[stdlib] Fixing compilation warnings (#7314)

<rdar://problem/30320630>

Author: moiseev

stdlib/public/SDK/Dispatch/Data.swift

@@ -272,7 +272,7 @@ public struct DispatchDataIterator : IteratorProtocol, Sequence {
 extension DispatchData {
 	@_semantics("convertToObjectiveC")
 	public func _bridgeToObjectiveC() -> __DispatchData {
-		return unsafeBitCast(__wrapped, to: __DispatchData.self)
+		return __wrapped
 	}
 
 	public static func _forceBridgeFromObjectiveC(_ input: __DispatchData, result: inout DispatchData?) {

stdlib/public/SDK/Foundation/Data.swift

@@ -83,7 +83,7 @@ public final class _DataStorage {
         var dest = dest_
         var source = source_
         var num = num_
-        if _DataStorage.vmOpsThreshold <= num && ((unsafeBitCast(source, to: Int.self) | unsafeBitCast(dest, to: Int.self)) & (NSPageSize() - 1)) == 0 {
+        if _DataStorage.vmOpsThreshold <= num && ((unsafeBitCast(source, to: Int.self) | Int(bitPattern: dest)) & (NSPageSize() - 1)) == 0 {
             let pages = NSRoundDownToMultipleOfPageSize(num)
             NSCopyMemoryPages(source!, dest, pages)
             source = source!.advanced(by: pages)

stdlib/public/SDK/Foundation/DateInterval.swift

@@ -157,7 +157,9 @@ public struct DateInterval : ReferenceConvertible, Comparable, Hashable {
     public var hashValue: Int {
         var buf: (UInt, UInt) = (UInt(start.timeIntervalSinceReferenceDate), UInt(end.timeIntervalSinceReferenceDate))
         return withUnsafeMutablePointer(to: &buf) {
-            return Int(bitPattern: CFHashBytes(unsafeBitCast($0, to: UnsafeMutablePointer<UInt8>.self), CFIndex(MemoryLayout<UInt>.size * 2)))
+            $0.withMemoryRebound(to: UInt8.self, capacity: 2 * MemoryLayout<UInt>.size / MemoryLayout<UInt8>.size) {
+                return Int(bitPattern: CFHashBytes($0, CFIndex(MemoryLayout<UInt>.size * 2)))
+            }
         }
     }
 

stdlib/public/SDK/Foundation/IndexSet.swift

@@ -956,7 +956,7 @@ private final class _MutablePairHandle<ImmutableType : NSObject, MutableType : N
             return try whatToDo(i)
         case .Mutable(let m):
             // TODO: It should be possible to reflect the constraint that MutableType is a subtype of ImmutableType in the generics for the class, but I haven't figured out how yet. For now, cheat and unsafe bit cast.
-            return try whatToDo(unsafeBitCast(m, to: ImmutableType.self))
+            return try whatToDo(unsafeDowncast(m, to: ImmutableType.self))
         }
     }
 
@@ -966,7 +966,7 @@ private final class _MutablePairHandle<ImmutableType : NSObject, MutableType : N
             return i
         case .Mutable(let m):
             // TODO: It should be possible to reflect the constraint that MutableType is a subtype of ImmutableType in the generics for the class, but I haven't figured out how yet. For now, cheat and unsafe bit cast.
-            return unsafeBitCast(m, to: ImmutableType.self)
+            return unsafeDowncast(m, to: ImmutableType.self)
         }
     }
 }

stdlib/public/SDK/Foundation/UUID.swift

@@ -23,14 +23,18 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     /* Create a new UUID with RFC 4122 version 4 random bytes */
     public init() {
         withUnsafeMutablePointer(to: &uuid) {
-            uuid_generate_random(unsafeBitCast($0, to: UnsafeMutablePointer<UInt8>.self))
+            $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
+                uuid_generate_random($0)
+            }
         }
     }
 
     fileprivate init(reference: NSUUID) {
         var bytes: uuid_t = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
         withUnsafeMutablePointer(to: &bytes) {
-            reference.getBytes(unsafeBitCast($0, to: UnsafeMutablePointer<UInt8>.self))
+            $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
+                reference.getBytes($0)
+            }
         }
         uuid = bytes
     }
@@ -40,7 +44,9 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     /// Returns nil for invalid strings.
     public init?(uuidString string: String) {
         let res = withUnsafeMutablePointer(to: &uuid) {
-            return uuid_parse(string, unsafeBitCast($0, to: UnsafeMutablePointer<UInt8>.self))
+            $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
+                return uuid_parse(string, $0)
+            }
         }
         if res != 0 {
             return nil
@@ -56,18 +62,24 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     public var uuidString: String {
         var bytes: uuid_string_t = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
         var localValue = uuid
-        return withUnsafeMutablePointer(to: &localValue) { val in
-            withUnsafeMutablePointer(to: &bytes) { str in
-                uuid_unparse(unsafeBitCast(val, to: UnsafePointer<UInt8>.self), unsafeBitCast(str, to: UnsafeMutablePointer<Int8>.self))
-                return String(cString: unsafeBitCast(str, to: UnsafePointer<CChar>.self), encoding: .utf8)!
+        return withUnsafeMutablePointer(to: &localValue) {
+            $0.withMemoryRebound(to: UInt8.self, capacity: 16) { val in
+                withUnsafeMutablePointer(to: &bytes) {
+                    $0.withMemoryRebound(to: Int8.self, capacity: 37) { str in
+                        uuid_unparse(val, str)
+                        return String(cString: UnsafePointer(str), encoding: .utf8)!
+                    }
+                }
             }
         }
     }
 
     public var hashValue: Int {
         var localValue = uuid
         return withUnsafeMutablePointer(to: &localValue) {
-            return Int(bitPattern: CFHashBytes(unsafeBitCast($0, to: UnsafeMutablePointer<UInt8>.self), CFIndex(MemoryLayout<uuid_t>.size)))
+              $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
+                  return Int(bitPattern: CFHashBytes($0, CFIndex(MemoryLayout<uuid_t>.size)))
+              }
         }
     }
 
@@ -84,7 +96,9 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     fileprivate var reference: NSUUID {
         var bytes = uuid
         return withUnsafePointer(to: &bytes) {
-            return NSUUID(uuidBytes: unsafeBitCast($0, to: UnsafePointer<UInt8>.self))
+            $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
+                return NSUUID(uuidBytes: $0)
+            }
         }
     }
 

stdlib/public/SDK/Intents/INRequestRideIntent.swift

@@ -25,7 +25,7 @@ extension INRequestRideIntent {
     paymentMethod: INPaymentMethod? = nil,
     scheduledPickupTime: INDateComponentsRange? = nil
   ) {
-    if #available(iOS 10.3, watchOS 3.2, *) {
+    if #available(iOS 10.3, *) {
       self.init(__pickupLocation: pickupLocation,
         dropOffLocation: dropOffLocation,
         rideOptionName: rideOptionName,