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

[Xiaodi Wu]

On Wed, Jun 15, 2016 at 4:14 PM, Matthew Johnson <matthew at anandabits.com>
wrote:

>
> On Jun 15, 2016, at 4:08 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>
> On Wed, Jun 15, 2016 at 3:09 PM, Matthew Johnson <matthew at anandabits.com>
> wrote:
>
>>
>> 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>wrote:
>>
>>>
>>> On Jun 15, 2016, at 2:46 PM, Adrian Zubarev via swift-evolution <
>>> 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).
>>
>
> Right, I think both would be OK. More radically, we might want to
> re-evaluate the continued utility of a `fileprivate` scope. It seems the
> use cases for such a scope not adequately served by either `internal` or
> the new `private` would be exceedingly rare.
>
>
> I disagree with that.  `fileprivate` is indispensable when you need it.
> There are times when you want to keep visibility limited to the current
> file but the new `private` is too restrictive (for example, you need to
> access a member of one type in a closely related extension of a different
> type that lives in the same file).
>

Sure. This was more of a thought for the future. As we move towards fully
embracing a scope-based model for organizing code, modules will no longer
need to be strictly "single units of code distribution," and a move towards
supporting submodules could serve your use case without `fileprivate`.
That, IMO, would be a logical endpoint of moving from file-based access to
scope-based access.


>
>
>> -Matthew
>>
>>
>>>
>>>
>>> --
>>> Adrian Zubarev
>>> Sent with Airmail
>>>
>>> Am 15. Juni 2016 um 21:40:37, Matthew Johnson (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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>>>
>>>
>>>
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>>
>>
>
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