Fix neg test

Author: odersky

tests/neg/implicitDefs.scala

@@ -7,7 +7,7 @@ object implicitDefs {
 
   implicit val x = 2 // error: type of implicit definition needs to be given explicitly
   implicit def y(x: Int) = 3 // error: result type of implicit definition needs to be given explicitly
-  implicit def z(a: x.type): String = "" // error: implicit conversion may not have a parameter of singleton type
+  implicit def z(a: x.type): String = "" // ok, used to be: implicit conversion may not have a parameter of singleton type
 
   def foo(implicit x: String) = 1