[swift-evolution] warnings for out of scope?

Robert Widmann devteam.codafi at gmail.com
Wed Jan 25 16:34:50 CST 2017

Responding on the pro side, but I don't endorse this proposal without more details:

~Robert Widmann

2017/01/25 13:40、Xiaodi Wu <xiaodi.wu at gmail.com> のメッセージ:

> This is contrary to several deliberate design decisions, if I understand correctly.
> First, revisions to visibility rules in the Swift 3 timeline were made with the deliberate intention that it should be possible to model greater visibility within a type (e.g. public members) without actually exporting that type. As Swift does not have optional warnings that can be turned off, it would be incongruous if the language also warned users away from creating internal types or variables before they are used. Unlike warnings about unused variables within a scope, which are by definition local, a warning such as proposed would be much more disruptive.

That decision wasn't really one made to support a deliberate design, but to help make migration of fileprivate easier IIRC (Jordan Rose probably remembers better than I do of the conversation we had about this).

It's important to note we already provide module-wide warnings (namely if we detect you mutating a let-bound member we offer a fixit at the site of the member decl) so this isn't new.

> Second, a variable with no access modifier defaults to internal, and this is deliberate for the purpose of progressive disclosure (i.e. it is, by design, possible for a new user to write useful code separated across multiple files without learning what access modifiers are). This would be undone if nearly every such use prompted a warning.

That enforces hiding from clients, OP wants to enforce a model where we enforce data hiding from yourself as well.  If a variable's access needs to be escalated we can provide that fixit as well (instead of the current errors we offer now which are usually spurious type errors because lookup barfs).

> In summary, I think the issue here is more one of style than safety, and IMO is more within the scope of a linter.
>> On Wed, Jan 25, 2017 at 12:27 Robert Widmann via swift-evolution <swift-evolution at swift.org> wrote:
>> So, to be clear, a warning about making internal variables more private based on their usage in the entire module?  
>> Sounds doable.  Probably wouldn't need to go through evolution to get it too (but I'll let others make that call).  Please file an SR about this too.
>> ~Robert Widmann
>> 2017/01/25 3:25、Dave Kliman via swift-evolution <swift-evolution at swift.org> のメッセージ:
>>> Hi!
>>> I’m somewhat new to swift, so this issue may have been covered.
>>> I really like how I get a warning for variables I’ve declared, but have not mutated, or constants that I did not read.
>>> What about warnings for anything not accessed outside its declared scope, encouraging the use of private, or fileprivate more often?
>>> -Dave
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