SI-6415, overly eager evaluation in Stream.

The lengthCompare method in LinearSeqOptimized was looking one
step further than it needed to in order to give the correct
result, which was creating some unwanted side effects related to
Streams.

1 files changed, 13 insertions, 7 deletions

diff --git a/src/library/scala/collection/LinearSeqOptimized.scala b/src/library/scala/collection/LinearSeqOptimized.scala
index 0f0a405a85..48b0b5469e 100755
--- a/src/library/scala/collection/LinearSeqOptimized.scala
+++ b/src/library/scala/collection/LinearSeqOptimized.scala
@@ -247,14 +247,20 @@ trait LinearSeqOptimized[+A, +Repr <: LinearSeqOptimized[A, Repr]] extends Linea
   }
 
   override /*SeqLike*/
-  def lengthCompare(len: Int): Int =  {
-    var i = 0
-    var these = self
-    while (!these.isEmpty && i <= len) {
-      i += 1
-      these = these.tail
+  def lengthCompare(len: Int): Int = {
+    // TODO: Remove this method when incrementing a major revision
+    // This method is the same as in SeqLike, no need to redefine it
+    if (len < 0) 1
+    else {
+      var i = 0
+      val it = iterator
+      while (it.hasNext) {
+        if (i == len) return if (it.hasNext) 1 else 0
+        it.next()
+        i += 1
+      }
+      i - len
     }
-    i - len
   }
 
   override /*SeqLike*/