[swift-evolution] [Review] SE-0159: Fix Private Access Levels

Sun Mar 26 10:50:23 CDT 2017

• What is your evaluation of the proposal?
-1 as written (see below)

• Is the problem being addressed significant enough to warrant a change to Swift?
Not as written

• Does this proposal fit well with the feel and direction of Swift?
It does in terms of apparent simplicity, but not in terms of practicality. I like to think of Swift as a practical language that does not sacrifice utility for apparent simplicity.

• If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
Can’t be compared. Swift has already set a precedent by making “private” mean something non-traditional (pre SE-0025), and I think it was a good decision, taking us away from the idea that private is only useful with parent inheritance structures. 

• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
Have been following it since SE-0025, the aftermath, extensive experience using the modifiers in framework code I write and reading all related threads on SE.

***

I propose instead that we revise to use Alternative #3, per Vladimir’s comment and revision.

Revised version:

“3. Revert private to be file-based and introduce the scope-based access level under a new name (e.g.: scoped, local, etc), provided that the scope-based access modifier is not used at the top level of the file.” 
(addendum via Vladimir’s revised comment)

David

> On Mar 26, 2017, at 2:30 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> 
> Sent from my iPad
> 
> On Mar 26, 2017, at 4:13 AM, John McCall via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>>> On Mar 26, 2017, at 4:27 AM, Goffredo Marocchi <panajev at gmail.com <mailto:panajev at gmail.com>> wrote:
>>> On 26 Mar 2017, at 06:54, John McCall via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>>>> On Mar 25, 2017, at 2:11 AM, Carl Brown1 via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>> Yes, it would change my opinion of it. I wouldn't become a strong supporter because I don't see any value in it, but a rigorous proof that this proposal could not possibly introduce regressions to any existing codebases would change my opinion from "strongly against" to "doesn't matter to me, I'll stop arguing against it and go get my real work done".
>>>>> 
>>>> Speaking just for myself, this was a key part of why I was attracted to this proposal: it seemed to me to be extremely unlikely to cause regressions in behavior.  Even without any special behavior in the migrator, code will mostly work exactly as before: things that would have been invalid before will become valid, but not the other way around.  The exception is that old-private declarations from scopes in the same file can now be found by lookups in different scopes (but still only within the same file).  It should be quite straightforward for the migrator to detect when this has happened and report it as something for the programmer to look at.  The proposal causes a small regression in functionality, in that there's no longer any way to protect scopes from accesses within the file, but (1) it's okay for Swift to be opinionated about file size and (2) it seems to me that a workable sub-module proposal should solve that more elegantly while simultaneously addressing the concerns of the people who dislike acknowledging the existence of files.
>>> 
>>> The opinionated flag sometimes, like being Swifty, is being used to swath away disagreement, but opinions should be reasonable and pragmatic too... opinionated as "you will code this way and you will like it" seems hardly ideal too if abused constantly. Programming is a creative endeavour too.
>>> 
>>> Also, removing a feature that is used and is useful because "maybe" a year or more away there could be a feature that may address the concerns of the people we are stripping away the current feature from seems quite harsh and unfriendly at best... not very logical either.
>> 
>> Scoped-private is not some awesomely expressive feature.  It's an access restriction.  The "opinion" I'm talking about hardly prevents you from coding however you like.  It's just this: organizing your code into smaller, more self-contained components separated by file is good practice anyway, and when you do that, Swift will let you enforce that each component is properly encapsulated.
> 
> This does not address the case where we have a small helper type that is only 10s of lines long, is not visible outside the file, and encapsulates an important part of the implementation using scoped private.  The whole file is usually only a couple hundred lines.  This is not an excessively long file and already contains a single component that is presented to the rest of the program.
> 
> Some designs of submodules might allow us to properly encapsulate everything but if that requires us to put a small helper type in a separate file that would be a very unfortunate and inflexible constraint on how we are able to organize our code. 
> 
>  I don't want encapsulation concerns dictating how I physically organize my code.  That is significant and unnecessary complexity if you ask me.  It forces a tradeoff between desired physical organization and desired encapsulation.  We should not force users to make this tradeoff.
> 
>> 
>> John.
>> 
>>> 
>>>> 
>>>> John.
>>>>> -Carl
>>>>> 
>>>>> <graycol.gif>Xiaodi Wu ---03/25/2017 12:33:55 AM---Would it change your opinion on the proposal? On Sat, Mar 25, 2017 at 12:10 AM, Carl Brown1 <Carl.Br
>>>>> 
>>>>> From:  Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>>
>>>>> To:  Carl Brown1/US/IBM at IBM
>>>>> Cc:  Drew Crawford <drew at sealedabstract.com <mailto:drew at sealedabstract.com>>, Jonathan Hull <jhull at gbis.com <mailto:jhull at gbis.com>>, swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>
>>>>> Date:  03/25/2017 12:33 AM
>>>>> Subject:  Re: [swift-evolution] [Review] SE-0159: Fix Private Access Levels
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> Would it change your opinion on the proposal?
>>>>> 
>>>>> 
>>>>> On Sat, Mar 25, 2017 at 12:10 AM, Carl Brown1 <Carl.Brown1 at ibm.com <mailto:Carl.Brown1 at ibm.com>> wrote:
>>>>> I would very much like to see your proof that the resultant code is unchanged in an arbitrary codebase. 
>>>>> 
>>>>> -Carl
>>>>> 
>>>>> <graycol.gif>Xiaodi Wu ---03/25/2017 12:01:26 AM---On Fri, Mar 24, 2017 at 11:55 PM, Carl Brown1 <Carl.Brown1 at ibm.com <mailto:Carl.Brown1 at ibm.com>> wrote: > Maybe this is the core
>>>>> 
>>>>> From: Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>>
>>>>> To: Carl Brown1/US/IBM at IBM
>>>>> Cc: Drew Crawford <drew at sealedabstract.com <mailto:drew at sealedabstract.com>>, Jonathan Hull <jhull at gbis.com <mailto:jhull at gbis.com>>, swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>
>>>>> Date: 03/25/2017 12:01 AM
>>>>> Subject: Re: [swift-evolution] [Review] SE-0159: Fix Private Access Levels
>>>>> 
>>>>> 
>>>>> 
>>>>> On Fri, Mar 24, 2017 at 11:55 PM, Carl Brown1 <Carl.Brown1 at ibm.com <mailto:Carl.Brown1 at ibm.com>> wrote: 
>>>>> My point is that, in rolling back the specific portion of SE-0025, case-sensitive find-and-replace will be the trickiest thing in most codebases, save those that result in invalid redeclarations. The behavior of the resultant code is, unless I'm mistaken, provably unchanged.
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> swift-evolution mailing list
>>>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>> 
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>> 
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
David James

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170326/05fb174a/attachment.html>