close #3667.

scala> def ser(o: AnyRef) = new java.io.ObjectOutputStream(new java.io.ByteArrayOutputStream()).writeObject(o)
ser: (o: AnyRef)Unit

scala> @serializable class Outer {
     |   case class Inner(x: Int)
     | }
defined class Outer

scala> val o = new Outer
o: Outer = Outer@34469729

scala> ser(new o.Inner(1))

scala> o.Inner // initialize the Inner$module field of o

res1: o.Inner.type = Inner

scala> ser(new o.Inner(1))
java.io.NotSerializableException: Outer$Inner$

review by extempore.

1 files changed, 3 insertions, 0 deletions

diff --git a/test/files/run/t3667.check b/test/files/run/t3667.check
new file mode 100644
index 0000000000..01e79c32a8
--- /dev/null
+++ b/test/files/run/t3667.check
@@ -0,0 +1,3 @@
+1
+2
+3