Foundation: Manually define hashValue witnesses for CocoaError, URLError, POSIXError and MachError

Author: slavapestov

Darwin/Foundation-swiftoverlay/NSError.swift

@@ -568,6 +568,10 @@ public struct CocoaError : _BridgedStoredNSError {
 
   public static var errorDomain: String { return NSCocoaErrorDomain }
 
+  public var hashValue: Int {
+    return _nsError.hashValue
+  }
+
   /// The error code itself.
   public struct Code : RawRepresentable, Hashable, _ErrorCodeProtocol {
     public typealias _ErrorType = CocoaError
@@ -1795,6 +1799,10 @@ public struct URLError : _BridgedStoredNSError {
 
   public static var errorDomain: String { return NSURLErrorDomain }
 
+  public var hashValue: Int {
+    return _nsError.hashValue
+  }
+
   /// The error code itself.
   public struct Code : RawRepresentable, Hashable, _ErrorCodeProtocol {
     public typealias _ErrorType = URLError
@@ -2451,6 +2459,10 @@ public struct POSIXError : _BridgedStoredNSError {
 
   public static var errorDomain: String { return NSPOSIXErrorDomain }
 
+  public var hashValue: Int {
+    return _nsError.hashValue
+  }
+
   public typealias Code = POSIXErrorCode
 }
 
@@ -2937,6 +2949,10 @@ public struct MachError : _BridgedStoredNSError {
 
   public static var errorDomain: String { return NSMachErrorDomain }
 
+  public var hashValue: Int {
+    return _nsError.hashValue
+  }
+
   public typealias Code = MachErrorCode
 }