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

[Slava Pestov]

How about private(world), public(module), internal(file)? :-)

Slava

> On Mar 25, 2017, at 4:15 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Please do not start a debate about `private(module)` which is equavalent to `internal`, otherwise you could equally use a parametrized `public` for everything. 
> 
> public(outside_module), public(only_inside_module), public(only_in_this_file) or public(nowhere)
> 
> `internal` is just fine as it is.
> 
> -- 
> Adrian Zubarev
> Sent with Airmail
> Am 25. März 2017 um 16:43:23, Matt Whiteside via swift-evolution (swift-evolution at swift.org <mailto:swift-evolution at swift.org>) schrieb:
> 
>> 
>>> On Mar 23, 2017, at 18:35, Matthew Johnson via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> On Mar 23, 2017, at 8:27 PM, Drew Crawford <drew at sealedabstract.com <mailto:drew at sealedabstract.com>> wrote:
>>> 
>>>> 
>>>> The obvious example would be Rust.  Rust has exactly two visibilities, and merely one keyword.  By default, members are "private" which is visible inside the module (so, like Swift's internal). The "public" keyword is similar to Swift. 
>>>> 
>>>> The reason this works is that unlike in Swift where a module is something like a library or framework (Rust calls those "crates"), in Rust modules in are (explicitly) lexically scoped; a "mod myscope {}" module can be created for the portion of the file for which the member should be visible and it won't be visible outside that scope. Likewise, "fileprivate" can be achieved by enclosing the file in a "mod MyFile {}". And like all lexical scopes, they can be recursively nested to arbitrary depth to achieve any number of visibility behaviors (e.g., declare a module for the first half of two files) that would require complex new keywords to achieve in Swift. Finally there are some shortcut features like the ability to infer a module structure from the file system. 
>>> 
>>> This is a good example of what I meant.  There is an extremely broad range of possible designs for submodules.  Some of them, such as this example, would make it relatively easy to get by without fileprivate.  There are also many other possible designs that would not.  
>> 
>> The Rust approach sounds ideal to me.  I hope Swift can get to this point some day.
>> 
>> But as for the current proposal, I’ve become convinced that it would cause headaches for too many people.  Parametrizing the private keyword seems a compromise between pragmatism and elegance:
>> 
>> public
>> private(module)
>> private(file)
>> private(scope)
>> 
>> -Matt
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