Fixes #4298. Review by extempore.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/library/scala/collection/mutable/StringBuilder.scala b/src/library/scala/collection/mutable/StringBuilder.scala
index 73d3778650..0d1c51c42f 100644
--- a/src/library/scala/collection/mutable/StringBuilder.scala
+++ b/src/library/scala/collection/mutable/StringBuilder.scala
@@ -24,17 +24,17 @@ import immutable.StringLike
  */
 @SerialVersionUID(0 - 8525408645367278351L)
 final class StringBuilder(private val underlying: JavaStringBuilder)
-      extends Builder[Char, StringBuilder]
-         with java.lang.CharSequence
+      extends java.lang.CharSequence
          with IndexedSeq[Char]
          with StringLike[StringBuilder]
+         with Builder[Char, String]
          with Serializable {
 
   override protected[this] def thisCollection: StringBuilder = this
   override protected[this] def toCollection(repr: StringBuilder): StringBuilder = repr
 
   /** Creates a string builder buffer as builder for this class */
-  override protected[this] def newBuilder = new StringBuilder
+  override protected[this] def newBuilder = new GrowingBuilder(new StringBuilder)
 
   /** Constructs a string builder initialized with String initValue
    *  and with additional Char capacity initCapacity.
@@ -450,9 +450,9 @@ final class StringBuilder(private val underlying: JavaStringBuilder)
    *
    *  @return  this StringBuilder
    */
-  def result(): StringBuilder = this
+  def result(): String = toString
 }
 
 object StringBuilder {
-  def newBuilder = new StringBuilder mapResult (_.toString)
-}
\ No newline at end of file
+  def newBuilder = new StringBuilder
+}