Merge pull request swiftlang#1397 from hartbit/recursive-constraint-warnings

Fix recursive constraint warnings

Author: ddunbar

Sources/Basic/OutputByteStream.swift

@@ -116,8 +116,7 @@ public class OutputByteStream: TextOutputStream {
 
     /// Write a collection of bytes to the buffer.
     public final func write<C: Collection>(collection bytes: C) where
-        C.Iterator.Element == UInt8,
-        C.SubSequence: Collection {
+        C.Iterator.Element == UInt8 {
         queue.sync {
             // This is based on LLVM's raw_ostream.
             let availableBufferSize = self.availableBufferSize
@@ -295,8 +294,7 @@ public func <<< (stream: OutputByteStream, value: ArraySlice<UInt8>) -> OutputBy
 
 @discardableResult
 public func <<< <C: Collection>(stream: OutputByteStream, value: C) -> OutputByteStream where
-    C.Iterator.Element == UInt8,
-    C.SubSequence: Collection {
+    C.Iterator.Element == UInt8 {
     stream.write(collection: value)
     return stream
 }