SPARK-1488. Resolve scalac feature warnings during build

For your consideration: scalac currently notes a number of feature warnings during compilation:

```
[warn] there were 65 feature warning(s); re-run with -feature for details
```

Warnings are like:

```
[warn] /Users/srowen/Documents/spark/core/src/main/scala/org/apache/spark/SparkContext.scala:1261: implicit conversion method rddToPairRDDFunctions should be enabled
[warn] by making the implicit value scala.language.implicitConversions visible.
[warn] This can be achieved by adding the import clause 'import scala.language.implicitConversions'
[warn] or by setting the compiler option -language:implicitConversions.
[warn] See the Scala docs for value scala.language.implicitConversions for a discussion
[warn] why the feature should be explicitly enabled.
[warn]   implicit def rddToPairRDDFunctions[K: ClassTag, V: ClassTag](rdd: RDD[(K, V)]) =
[warn]                ^
```

scalac is suggesting that it's just best practice to explicitly enable certain language features by importing them where used.

This PR simply adds the imports it suggests (and squashes one other Java warning along the way). This leaves just deprecation warnings in the build.

Author: Sean Owen <sowen@cloudera.com>

Closes #404 from srowen/SPARK-1488 and squashes the following commits:

8598980 [Sean Owen] Quiet scalac warnings about language features by explicitly importing language features.
39bc831 [Sean Owen] Enable -feature in scalac to emit language feature warnings

49 files changed, 58 insertions, 5 deletions

diff --git a/bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala b/bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala
index 69144e3e65..8e0f82ddb8 100644
--- a/bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala
+++ b/bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala
@@ -24,6 +24,8 @@ import org.scalatest.time.SpanSugar._
 import org.apache.spark._
 import org.apache.spark.storage.StorageLevel
 
+import scala.language.postfixOps
+
 class TestVertex(val active: Boolean, val age: Int) extends Vertex with Serializable
 class TestMessage(val targetId: String) extends Message[String] with Serializable
 
diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index 456070fa7c..3ddc0d5eee 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -25,6 +25,7 @@ import java.util.UUID.randomUUID
 import scala.collection.{Map, Set}
 import scala.collection.generic.Growable
 import scala.collection.mutable.{ArrayBuffer, HashMap}
+import scala.language.implicitConversions
 import scala.reflect.{ClassTag, classTag}
 import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs.Path
diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaDoubleRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaDoubleRDD.scala
index 537f410b0c..4330cef396 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaDoubleRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaDoubleRDD.scala
@@ -19,6 +19,7 @@ package org.apache.spark.api.java
 
 import java.lang.{Double => JDouble}
 
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark.Partitioner
diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
index a41c7dbda2..e5b2c8a5e7 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
@@ -21,6 +21,7 @@ import java.util.{Comparator, List => JList}
 import java.lang.{Iterable => JIterable}
 
 import scala.collection.JavaConversions._
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import com.google.common.base.Optional
diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
index 01d9357a25..327c1552dc 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.api.java
 
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark._
diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala b/core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala
index 7fbefe1cb0..e6a3f06b0e 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala
@@ -22,6 +22,7 @@ import java.util.{Map => JMap}
 
 import scala.collection.JavaConversions
 import scala.collection.JavaConversions._
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import com.google.common.base.Optional
diff --git a/core/src/main/scala/org/apache/spark/deploy/FaultToleranceTest.scala b/core/src/main/scala/org/apache/spark/deploy/FaultToleranceTest.scala
index f4eb1601be..47dbcd87c3 100644
--- a/core/src/main/scala/org/apache/spark/deploy/FaultToleranceTest.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/FaultToleranceTest.scala
@@ -25,6 +25,7 @@ import scala.collection.mutable.ListBuffer
 import scala.concurrent.{Await, future, promise}
 import scala.concurrent.ExecutionContext.Implicits.global
 import scala.concurrent.duration._
+import scala.language.postfixOps
 import scala.sys.process._
 
