1 files changed, 62 insertions, 0 deletions
diff --git a/test/files/run/t6690.scala b/test/files/run/t6690.scala
new file mode 100644
index 0000000000..43ede967a0
--- /dev/null
+++ b/test/files/run/t6690.scala
@@ -0,0 +1,62 @@
+import scala.collection.mutable
+
+object Test extends App {
+  def last0(ml: mutable.MutableList[Int]) =
+    ml.asInstanceOf[{def last0: mutable.LinkedList[Int]}].last0
+
+  def first0(ml: mutable.MutableList[Int]) =
+    ml.asInstanceOf[{def first0: mutable.LinkedList[Int]}].first0
+
+  val f = mutable.Queue[Int]()
+  def check(desc: String) {
+    assert(f.length == 0, s"$desc: non empty: $f")
+    assert(last0(f).isEmpty, s"$desc: last0 leak: ${last0(f)}")
+    assert(first0(f).isEmpty, s"$desc: first0 leak: ${last0(f)}")
+  }
+
+  f.enqueue(1)
+  f.dequeue()
+  check("dequeue 1")
+
+  f.enqueue(1)
+  f.enqueue(2)
+  f.dequeue()
+  assert(last0(f).toList == List(2), last0(f))
+  f.dequeue()
+  check("dequeue 2")
+
+  f.enqueue(1)
+  f.dequeueAll(_ => false)
+  f.dequeueAll(_ => true)
+  check("dequeueAll")
+
+  f.enqueue(1)
+  f.dequeueFirst(_ => true)
+  check("dequeueFirst")
+
+  {
+    f.enqueue(1)
+    val tail = f.tail
+    assert(last0(tail).isEmpty, last0(tail))
+    assert(first0(tail).isEmpty, first0(tail))
+  }
+
+  {
+    val ml = mutable.MutableList[Int]()
+    1 +=: ml
+    val tail = ml.tail
+    assert(last0(tail).isEmpty, last0(tail))
+    assert(first0(tail).isEmpty, first0(tail))
+  }
+
+  {
+    val ml = mutable.MutableList[Int]()
+    1 +=: ml
+    ml += 2
+    val tail = ml.tail
+    assert(last0(tail).toList == List(2), last0(tail))
+    assert(first0(tail) == last0(tail).toList, first0(tail))
+    assert(last0(tail.tail).toList == Nil, last0(tail.tail).toList)
+    assert(first0(tail.tail) == Nil, first0(tail.tail))
+  }
+}