Made sliding/grouped throw an exception when re...

Made sliding/grouped throw an exception when read past the end. Closes
#3017.

2 files changed, 15 insertions, 0 deletions

diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 4e8a409efd..2cee708869 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -937,6 +937,8 @@ trait Iterator[+A] { self =>
       if (!filled)
         fill()
 
+      if (!filled)
+        throw new NoSuchElementException("next on empty iterator")
       filled = false
       buffer.toList
     }
diff --git a/test/files/run/unittest_iterator.scala b/test/files/run/unittest_iterator.scala
index 93aaa4a834..28a548160f 100644
--- a/test/files/run/unittest_iterator.scala
+++ b/test/files/run/unittest_iterator.scala
@@ -33,5 +33,18 @@ object Test
     assertThat(1, (1 to 8).toList) { it.sliding(8, 8) withPartial false }
     assertThat(2, List(9, 10, -1, -1, -1)) { it.sliding(5, 8) withPadding -1 }
     assertThat(1, (1 to 5).toList) { it.sliding(5, 8) withPartial false }
+
+    // make sure it throws past th end
+    val thrown = try {
+      val it = List(1,2,3).sliding(2)
+      it.next
+      it.next
+      it.next
+      false
+    }
+    catch {
+      case _: NoSuchElementException => true
+    }
+    assert(thrown)
   }
 }