immutable map crashes on stackoverflow (recursive ListMap)

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scala> class Foo{ override def equals(o: Any) = false; override def hashCode = 1}
defined class Foo


scala> var m = Map[Foo, Int]()
m: scala.collection.immutable.Map[Foo,Int] = Map()

scala> for (i <- 1 to 8000) m += (new Foo) -> i
java.lang.StackOverflowError
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable.ListMap$$Node.get(ListMap.scala:148)
        at scala.collection.immutable....

The issue is that ListMap.Node#get is recursive instead of iterative. ListMap is used by HashMapCollision1.

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Imported From: https://issues.scala-lang.org/browse/SI-3989?orig=1
Reporter: Ittay Dror (ittayd)

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@axel22 said:
(In r23534) Fixes #3989, adding test cases for #3989 and #3996.

No review.

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@axel22 said:
(In r23535) Fixes #3989.

No review.