On Sun, Feb 12, 2017 at 3:47 PM, Matthew Johnson <matt...@anandabits.com> wrote:
> > On Feb 12, 2017, at 3:45 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > On Sun, Feb 12, 2017 at 3:24 PM, Matthew Johnson <matt...@anandabits.com> > wrote: > >> >> On Feb 12, 2017, at 2:35 PM, Xiaodi Wu via swift-evolution < >> swift-evolution@swift.org> wrote: >> >> _Potentially_ meaningful, certainly. But what I'm hearing is that it >> isn't actually meaningful. Here's why: >> >> If I see `fileprivate` and can understand that to mean "gee, the author >> _designed_ this member to be visible elsewhere inside the file," then it's >> actually meaningful. OTOH, if I see `fileprivate` and can only deduce "gee, >> the author mashed some button in his or her IDE," then it's not really >> telling me anything. >> >> >> You’re looking at it backward. It’s when you see `private` and can >> deduce “this member is only visible inside it’s declaring scope” that can >> be really helpful. *This* is what matters. >> > > In what ways can that information help you? > > What you've said above, as I understand it, is that it's not currently >> meaningful to see `fileprivate` because the migrator is writing it and not >> the author. The improved approach you proposed is the additional warning. >> In that case, the compiler will help to ensure that when I see >> `fileprivate`, at least I know it's necessary. But that's only telling me a >> fact (this member is accessed at least once outside the private scope), but >> it's still machine-based bookkeeping, not authorial intent. >> >> >> The important thing is that this machine-based bookkeeping results in a >> proof about the code. This facilitates reasoning about the code. You can >> make an argument that this proof is not important enough to matter, but you >> must admit that this is a real concrete gain in information that is >> immediately available to a reader of the code (after they know that it >> compiles). Personally, I find this proof to be valuable. >> > > Comparison has been made to `let` and `var`. In that case, whether a > variable is mutated can be non-trivial to deduce (as Swift has no uniform > scheme for distinguishing mutating from non-mutating functions; the ed/ing > rule has many exceptions). By contrast, here, I don't see any gain in > information. You can literally *see* where the (file)private member is > accessed, and when a file gets too long, even a simple text editor can do a > decent enough find. > > If you're right that the real value is that seeing `private` helps you > reason about the code, then that value must be commensurate to how often we > see Swift users amending the migrator to take advantage of it. For me, the > compelling evidence that Swift users don't find this proof to be valuable > is that, by examination of Swift 3 code, Swift users haven't bothered. If > we add a new fix-it to force them to, then of course they'll mash the > buttons, but it's pretty much declaring that they are wrong not to care > about what it seems they do not care at present. > > > This is really subjective and it’s not clear to me that there is > substantial evidence one way or another. I know that `private` is valued > and used heavily by the teams I have worked with. > It wasn't a rhetorical question that I asked: what value do you perceive in the new `private` in terms of helping you reason through code? Maybe that’s an exception, but maybe not. I don’t think we know yet and I > think this is what Chris is hoping to learn. > > > On Sun, Feb 12, 2017 at 2:14 PM, Chris Lattner <sa...@nondot.org> wrote: >> >>> I don't fully agree: you are right that that is the case when writing >>> code. However, when reading/maintaining code, the distinction is >>> meaningful and potentially important. >>> >>> -Chris >>> >>> On Feb 12, 2017, at 12:02 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: >>> >>> If the overwhelming use case is that developers should pick one over the >>> other primarily because it looks nicer, then blindly click the fix-it when >>> things stop working, then the distinction between private and fileprivate >>> is pretty clearly a mere nuisance that doesn't carry its own weight. >>> On Sun, Feb 12, 2017 at 13:33 Jean-Daniel via swift-evolution < >>> swift-evolution@swift.org> wrote: >>> >>>> Le 12 févr. 2017 à 18:24, Chris Lattner via swift-evolution < >>>> swift-evolution@swift.org> a écrit : >>>> >>>> On Feb 12, 2017, at 8:19 AM, David Hart via swift-evolution < >>>> swift-evolution@swift.org> wrote: >>>> >>>> *Final* >>>> Can someone tell me what is the use of 'final' now that we have >>>> 'public' default to disallowing subclassing in importing modules? I know >>>> that 'final' has the added constraint of disallowing subclassing in the >>>> same module, but how useful is that? Does it hold its weight? Would we add >>>> it now if it did not exist? >>>> >>>> >>>> As Matthew says, this is still important. >>>> >>>> *Lazy* >>>> This one is clearer: if Joe Groff's property behaviors proposal from >>>> last year is brought forward again, lazy can be demoted from a language >>>> keyword to a Standard Library property behavior. If Joe or anybody from the >>>> core team sees this: do we have any luck of having this awesome feature we >>>> discussed/designed/implemented in the Swift 4 timeframe? >>>> >>>> >>>> Sadly, there is no chance to get property behaviors into Swift 4. >>>> Hopefully Swift 5, but it’s impossible to say right now. >>>> >>>> *Fileprivate* >>>> >>>> I started the discussion early during the Swift 4 timeframe that I >>>> regret the change in Swift 3 which introduced a scoped private keyword. For >>>> me, it's not worth the increase in complexity in access modifiers. I was >>>> very happy with the file-scope of Swift pre-3. When discussing that, Chris >>>> Latner mentioned we'd have to wait for Phase 2 to re-discuss it and also >>>> show proof that people mostly used 'fileprivate' and not the new 'private' >>>> modifier as proof if we want the proposal to have any weight. Does anybody >>>> have a good idea for compiling stats from GitHub on this subject? First of >>>> all, I've always found the GitHub Search quite bad and don't know how much >>>> it can be trusted. Secondly, because 'private' in Swift 2 and 3 have >>>> different meanings, a simple textual search might get us wrong results if >>>> we don't find a way to filter on Swift 3 code. >>>> >>>> >>>> I would still like to re-evaluate fileprivate based on information in >>>> the field. The theory of the SE-0025 (https://github.com/apple/swif >>>> t-evolution/blob/master/proposals/0025-scoped-access-level.md) was >>>> that the fileprivate keyword would be used infrequently: this means that it >>>> would uglify very little code and when it occurred, it would carry meaning >>>> and significance. >>>> >>>> >>>> Infrequent use and significance are orthogonal. >>>> I still think developers would declare all ivars private (this is less >>>> ugly and shorter), and then will happily convert them to fileprivate each >>>> time the compiler will tell them they are not accessible somewhere else in >>>> the file. >>>> As the code that try to access that ivar is in the same file anyway, it >>>> has full knowledge of the implementation details and there is no good >>>> reason it shouldn’t be able to access the ivar when needed. >>>> >>>> We have a problem with evaluating that theory though: the Swift 2->3 >>>> migrator mechanically changed all instances of private into fileprivate. >>>> This uglified a ton of code unnecessarily and (even worse) lead programmers >>>> to think they should use fileprivate everywhere. Because of this, it is >>>> hard to look at a random Swift 3 codebase and determine whether SE-0025 is >>>> working out as intended. >>>> >>>> The best way out of this that I can think of is to add a *warning* to >>>> the Swift 3.1 or 4 compiler which detects uses of fileprivate that can be >>>> tightened to “private” and provide a fixit to do the change. This would be >>>> similar to how we suggest changing ‘var’ into ‘let’ where possible. Over >>>> time, this would have the effect of getting us back to the world we >>>> intended in SE-0025. >>>> >>>> -Chris >>>> >>>> _______________________________________________ >>>> swift-evolution mailing list >>>> swift-evolution@swift.org >>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>>> >>>> _______________________________________________ >>>> swift-evolution mailing list >>>> swift-evolution@swift.org >>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>>> >>> >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org >> https://lists.swift.org/mailman/listinfo/swift-evolution >> >> >> > >
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