TreeSet contains method null point exception

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Run the following under 2.11.0. It throws null point exception as well for 2.10.4 and 2.9.3 although the implementation has been changed.

Welcome to Scala version 2.11.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_60).
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scala> val set2 = new scala.collection.immutable.TreeSet[String]()
set2: scala.collection.immutable.TreeSet[String] = TreeSet()

scala> set2 + "A" + "B"
res0: scala.collection.immutable.TreeSet[String] = TreeSet(A, B)

scala> res0.contains(null)
java.lang.NullPointerException
  at scala.math.Ordering$StringOrdering$class.compare(Ordering.scala:327)
  at scala.math.Ordering$String$.compare(Ordering.scala:329)
  at scala.math.Ordering$String$.compare(Ordering.scala:329)
  at scala.collection.immutable.RedBlackTree$.lookup(RedBlackTree.scala:40)
  at scala.collection.immutable.RedBlackTree$.contains(RedBlackTree.scala:32)
  at scala.collection.immutable.TreeSet.contains(TreeSet.scala:144)
  ... 40 elided

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Imported From: https://issues.scala-lang.org/browse/SI-9024?orig=1 Reporter: Jiezhen Yi (Jiezhen)

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@kanielc said (edited on Dec 5, 2014 6:06:42 AM UTC): Judging by the spec of the Java TreeSet, this seems consistent. With natural ordering, asking for null should throw a NPE. You can provide a custom null aware Ordering.

val set2 = new scala.collection.immutable.TreeSetString

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Jiezhen Yi (Jiezhen) said: Mark as won't fix.