> On Feb 22, 2017, at 12:32 AM, David Hart <da...@hartbit.com> wrote: > > >> On 21 Feb 2017, at 23:41, Xiaodi Wu <xiaodi...@gmail.com >> <mailto:xiaodi...@gmail.com>> wrote: >> >> Well-written as-is. >> >> Overall, my feedback is that solution 2 should not be on the table (though >> there are people who clamor for it), and not because I don't agree with it. >> However, simply as a matter of following an appropriate process, solution 2 >> was originally proposed in SE-0025, fully considered, and modified by the >> core team to the current design. One can disagree whether `scoped` is more >> appropriate than `private` as a name for that access modifier, and one is >> likely to say that `private` looks nicer than `fileprivate`, but that's >> neither here nor there. The appropriateness or niceness of these terms is >> unchanged from last year. Re-submitting SE-0025 cannot be the solution for >> fixing SE-0025. > > I agree with you, as you know that I support Solution 1. But I was hoping to > reduce the amount of community flamewar by giving each alternative a level > chance and letting the core team decide. But you make a good point about the > fact that it was the state SE-0025 was it before it was modified by the core > team. And I’m starting to have doubts. What do you think Matthew?
I’d like to let the submodule discussion simmer a little bit more before commenting on this question. The outcome of that could have a significant impact on what I think we should do about SE-0025. When we put this proposal together I was assuming submodules were going to be out of scope for Swift 4, but it looks like at least the discussion is not. Even if we don’t end up with a formal review of a submodule proposal the discussion might lead to a better idea of what kind of proposal might have a chance to be accepted in the future (by gauging community sentiment in the discussions, etc). > >> On Tue, Feb 21, 2017 at 12:58 AM, David Hart <da...@hartbit.com >> <mailto:da...@hartbit.com>> wrote: >> Hello list, >> >> Matthew Johnson and I have been putting our proposals together towards a >> joint “let’s fix private access levels” proposal. As the community seems >> quite divided on the issue, we offer two solutions in our proposal to let >> the community debate and to let the core team make the final decision. >> >> I’d like to concentrate this round of feedback on the quality of the >> proposal, and not on the merits of Solution 1 or 2. thoughts? >> >> https://github.com/hartbit/swift-evolution/blob/fix-private-access-levels/proposals/XXXX-fix-private-access-levels.md >> >> <https://github.com/hartbit/swift-evolution/blob/fix-private-access-levels/proposals/XXXX-fix-private-access-levels.md> >> >> David. >> >> Fix Private Access Levels >> >> Proposal: SE-XXXX >> <https://github.com/hartbit/swift-evolution/blob/fix-private-access-levels/proposals> >> Authors: David Hart <http://github.com/hartbit>, Matthew Johnson >> <https://github.com/anandabits> >> Review Manager: TBD >> Status: TBD >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#introduction>Introduction >> >> This proposal presents the problems the came with the the access level >> modifications in SE-0025 >> <https://github.com/apple/swift-evolution/blob/master/proposals/0025-scoped-access-level.md> >> and presents two community driven solutions to fix them. As a consensus >> will not easily emerge, this proposal will allow a last round of voting and >> let the core team decide. Once that is done, this proposal will be ammended >> to describe the chosen solution. >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#motivation>Motivation >> >> Since the release of Swift 3, the access level change of SE-0025 was met >> with dissatisfaction by a substantial proportion of the general Swift >> community. Before offering solutions, lets discuss how and why it can be >> viewed as actiely harmful, the new requirement for syntax/API changes. >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#criticisms-of-se-0025>Criticisms >> of SE-0025 >> >> There are two primary criticism that have been offered. >> >> The first is that private is a "soft default" access modifier for >> restricting access within a file. Scoped access is not a good behavior for a >> "soft default" because it is extremely common to use several extensions >> within a file. A "soft default" (and therefore private) should work well >> with this idiom. It is fair to say that changing the behavior of private >> such that it does not work well with extensions meets the criteria of >> actively harmful in the sense that it subtly encourages overuse of scoped >> access control and discourages the more reasonable default by giving it the >> awkward name fileprivate. >> >> The second is that Swift's system of access control is too complex. Many >> people feel like restricting access control to scopes less than a file is of >> dubious value and therefore wish to simplify Swift's access control story by >> removing scoped access. However, there are many others who like the ability >> to have the compiler verify tighter access levels and believe it helps make >> it easier to reason about code which is protecting invariants. >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#detailed-design>Detailed >> design >> >> Both authors agree that the private keyword should be reverted back to its >> Swift 2 file-based meaning, resolving the first criticism. But the authors >> disagree on what should be done about the scoped access level and the >> following solutions represent the two main opinions in the community: >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#solution-1-remove-the-scoped-access-level>Solution >> 1: Remove the scoped access level >> >> Compared to a file-based access level, the scoped-based access level adds >> meaningful information by hiding implementation details which do not concern >> other types or extensions in the same file. But is that distinction between >> private and fileprivate actively used by the larger community of Swift >> developers? And if it were used pervasively, would it be worth the cognitive >> load and complexity of keeping two very similar access levels in the >> language? This solution argues that answer to both questions is no and that >> the scoped access level should be removed to resolve the complexity >> criticism. >> >> This solution has the added advantage of leaving the most design >> breathing-room for future discussions about access levels in regards to >> submodules. >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#solution-2-rename-the-scoped-access-level-to-scoped>Solution >> 2: Rename the scoped access level to scoped >> >> It is difficult to make the case that a feature which a nontrivial number of >> Swift users find valuable and which is easy for teams to avoid is actively >> harmful. It seems like something that falls more into the category of a >> debate over style (which could be addressed by a linter). Should we remove a >> feature whose utility is a question of style, but is not actively harmful in >> the sense of causing programmer error? The second solution argues against it >> and proposes renaming it to scoped. >> >> The scoped keyword is a good choice not only because the community has been >> calling this feature “scoped access control” all along, but also because the >> principle underlying all of Swift’s access levels is the idea of a scope. >> >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#source-compatibility>Source >> compatibility >> >> In Swift 3 compatibility mode, the compiler will continue to treat private >> and fileprivate as was previously the case. >> >> In Swift 4 mode, the compiler will deprecate the fileprivate keyword and >> revert the semantics of the private access level to be file based. The >> migrator will rename all uses of fileprivate to private. In solution 2, the >> migrator will also rename all uses of private to scoped. >> >> With solution 1 (and with solution 2 if the migrator is not run), cases >> where a type had private declarations with the same signature in different >> scopes will produce a compiler error. For example, the following piece of >> code compiles in Swift 3 compatibilty mode but generates a Invalid >> redeclaration of 'foo()' error in Swift 4 mode. >> >> struct Foo { >> private func bar() {} >> } >> >> extension Foo { >> private func bar() {} >> } >> >> <https://github.com/hartbit/swift-evolution/tree/fix-private-access-levels#alternatives-considered>Alternatives >> Considered >> >> Deprecate fileprivate and modify the semantics of private to include >> same-type extension scopes in the same file. >> Deprecate fileprivate and modify the semantics of private to include >> same-type extension scopes in the same module. >> The alternatives are potentially interesting but completely remove the file >> access level while making the new privateaccess level more complicated to >> explain and understand. >> >
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