Fixes #3091. Review by community.

2 files changed, 8 insertions, 4 deletions

diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala
index 9d65e2c224..5ef7b5205a 100644
--- a/src/library/scala/collection/TraversableLike.scala
+++ b/src/library/scala/collection/TraversableLike.scala
@@ -645,10 +645,14 @@ self =>
    * @return        collection with intermediate results
    */
   def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
-    val (_, b) = foldRight(z, bf(repr) += z) { (x, acc) =>
-      val next = op(x, acc._1)
-      (next, acc._2 += next)
+    var lst = List(z)
+    foldRight(z) { (x, acc) =>
+      val next = op(x, acc)
+      lst ::= next
+      next
     }
+    val b = bf(repr)
+    for (elem <- lst) b += elem
     b.result
   }
 
diff --git a/test/files/pos/scan.scala b/test/files/pos/scan.scala
index 98361b9167..a88abe63d2 100644
--- a/test/files/pos/scan.scala
+++ b/test/files/pos/scan.scala
@@ -8,7 +8,7 @@ object Test {
     val lst = List(1, 2, 3, 4, 5)
 
     assert(lst.scanLeft(0)(_ + _) == List(0, 1, 3, 6, 10, 15))
-    assert(lst.scanRight(0)(_ + _) == List(0, 5, 9, 12, 14, 15))
+    assert(lst.scanRight(0)(_ + _) == List(15, 14, 12, 9, 5, 0))
 
     val emp = List[Int]()
     assert(emp.scanLeft(0)(_ + _) == List(0))