Rooting out mismatched zips.

I added local logging to zip and zipped and listened for who was
dropping things on the floor. Everything in this commit stems from that.
Sometimes the fix was uncertain and I sprinkled some logging. If you've
been hanging back with lots of internals knowledge waiting for the right
commit to review, this would be a good one. But since knowledgeable
people are hard to find, I'll go with review by moors.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 3c7aff5b60..a56055e210 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -346,4 +346,18 @@ object ScalaRunTime {
 
     nl + s + "\n"
   }
+  private[scala] def checkZip(what: String, coll1: TraversableOnce[_], coll2: TraversableOnce[_]) {
+    if (sys.props contains "scala.debug.zip") {
+      val xs = coll1.toIndexedSeq
+      val ys = coll2.toIndexedSeq
+      if (xs.length != ys.length) {
+        Console.err.println(
+          "Mismatched zip in " + what + ":\n" +
+          "  this: " + xs.mkString(", ") + "\n" +
+          "  that: " + ys.mkString(", ")
+        )
+        (new Exception).getStackTrace.drop(2).take(10).foreach(println)
+      }
+    }
+  }
 }