_SwiftNativeFoundationType: Add hash(into:) requirement with a default implementation

Author: lorentey

Foundation/Boxing.swift

@@ -75,7 +75,9 @@ internal protocol _SwiftNativeFoundationType : class {
 
     func mutableCopy(with zone : NSZone) -> Any
 
+    func hash(into hasher: inout Hasher)
     var hashValue: Int { get }
+
     var description: String { get }
     var debugDescription: String { get }
 
@@ -115,6 +117,10 @@ extension _SwiftNativeFoundationType {
         return _mapUnmanaged { ($0 as NSObject).mutableCopy() }
     }
 
+    func hash(into hasher: inout Hasher) {
+        _mapUnmanaged { hasher.combine($0) }
+    }
+
     var hashValue: Int {
         return _mapUnmanaged { return $0.hashValue }
     }

TestFoundation/TestDateInterval.swift

@@ -0,0 +1,9 @@
+//
+//  TestDateInterval.swift
+//  TestFoundation
+//
+//  Created by Karoly Lorentey on 2019-04-10.
+//  Copyright © 2019 Apple. All rights reserved.
+//
+
+import Foundation

TestFoundation/TestMeasurement.swift

@@ -0,0 +1,9 @@
+//
+//  TestMeasurement.swift
+//  TestFoundation
+//
+//  Created by Karoly Lorentey on 2019-04-10.
+//  Copyright © 2019 Apple. All rights reserved.
+//
+
+import Foundation