3 files changed, 67 insertions, 0 deletions
diff --git a/src/library/scala/collection/TraversableViewLike.scala b/src/library/scala/collection/TraversableViewLike.scala
index 36fe6251df..03286fef67 100644
--- a/src/library/scala/collection/TraversableViewLike.scala
+++ b/src/library/scala/collection/TraversableViewLike.scala
@@ -82,6 +82,27 @@ trait TraversableViewLike[+A,
   trait Transformed[+B] extends TraversableView[B, Coll] with super.Transformed[B] {
     def foreach[U](f: B => U): Unit
 
+    // Methods whose standard implementations use "isEmpty" need to be rewritten
+    // for views, else they will end up traversing twice in a situation like:
+    //   xs.view.flatMap(f).headOption
+    override def headOption: Option[B] = {
+      for (x <- this)
+        return Some(x)
+
+      None
+    }
+    override def lastOption: Option[B] = {
+      // (Should be) better than allocating a Some for every element.
+      var empty = true
+      var result: B = null.asInstanceOf[B]
+      for (x <- this) {
+        empty = false
+        result = x
+      }
+      if (empty) None else Some(result)
+    }
+
+    // XXX: As yet not dealt with, tail and init both call isEmpty.
     override def stringPrefix = self.stringPrefix
     override def toString = viewToString
   }
diff --git a/test/files/run/view-headoption.check b/test/files/run/view-headoption.check
new file mode 100644
index 0000000000..5c98b54b46
--- /dev/null
+++ b/test/files/run/view-headoption.check
@@ -0,0 +1,28 @@
+fail
+success
+f1: Some(5)
+fail
+success
+f2: 5
+fail
+success
+fail
+fail
+success
+fail
+fail
+fail
+success
+f3: Some(5)
+fail
+success
+fail
+success
+fail
+fail
+success
+fail
+fail
+fail
+success
+f4: 5
diff --git a/test/files/run/view-headoption.scala b/test/files/run/view-headoption.scala
new file mode 100644
index 0000000000..659c7e6b82
--- /dev/null
+++ b/test/files/run/view-headoption.scala
@@ -0,0 +1,18 @@
+object Test {
+  val failer    = () => { println("fail") ; None }
+  val succeeder = () => { println("success") ; Some(5) }
+  val fs = List(failer, succeeder, failer, failer, succeeder, failer, failer, failer, succeeder)
+
+  def f0 = fs.view flatMap (f => f())
+  def f1 = f0.headOption
+  def f2 = f0.head
+  def f3 = f0.lastOption
+  def f4 = f0.last
+
+  def main(args: Array[String]): Unit = {
+    println("f1: " + f1)
+    println("f2: " + f2)
+    println("f3: " + f3)
+    println("f4: " + f4)
+  }
+}