Merge pull request #2866 from retronym/ticket/7269

SI-7269 Rework MapLike#retains to account for desugaring change

2 files changed, 5 insertions, 3 deletions

diff --git a/src/library/scala/collection/mutable/MapLike.scala b/src/library/scala/collection/mutable/MapLike.scala
index a53aa3b76a..42e5a0a4c4 100644
--- a/src/library/scala/collection/mutable/MapLike.scala
+++ b/src/library/scala/collection/mutable/MapLike.scala
@@ -209,8 +209,8 @@ trait MapLike[A, B, +This <: MapLike[A, B, This] with Map[A, B]]
    * @param p  The test predicate
    */
   def retain(p: (A, B) => Boolean): this.type = {
-    for ((k, v) <- this.seq ; if !p(k, v))
-      this -= k
+    for ((k, v) <- this.toList) // SI-7269 toList avoids ConcurrentModificationException
+      if (!p(k, v)) this -= k
 
     this
   }
diff --git a/src/library/scala/collection/mutable/SetLike.scala b/src/library/scala/collection/mutable/SetLike.scala
index 01f87447ae..71da4c89dc 100644
--- a/src/library/scala/collection/mutable/SetLike.scala
+++ b/src/library/scala/collection/mutable/SetLike.scala
@@ -120,7 +120,9 @@ trait SetLike[A, +This <: SetLike[A, This] with Set[A]]
    *             which `p` returns `true` are retained in the set; all others
    *             are removed.
    */
-  def retain(p: A => Boolean): Unit = for (elem <- this.toList) if (!p(elem)) this -= elem
+  def retain(p: A => Boolean): Unit =
+    for (elem <- this.toList) // SI-7269 toList avoids ConcurrentModificationException
+      if (!p(elem)) this -= elem
 
   /** Removes all elements from the set. After this operation is completed,
    *  the set will be empty.