[swift-evolution] Consolidate Code for Each Case in Enum

David Waite david at alkaline-solutions.com
Mon Jan 9 15:38:37 CST 2017

> Enum cases _feel_ like separately defined, but tightly related structs because each case can have distinct associated values. They have special privileges that a family of structs doesn't have, like `self = .otherCase`. Enums are really awesome.


I think this is the primary difference between a “tagged union” and a Swift enum - I might have a union of several discrete types in other languages, but in swift it is actually an enumeration of cases within a single type. The individual cases are not types.

This was actually one of the reasons that drove case labels and static values to stylistically change to lowercase in Swift 3 - to avoid building a misconception of enum cases being distinct types.

I’ve wanted this feature in the past as well, but wonder if at some point encouraging support for a distinct union of types makes more sense than expanding enum - say, a closed protocol only allowing implementation by specific types declared within its module. 


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