Merge pull request #44 from tonyarnold/fix/swift-3.1

Only use duplicate typealias in Swift versions lower than 3.1

Author: wokalski

Sources/Diff.swift

@@ -2,7 +2,13 @@
 public protocol DiffProtocol: Collection, Sequence {
 
     associatedtype DiffElementType
+
+    #if swift(>=3.1)
+    // The typealias is causing crashes in SourceKitService under Swift 3.1 snapshots.
+    #else
+    // TODO: Verify that the typealias workaround is still required when Xcode 8.3 is released.
     typealias Index = Int
+    #endif
 
     var elements: [DiffElementType] { get }
 }