[swift-evolution] [Proposal] Revising access modifiers on extensions

[Jordan Rose]

I still have no idea why you want to make this change, other than "putting an access modifier on an extension is different from putting an access modifier on a type". Are you trying to hide protocol conformances that would be otherwise public? That has much greater consequences and a much stronger domino effect than what you've discussed here.

Jordan


> On Jun 27, 2016, at 5:44, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Correcting myself over and over. Here is the correct url: https://github.com/DevAndArtist/swift-evolution/blob/extensions_access_modifiers/proposals/nnnn-extensions-access-modifiers.md <https://github.com/DevAndArtist/swift-evolution/blob/extensions_access_modifiers/proposals/nnnn-extensions-access-modifiers.md>
> 
> 
> 
> -- 
> Adrian Zubarev
> Sent with Airmail
> 
> Am 27. Juni 2016 um 14:39:41, Adrian Zubarev (adrian.zubarev at devandartist.com <mailto:adrian.zubarev at devandartist.com>) schrieb:
> 
>> I completely rewritten the proposal, you can read the formatted version here:
>> 
>> https://github.com/DevAndArtist/swift-evolution/blob/19f2583209a5763880e6f6fa6738ea0c6011f2d6/proposals/nnnn-extensions-access-modifiers.md <https://github.com/DevAndArtist/swift-evolution/blob/19f2583209a5763880e6f6fa6738ea0c6011f2d6/proposals/nnnn-extensions-access-modifiers.md>
>> 
>> 
>> -- 
>> Adrian Zubarev
>> Sent with Airmail
>> 
>> Am 27. Juni 2016 um 12:58:53, Adrian Zubarev (adrian.zubarev at devandartist.com <mailto:adrian.zubarev at devandartist.com>) schrieb:
>> 
>>> And yet another correction of the default protocol implementations part of my reply.
>>> 
>>> The imported module is correct, but the default implementation is not imported (I relied on Xcode which didn’t raise an error before I started building the project where I was using the module, and I didn’t build it at the first time).
>>> 
>>> So we’d need to implement foo by ourself.
>>> 
>>> struct B : A {
>>>        
>>>     public func foo() {}
>>> }    
>>> The rest of my reply should be fine. With the same access control it would be more clearer and intuitive how the extension will be imported.
>>> 
>>> 
>>> -- 
>>> Adrian Zubarev
>>> Sent with Airmail
>>> 
>>> Am 27. Juni 2016 um 10:38:12, Adrian Zubarev (adrian.zubarev at devandartist.com <mailto:adrian.zubarev at devandartist.com>) schrieb:
>>> 
>>>> Lets examine the impact on default protocol implementations:
>>>> 
>>>> Currently we have this behavior:
>>>> 
>>>> public protocol A {
>>>>     func foo()
>>>> }
>>>> 
>>>> extension A {
>>>>     func foo() { /* implement */ }     
>>>> }
>>>> The imported version would look like this.
>>>> 
>>>> public protocol A {
>>>>     public func foo()
>>>> }
>>>> As the module user you have no clue that there might be a default implementation, but you sill will be able to use it, because when conforming to A you don’t have to implement foo. This implicitly signals you that there is indeed a default implemenation
>>>> 
>>>> struct B : A {} // This will be enough
>>>> 
>>>> A().foo() // this is fine
>>>> One could signal the module user that there is a default implementation by making the extension explicit public as well.
>>>> 
>>>> // explicitly marked as public to grant visibility to     
>>>> // the default implementation extension bag
>>>> public extension A {
>>>>         
>>>>     /// will do something cool
>>>>     func foo() { /* implement */ }     
>>>> }
>>>> The result of the imported module would change and look like this:
>>>> 
>>>> public protocol A {
>>>>     public func foo()
>>>> }
>>>> 
>>>> extension A {
>>>>         
>>>>     /// will do something cool
>>>>     public func foo()
>>>> }
>>>> With the proposed change all default implementations will become visible by default and I think this is great step as well.
>>>> 
>>>> 
>>> 
>> 
> 
> 
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