 import org.json4s._
diff --git a/core/src/main/scala/org/apache/spark/deploy/master/Master.scala b/core/src/main/scala/org/apache/spark/deploy/master/Master.scala
index 6c58e741df..81f990bfa6 100644
--- a/core/src/main/scala/org/apache/spark/deploy/master/Master.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/master/Master.scala
@@ -23,6 +23,7 @@ import java.util.Date
 import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet}
 import scala.concurrent.Await
 import scala.concurrent.duration._
+import scala.language.postfixOps
 import scala.util.Random
 
 import akka.actor._
diff --git a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
index 52c164ca3c..dd0a1360ab 100755
--- a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
@@ -23,6 +23,7 @@ import java.util.Date
 
 import scala.collection.mutable.HashMap
 import scala.concurrent.duration._
+import scala.language.postfixOps
 
 import akka.actor._
 import akka.remote.{DisassociatedEvent, RemotingLifecycleEvent}
diff --git a/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala b/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala
index cfee41c613..dcbbc18531 100644
--- a/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala
+++ b/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala
@@ -33,6 +33,7 @@ import scala.collection.mutable.SynchronizedQueue
 
 import scala.concurrent.{Await, ExecutionContext, Future, Promise}
 import scala.concurrent.duration._
+import scala.language.postfixOps
 
 import org.apache.spark._
 import org.apache.spark.util.{SystemClock, Utils}
diff --git a/core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala b/core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala
index c6e79557f0..9ff76892ae 100644
--- a/core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala
@@ -20,6 +20,7 @@ package org.apache.spark.rdd
 import java.io.{IOException, ObjectOutputStream}
 
 import scala.collection.mutable.ArrayBuffer
+import scala.language.existentials
 
 import org.apache.spark.{InterruptibleIterator, Partition, Partitioner, SparkEnv, TaskContext}
 import org.apache.spark.{Dependency, OneToOneDependency, ShuffleDependency}
diff --git a/core/src/main/scala/org/apache/spark/rdd/CoalescedRDD.scala b/core/src/main/scala/org/apache/spark/rdd/CoalescedRDD.scala
index 44401a6634..c45b759f00 100644
--- a/core/src/main/scala/org/apache/spark/rdd/CoalescedRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/CoalescedRDD.scala
@@ -21,6 +21,7 @@ import java.io.{IOException, ObjectOutputStream}
 
 import scala.collection.mutable
 import scala.collection.mutable.ArrayBuffer
+import scala.language.existentials
 import scala.reflect.ClassTag
 
 import org.apache.spark._
diff --git a/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala b/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
index 7367c08b5d..0800c5684c 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
@@ -20,6 +20,7 @@ package org.apache.spark.scheduler
 import java.util.Properties
 
 import scala.collection.mutable.Map
+import scala.language.existentials
 
 import org.apache.spark._
 import org.apache.spark.executor.TaskMetrics
diff --git a/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala b/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
index 0b381308b6..0e8d551e4b 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
@@ -21,6 +21,7 @@ import java.io._
 import java.util.zip.{GZIPInputStream, GZIPOutputStream}
 
 import scala.collection.mutable.HashMap
+import scala.language.existentials
 
 import org.apache.spark._
 import org.apache.spark.rdd.{RDD, RDDCheckpointData}
diff --git a/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala b/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
index 23f3b3e824..02b62de7e3 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
@@ -21,6 +21,7 @@ import java.io._
 import java.util.zip.{GZIPInputStream, GZIPOutputStream}
 
 import scala.collection.mutable.HashMap
+import scala.language.existentials
 
 import org.apache.spark._
 import org.apache.spark.executor.ShuffleWriteMetrics
diff --git a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
index acd152dda8..a3439b525f 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
@@ -25,6 +25,7 @@ import scala.concurrent.duration._
 import scala.collection.mutable.ArrayBuffer
 import scala.collection.mutable.HashMap
 import scala.collection.mutable.HashSet
+import scala.language.postfixOps
 import scala.util.Random
 
 import org.apache.spark._
diff --git a/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala b/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
index 3ae147a36c..750f5a501c 100644
--- a/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
+++ b/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
@@ -22,6 +22,7 @@ import javax.servlet.DispatcherType
 import javax.servlet.http.{HttpServlet, HttpServletRequest, HttpServletResponse}
 
 import scala.annotation.tailrec
+import scala.language.implicitConversions
 import scala.util.{Failure, Success, Try}
 import scala.xml.Node
 
