Does what can probably be done about strange it...

Does what can probably be done about strange iterator exhaustion
behavior. Maybe we should start thinking about iteratees... Closes
#3760, no review.

3 files changed, 31 insertions, 2 deletions

diff --git a/src/library/scala/collection/LinearSeqLike.scala b/src/library/scala/collection/LinearSeqLike.scala
index c2c4996f47..8bf45348db 100644
--- a/src/library/scala/collection/LinearSeqLike.scala
+++ b/src/library/scala/collection/LinearSeqLike.scala
@@ -56,6 +56,14 @@ trait LinearSeqLike[+A, +Repr <: LinearSeqLike[A, Repr]] extends SeqLike[A, Repr
       if (hasNext) {
         val result = these.head; these = these.tail; result
       } else Iterator.empty.next
-    override def toList: List[A] = these.toList
+
+    /** Have to clear these so the iterator is exhausted like
+     *  it would be without the optimization.
+     */
+    override def toList: List[A] = {
+      val xs = these.toList
+      these = newBuilder.result
+      xs
+    }
   }
 }
diff --git a/src/library/scala/collection/immutable/Stream.scala b/src/library/scala/collection/immutable/Stream.scala
index 5339b29e7c..02a17427ef 100644
--- a/src/library/scala/collection/immutable/Stream.scala
+++ b/src/library/scala/collection/immutable/Stream.scala
@@ -262,7 +262,11 @@ self =>
         these = new LazyCell(cur.tail)
         result
       }
-    override def toStream = these.v
+    override def toStream = {
+      val result = these.v
+      these = new LazyCell(Stream.empty)
+      result
+    }
     override def toList   = toStream.toList
   }
 
diff --git a/test/files/run/bug3760.scala b/test/files/run/bug3760.scala
new file mode 100644
index 0000000000..b78406824e
--- /dev/null
+++ b/test/files/run/bug3760.scala
@@ -0,0 +1,17 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    {
+      val it = Iterable(1,2).iterator
+      val xs = it.toList
+
+      assert(it.isEmpty)
+    }
+
+    {
+      val it = Iterator(1, 2)
+      val xs = it.toStream.toList
+
+      assert(it.isEmpty)
+    }
+  }
+}