2 files changed, 36 insertions, 0 deletions
diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 5238a66f70..e2252d5aab 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -429,6 +429,17 @@ trait Iterator[+A] extends TraversableOnce[A] {
     }
   }
 
+  def scanLeft[B](z: B)(op: (B, A) => B): Iterator[B] = new Iterator[B] {
+    var hasNext = true
+    var elem = z
+    def next() = if (hasNext) {
+      val res = elem
+      if (self.hasNext) elem = op(elem, self.next())
+      else hasNext = false
+      res
+    } else Iterator.empty.next()
+  }
+
   /** Takes longest prefix of values produced by this iterator that satisfy a predicate.
    *  @param   p  The predicate used to test elements.
    *  @return  An iterator returning the values produced by this iterator, until
diff --git a/test/files/run/t4054.scala b/test/files/run/t4054.scala
new file mode 100644
index 0000000000..83a58ef97c
--- /dev/null
+++ b/test/files/run/t4054.scala
@@ -0,0 +1,25 @@
+
+
+
+
+
+
+
+
+object Test {
+  def main(args: Array[String]) {
+    val it = Iterator.from(1).map(n => n * n).scanLeft(0)(_+_)
+
+    assert(it.next == 0)
+    assert(it.next == 1)
+    assert(it.next == 5)
+    assert(it.next == 14)
+    assert(it.next == 30)
+    assert(it.next == 55)
+    assert(it.next == 91)
+    assert(it.next == 140)
+    assert(it.next == 204)
+    assert(it.next == 285)
+    assert(it.next == 385)
+  }
+}