[swift-evolution] [Proposal] Explicit Synthetic Behaviour

[Gwendal Roué]

> Le 13 sept. 2017 à 06:28, Xiaodi Wu <xiaodi.wu at gmail.com> a écrit :
> 
> 
> On Tue, Sep 12, 2017 at 23:26 Gwendal Roué <gwendal.roue at gmail.com <mailto:gwendal.roue at gmail.com>> wrote:
> 
> > Le 13 sept. 2017 à 04:05, Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>> a écrit :
> >
> > On Tue, Sep 12, 2017 at 2:30 PM, Gwendal Roué <gwendal.roue at gmail.com <mailto:gwendal.roue at gmail.com>> wrote:
> > >> In none of those cases, the compiler emits any warning. It's thus easy to forget or miss the problem, and uneasy to fix it (you'll need a runtime failure to spot it, or a thorough code review).
> > >>
> > >> I hope you agree with this last sentence. This unbalance between the easiness of the mistake and the easiness of the fix should ring a bell to language designers.
> > >
> > > Suppose instead this were about a protocol named Fooable and a requirement called foo() that has a default implementation. Everything you just talked about would apply equally. Am I to understand that you are opposed to default implementations in general? If so, then that’s got nothing to do with synthesized Equatable conformance. If not, then you’ll have to justify why.
> >
> > Sounds like a good argument, until one realises that if a protocol does not provide a default implementations for a method, it may be because a default implementations is impossible to provide (the most usual case), or because it would be unwise to do so.
> >
> > And indeed, the topic currently discussed is not if we should remove or not default implementations. Instead, the question is: is it wise or not to provide an *implicit* default Equatable/Hashable/XXX implementation?
> >
> > Right, _that_ is the question. It was asked during review for the proposal, and the agreed upon answer is _yes_.
> 
> Wrong. This whole thread is about *explicit* synthetic behavior;. If an agreed proposal has to be invalidated in the way, _so be it_.
> 
> Gwendal
> 
> Explicit (e.g., "AutoEquatable") and implicit synthetic behavior were both considered during the proposal which approved the implicit behavior. This question has been asked and answered.

We're in a new thread now, which may drive the core team into reconsidering a previous decision.

It happens. You may remember a funny debate about SE-0110. In the end a question that had been asked and answered got a whole new answer.

We're all here to improve the language. That's why I sometimes participate in this mailing list.

Gwendal

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