[swift-evolution] private extension

Xiaodi Wu xiaodi.wu at gmail.com
Wed Aug 9 16:47:41 CDT 2017


I brought this up after SE-0169, but it was deemed to be a separate issue
and any further consideration was declined. Let’s not initiate another
round of access control discussions.
On Wed, Aug 9, 2017 at 16:31 David Hart via swift-evolution <
swift-evolution at swift.org> wrote:

> Actually, I think this is this way only as a relic from the original
> private/fileprivate proposal. Swift 3’s private has no meaning as an
> extension modifier, so it was made to alias to fileprivate. But
> since SE-0169 modified private’s meaning so that it would make sense as
> an extension modifier, I think we should fix this.
>
> On 9 Aug 2017, at 23:22, David Hart via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> That behaviour was never explicitly mentioned in SE-0169 but I agree its
> confusing. But I’m also fairly sure the only window to do anything about it
> is Swift 4. Everybody is really worn down by those access level discussions.
>
> For illustration, Vladimir is confused that:
>
> private extension Foo {
>     func foo() {}
> }
>
> is equivalent to:
>
> fileprivate extension Foo {
>     func foo() {}
> }
>
> making it accessible to another type in the same file:
>
> struct Bar {
>     func bar(foo: Foo) {
>         foo.foo()
>     }
> }
>
> Aren't access levels on extensions supposed to define the default access
> level of the members of the extension?Is this a bug then?
>
> On 9 Aug 2017, at 21:18, Vladimir.S via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Could someone remind please, was it decided to stick with 'private
> extension' means actually fileprivate access level for members declared in
> such extension or this could be discussed for Swift5?
>
> Currently, when private members are visible in type/extensions of that
> type in the same file, IMO there is no sense to treat 'private extension'
> as 'fileprivate extension', it is reasonable to group some private members
> of type into extension without making them fileprivate, and such members
> can be used from the type/other extensions.
>
> And also this is a huge inconsistency in my opinion: all other access
> modifiers 'work' as expected for extensions, but only 'private extension'
> means not what written, very surprising for one who don't expect this.
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