on Wed May 04 2016, Adrian Zubarev <swift-evolution@swift.org> wrote:
> Not sure what to think about the enum cases inside a protocol (if AnyEnum > would > even exist), it could be a nice addition to the language, but this is an own > proposal I guess. > > We should start by adding AnyValue protocol to which all value types > conforms. Having a way to constrain conformance to things with value semantics is something I've long wanted. *However*, the approach described is too simplistic. It's possible to build classes whose instances have value semantics (just make them immutable) and it's possible to build structs whose instances have reference semantics (just put the struct's storage in a mutable class instance that it holds as a property, and don't do copy-on-write). In order for something like AnyValue to have meaning, we need to impose greater order. After thinking through many approaches over the years, I have arrived at the (admittedly rather drastic) opinion that the language should effectively outlaw the creation of structs and enums that don't have value semantics. (I have no problem with the idea that immutable classes that want to act as values should be wrapped in a struct). The language could then do lots of things much more intelligently, such as correctly generating implementations of equality. -- Dave _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution