Remove unused imports and other minor cleanups

 - Language imports are preceding other imports
 - Deleted empty file: InlineErasure
 - Removed some unused private[parallel] methods in
   scala/collection/parallel/package.scala

This removes hundreds of warnings when compiling with
"-Xlint -Ywarn-dead-code -Ywarn-unused -Ywarn-unused-import".

64 files changed, 177 insertions, 264 deletions

diff --git a/src/library/scala/Enumeration.scala b/src/library/scala/Enumeration.scala
index c4aa511cd7..9d9a3f849b 100644
--- a/src/library/scala/Enumeration.scala
+++ b/src/library/scala/Enumeration.scala
@@ -9,7 +9,7 @@
 package scala
 
 import scala.collection.{ mutable, immutable, generic, SortedSetLike, AbstractSet }
-import java.lang.reflect.{ Modifier, Method => JMethod, Field => JField }
+import java.lang.reflect.{ Method => JMethod, Field => JField }
 import scala.reflect.NameTransformer._
 import scala.util.matching.Regex
 
@@ -154,14 +154,14 @@ abstract class Enumeration (initial: Int) extends Serializable {
   protected final def Value(i: Int, name: String): Value = new Val(i, name)
 
   private def populateNameMap() {
-    val fields = getClass.getDeclaredFields
-    def isValDef(m: JMethod) = fields exists (fd => fd.getName == m.getName && fd.getType == m.getReturnType)
+    val fields: Array[JField] = getClass.getDeclaredFields
+    def isValDef(m: JMethod): Boolean = fields exists (fd => fd.getName == m.getName && fd.getType == m.getReturnType)
 
     // The list of possible Value methods: 0-args which return a conforming type
-    val methods = getClass.getMethods filter (m => m.getParameterTypes.isEmpty &&
-                                                   classOf[Value].isAssignableFrom(m.getReturnType) &&
-                                                   m.getDeclaringClass != classOf[Enumeration] &&
-                                                   isValDef(m))
+    val methods: Array[JMethod] = getClass.getMethods filter (m => m.getParameterTypes.isEmpty &&
+                                                                   classOf[Value].isAssignableFrom(m.getReturnType) &&
+                                                                   m.getDeclaringClass != classOf[Enumeration] &&
+                                                                   isValDef(m))
     methods foreach { m =>
       val name = m.getName
       // invoke method to obtain actual `Value` instance
diff --git a/src/library/scala/Predef.scala b/src/library/scala/Predef.scala
index a6f0fa9e78..50a53732f1 100644
--- a/src/library/scala/Predef.scala
+++ b/src/library/scala/Predef.scala
@@ -8,13 +8,14 @@
 
 package scala
 
+import scala.language.implicitConversions
+
 import scala.collection.{ mutable, immutable, generic }
 import immutable.StringOps
 import mutable.ArrayOps
 import generic.CanBuildFrom
 import scala.annotation.{ elidable, implicitNotFound }
 import scala.annotation.elidable.ASSERTION
-import scala.language.{implicitConversions, existentials}
 import scala.io.StdIn
 
 /** The `Predef` object provides definitions that are accessible in all Scala
diff --git a/src/library/scala/annotation/elidable.scala b/src/library/scala/annotation/elidable.scala
index f9c5e8a744..dd0d9b511c 100644
--- a/src/library/scala/annotation/elidable.scala
+++ b/src/library/scala/annotation/elidable.scala
@@ -8,8 +8,6 @@
 
 package scala.annotation
 
-import java.util.logging.Level
-
 /** An annotation for methods whose bodies may be excluded
  *  from compiler-generated bytecode.
  *
@@ -62,7 +60,7 @@ import java.util.logging.Level
  *  @author   Paul Phillips
  *  @since    2.8
  */
-final class elidable(final val level: Int) extends scala.annotation.StaticAnnotation {}
+final class elidable(final val level: Int) extends scala.annotation.StaticAnnotation
 
 /** This useless appearing code was necessary to allow people to use
  *  named constants for the elidable annotation.  This is what it takes
diff --git a/src/library/scala/annotation/implicitAmbiguous.scala b/src/library/scala/annotation/implicitAmbiguous.scala
index f190865623..44e8d23085 100644
--- a/src/library/scala/annotation/implicitAmbiguous.scala
+++ b/src/library/scala/annotation/implicitAmbiguous.scala
@@ -1,7 +1,5 @@
 package scala.annotation
 
-import scala.annotation.meta._
-
 /**
   * To customize the error message that's emitted when an implicit search finds
   * multiple ambiguous values, annotate at least one of the implicit values
@@ -31,4 +29,4 @@ import scala.annotation.meta._
   * @author Brian McKenna
   * @since 2.12.0
   */
-final class implicitAmbiguous(msg: String) extends scala.annotation.StaticAnnotation {}
+final class implicitAmbiguous(msg: String) extends scala.annotation.StaticAnnotation
diff --git a/src/library/scala/collection/IndexedSeqLike.scala b/src/library/scala/collection/IndexedSeqLike.scala
index 18c9175ee1..f4bf58ffe3 100644
--- a/src/library/scala/collection/IndexedSeqLike.scala
+++ b/src/library/scala/collection/IndexedSeqLike.scala
@@ -9,9 +9,6 @@
 package scala
 package collection
 
-import mutable.ArrayBuffer
-import scala.annotation.tailrec
-
 /** A template trait for indexed sequences of type `IndexedSeq[A]`.
  *
  *  $indexedSeqInfo
diff --git a/src/library/scala/collection/IndexedSeqOptimized.scala b/src/library/scala/collection/IndexedSeqOptimized.scala
index a7e06b4d1a..3765b2fff0 100644
--- a/src/library/scala/collection/IndexedSeqOptimized.scala
+++ b/src/library/scala/collection/IndexedSeqOptimized.scala
@@ -10,7 +10,6 @@ package scala
 package collection
 
 import generic._
-import mutable.ArrayBuffer
 import scala.annotation.tailrec
 
 /** A template trait for indexed sequences of type `IndexedSeq[A]` which optimizes
diff --git a/src/library/scala/collection/IterableLike.scala b/src/library/scala/collection/IterableLike.scala
index ecf64624e8..b89720da78 100644
--- a/src/library/scala/collection/IterableLike.scala
+++ b/src/library/scala/collection/IterableLike.scala
@@ -10,8 +10,7 @@ package scala
 package collection
 
 import generic._
-import immutable.{ List, Stream }
-import scala.annotation.unchecked.uncheckedVariance
+import immutable.Stream
 
 /** A template trait for iterable collections of type `Iterable[A]`.
  *  $iterableInfo
@@ -83,8 +82,8 @@ self =>
     iterator.foldRight(z)(op)
   override /*TraversableLike*/ def reduceRight[B >: A](op: (A, B) => B): B =
     iterator.reduceRight(op)
-    
-  
+
+
   /** Returns this $coll as an iterable collection.
    *
    *  A new collection will not be built; lazy collections will stay lazy.
@@ -94,7 +93,7 @@ self =>
    */
   override /*TraversableLike*/ def toIterable: Iterable[A] =
     thisCollection
-  
+
   /** Returns an Iterator over the elements in this $coll.  Produces the same
    *  result as `iterator`.
    *  $willNotTerminateInf
@@ -102,7 +101,7 @@ self =>
    */
   @deprecatedOverriding("toIterator should stay consistent with iterator for all Iterables: override iterator instead.", "2.11.0")
   override def toIterator: Iterator[A] = iterator
-  
+
   override /*TraversableLike*/ def head: A =
     iterator.next()
 
diff --git a/src/library/scala/collection/IterableProxyLike.scala b/src/library/scala/collection/IterableProxyLike.scala
index 90e630ee28..334b511fb9 100644
--- a/src/library/scala/collection/IterableProxyLike.scala
+++ b/src/library/scala/collection/IterableProxyLike.scala
@@ -12,7 +12,6 @@ package scala
 package collection
 
 import generic._
-import mutable.Buffer
 
 // Methods could be printed by  cat IterableLike.scala | egrep '^  (override )?def'
 
diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 922bb2b5e0..17bb83e52e 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -12,8 +12,6 @@ package collection
 import mutable.ArrayBuffer
 import scala.annotation.migration
 import immutable.Stream
-import scala.collection.generic.CanBuildFrom
-import scala.annotation.unchecked.{ uncheckedVariance => uV }
 
 /** The `Iterator` object provides various functions for creating specialized iterators.
  *
@@ -521,13 +519,13 @@ trait Iterator[+A] extends TraversableOnce[A] {
   def collect[B](pf: PartialFunction[A, B]): Iterator[B] = new AbstractIterator[B] {
     // Manually buffer to avoid extra layer of wrapping with buffered
     private[this] var hd: A = _
-    
+
     // Little state machine to keep track of where we are
     // Seek = 0; Found = 1; Empty = -1
     // Not in vals because scalac won't make them static (@inline def only works with -optimize)
     // BE REALLY CAREFUL TO KEEP COMMENTS AND NUMBERS IN SYNC!
     private[this] var status = 0/*Seek*/
-    
+
     def hasNext = {
       while (status == 0/*Seek*/) {
         if (self.hasNext) {
@@ -700,9 +698,9 @@ trait Iterator[+A] extends TraversableOnce[A] {
         }
       }
     }
-    
+
     val leading = new Leading
-    
+
     val trailing = new AbstractIterator[A] {
       private[this] var myLeading = leading
       /* Status flags meanings:
@@ -738,7 +736,7 @@ trait Iterator[+A] extends TraversableOnce[A] {
         }
         else Iterator.empty.next()
       }
-            
+
       override def toString = "unknown-if-empty iterator"
     }
 
@@ -772,7 +770,7 @@ trait Iterator[+A] extends TraversableOnce[A] {
         status = 1
         false
       }
-    def next() = 
+    def next() =
       if (hasNext) {
         if (status == 1) self.next()
         else {
@@ -1325,7 +1323,7 @@ trait Iterator[+A] extends TraversableOnce[A] {
    */
   def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit = {
     var i = start
-    val end = start + math.min(len, xs.length - start)   
+    val end = start + math.min(len, xs.length - start)
     while (i < end && hasNext) {
       xs(i) = next()
       i += 1
diff --git a/src/library/scala/collection/LinearSeqOptimized.scala b/src/library/scala/collection/LinearSeqOptimized.scala
index 978f1c9075..a3860f10a4 100644
--- a/src/library/scala/collection/LinearSeqOptimized.scala
+++ b/src/library/scala/collection/LinearSeqOptimized.scala
@@ -9,8 +9,6 @@
 package scala
 package collection
 
-import mutable.ListBuffer
-import immutable.List
 import scala.annotation.tailrec
 
 /** A template trait for linear sequences of type `LinearSeq[A]` which optimizes
diff --git a/src/library/scala/collection/MapLike.scala b/src/library/scala/collection/MapLike.scala
index 183279d093..4ac87b29a9 100644
--- a/src/library/scala/collection/MapLike.scala
+++ b/src/library/scala/collection/MapLike.scala
@@ -11,7 +11,7 @@ package collection
 
 import generic._
 import mutable.{ Builder, MapBuilder }
-import scala.annotation.{migration, bridge}
+import scala.annotation.migration
 import parallel.ParMap
 
 /** A template trait for maps, which associate keys with values.
@@ -331,8 +331,8 @@ self =>
       foreach(vb += _)
       vb.result
     }
-  }  
-  
+  }
+
   override def toBuffer[C >: (A, B)]: mutable.Buffer[C] = {
     val result = new mutable.ArrayBuffer[C](size)
     // Faster to let the map iterate itself than to defer through copyToBuffer
diff --git a/src/library/scala/collection/SeqLike.scala b/src/library/scala/collection/SeqLike.scala
index b775480532..a26765027c 100644
--- a/src/library/scala/collection/SeqLike.scala
+++ b/src/library/scala/collection/SeqLike.scala
@@ -9,11 +9,10 @@
 package scala
 package collection
 
-import mutable.{ ListBuffer, ArraySeq }
 import immutable.{ List, Range }
 import generic._
 import parallel.ParSeq
-import scala.math.{ min, max, Ordering }
+import scala.math.Ordering
 
 /** A template trait for sequences of type `Seq[A]`
  *  $seqInfo
@@ -146,7 +145,7 @@ trait SeqLike[+A, +Repr] extends Any with IterableLike[A, Repr] with GenSeqLike[
    *  more than one way to generate the same subsequence, only one will be returned.
    *
    *  For example, `"xyyy"` has three different ways to generate `"xy"` depending on
-   *  whether the first, second, or third `"y"` is selected.  However, since all are 
+   *  whether the first, second, or third `"y"` is selected.  However, since all are
    *  identical, only one will be chosen.  Which of the three will be taken is an
    *  implementation detail that is not defined.
    *
diff --git a/src/library/scala/collection/SetLike.scala b/src/library/scala/collection/SetLike.scala
index d03c808c2c..9143c40870 100644
--- a/src/library/scala/collection/SetLike.scala
+++ b/src/library/scala/collection/SetLike.scala
@@ -11,7 +11,7 @@ package collection
 
 import generic._
 import mutable.{ Builder, SetBuilder }
-import scala.annotation.{migration, bridge}
+import scala.annotation.migration
 import parallel.ParSet
 
 /** A template trait for sets.
@@ -86,7 +86,7 @@ self =>
       vb.result
     }
   }
-  
+
   override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
     val result = new mutable.ArrayBuffer[A1](size)
     // Faster to let the map iterate itself than to defer through copyToBuffer
diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala
index 32718ddf03..fa9a3a7482 100644
--- a/src/library/scala/collection/TraversableLike.scala
+++ b/src/library/scala/collection/TraversableLike.scala
@@ -11,7 +11,7 @@ package collection
 
 import generic._
 import mutable.{ Builder }
-import scala.annotation.{tailrec, migration, bridge}
+import scala.annotation.migration
 import scala.annotation.unchecked.{ uncheckedVariance => uV }
 import parallel.ParIterable
 import scala.language.higherKinds
diff --git a/src/library/scala/collection/TraversableOnce.scala b/src/library/scala/collection/TraversableOnce.scala
index 910c59b179..41362e8dd7 100644
--- a/src/library/scala/collection/TraversableOnce.scala
+++ b/src/library/scala/collection/TraversableOnce.scala
@@ -9,7 +9,7 @@
 package scala
 package collection
 
-import mutable.{ Buffer, Builder, ListBuffer, ArrayBuffer }
+import mutable.{ Buffer, Builder, ArrayBuffer }
 import generic.CanBuildFrom
 import scala.annotation.unchecked.{ uncheckedVariance => uV }
 import scala.language.{implicitConversions, higherKinds}
diff --git a/src/library/scala/collection/concurrent/TrieMap.scala b/src/library/scala/collection/concurrent/TrieMap.scala
index 426f9bf864..d113cbfcdf 100644
--- a/src/library/scala/collection/concurrent/TrieMap.scala
+++ b/src/library/scala/collection/concurrent/TrieMap.scala
@@ -11,13 +11,11 @@ package collection
 package concurrent
 
 import java.util.concurrent.atomic._
-import scala.collection.immutable.{ ListMap => ImmutableListMap }
 import scala.collection.parallel.mutable.ParTrieMap
 import scala.util.hashing.Hashing
 import scala.util.control.ControlThrowable
 import generic._
 import scala.annotation.tailrec
-import scala.annotation.switch
 
 private[collection] final class INode[K, V](bn: MainNode[K, V], g: Gen) extends INodeBase[K, V](g) {
   import INodeBase._
diff --git a/src/library/scala/collection/generic/GenericParTemplate.scala b/src/library/scala/collection/generic/GenericParTemplate.scala
index b9b7043270..44a778a953 100644
--- a/src/library/scala/collection/generic/GenericParTemplate.scala
+++ b/src/library/scala/collection/generic/GenericParTemplate.scala
@@ -13,7 +13,6 @@ package generic
 import scala.collection.parallel.Combiner
 import scala.collection.parallel.ParIterable
 import scala.collection.parallel.ParMap
-import scala.collection.parallel.TaskSupport
 
 import scala.annotation.unchecked.uncheckedVariance
 import scala.language.higherKinds
diff --git a/src/library/scala/collection/generic/MapFactory.scala b/src/library/scala/collection/generic/MapFactory.scala
index b9f3d4b010..255d695303 100644
--- a/src/library/scala/collection/generic/MapFactory.scala
+++ b/src/library/scala/collection/generic/MapFactory.scala
@@ -10,8 +10,6 @@ package scala
 package collection
 package generic
 
-
-import mutable.{Builder, MapBuilder}
 import scala.language.higherKinds
 
 /** A template for companion objects of `Map` and subclasses thereof.
diff --git a/src/library/scala/collection/generic/ParFactory.scala b/src/library/scala/collection/generic/ParFactory.scala
index 4486cea419..901e9fc239 100644
--- a/src/library/scala/collection/generic/ParFactory.scala
+++ b/src/library/scala/collection/generic/ParFactory.scala
@@ -11,7 +11,6 @@ package collection
 package generic
 
 import scala.collection.parallel.ParIterable
-import scala.collection.parallel.Combiner
 import scala.language.higherKinds
 
 /** A template class for companion objects of `ParIterable` and subclasses
diff --git a/src/library/scala/collection/generic/ParSetFactory.scala b/src/library/scala/collection/generic/ParSetFactory.scala
index 4320635ae6..1341ddcb38 100644
--- a/src/library/scala/collection/generic/ParSetFactory.scala
+++ b/src/library/scala/collection/generic/ParSetFactory.scala
@@ -10,7 +10,6 @@ package scala
 package collection
 package generic
 
-import scala.collection.mutable.Builder
 import scala.collection.parallel.Combiner
 import scala.collection.parallel.ParSet
 import scala.collection.parallel.ParSetLike
diff --git a/src/library/scala/collection/generic/SetFactory.scala b/src/library/scala/collection/generic/SetFactory.scala
index fcd8d00c18..5e50844cc9 100644
--- a/src/library/scala/collection/generic/SetFactory.scala
+++ b/src/library/scala/collection/generic/SetFactory.scala
@@ -12,7 +12,6 @@ package scala
 package collection
 package generic
 
-import mutable.Builder
 import scala.language.higherKinds
 
 abstract class SetFactory[CC[X] <: Set[X] with SetLike[X, CC[X]]]
diff --git a/src/library/scala/collection/generic/package.scala b/src/library/scala/collection/generic/package.scala
index 1beb4a8599..015c3455db 100644
--- a/src/library/scala/collection/generic/package.scala
+++ b/src/library/scala/collection/generic/package.scala
@@ -1,6 +1,5 @@
 package scala
 package collection
-import generic.CanBuildFrom
 
 import scala.language.higherKinds
 
diff --git a/src/library/scala/collection/immutable/BitSet.scala b/src/library/scala/collection/immutable/BitSet.scala
index 70543aa3a6..846bc22182 100644
--- a/src/library/scala/collection/immutable/BitSet.scala
+++ b/src/library/scala/collection/immutable/BitSet.scala
@@ -14,7 +14,7 @@ package immutable
 
 import generic._
 import BitSetLike.{LogWL, updateArray}
-import mutable.{ Builder, SetBuilder }
+import mutable.Builder
 