diff --git a/core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala b/core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala
index b65017d680..f5be5856c2 100644
--- a/core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala
+++ b/core/src/main/scala/org/apache/spark/util/TimeStampedWeakValueHashMap.scala
@@ -21,6 +21,7 @@ import java.lang.ref.WeakReference
 import java.util.concurrent.atomic.AtomicInteger
 
 import scala.collection.mutable
+import scala.language.implicitConversions
 
 import org.apache.spark.Logging
 
diff --git a/core/src/main/scala/org/apache/spark/util/Vector.scala b/core/src/main/scala/org/apache/spark/util/Vector.scala
index 1a647fa1c9..c6cab82c3e 100644
--- a/core/src/main/scala/org/apache/spark/util/Vector.scala
+++ b/core/src/main/scala/org/apache/spark/util/Vector.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.util
 
+import scala.language.implicitConversions
 import scala.util.Random
 
 import org.apache.spark.util.random.XORShiftRandom
diff --git a/core/src/test/scala/org/apache/spark/ConnectionManagerSuite.scala b/core/src/test/scala/org/apache/spark/ConnectionManagerSuite.scala
index 80f7ec00c7..df6b2604c8 100644
--- a/core/src/test/scala/org/apache/spark/ConnectionManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/ConnectionManagerSuite.scala
@@ -25,7 +25,7 @@ import org.apache.spark.network.{ConnectionManager, Message, ConnectionManagerId
 import scala.concurrent.Await
 import scala.concurrent.TimeoutException
 import scala.concurrent.duration._
-
+import scala.language.postfixOps
 
 /**
   * Test the ConnectionManager with various security settings.
diff --git a/core/src/test/scala/org/apache/spark/ContextCleanerSuite.scala b/core/src/test/scala/org/apache/spark/ContextCleanerSuite.scala
index e50981cf6f..5a83100908 100644
--- a/core/src/test/scala/org/apache/spark/ContextCleanerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/ContextCleanerSuite.scala
@@ -20,6 +20,8 @@ package org.apache.spark
 import java.lang.ref.WeakReference
 
 import scala.collection.mutable.{HashSet, SynchronizedSet}
+import scala.language.existentials
+import scala.language.postfixOps
 import scala.util.Random
 
 import org.scalatest.{BeforeAndAfter, FunSuite}
diff --git a/core/src/test/scala/org/apache/spark/DriverSuite.scala b/core/src/test/scala/org/apache/spark/DriverSuite.scala
index 7f59bdcce4..de4bd90c8f 100644
--- a/core/src/test/scala/org/apache/spark/DriverSuite.scala
+++ b/core/src/test/scala/org/apache/spark/DriverSuite.scala
@@ -29,6 +29,8 @@ import org.scalatest.time.SpanSugar._
 
 import org.apache.spark.util.Utils
 
+import scala.language.postfixOps
+
 class DriverSuite extends FunSuite with Timeouts {
 
   test("driver should exit after finishing") {
diff --git a/core/src/test/scala/org/apache/spark/PipedRDDSuite.scala b/core/src/test/scala/org/apache/spark/PipedRDDSuite.scala
index 867b28cc0d..dfe057515e 100644
--- a/core/src/test/scala/org/apache/spark/PipedRDDSuite.scala
+++ b/core/src/test/scala/org/apache/spark/PipedRDDSuite.scala
@@ -19,8 +19,6 @@ package org.apache.spark
 
 import java.io.File
 
-import com.google.common.io.Files
-
 import org.scalatest.FunSuite
 
 import org.apache.spark.rdd.{HadoopRDD, PipedRDD, HadoopPartition}
@@ -28,6 +26,7 @@ import org.apache.hadoop.mapred.{JobConf, TextInputFormat, FileSplit}
 import org.apache.hadoop.fs.Path
 
 import scala.collection.Map
+import scala.language.postfixOps
 import scala.sys.process._
 import scala.util.Try
 
