[swift-evolution] [Pitch] consistent public access modifiers

Adrian Zubarev adrian.zubarev at devandartist.com
Mon Feb 13 10:14:35 CST 2017

Is that assumption correct?

// Module A
public protocol SQLiteValue {
    init(statement: SQLiteStatement, columnAt index: Int) throws
    func bind(to statement: SQLiteStatement, at index: Int) throws

// Module B
protocol SQLiteLoggable : SQLiteValue {
    var logDescription: String { get }
I could not follow your example there. If SQLiteLoggable is from module B than this should be an error in my opinion. Otherwise open would have less meaning on protocols, because you always could create an empty protocol that has a super public protocol which you’re not allowed to conform to in module B. This would be a silly workaround to being able to conform to it SQLiteValue indirectly without any further requirement like in SQLiteValueConvertible.

That said, it makes no sense to me to allow that, because it’s simply a workaround to conform to a protocol which public-but-not-open tries to prevent.

// Module X
public protocol A {}

open protocol AA : A { func foo() } // Fine

// Module Y
struct B : A {} // Error
struct B : AA { func foo() { .. } } // Okay

protocol C : A {} // Error because `struct B : C` would equal `struct B : A`
protocol CC : AA {} // Should work even empty, because we have more requirement from `AA`
public should have a consistent meaning across all types from module A in module B, which is ‘not allowed to sub-type from’ and in case of protocols additionally ‘not allowed to conform to’.
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