Proposal is moved to a git repo:
https://github.com/DevAndArtist/swift-evolution/blob/extensions_access_modifiers/proposals/nnnn-extensions-access-modifiers.md
I also updated a few things for readability.
Revising access modifiers on extensions
Proposal: SE-NNNN
Author: Adrian Zubarev
Status: Awaiting review
Review manager: TBD
Introduction
One great goal for Swift 3 is to sort out any source breaking language changes.
This proposal aims to fix access modifier inconsistency on extensions compared
to other scope declarations types.
Swift-evolution thread: [Proposal] Revising access modifiers on extensions
Motivation
When declaring members on extensions which don’t have an explicit access
modifier in Swift 2.2, it is possible to create an implicitly public extension
by applying a public modifier to at least one extension member.
public struct A { … }
// Implicitly public
extension A {
public var member1: SomeType { … }
// Implicitly internal
func member2() { … }
}
// Implicitly internal
extension A {
// Implicitly internal
var member3: SomeType { … }
}
Furthermore in Swift 2.2 it is not allowed to apply an access modifier on
extensions when a type inheritance clause is present:
public protocol B { … }
// 'public' modifier cannot be used with
// extensions that declare protocol conformances
public extension A : B { … }
Proposed solution
Allow access modifier on extensions when a type inheritance clause is present.
Remove the behavior of an implicit public extension.
This changes should make access modifier on extensions consistent to classes,
structs and enums (and SE–0025).
The current grammar will not change:
extension-declaration → access-level-modifieropt extension type-identifier
type-inheritance-clauseopt extension-body
extension-declaration → access-level-modifieropt extension type-identifier
requirement-clause extension-body
extension-body → { declarationsopt }
Iff the access-level-modifier is not present, the access modifier on extensions
should always be implicitly internal.
Impact on APIs:
Current version:
/// Implementation version
///========================
public protocol Y {
func member()
}
public struct X { … }
// Implicitly public
extension X : Y {
public func member() { ... }
// Implicitly internal
func anotherMember() { ... }
}
/// Imported modele version
///========================
public protocol Y {
func member()
}
public struct X { ... }
// Missing `public` modifier
extension X : Y {
public func member() { ... }
}
New Version:
/// Implementation version
///========================
public extension X : Y {
public func member() { ... }
// Implicitly internal
func anotherMember() { ... }
}
/// Imported modele version
///========================
public extension X : Y {
public func member() { ... }
}
Impact on existing code
This is a source-breaking change that can be automated by a migrator, by simply
scanning the extension-body for at least one public modifier on its members.
Iff a public modifier was found on any member, the migrator can add an explicit
public modifier to the extension itself.
Alternatives considered
No other alternative were considered for this proposal.
Rationale
On [Date], the core team decided to (TBD) this proposal. When the core team
makes a decision regarding this proposal, their rationale for the decision will
be written here.
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