SI-9497 Fix SetLike#clear() default implementation

When dealing with mutable collections, it is not safe to assume iterators will remain consistent when the collection is modified mid-traversal. The bug reported in SI-9497 is very similar to SI-7269, "ConcurrentModificationException when filtering converted Java HashMap". Then, only the `retain` method was fixed. This commit fixes `clear`, which had the same problem.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/library/scala/collection/mutable/SetLike.scala b/src/library/scala/collection/mutable/SetLike.scala
index 81a71adc91..01075a2633 100644
--- a/src/library/scala/collection/mutable/SetLike.scala
+++ b/src/library/scala/collection/mutable/SetLike.scala
@@ -129,7 +129,9 @@ trait SetLike[A, +This <: SetLike[A, This] with Set[A]]
   /** Removes all elements from the set. After this operation is completed,
    *  the set will be empty.
    */
-  def clear() { foreach(-=) }
+  def clear(): Unit =
+    for (elem <- this.toList)
+      this -= elem
 
   override def clone(): This = empty ++= repr.seq