Equals function doesn't work with custom object in spark

Question

I'm haveing trouble, I presume with serialization, in a Spark repl.

I have the following code snippet:

class Foobar (val a: Int, val b: Int) extends Serializable {
  override def equals (other: Any): Boolean =
    other match {
      case that: Foobar =>
        println("Comparison of similar objects")
        this.a == that.a && this.b == that.b
      case _ =>
        println("Comparison of disparate objects")
        false
    }
  override def toString = s"[$a:$b]"
}

If I create two instances, one (foo) on a worker, and one (bar) on the driver:

val foo = sc.parallelize(Seq(1)).map(n => new Foobar(n, n)).collect.apply(0)
val bar = new Foobar(1, 1)

then foo != bar (and spouts "Comparison of disparate objects") - yet

• foo.getClass == bar.getClass
• foo.a == bar.a, and
• foo.b == bar.b

Can anyone explain why this happens?