 /** A class for immutable bitsets.
  *  $bitsetinfo
diff --git a/src/library/scala/collection/immutable/List.scala b/src/library/scala/collection/immutable/List.scala
index 3ad567375c..c09328cae6 100644
--- a/src/library/scala/collection/immutable/List.scala
+++ b/src/library/scala/collection/immutable/List.scala
@@ -89,8 +89,6 @@ sealed abstract class List[+A] extends AbstractSeq[A]
                                   with scala.Serializable {
   override def companion: GenericCompanion[List] = List
 
-  import scala.collection.{Iterable, Traversable, Seq, IndexedSeq}
-
   def isEmpty: Boolean
   def head: A
   def tail: List[A]
@@ -265,7 +263,7 @@ sealed abstract class List[+A] extends AbstractSeq[A]
     }
     (b.toList, these)
   }
-  
+
   final override def map[B, That](f: A => B)(implicit bf: CanBuildFrom[List[A], B, That]): That = {
     if (bf eq List.ReusableCBF) {
       if (this eq Nil) Nil.asInstanceOf[That] else {
@@ -283,7 +281,7 @@ sealed abstract class List[+A] extends AbstractSeq[A]
     }
     else super.map(f)
   }
-  
+
   final override def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[List[A], B, That]): That = {
     if (bf eq List.ReusableCBF) {
       if (this eq Nil) Nil.asInstanceOf[That] else {
@@ -312,7 +310,7 @@ sealed abstract class List[+A] extends AbstractSeq[A]
     }
     else super.collect(pf)
   }
-  
+
   final override def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[List[A], B, That]): That = {
     if (bf eq List.ReusableCBF) {
       if (this eq Nil) Nil.asInstanceOf[That] else {
@@ -452,7 +450,7 @@ object List extends SeqFactory[List] {
   override def empty[A]: List[A] = Nil
 
   override def apply[A](xs: A*): List[A] = xs.toList
-  
+
   private[collection] val partialNotApplied = new Function1[Any, Any] { def apply(x: Any): Any = this }
 
   @SerialVersionUID(1L)
diff --git a/src/library/scala/collection/immutable/ListMap.scala b/src/library/scala/collection/immutable/ListMap.scala
index c59f4f7436..f30c0cbf8e 100644
--- a/src/library/scala/collection/immutable/ListMap.scala
+++ b/src/library/scala/collection/immutable/ListMap.scala
@@ -13,7 +13,7 @@ package collection
 package immutable
 
 import generic._
-import scala.annotation.{tailrec, bridge}
+import scala.annotation.tailrec
 
 /** $factoryInfo
  *  @since 1
@@ -30,7 +30,7 @@ object ListMap extends ImmutableMapFactory[ListMap] {
   def empty[A, B]: ListMap[A, B] = EmptyListMap.asInstanceOf[ListMap[A, B]]
 
   @SerialVersionUID(-8256686706655863282L)
-  private object EmptyListMap extends ListMap[Any, Nothing] { 
+  private object EmptyListMap extends ListMap[Any, Nothing] {
     override def apply(key: Any) = throw new NoSuchElementException("key not found: " + key)
     override def contains(key: Any) = false
   }
@@ -179,16 +179,16 @@ extends AbstractMap[A, B]
     @tailrec private def get0(cur: ListMap[A, B1], k: A): Option[B1] =
       if (k == cur.key) Some(cur.value)
       else if (cur.next.nonEmpty) get0(cur.next, k) else None
-      
-      
+
+
     override def contains(key: A): Boolean = contains0(this, key)
-    
+
     @tailrec private def contains0(cur: ListMap[A, B1], k: A): Boolean =
       if (k == cur.key) true
       else if (cur.next.nonEmpty) contains0(cur.next, k)
       else false
 
-      
+
     /** This method allows one to create a new map with an additional mapping
      *  from `key` to `value`. If the map contains already a mapping for `key`,
      *  it will be overridden by this function.
@@ -198,7 +198,7 @@ extends AbstractMap[A, B]
       new m.Node[B2](k, v)
     }
 
