Remove unnecessary NSError bridging code

Author: Itai Ferber

Foundation/NSError.swift

@@ -344,14 +344,6 @@ public func _swift_Foundation_getErrorDefaultUserInfo(_ error: Error) -> Any? {
 // NSError and CFError conform to the standard Error protocol. Compiler
 // magic allows this to be done as a "toll-free" conversion when an NSError
 // or CFError is used as an Error existential.
-
-extension NSError {
-    /// The "embedded" NSError is itself.
-    public func _getEmbeddedNSError() -> AnyObject? {
-        return self
-    }
-}
-
 extension CFError : Error {
     public var _domain: String {
         return CFErrorGetDomain(self)._swiftObject
@@ -364,17 +356,6 @@ extension CFError : Error {
     public var _userInfo: Any? {
         return CFErrorCopyUserInfo(self) as Any
     }
-
-    /// The "embedded" NSError is itself.
-    public func _getEmbeddedNSError() -> AnyObject? {
-        return self
-    }
-}
-
-// An error value to use when an Objective-C API indicates error
-// but produces a nil error object.
-public enum _GenericObjCError : Error {
-    case nilError
 }
 
 /// An internal protocol to represent Swift error enums that map to standard
@@ -526,9 +507,6 @@ public extension _BridgedStoredNSError {
 
 /// Implementation of CustomNSError for all _BridgedStoredNSErrors.
 public extension _BridgedStoredNSError {
-    // FIXME: Would prefer to have a clear "extract an NSError
-    // directly" operation.
-
     static var errorDomain: String { return _nsErrorDomain }
 
     var errorCode: Int { return _nsError.code }
@@ -566,11 +544,6 @@ extension _ErrorCodeProtocol where Self._ErrorType: _BridgedStoredNSError {
 }
 
 extension _BridgedStoredNSError {
-    /// Retrieve the embedded NSError from a bridged, stored NSError.
-    public func _getEmbeddedNSError() -> AnyObject? {
-        return _nsError
-    }
-
     public static func == (lhs: Self, rhs: Self) -> Bool {
         return lhs._nsError.isEqual(rhs._nsError)
     }