1 files changed, 2 insertions, 6 deletions
diff --git a/src/dotty/tools/dotc/core/pickling/TreePickler.scala b/src/dotty/tools/dotc/core/pickling/TreePickler.scala
index e23efd860..c5e07ffa9 100644
--- a/src/dotty/tools/dotc/core/pickling/TreePickler.scala
+++ b/src/dotty/tools/dotc/core/pickling/TreePickler.scala
@@ -535,12 +535,8 @@ class TreePickler(pickler: TastyPickler) {
       withLength { pickleType(ann.symbol.typeRef); pickleTree(ann.tree) }
     }
 
-    def updateMapWithDeltas[T](mp: collection.mutable.Map[T, Addr]) = {
-      mp.map{
-        case (key, addr) => (key, adjusted(addr))
-      }.foreach(mp += _)
-    }
-
+    def updateMapWithDeltas[T](mp: collection.mutable.Map[T, Addr]) =
+      for (key <- mp.keysIterator.toBuffer[T]) mp(key) = adjusted(mp(key))
 
     trees.foreach(tree => if (!tree.isEmpty) pickleTree(tree))
     assert(forwardSymRefs.isEmpty, i"unresolved symbols: ${forwardSymRefs.keySet.toList}%, %")