Fixed bug in transpose, closes #3397, no review.

2 files changed, 8 insertions, 1 deletions

diff --git a/src/library/scala/collection/generic/GenericTraversableTemplate.scala b/src/library/scala/collection/generic/GenericTraversableTemplate.scala
index ecbfa8c20c..263e1902a0 100644
--- a/src/library/scala/collection/generic/GenericTraversableTemplate.scala
+++ b/src/library/scala/collection/generic/GenericTraversableTemplate.scala
@@ -108,7 +108,7 @@ trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBui
    *          the ''n''th column of this $coll.
    */
   def transpose[B](implicit asTraversable: A => /*<:<!!!*/ Traversable[B]): CC[CC[B] @uncheckedVariance] = {
-    val bs: IndexedSeq[Builder[B, CC[B]]] = asTraversable(head).map(_ => genericBuilder[B]).toIndexedSeq
+    val bs: IndexedSeq[Builder[B, CC[B]]] = IndexedSeq.fill(asTraversable(head).size)(genericBuilder[B])
     for (xs <- this) {
       var i = 0
       for (x <- asTraversable(xs)) {
diff --git a/test/files/run/bug3397.scala b/test/files/run/bug3397.scala
new file mode 100644
index 0000000000..2c8cbed3ab
--- /dev/null
+++ b/test/files/run/bug3397.scala
@@ -0,0 +1,7 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    val x = Seq(Set(1,2,3),Set(4,5,6),Set(7,8,9)).transpose
+
+    ()
+  }
+}