---

yaml
---
r: 348941
b: refs/heads/master
c: eb02f20
h: refs/heads/master
i:
  348939: 8ef3a5d

Author: adrian-prantl

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 9b6ff03f9eff89ee93831080a27e47b16c784f99
+refs/heads/master: eb02f20f9950ab1f0149c4712ac50ae44bd0b25f
 refs/heads/master-next: 203b3026584ecad859eb328b2e12490099409cd5
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea

trunk/.gitattributes

@@ -0,0 +1,2 @@
+*.swift.gyb linguist-language=Swift
+*.cpp.gyb linguist-language=C++

trunk/CHANGELOG.md

@@ -4,50 +4,159 @@ CHANGELOG
 <details>
 <summary>Note: This is in reverse chronological order, so newer entries are added to the top.</summary>
 
-| Contents               |
-| :--------------------- |
-| [Swift Next](#swift-next) |
-| [Swift 5.1](#swift-51) |
-| [Swift 5.0](#swift-50) |
-| [Swift 4.2](#swift-42) |
-| [Swift 4.1](#swift-41) |
-| [Swift 4.0](#swift-40) |
-| [Swift 3.1](#swift-31) |
-| [Swift 3.0](#swift-30) |
-| [Swift 2.2](#swift-22) |
-| [Swift 2.1](#swift-21) |
-| [Swift 2.0](#swift-20) |
-| [Swift 1.2](#swift-12) |
-| [Swift 1.1](#swift-11) |
-| [Swift 1.0](#swift-10) |
+| Version                | Released   | Toolchain   |
+| :--------------------- | :--------- | :---------- |
+| [Swift 5.2](#swift-52) |            |             |
+| [Swift 5.1](#swift-51) | 2019-09-20 | Xcode 11.0  |
+| [Swift 5.0](#swift-50) | 2019-03-25 | Xcode 10.2  |
+| [Swift 4.2](#swift-42) | 2018-09-17 | Xcode 10.0  |
+| [Swift 4.1](#swift-41) | 2018-03-29 | Xcode 9.3   |
+| [Swift 4.0](#swift-40) | 2017-09-19 | Xcode 9.0   |
+| [Swift 3.1](#swift-31) | 2017-03-27 | Xcode 8.3   |
+| [Swift 3.0](#swift-30) | 2016-09-13 | Xcode 8.0   |
+| [Swift 2.2](#swift-22) | 2016-03-21 | Xcode 7.3   |
+| [Swift 2.1](#swift-21) | 2015-10-21 | Xcode 7.1   |
+| [Swift 2.0](#swift-20) | 2015-09-17 | Xcode 7.0   |
+| [Swift 1.2](#swift-12) | 2015-04-08 | Xcode 6.3   |
+| [Swift 1.1](#swift-11) | 2014-12-02 | Xcode 6.1.1 |
+| [Swift 1.0](#swift-10) | 2014-09-15 | Xcode 6.0   |
 
 </details>
 
-Swift Next
-----------
+Swift 5.2
+---------
 
-* [SR-8974][]:
+* [SR-11429][]:
 
-  Duplicate tuple element labels are no longer allowed, because it leads
-  to incorrect behavior. For example:
+  The compiler will now correctly strip argument labels from function references
+  used with the `as` operator in a function call. As a result, the `as` operator
+  can now be used to disambiguate a call to a function with argument labels. 
+  
+  ```swift
+  func foo(x: Int) {}
+  func foo(x: UInt) {}
+  
+  (foo as (Int) -> Void)(5)  // Calls foo(x: Int)
+  (foo as (UInt) -> Void)(5) // Calls foo(x: UInt)
+  ```
+  
+  Previously this was only possible for functions without argument labels.
+  
+  This change also means that a generic type alias can no longer be used to
+  preserve the argument labels of a function reference through the `as`
+  operator. The following is now rejected:
+  
+  ```swift
+  typealias Magic<T> = T
+  func foo(x: Int) {}
+  (foo as Magic)(x: 5) // error: Extraneous argument label 'x:' in call
+  ```
+  
+  The function value must instead be called without argument labels:
+  
+  ```swift
+  (foo as Magic)(5)
+  ```
+
+* [SR-11298][]:
+
+  A class-constrained protocol extension, where the extended protocol does
+  not impose a class constraint, will now infer the constraint implicitly.
 
+  ```swift
+  protocol Foo {}
+  class Bar: Foo {
+    var someProperty: Int = 0
+  }
+
+  // Even though 'Foo' does not impose a class constraint, it is automatically
+  // inferred due to the Self: Bar constraint.
+  extension Foo where Self: Bar {
+    var anotherProperty: Int {
+      get { return someProperty }
+      // As a result, the setter is now implicitly nonmutating, just like it would
+      // be if 'Foo' had a class constraint.
+      set { someProperty = newValue }
+    }
+  }
+  ```
+  
+  As a result, this could lead to code that currently compiles today to throw an error.
+  
+  ```swift
+  protocol Foo {
+    var someProperty: Int { get set }
+  }
+  
+  class Bar: Foo {
+    var someProperty = 0
+  }
+  
+  extension Foo where Self: Bar {
+    var anotherProperty1: Int {
+      get { return someProperty }
+      // This will now error, because the protocol requirement
+      // is implicitly mutating and the setter is implicitly 
+      // nonmutating.
+      set { someProperty = newValue } // Error
+    }
+  }
   ```
-  let dupLabels: (foo: Int, foo: Int) = (foo: 1, foo: 2)
 
