provides non-public initializers that default optionals to
nil. A design tenet of MemberwiseInit has been to strive to be a pure superset of Swift's memberwise initializer, and this approach has largely served it well.However, I'm convinced that MemberwiseInit should deviate from Swift 5 and always default
_optionalsDefaultNilto false, regardless of access level.Swift's behavior is:
Int?andOptional<Int>(defaultedniland not defaulted, respectively),MemberwiseInit can offer a more straightforward approach: Optionals should not default to
nilunless explicitly specified by the developer.This has been debated at length on the forums: