Fix ShowTests: Add Show[Some[T]]

Author: OlivierBlanvillain

library/src/dotty/Show.scala

@@ -16,7 +16,7 @@ object Show extends LowPrioShow {
     * any `T`, we default to `T#toString`.
     */
   implicit class ShowValue[V](val v: V) extends AnyVal {
-    def show(implicit ev: Show[V] = defaultShow): String =
+    def show(implicit ev: Show[V]): String =
       ev.show(v)
   }
 
@@ -71,6 +71,10 @@ object Show extends LowPrioShow {
     }
   }
 
+  implicit def showSome[T](implicit st: Show[T]): Show[Some[T]] = new Show[Some[T]] {
+    def show(ot: Some[T]): String = "Some("+ st.show(ot.get) + ")"
+  }
+
   implicit def showMap[K,V](implicit sk: Show[K], sv: Show[V]): Show[Map[K,V]] = new Show[Map[K,V]] {
     def show(m: Map[K, V]) =
       "Map(" + m.map { case (k, v) => sk.show(k) + " -> " + sv.show(v) } .mkString (", ") + ")"

library/test/dotty/ShowTests.scala

@@ -62,14 +62,13 @@ class ShowTests {
 
   @Test def withoutShow = {
     case class Car(model: String, manufacturer: String, year: Int)
-
     assertEquals("Car(Mustang,Ford,1967)", Car("Mustang", "Ford", 1967).show)
     assertEquals("Map()", Map[Nothing, Nothing]().show)
+    assertEquals("List()", List().show)
   }
 
   @Test def partialShow = {
     case object Foo
-
     assertEquals("Map(Foo -> \"Hello\")", Map(Foo -> "Hello").show)
   }
 }