Some collections overrides for more efficient t...

Some collections overrides for more efficient toSeq and toBuffer where
possible. Closes #2972, review by malayeri.

4 files changed, 25 insertions, 7 deletions

diff --git a/src/library/scala/collection/IndexedSeqLike.scala b/src/library/scala/collection/IndexedSeqLike.scala
index a2044ae7ba..92047288fb 100644
--- a/src/library/scala/collection/IndexedSeqLike.scala
+++ b/src/library/scala/collection/IndexedSeqLike.scala
@@ -81,6 +81,15 @@ trait IndexedSeqLike[+A, +Repr] extends SeqLike[A, Repr] { self =>
 
   override /*IterableLike*/
   def iterator: Iterator[A] = new Elements(0, length)
+
+  /** Overridden for efficiency */
+  override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
+    val result = new mutable.ArrayBuffer[A1](size)
+    copyToBuffer(result)
+    result
+  }
+
+
 /*
   override /*SeqLike*/
   def view = new IndexedSeqView[A, Repr] {
diff --git a/src/library/scala/collection/IterableLike.scala b/src/library/scala/collection/IterableLike.scala
index 97787c5867..72dabbf740 100644
--- a/src/library/scala/collection/IterableLike.scala
+++ b/src/library/scala/collection/IterableLike.scala
@@ -353,13 +353,6 @@ self =>
 
   override /*TraversableLike*/ def toStream: Stream[A] = iterator.toStream
 
-  /** Converts this $coll to a sequence.
-   *
-   *  $willNotTerminateInf
-   *  @return a sequence containing all the elements of this $coll.
-   */
-  override /*TraversableOnce*/ def toSeq: Seq[A] = toList
-
   /** Method called from equality methods, so that user-defined subclasses can
    *  refuse to be equal to other collections of the same kind.
    *  @param   that   The object with which this $coll should be compared
diff --git a/src/library/scala/collection/MapLike.scala b/src/library/scala/collection/MapLike.scala
index ae1d2cc6e8..df3e3c62ff 100644
--- a/src/library/scala/collection/MapLike.scala
+++ b/src/library/scala/collection/MapLike.scala
@@ -306,6 +306,14 @@ self =>
     res
   }
 
+  /** Overridden for efficiency. */
+  override def toSeq: Seq[(A, B)] = toBuffer[(A, B)]
+  override def toBuffer[C >: (A, B)]: mutable.Buffer[C] = {
+    val result = new mutable.ArrayBuffer[C](size)
+    copyToBuffer(result)
+    result
+  }
+
   /** Appends all bindings of this map to a string builder using start, end, and separator strings.
    *  The written text begins with the string `start` and ends with the string
    *  `end`. Inside, the string representations of all bindings of this map
diff --git a/src/library/scala/collection/SetLike.scala b/src/library/scala/collection/SetLike.scala
index 5a3b9734ed..8df0fb9c9d 100644
--- a/src/library/scala/collection/SetLike.scala
+++ b/src/library/scala/collection/SetLike.scala
@@ -73,6 +73,14 @@ self =>
    */
   override protected[this] def newBuilder: Builder[A, This] = new AddingBuilder[A, This](empty)
 
+  /** Overridden for efficiency. */
+  override def toSeq: Seq[A] = toBuffer[A]
+  override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
+    val result = new mutable.ArrayBuffer[A1](size)
+    copyToBuffer(result)
+    result
+  }
+
   // note: this is only overridden here to add the migration annotation,
   // which I hope to turn into an Xlint style warning as the migration aspect
   // is not central to its importance.