SI-7445 ListMap.tail is returning wrong result

Reverted the commit that introduced the bug, and modified HashMap to no
longer assume that tail is O(1).

Review by @Ichoran, @soc

2 files changed, 6 insertions, 7 deletions

diff --git a/test/files/run/t6261.scala b/test/files/run/t6261.scala
index b4463256c9..bf6d640de3 100644
--- a/test/files/run/t6261.scala
+++ b/test/files/run/t6261.scala
@@ -2,12 +2,6 @@ import scala.collection.immutable._
 
 object Test extends App {
 
-  def test0() {
-    val m=ListMap(1->2,3->4)
-    if(m.tail ne m.tail)
-      println("ListMap.tail uses a builder, so it is not O(1)")
-  }
-
   def test1() {
     // test that a HashTrieMap with one leaf element is not created!
     val x = HashMap.empty + (1->1) + (2->2)
@@ -92,7 +86,6 @@ object Test extends App {
     // StructureTests.printStructure(z)
     require(z.size == 2 && z.contains(a._1) && z.contains(c._1))
   }
-  test0()
   test1()
   test2()
   test3()
diff --git a/test/files/run/t7445.scala b/test/files/run/t7445.scala
new file mode 100644
index 0000000000..e4ffeb8e1a
--- /dev/null
+++ b/test/files/run/t7445.scala
@@ -0,0 +1,6 @@
+import scala.collection.immutable.ListMap
+
+object Test extends App {
+	val a = ListMap(1 -> 1, 2 -> 2, 3 -> 3, 4 -> 4, 5 -> 5);
+	require(a.tail == ListMap(2 -> 2, 3 -> 3, 4 -> 4, 5 -> 5));
+}