[swift-evolution] [Proposal] Revising access modifiers on extensions

[Adrian Zubarev]

I completely rewritten the proposal, you can read the formatted version here:

https://github.com/DevAndArtist/swift-evolution/blob/19f2583209a5763880e6f6fa6738ea0c6011f2d6/proposals/nnnn-extensions-access-modifiers.md



-- 
Adrian Zubarev
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Am 27. Juni 2016 um 12:58:53, Adrian Zubarev (adrian.zubarev at devandartist.com) schrieb:

And yet another correction of the default protocol implementations part of my reply.

The imported module is correct, but the default implementation is not imported (I relied on Xcode which didn’t raise an error before I started building the project where I was using the module, and I didn’t build it at the first time).

So we’d need to implement foo by ourself.

struct B : A {
      
    public func foo() {}
}   
The rest of my reply should be fine. With the same access control it would be more clearer and intuitive how the extension will be imported.


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Adrian Zubarev
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Am 27. Juni 2016 um 10:38:12, Adrian Zubarev (adrian.zubarev at devandartist.com) schrieb:

Lets examine the impact on default protocol implementations:

Currently we have this behavior:

public protocol A {
    func foo()
}

extension A {
    func foo() { /* implement */ }    
}
The imported version would look like this.

public protocol A {
    public func foo()
}
As the module user you have no clue that there might be a default implementation, but you sill will be able to use it, because when conforming to A you don’t have to implement foo. This implicitly signals you that there is indeed a default implemenation

struct B : A {} // This will be enough

A().foo() // this is fine
One could signal the module user that there is a default implementation by making the extension explicit public as well.

// explicitly marked as public to grant visibility to    
// the default implementation extension bag
public extension A {
       
    /// will do something cool
    func foo() { /* implement */ }    
}
The result of the imported module would change and look like this:

public protocol A {
    public func foo()
}

extension A {
       
    /// will do something cool
    public func foo()
}
With the proposed change all default implementations will become visible by default and I think this is great step as well.

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