[swift-evolution] [Draft] open and public protocols

[Zach Waldowski]

On Sun, Feb 19, 2017, at 10:57 PM, Xiaodi Wu via swift-evolution wrote:
> Left unsaid from my reply about enums is that implicit conversions
> should absolutely be added. We already have this magic for one
> particular enum, Optional.


I can only see a generalization of this being used for evil.
Perhaps that's best left to be discussed on some other knock-down,
drag-out thread.


> I'm not arguing with you that enums are currently unsuitable. In fact
> I entirely agree. But Chris Lattner and others have said (now I'm
> paraphrasing, but I believe accurately) that they *should* be. What
> will it take? At minimum, some way to opt into implicit conversions.
> It's a no-brainer in my mind.
> 

> Bottom line: the language needs one excellent way to model Foo | Bar |
> Baz, not two or three mediocre workarounds. The core team has said
> that they want that excellence to be built through enums. Let's do it.


I don't understand how extending protocols to parallel the changes we
already made to classes — and in line with what's planned for enums — is
a mediocre workaround.


I have low confidence in Evolution being able to produce a passable
union type design in a meaningful amount of time, particularly for Swift
4 Phase 2; I also question their need in the first place.


Sincerely,

  Zachary Waldowski

  zach at waldowski.me


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