Sorted out some buck passing among TraversableO...

Sorted out some buck passing among TraversableOnce and its subclasses
about how exactly one creates a Stream. This is a continuation of r22115
for #3516. Review by prokopec.

3 files changed, 8 insertions, 11 deletions

diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala
index 88a6379da2..71e9b0f0e9 100644
--- a/src/library/scala/collection/TraversableLike.scala
+++ b/src/library/scala/collection/TraversableLike.scala
@@ -694,13 +694,8 @@ trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with Traversable
   }
 
   def toTraversable: Traversable[A] = thisCollection
-  def toIterator: Iterator[A] = toIterable.iterator
-
-  /** Converts this $coll to a stream.
-   *  $willNotTerminateInf
-   *  @return a stream containing all elements of this $coll.
-   */
-  def toStream: Stream[A] = toIterable.toStream
+  def toIterator: Iterator[A] = toStream.iterator
+  def toStream: Stream[A] = Stream.empty[A] ++ thisCollection
 
   /** Converts this $coll to a string.
    *  @return   a string representation of this collection. By default this
diff --git a/src/library/scala/collection/TraversableOnce.scala b/src/library/scala/collection/TraversableOnce.scala
index 1797ff39db..5d09b6d2c6 100644
--- a/src/library/scala/collection/TraversableOnce.scala
+++ b/src/library/scala/collection/TraversableOnce.scala
@@ -398,17 +398,20 @@ trait TraversableOnce[+A] {
    */
   def toList: List[A] = new ListBuffer[A] ++= self toList
 
-  /** Converts this $coll to an iterable collection.
+  /** Converts this $coll to an iterable collection.  Note that
+   *  the choice of target Iterable must be lazy as this TraversableOnce
+   *  may be lazy and unevaluated.
+   *
    *  $willNotTerminateInf
    *  @return an `Iterable` containing all elements of this $coll.
    */
   def toIterable: Iterable[A] = toStream
 
-  /** Converts this $coll to a sequence.
+  /** Converts this $coll to a sequence.  As with toIterable, it must be lazy.
    *  $willNotTerminateInf
    *  @return a sequence containing all elements of this $coll.
    */
-  def toSeq: Seq[A] = toList
+  def toSeq: Seq[A] = toStream
 
   /** Converts this $coll to an indexed sequence.
    *  $willNotTerminateInf
diff --git a/src/library/scala/collection/immutable/List.scala b/src/library/scala/collection/immutable/List.scala
index 26d5948f2c..7785d73175 100644
--- a/src/library/scala/collection/immutable/List.scala
+++ b/src/library/scala/collection/immutable/List.scala
@@ -244,7 +244,6 @@ sealed abstract class List[+A] extends LinearSeq[A]
     if (isEmpty) Stream.Empty
     else new Stream.Cons(head, tail.toStream)
 
-
   /** Like <code>span</code> but with the predicate inverted.
    */
   @deprecated("use `span { x => !p(x) }` instead")