Closes #3157 by overriding +: in List.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/library/scala/collection/immutable/List.scala b/src/library/scala/collection/immutable/List.scala
index 70b0649264..6e4c1ffe37 100644
--- a/src/library/scala/collection/immutable/List.scala
+++ b/src/library/scala/collection/immutable/List.scala
@@ -133,7 +133,7 @@ sealed abstract class List[+A] extends LinearSeq[A]
     loop(this)
   }
 
-  // Overridden methods from IterableLike or overloaded variants of such methods
+  // Overridden methods from IterableLike and SeqLike or overloaded variants of such methods
 
   override def ++[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[List[A], B, That]): That = {
     val b = bf(this)
@@ -144,6 +144,11 @@ sealed abstract class List[+A] extends LinearSeq[A]
   override def ++[B >: A, That](that: Iterator[B])(implicit bf: CanBuildFrom[List[A], B, That]): That =
     this ++ that.toList
 
+  override def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[List[A], B, That]): That = bf match {
+    case _: List.GenericCanBuildFrom[_] => (elem :: this).asInstanceOf[That]
+    case _ => super.+:(elem)(bf)
+  }
+
   override def toList: List[A] = this
 
   override def take(n: Int): List[A] = {