src/Pure/library.scala

--- a/src/Pure/library.scala	Tue Sep 20 22:29:51 2016 +0200
+++ b/src/Pure/library.scala	Tue Sep 20 22:31:50 2016 +0200
@@ -19,6 +19,8 @@
 
   def using[A <: { def close() }, B](x: A)(f: A => B): B =
   {
+    import scala.language.reflectiveCalls
+
     try { f(x) }
     finally { if (x != null) x.close() }
   }