diff --git a/core/src/test/scala/org/apache/spark/rdd/AsyncRDDActionsSuite.scala b/core/src/test/scala/org/apache/spark/rdd/AsyncRDDActionsSuite.scala
index 3b833f2e41..28197657e9 100644
--- a/core/src/test/scala/org/apache/spark/rdd/AsyncRDDActionsSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rdd/AsyncRDDActionsSuite.scala
@@ -22,6 +22,7 @@ import java.util.concurrent.Semaphore
 import scala.concurrent.{Await, TimeoutException}
 import scala.concurrent.duration.Duration
 import scala.concurrent.ExecutionContext.Implicits.global
+import scala.language.postfixOps
 
 import org.scalatest.{BeforeAndAfterAll, FunSuite}
 import org.scalatest.concurrent.Timeouts
diff --git a/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
index db4df1d121..35a7ac9d04 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
@@ -19,6 +19,7 @@ package org.apache.spark.scheduler
 
 import scala.Tuple2
 import scala.collection.mutable.{HashSet, HashMap, Map}
+import scala.language.reflectiveCalls
 
 import org.scalatest.{BeforeAndAfter, FunSuite}
 
diff --git a/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala b/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
index e10ec7d262..907428db80 100644
--- a/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
@@ -33,6 +33,9 @@ import org.apache.spark.scheduler.LiveListenerBus
 import org.apache.spark.serializer.{JavaSerializer, KryoSerializer}
 import org.apache.spark.util.{AkkaUtils, ByteBufferInputStream, SizeEstimator, Utils}
 
+import scala.language.implicitConversions
+import scala.language.postfixOps
+
 class BlockManagerSuite extends FunSuite with BeforeAndAfter with PrivateMethodTester {
   private val conf = new SparkConf(false)
   var store: BlockManager = null
diff --git a/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala b/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
index 808ddfdcf4..9b29e2a8a5 100644
--- a/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
@@ -20,6 +20,7 @@ package org.apache.spark.storage
 import java.io.{File, FileWriter}
 
 import scala.collection.mutable
+import scala.language.reflectiveCalls
 
 import com.google.common.io.Files
 import org.scalatest.{BeforeAndAfterEach, FunSuite}
diff --git a/core/src/test/scala/org/apache/spark/ui/UISuite.scala b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
index b85c483ca2..ed02b0ba00 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
@@ -21,6 +21,7 @@ import java.net.ServerSocket
 import javax.servlet.http.HttpServletRequest
 
 import scala.io.Source
+import scala.language.postfixOps
 import scala.util.{Failure, Success, Try}
 
 import org.eclipse.jetty.server.Server
diff --git a/core/src/test/scala/org/apache/spark/util/random/XORShiftRandomSuite.scala b/core/src/test/scala/org/apache/spark/util/random/XORShiftRandomSuite.scala
index 39199a1a17..0865c6386f 100644
--- a/core/src/test/scala/org/apache/spark/util/random/XORShiftRandomSuite.scala
+++ b/core/src/test/scala/org/apache/spark/util/random/XORShiftRandomSuite.scala
@@ -22,6 +22,8 @@ import org.scalatest.matchers.ShouldMatchers
 
 import org.apache.spark.util.Utils.times
 
+import scala.language.reflectiveCalls
+
 class XORShiftRandomSuite extends FunSuite with ShouldMatchers {
 
   def fixture = new {
diff --git a/examples/src/main/scala/org/apache/spark/streaming/examples/ZeroMQWordCount.scala b/examples/src/main/scala/org/apache/spark/streaming/examples/ZeroMQWordCount.scala
index 445d202858..6f88db1abf 100644
--- a/examples/src/main/scala/org/apache/spark/streaming/examples/ZeroMQWordCount.scala
+++ b/examples/src/main/scala/org/apache/spark/streaming/examples/ZeroMQWordCount.scala
@@ -27,6 +27,8 @@ import org.apache.spark.streaming.{Seconds, StreamingContext}
 import org.apache.spark.streaming.StreamingContext._
 import org.apache.spark.streaming.zeromq._
 
+import scala.language.implicitConversions
+
 /**
  * A simple publisher for demonstration purposes, repeatedly publishes random Messages
  * every one second.
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/Graph.scala b/graphx/src/main/scala/org/apache/spark/graphx/Graph.scala
index ef05623d7a..45349692cb 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/Graph.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/Graph.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.graphx
 
