[swift-evolution] Should we rename "class" when referring to protocol conformance?

Dave Abrahams dabrahams at apple.com
Thu May 5 18:55:25 CDT 2016

on Thu May 05 2016, David Sweeris <davesweeris-AT-mac.com> wrote:

>> On May 5, 2016, at 5:01 PM, Dave Abrahams <dabrahams at apple.com> wrote:
>> on Wed May 04 2016, David Sweeris <davesweeris-AT-mac.com> wrote:
>>>> On May 4, 2016, at 13:29, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
>>>> 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. 
>>> You mean that a struct's properties would have to have value
>>> semantics, too? 
>> Either that, or you'd have to implement CoW, or you'd not use the
>> storage behind any properties that were references in a way that affects
>> value semantics.
>>> I think I'm okay with that, especially if it's done through new types
>>> of structs/enums.
>> New types of structs/enums?  What does that mean?
> I meant leave `struct` and `enum` the way they are, and introduce a
> `different_struct` and `different_enum` (placeholder names, of course)
> which enforced the “no reference-semantics” rules.

I would be pretty strongly opposed to that.  That's almost the opposite
of what I'm proposing.

> I’m inclined to think we should adopt your “no reference-semantics”
> rule, but I’m not entirely sure what the impact would be. Adding new
> types side-steps the issue, at the cost of increasing the complexity
> of the language/compiler. I’m unsure if that'd be a worth-while
> trade-off.

The whole point of my proposal is to simplify the model.


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