-  enum Foo { case bar(x: Int, x: Int) }
-  let f: Foo = .bar(x: 0, x: 1)
+  **Workaround**: Define a new mutable variable inside the setter that has a reference to `self`:
+  
+  ```swift
+  var anotherProperty1: Int {
+    get { return someProperty }
+    set {
+      var mutableSelf = self
+      mutableSelf.someProperty = newValue // Okay
+    }
+  }
   ```
 
-  will now be diagnosed as an error. 
+* [SE-0253][]:
 
-  Note: You can still use duplicate labels when declaring functions and
-  subscripts, as long as the internal labels are different. For example:
+  Values of types that declare `func callAsFunction` methods can be called
+  like functions. The call syntax is shorthand for applying
+  `func callAsFunction` methods.
 
+  ```swift
+  struct Adder {
+    var base: Int
+    func callAsFunction(_ x: Int) -> Int {
+      return x + base
+    }
+  }
+  var adder = Adder(base: 3)
+  adder(10) // returns 13, same as `adder.callAsFunction(10)`
   ```
-  func foo(bar x: Int, bar y: Int) {}
-  subscript(a x: Int, a y: Int) -> Int {}
+
+  * `func callAsFunction` argument labels are required at call sites.
+  * Multiple `func callAsFunction` methods on a single type are supported.
+  * `mutating func callAsFunction` is supported.
+  * `func callAsFunction` works with `throws` and `rethrows`.
+  * `func callAsFunction` works with trailing closures.
+
+* [SR-4206][]:
+
+  A method override is no longer allowed to have a generic signature with
+  requirements not imposed by the base method. For example:
+
+  ```
+  protocol P {}
+  
+  class Base {
+    func foo<T>(arg: T) {}
+  }
+  
+  class Derived: Base {
+    override func foo<T: P>(arg: T) {}
+  }
   ```
 
+  will now be diagnosed as an error.
+
 * [SR-6118][]:
 
   Subscripts can now declare default arguments:
@@ -68,6 +177,30 @@ Swift Next
 Swift 5.1
 ---------
 
+### 2019-09-20 (Xcode 11.0)
+
+* [SR-8974][]:
+
+  Duplicate tuple element labels are no longer allowed, because it leads
+  to incorrect behavior. For example:
+
+  ```
+  let dupLabels: (foo: Int, foo: Int) = (foo: 1, foo: 2)
+
+  enum Foo { case bar(x: Int, x: Int) }
+  let f: Foo = .bar(x: 0, x: 1)
+  ```
+
+  will now be diagnosed as an error. 
+
+  Note: You can still use duplicate argument labels when declaring functions and
+  subscripts, as long as the internal parameter names are different. For example:
+
+  ```
+  func foo(bar x: Int, bar y: Int) {}
+  subscript(a x: Int, a y: Int) -> Int {}
+  ```
+
 * [SE-0244][]:
 
   Functions can now hide their concrete return type by declaring what protocols
@@ -7692,6 +7825,7 @@ Swift 1.0
 [SE-0244]: <https://github.com/apple/swift-evolution/blob/master/proposals/0244-opaque-result-types.md>
 [SE-0245]: <https://github.com/apple/swift-evolution/blob/master/proposals/0245-array-uninitialized-initializer.md>
 [SE-0252]: <https://github.com/apple/swift-evolution/blob/master/proposals/0252-keypath-dynamic-member-lookup.md>
+[SE-0253]: <https://github.com/apple/swift-evolution/blob/master/proposals/0253-callable.md>
 [SE-0254]: <https://github.com/apple/swift-evolution/blob/master/proposals/0254-static-subscripts.md>
 
 [SR-106]: <https://bugs.swift.org/browse/SR-106>
@@ -7708,6 +7842,7 @@ Swift 1.0
 [SR-2608]: <https://bugs.swift.org/browse/SR-2608>
 [SR-2672]: <https://bugs.swift.org/browse/SR-2672>
 [SR-2688]: <https://bugs.swift.org/browse/SR-2688>
+[SR-4206]: <https://bugs.swift.org/browse/SR-4206>
 [SR-4248]: <https://bugs.swift.org/browse/SR-4248>
 [SR-5581]: <https://bugs.swift.org/browse/SR-5581>
 [SR-5719]: <https://bugs.swift.org/browse/SR-5719>
@@ -7721,3 +7856,5 @@ Swift 1.0
 [SR-8974]: <https://bugs.swift.org/browse/SR-8974>
 [SR-9043]: <https://bugs.swift.org/browse/SR-9043>
 [SR-9827]: <https://bugs.swift.org/browse/SR-9827>
+[SR-11298]: <https://bugs.swift.org/browse/SR-11298>
+[SR-11429]: <https://bugs.swift.org/browse/SR-11429>