Add test file

Author: odersky

tests/pos/reference/implicit-byname-parameters.scala

@@ -0,0 +1,22 @@
+object Test {
+
+trait Codec[T] {
+  def write(x: T): Unit
+}
+
+implicit def intCodec: Codec[Int] = ???
+
+implicit def optionCodec[T]
+    (implicit ev: => Codec[T]): Codec[Option[T]] =
+  new {
+    def write(xo: Option[T]) = xo match {
+      case Some(x) => ev.write(x)
+      case None =>
+    }
+  }
+
+val s = implicitly[Codec[Option[Int]]]
+
+s.write(Some(33))
+s.write(None)
+}