Add back implicit signatures to hk-infer.scala test

Author: smarter

tests/pos-scala2/hk-infer.scala

@@ -20,7 +20,7 @@ object ShouldWorkHK {
     def underlying = xs
     def BOOP(ys: Seq[M[_]]) = new Booper(xs ++ ys)
   }
-  implicit def mkBoop[M[_]](xs: Seq[M[_]]) = new Booper(xs)
+  implicit def mkBoop[M[_]](xs: Seq[M[_]]): ShouldWorkHK.Booper[M] = new Booper(xs)
 
   def f1 = x BOOP y BOOP x1 BOOP x2
 }
@@ -30,7 +30,7 @@ object DoesWorkHK {
     def underlying = xs
     def BOOP(ys: Seq[M[_]]) = new Booper[M](xs ++ ys)
   }
-  implicit def mkBoop[M[_]](xs: Seq[M[_]]) = new Booper[M](xs)
+  implicit def mkBoop[M[_]](xs: Seq[M[_]]): DoesWorkHK.Booper[M] = new Booper[M](xs)
 
   def f1 = x BOOP y BOOP x1 BOOP x2
 }