[swift-evolution] Mark protocol methods with their protocol

Vladimir.S svabox at gmail.com
Wed Sep 21 06:39:14 CDT 2016

On 21.09.2016 2:34, Dave Abrahams via swift-evolution wrote:
> on Tue Sep 20 2016, Karl <razielim-AT-gmail.com> wrote:
>> I think the best way is to prefix the member name with the protocol, e.g:
>> protocol MyProto {
>>     var aVariable : Int
>>     func aFunction()
>> }
>> class MyClass : MyProto {
>>     var MyProto.aVariable : Int
>>     func MyProto.aFunction() { … }
>> }
> ...
>> CC-ing Dave A, to understand better if this fits with the vision of protocols
> I generally agree with Doug.  The canonical way to indicate “this
> method/property/type implements a requirement of protocol P” should be
> to define the entity in an extension that also adds conformance to P.

Could you clarify, how do you see a solution in case extension can't have 
stored properties? So, if protocol has such requirement(i.e. we want to 
implement the protocol requirement as stored property) we can't move it to 
Do you expect we'll have stored props in extension in near future?

Also, what about protocol extensions? What do you suggest to mark default 
implementation method here to express intention and to separate default 
implementation (that depends on protocol definition and so, IMO compiler 
should help us if protocol definition changed) from just helper methods in 
protocol extension? Like here:

protocol A {
     func foov()

protocol B : A {

extension A {
     func foov() {}

extension B {
     // I was expecting this is a default implementation of foov() for B
     // but in reality this is a helper method
     // who knows when this error will be detected
     func foow() {}

> If that's inadequate indication in some way we should find a way to
> enhance it.  I wouldn't mind the notation above, but only as a fallback,
> not a reuquirement.

Could you share your opinion (and probably some common opinion of the core 
team) regarding `implement`(or `override`) keyword requirement for 
methods/props in type declared exactly to implement protocol's requirements?

Don't you feel that if Swift will not *require* this, we'll have fragile 
code base as, even if *I* can use linter for this, 3rd party source code 
that will be in my project probably will not use the "safe" method of 
protocol conformance?

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