Make case classes Serializable

Author: OlivierBlanvillain

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -513,7 +513,7 @@ object desugar {
     if (isEnumCase && parents.isEmpty)
       parents1 = enumClassTypeRef :: Nil
     if (isCaseClass | isCaseObject)
-      parents1 = parents1 :+ scalaDot(str.Product.toTypeName)
+      parents1 = parents1 :+ scalaDot(str.Product.toTypeName) :+ scalaDot(nme.Serializable.toTypeName)
     if (isEnum)
       parents1 = parents1 :+ ref(defn.EnumType)
 

tests/run/case-class-serializable.scala

@@ -0,0 +1,6 @@
+case class Foo()
+
+object Test {
+  def main(args: Array[String]): Unit =
+    assert(Foo().isInstanceOf[Serializable])
+}