From 1697132ec8e0df21c98a1420d186c58e02af69ab Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Fri, 30 Nov 2012 05:19:07 +0100
Subject: Eliminate allocations in Growable.

---
 src/library/scala/collection/generic/Growable.scala   | 17 +++++++++++++++--
 src/library/scala/collection/mutable/ListBuffer.scala | 15 ---------------
 2 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/library/scala/collection/generic/Growable.scala b/src/library/scala/collection/generic/Growable.scala
index cb75212e3d..52a0d32de1 100644
--- a/src/library/scala/collection/generic/Growable.scala
+++ b/src/library/scala/collection/generic/Growable.scala
@@ -6,10 +6,11 @@
 **                          |/                                          **
 \*                                                                      */
 
-
 package scala.collection
 package generic
 
+import scala.annotation.tailrec
+
 /** This trait forms part of collections that can be augmented
  *  using a `+=` operator and that can be cleared of all elements using
  *  a `clear` method.
@@ -45,7 +46,19 @@ trait Growable[-A] extends Clearable {
    *  @param xs   the TraversableOnce producing the elements to $add.
    *  @return  the $coll itself.
    */
-  def ++=(xs: TraversableOnce[A]): this.type = { xs.seq foreach += ; this }
+  def ++=(xs: TraversableOnce[A]): this.type = {
+    @tailrec def loop(xs: collection.LinearSeq[A]) {
+      if (xs.nonEmpty) {
+        this += xs.head
+        loop(xs.tail)
+      }
+    }
+    xs.seq match {
+      case xs: collection.LinearSeq[_] => loop(xs)
+      case xs                          => xs foreach +=
+    }
+    this
+  }
 
   /** Clears the $coll's contents. After this operation, the
    *  $coll is empty.
diff --git a/src/library/scala/collection/mutable/ListBuffer.scala b/src/library/scala/collection/mutable/ListBuffer.scala
index e059f31929..97d469bca2 100644
--- a/src/library/scala/collection/mutable/ListBuffer.scala
+++ b/src/library/scala/collection/mutable/ListBuffer.scala
@@ -6,12 +6,9 @@
 **                          |/                                          **
 \*                                                                      */
 
-
-
 package scala.collection
 package mutable
 
-import scala.annotation.tailrec
 import generic._
 import immutable.{List, Nil, ::}
 import java.io._
@@ -179,20 +176,8 @@ final class ListBuffer[A]
     this
   }
 
-  private def ++=(elems: collection.LinearSeq[A]): this.type = {
-    @tailrec def loop(xs: collection.LinearSeq[A]) {
-      if (xs.nonEmpty) {
-        this += xs.head
-        loop(xs.tail)
-      }
-    }
-    loop(elems)
-    this
-  }
-
   override def ++=(xs: TraversableOnce[A]): this.type = xs match {
     case x: AnyRef if x eq this      => this ++= (this take size)
-    case xs: collection.LinearSeq[_] => this ++= xs
     case _                           => super.++=(xs)
 
   }
-- 
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