Another test - magnet pattern

Author: odersky

tests/run/magnet.scala

@@ -0,0 +1,46 @@
+import scala.concurrent.Future
+object magnets {
+
+  enum StatusCode {
+    case OK, Error
+  }
+
+  trait Marshaller[T] { def marshall(t: T): String }
+  class HttpResponse
+
+  sealed trait CompletionMagnet {
+    type Result
+    def apply(): Result
+  }
+
+  object CompletionMagnet {
+
+    extend (StatusCode, type T: Marshaller) implements CompletionMagnet {
+      type Result = String
+      def apply(): String = implicitly[Marshaller[T]].marshall(this._2)
+    }
+
+    extend Future[HttpResponse] implements CompletionMagnet {
+      type Result = Int
+      def apply(): Int = 1
+    }
+
+    extend Future[StatusCode] implements CompletionMagnet {
+      type Result = Int
+      def apply(): Int = 2
+    }
+  }
+
+  implicit object stringMarshaller extends Marshaller[String] {
+    def marshall(x: String): String = x
+  }
+
+  def complete(magnet: CompletionMagnet): magnet.Result = magnet()
+}
+
+object Test extends App {
+  import magnets._
+
+  assert(complete((StatusCode.OK, "hello")) == "hello")
+
+}