Made mkString work correctly on views.

about how to obtain a String and how not to. Closes #4297, no review.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/library/scala/collection/TraversableViewLike.scala b/src/library/scala/collection/TraversableViewLike.scala
index 0c01cb893e..8d94a7f381 100644
--- a/src/library/scala/collection/TraversableViewLike.scala
+++ b/src/library/scala/collection/TraversableViewLike.scala
@@ -200,9 +200,19 @@ self =>
     buf.result
   }
 
+  // Have to overload all three to work around #4299.  The overload
+  // is because mkString should force a view but toString should not.
+  override def mkString: String = mkString("")
+  override def mkString(sep: String): String = mkString("", sep, "")
+  override def mkString(start: String, sep: String, end: String): String = {
+    thisSeq.addString(new StringBuilder(), start, sep, end).toString
+  }
+
   override def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder =
     b append start append "..." append end
 
+  override def toString = stringPrefix+"(...)"
+
   override def filter(p: A => Boolean): This = newFiltered(p).asInstanceOf[This]
   override def withFilter(p: A => Boolean): This = newFiltered(p).asInstanceOf[This]
   override def partition(p: A => Boolean): (This, This) = (filter(p), filter(!p(_)))