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark.graphx.impl._
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/MessageToPartition.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/MessageToPartition.scala
index 9d4f3750cb..c45ba3d2f8 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/MessageToPartition.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/MessageToPartition.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.graphx.impl
 
+import scala.language.implicitConversions
 import scala.reflect.{classTag, ClassTag}
 
 import org.apache.spark.Partitioner
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/Serializers.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/Serializers.scala
index 2f2c524df6..2f0531ee5f 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/Serializers.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/Serializers.scala
@@ -20,10 +20,11 @@ package org.apache.spark.graphx.impl
 import java.io.{EOFException, InputStream, OutputStream}
 import java.nio.ByteBuffer
 
-import org.apache.spark.SparkConf
 import org.apache.spark.graphx._
 import org.apache.spark.serializer._
 
+import scala.language.existentials
+
 private[graphx]
 class VertexIdMsgSerializer extends Serializer with Serializable {
   override def newInstance(): SerializerInstance = new ShuffleSerializerInstance {
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/util/BytecodeUtils.scala b/graphx/src/main/scala/org/apache/spark/graphx/util/BytecodeUtils.scala
index 087b1156f6..be6b9047d9 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/util/BytecodeUtils.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/util/BytecodeUtils.scala
@@ -20,6 +20,7 @@ package org.apache.spark.graphx.util
 import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
 
 import scala.collection.mutable.HashSet
+import scala.language.existentials
 
 import org.apache.spark.util.Utils
 
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/rdd/RDDFunctions.scala b/mllib/src/main/scala/org/apache/spark/mllib/rdd/RDDFunctions.scala
index 873de871fd..365b5e75d7 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/rdd/RDDFunctions.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/rdd/RDDFunctions.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.mllib.rdd
 
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark.rdd.RDD
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/util/MFDataGenerator.scala b/mllib/src/main/scala/org/apache/spark/mllib/util/MFDataGenerator.scala
index 3f413faca6..b76fbe89c3 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/util/MFDataGenerator.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/util/MFDataGenerator.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.mllib.util
 
+import scala.language.postfixOps
 import scala.util.Random
 
 import org.jblas.DoubleMatrix
diff --git a/mllib/src/test/java/org/apache/spark/mllib/linalg/JavaVectorsSuite.java b/mllib/src/test/java/org/apache/spark/mllib/linalg/JavaVectorsSuite.java
index c6d8425ffc..1421067dc6 100644
--- a/mllib/src/test/java/org/apache/spark/mllib/linalg/JavaVectorsSuite.java
+++ b/mllib/src/test/java/org/apache/spark/mllib/linalg/JavaVectorsSuite.java
@@ -36,6 +36,7 @@ public class JavaVectorsSuite implements Serializable {
 
   @Test
   public void sparseArrayConstruction() {
+    @SuppressWarnings("unchecked")
     Vector v = Vectors.sparse(3, Lists.<Tuple2<Integer, Double>>newArrayList(
         new Tuple2<Integer, Double>(0, 2.0),
         new Tuple2<Integer, Double>(2, 3.0)));
diff --git a/pom.xml b/pom.xml
index 5f66cbe768..0eacedf7a6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -648,6 +648,7 @@
             <args>
               <arg>-unchecked</arg>
               <arg>-deprecation</arg>
+              <arg>-feature</arg>
             </args>
             <jvmArgs>
               <jvmArg>-Xms1024m</jvmArg>
diff --git a/project/SparkBuild.scala b/project/SparkBuild.scala
index a6058bba3d..aac07b9f61 100644
--- a/project/SparkBuild.scala
+++ b/project/SparkBuild.scala
@@ -162,7 +162,7 @@ object SparkBuild extends Build {
     organization       := "org.apache.spark",
     version            := SPARK_VERSION,
     scalaVersion       := "2.10.4",
-    scalacOptions := Seq("-Xmax-classfile-name", "120", "-unchecked", "-deprecation",
+    scalacOptions := Seq("-Xmax-classfile-name", "120", "-unchecked", "-deprecation", "-feature",
       "-target:" + SCALAC_JVM_VERSION),
     javacOptions := Seq("-target", JAVAC_JVM_VERSION, "-source", JAVAC_JVM_VERSION),
     unmanagedJars in Compile <<= baseDirectory map { base => (base / "lib" ** "*.jar").classpath },
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
index 5b6aea81cb..13a19d0adf 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.sql.catalyst
 
