Merge branch 'master' into therealbnut-fix-box-generic-warnings

Author: Andrew Bennett

.flake8

@@ -1,4 +1,5 @@
 [flake8]
+ignore = W291
 filename = *.py,
            ./utils/80+-check,
            ./utils/backtrace-check,

CHANGELOG.md

@@ -21,12 +21,39 @@ CHANGELOG
 Swift 4.0
 ---------
 
+* [SR-1529](https://bugs.swift.org/browse/SR-1529):
+
+  Covariant method overrides are now fully supported, fixing many crashes
+  and compile-time assertions when defining or calling such methods.
+  Examples:
+
+  ```swift
+  class Bed {}
+  class Nook : Bed {}
+
+  class Cat<T> {
+    func eat(snack: T) {}
+    func play(game: String) {}
+    func sleep(where: Nook) {}
+  }
+
+  class Dog : Cat<(Int, Int)> {
+    // 'T' becomes concrete
+    override func eat(snack: (Int, Int)) {}
+
+    // 'game' becomes optional
+    override func play(game: String?) {}
+
+    // 'where' becomes a superclass
+    override func sleep(where: Bed) {}
+  }```
+
 * [SE-0148][]:
 
   Subscript declarations can now be defined to have generic parameter lists.
   Example:
 
-  ```
+  ```swift
   extension JSON {
     subscript<T>(key: String) -> T?
         where T : JSONConvertible {
@@ -65,6 +92,8 @@ Swift 4.0
 Swift 3.1
 ---------
 
+### 2017-03-27 (Xcode 8.3)
+
 * [SE-0080][]:
 
   Adds a new family of conversion initializers to all numeric types that

CMakeLists.txt

@@ -272,7 +272,7 @@ option(SWIFT_STDLIB_ENABLE_RESILIENCE
 
 option(SWIFT_RUNTIME_ENABLE_COW_EXISTENTIALS
     "Build the runtime with a copy-on-write implementation for opaque existentials"
-    FALSE)
+    TRUE)
 
 option(SWIFT_STDLIB_USE_NONATOMIC_RC
     "Build the standard libraries and overlays with nonatomic reference count operations enabled"

README.md

@@ -54,7 +54,7 @@ discussed below.
 macOS, Ubuntu Linux LTS, and the latest Ubuntu Linux release are the current
 supported host development operating systems.
 
-For macOS, you need [Xcode 8.3 Beta 4](https://developer.apple.com/xcode/downloads/).
+For macOS, you need [Xcode 8.3](https://developer.apple.com/xcode/downloads/).
 
 For Ubuntu, you'll need the following development dependencies:
 

benchmark/CMakeLists.txt

@@ -37,15 +37,16 @@ set(SWIFT_BENCH_MODULES
     single-source/Chars
     single-source/ClassArrayGetter
     single-source/DeadArray
+    single-source/DictTest
+    single-source/DictTest2
+    single-source/DictTest3
     single-source/DictionaryBridge
     single-source/DictionaryLiteral
     single-source/DictionaryRemove
     single-source/DictionarySwap
-    single-source/DictTest
-    single-source/DictTest2
-    single-source/DictTest3
     single-source/DropLast
     single-source/ErrorHandling
+    single-source/ExistentialPerformance
     single-source/Fibonacci
     single-source/GlobalClass
     single-source/Hanoi
@@ -61,10 +62,10 @@ set(SWIFT_BENCH_MODULES
     single-source/Memset
     single-source/MonteCarloE
     single-source/MonteCarloPi
-    single-source/NopDeinit
     single-source/NSDictionaryCastToSwift
     single-source/NSError
     single-source/NSStringConversion
+    single-source/NopDeinit
     single-source/ObjectAllocation
     single-source/ObjectiveCBridging
     single-source/ObjectiveCBridgingStubs
@@ -81,11 +82,11 @@ set(SWIFT_BENCH_MODULES
     single-source/Prims
     single-source/ProtocolDispatch
     single-source/ProtocolDispatch2
-    single-source/RangeAssignment
     single-source/RC4
+    single-source/RGBHistogram
+    single-source/RangeAssignment
     single-source/RecursiveOwnedParameter
     single-source/ReversedCollections
-    single-source/RGBHistogram
     single-source/SetTests
     single-source/SevenBoom
     single-source/Sim2DArray
@@ -94,13 +95,13 @@ set(SWIFT_BENCH_MODULES
     single-source/StackPromo
     single-source/StaticArray
     single-source/StrComplexWalk
+    single-source/StrToInt
     single-source/StringBuilder
     single-source/StringEdits
     single-source/StringInterpolation
     single-source/StringMatch
     single-source/StringTests
     single-source/StringWalk
-    single-source/StrToInt
     single-source/Suffix
     single-source/SuperChars
     single-source/TwoSum