Fix serialization of partial function literals

Author: allanrenucci

compiler/src/dotty/tools/dotc/transform/ExpandSAMs.scala

@@ -111,8 +111,8 @@ class ExpandSAMs extends MiniPhase {
         val isDefinedAtDef = transformFollowingDeep(DefDef(isDefinedAtFn, isDefinedAtRhs(_)))
         val applyOrElseDef = transformFollowingDeep(DefDef(applyOrElseFn, applyOrElseRhs(_)))
 
-        val parent = defn.AbstractPartialFunctionType.appliedTo(tpe.argInfos)
-        val anonCls = AnonClass(parent :: Nil, List(isDefinedAtFn, applyOrElseFn), List(nme.isDefinedAt, nme.applyOrElse))
+        val parents = List(defn.AbstractPartialFunctionType.appliedTo(tpe.argInfos), defn.SerializableType)
+        val anonCls = AnonClass(parents, List(isDefinedAtFn, applyOrElseFn), List(nme.isDefinedAt, nme.applyOrElse))
         cpy.Block(tree)(List(isDefinedAtDef, applyOrElseDef), anonCls)
 
       case _ =>

tests/run/serialize.scala

@@ -0,0 +1,16 @@
+object Test {
+  def serializeDeserialize[T <: AnyRef](obj: T): T = {
+    import java.io._
+    val buffer = new ByteArrayOutputStream
+    val out = new ObjectOutputStream(buffer)
+    out.writeObject(obj)
+    val in = new ObjectInputStream(new ByteArrayInputStream(buffer.toByteArray))
+    in.readObject.asInstanceOf[T]
+  }
+
+  def main(args: Array[String]): Unit = {
+    val x: PartialFunction[Int, Int] = { case x => x + 1 }
+    val adder = serializeDeserialize(x)
+    assert(adder(1) == 2)
+  }
+}