Deprecated the @serializable annotation, introd...

Deprecated the @serializable annotation, introduce a new trait
"scala.Serializable" which has to be extended instead (cross-platform).

Known issues:
 - Companion objects of serializable classes (including case classes) are automatically made serializable. However, they don't extend "Serializable" statically because of the known difficulty (should be done before typing, but hard).
 - Writing "case class C() extends Serializable" gives "error: trait Serializable is inherited twice"
 - Functions are serializable, but don't extend Serializable dynamically (could be fixed by making FunctionN Serializable - shouldn't we?)

Note that @SerialVersionUID continues to be an annotation; it generates
a static field, which is not possible otherwise in scala.

Review by dragos, extempore.

Question to dragos: in JavaPlatform.isMaybeBoxed, why is there a test
for "JavaSerializableClass"? Is that correct?

1 files changed, 31 insertions, 0 deletions

diff --git a/test/files/run/t3667.scala b/test/files/run/t3667.scala
index 7bd0b4ec5e..f30d57ce3a 100644
--- a/test/files/run/t3667.scala
+++ b/test/files/run/t3667.scala
@@ -3,6 +3,9 @@ object Test {
     val o1 = new Outer1
     val o2 = new Outer2
     val o3 = new Outer3
+    val o4 = new Outer4
+    val o5 = new Outer5
+    val o6 = new Outer6
 
     println(1)
     ser(new o1.Inner(1))
@@ -19,6 +22,21 @@ object Test {
     o3.Inner
     ser(new o3.Inner(1))
 
+    println(4)
+    ser(new o4.Inner(1))
+    o4.Inner
+    ser(new o4.Inner(1))
+
+    println(2)
+    ser(new o5.Inner(1))
+    o5.Inner
+    ser(new o5.Inner(1))
+
+    println(3)
+    ser(new o6.Inner(1))
+    o6.Inner
+    ser(new o6.Inner(1))
+
     foo
   }
 
@@ -51,3 +69,16 @@ class Outer2 {
 class Outer3 {
   case class Inner(x: Int)
 }
+
+
+class Outer4 extends Serializable {
+  class Inner(x: Int = 1) extends Serializable
+}
+
+class Outer5 extends Serializable {
+  case class Inner(x: Int = 1)
+}
+
+class Outer6 extends Serializable {
+  case class Inner(x: Int)
+}