+import scala.language.implicitConversions
 import scala.util.parsing.combinator.lexical.StdLexical
 import scala.util.parsing.combinator.syntactical.StandardTokenParsers
 import scala.util.parsing.input.CharArrayReader.EofCh
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala b/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
index ff5d0aaa3d..e9a4f7ba22 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
@@ -22,6 +22,7 @@ import java.util.concurrent.atomic.AtomicInteger
 
 import scala.collection.Map
 import scala.collection.mutable.Queue
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import akka.actor.{Props, SupervisorStrategy}
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStream.scala
index 721d502732..13e2bacc92 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStream.scala
@@ -23,6 +23,7 @@ import org.apache.spark.api.java.JavaRDD
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.rdd.RDD
 
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 import org.apache.spark.streaming.dstream.DStream
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStreamLike.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStreamLike.scala
index bb2f492d06..a6184de4e8 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStreamLike.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaDStreamLike.scala
@@ -22,6 +22,7 @@ import java.lang.{Long => JLong}
 import java.util.{List => JList}
 
 import scala.collection.JavaConversions._
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark.api.java.{JavaPairRDD, JavaRDD, JavaRDDLike}
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala
index 2ac943d7bf..cb8e8f00a7 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala
@@ -21,6 +21,7 @@ import java.lang.{Long => JLong, Iterable => JIterable}
 import java.util.{List => JList}
 
 import scala.collection.JavaConversions._
+import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import com.google.common.base.Optional
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/receivers/ActorReceiver.scala b/streaming/src/main/scala/org/apache/spark/streaming/receivers/ActorReceiver.scala
index f5984d03c5..da0d364ae7 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/receivers/ActorReceiver.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/receivers/ActorReceiver.scala
@@ -23,6 +23,7 @@ import akka.actor.{ PossiblyHarmful, OneForOneStrategy }
 import akka.actor.SupervisorStrategy._
 
 import scala.concurrent.duration._
+import scala.language.postfixOps
 import scala.reflect.ClassTag
 
 import org.apache.spark.storage.{StorageLevel, StreamBlockId}
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/NetworkInputTracker.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/NetworkInputTracker.scala
index a1e6f51768..438e72a7ce 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/NetworkInputTracker.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/NetworkInputTracker.scala
@@ -18,6 +18,7 @@
 package org.apache.spark.streaming.scheduler
 
 import scala.collection.mutable.{HashMap, SynchronizedMap, SynchronizedQueue}
+import scala.language.existentials
 
 import akka.actor._
 
diff --git a/streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala
index efd0d22ecb..ad5367ab94 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala
@@ -28,6 +28,8 @@ import org.scalatest.concurrent.Timeouts
 import org.scalatest.exceptions.TestFailedDueToTimeoutException
 import org.scalatest.time.SpanSugar._
 
+import scala.language.postfixOps
+
 class StreamingContextSuite extends FunSuite with BeforeAndAfter with Timeouts with Logging {
 
   val master = "local[2]"
diff --git a/streaming/src/test/scala/org/apache/spark/streaming/UISuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/UISuite.scala
index 35538ec188..031e93ab24 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/UISuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/UISuite.scala
@@ -18,6 +18,7 @@
 package org.apache.spark.streaming
 
 import scala.io.Source
+import scala.language.postfixOps
 
 import org.scalatest.FunSuite
 import org.scalatest.concurrent.Eventually._
diff --git a/tools/src/main/scala/org/apache/spark/tools/JavaAPICompletenessChecker.scala b/tools/src/main/scala/org/apache/spark/tools/JavaAPICompletenessChecker.scala
index 420522433e..8d0f09933c 100644
--- a/tools/src/main/scala/org/apache/spark/tools/JavaAPICompletenessChecker.scala
+++ b/tools/src/main/scala/org/apache/spark/tools/JavaAPICompletenessChecker.scala
@@ -20,6 +20,7 @@ package org.apache.spark.tools
 import java.lang.reflect.Method
 
 import scala.collection.mutable.ArrayBuffer
+import scala.language.existentials
 
 import org.apache.spark._
 import org.apache.spark.api.java._