[swift-evolution] [Discussion] A Problem With SE-0025?

[Matthew Johnson]

> On Jun 15, 2016, at 2:55 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
> 
> On Wed, Jun 15, 2016 at 2:48 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>wrote:
> 
>> On Jun 15, 2016, at 2:46 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I was referencing to the issue Robert discovered in his implementation. 
>> 
>> I do understand what the proposal is all about, but thank you for re-clarifying that to me. :)
>> 
>> 
> 
> I don’t think it’s a bug, but it is definitely something that isn’t as clear as it should have been.
> 
> Was it intentional on the part of the proposal, then, that there should be two modifiers meaning the same thing for a top level declaration in a file? Or was it intended that only one or the other be used in that scenario?

I don’t think it was carefully considered, although I think it did come up at some point during discussion in the context of compatibility with existing code (i.e. nothing changes for current top-level `private` declarations).  

It is in some sense a “coincidence” that they mean the same thing at file scope.  The proposal would have had to introduce a specific prohibition to prevent this situation and it did not do so.  That said, I think this kind of issue falls well within the discretion of the core team to make a call without violating the spirit of the proposal.

There are two reasonable options here: 

1. Allow both `private` and `fileprivate` at file scope despite the fact that they have the same meaning.  This is more consistent in the sense that we are not introducing a special case that arbitrarily prohibits an otherwise valid access modifier.  It also means that nothing needs to change for top level `private` declarations in existing code.

2. Prohibit `private` at file scope.  Given that it appears as if the behavior of `private` at file scope may not be intuitive and is equivalent to `fileprivate` it might be reasonable to just disallow it.  This would result in more consistent *code* (even if there needs to be a special case in the language).

I don’t have a strong opinion on which option we choose.  But I do feel strongly that the semantics of `private` need to properly respect the scope in which the keyword is written and into which the associated declaration is introduced (rather than the scope *inside* the declaration it is attached to).

-Matthew
>> 
>> 
>> 
>> -- 
>> Adrian Zubarev
>> Sent with Airmail
>> 
>> Am 15. Juni 2016 um 21:40:37, Matthew Johnson (matthew at anandabits.com <mailto:matthew at anandabits.com>) schrieb:
>> 
>>> What seems like a nasty bug missed during review?  I don’t follow you there.
>>> 
>>> This proposal was specifically designed to follow Swift’s design of a scope-based access control mechanism rather than a type-based access control mechanism that is common in other languages.
>> 
>> 
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