trait Test
{
  def foo(a : Array[Int]) = {
    a.foreach { i => println(i) }
  }
}

class Test$$$$anonfun$$foo$$1 defines non-transient non-serializable instance

Non-transient non-serializable instance field in serializable class

This Serializable class defines a non-primitive instance field which is
neither transient, Serializable, or java.lang.Object, and does not appear
to implement the Externalizable interface or the readObject() and
writeObject() methods.  Objects of this class will not be deserialized
correctly if a non-Serializable object is stored in this field.