-    
+
     /** Creates a new mapping without the given `key`.
      *  If the map does not contain a mapping for the given key, the
      *  method returns the same map.
diff --git a/src/library/scala/collection/immutable/ListSet.scala b/src/library/scala/collection/immutable/ListSet.scala
index adc975479a..a65e25ed6e 100644
--- a/src/library/scala/collection/immutable/ListSet.scala
+++ b/src/library/scala/collection/immutable/ListSet.scala
@@ -11,8 +11,8 @@ package collection
 package immutable
 
 import generic._
-import scala.annotation.{tailrec, bridge}
-import mutable.{ ListBuffer, Builder }
+import scala.annotation.tailrec
+import mutable.Builder
 
 /** $factoryInfo
  *  @define Coll immutable.ListSet
@@ -179,6 +179,6 @@ class ListSet[A] extends AbstractSet[A]
 
     override def tail: ListSet[A] = self
   }
-  
+
   override def toSet[B >: A]: Set[B] = this.asInstanceOf[ListSet[B]]
 }
diff --git a/src/library/scala/collection/immutable/NumericRange.scala b/src/library/scala/collection/immutable/NumericRange.scala
index 11603a118b..c8d7519254 100644
--- a/src/library/scala/collection/immutable/NumericRange.scala
+++ b/src/library/scala/collection/immutable/NumericRange.scala
@@ -10,8 +10,6 @@ package scala
 package collection
 package immutable
 
-import mutable.{ Builder, ListBuffer }
-
 // TODO: Now the specialization exists there is no clear reason to have
 // separate classes for Range/NumericRange.  Investigate and consolidate.
 
@@ -193,7 +191,7 @@ extends AbstractSeq[T] with IndexedSeq[T] with Serializable {
         // Either numRangeElements or (head + last) must be even, so divide the even one before multiplying
         val a = head.toLong
         val b = last.toLong
-        val ans = 
+        val ans =
           if ((numRangeElements & 1) == 0) (numRangeElements / 2) * (a + b)
           else numRangeElements * {
             // Sum is even, but we might overflow it, so divide in pieces and add back remainder
diff --git a/src/library/scala/collection/immutable/PagedSeq.scala b/src/library/scala/collection/immutable/PagedSeq.scala
index d3dc65f834..fab5ad47eb 100644
--- a/src/library/scala/collection/immutable/PagedSeq.scala
+++ b/src/library/scala/collection/immutable/PagedSeq.scala
@@ -13,7 +13,6 @@ package collection
 package immutable
 
 import java.io.{File, FileReader, Reader}
-import scala.util.matching.Regex
 import scala.reflect.ClassTag
 
 /** The `PagedSeq` object defines a lazy implementations of
diff --git a/src/library/scala/collection/immutable/Queue.scala b/src/library/scala/collection/immutable/Queue.scala
index 53af3ce158..70b51f8251 100644
--- a/src/library/scala/collection/immutable/Queue.scala
+++ b/src/library/scala/collection/immutable/Queue.scala
@@ -12,7 +12,6 @@ package immutable
 
 import generic._
 import mutable.{ Builder, ListBuffer }
-import scala.annotation.tailrec
 
 /** `Queue` objects implement data structures that allow to
  *  insert and retrieve elements in a first-in-first-out (FIFO) manner.
diff --git a/src/library/scala/collection/immutable/SortedMap.scala b/src/library/scala/collection/immutable/SortedMap.scala
index 682788e18e..0f3bd2e195 100644
--- a/src/library/scala/collection/immutable/SortedMap.scala
+++ b/src/library/scala/collection/immutable/SortedMap.scala
@@ -14,7 +14,6 @@ package immutable
 
 import generic._
 import mutable.Builder
-import scala.annotation.unchecked.uncheckedVariance
 
 /** A map whose keys are sorted.
  *
diff --git a/src/library/scala/collection/immutable/SortedSet.scala b/src/library/scala/collection/immutable/SortedSet.scala
index 4a8859a7ab..107f77f287 100644
--- a/src/library/scala/collection/immutable/SortedSet.scala
+++ b/src/library/scala/collection/immutable/SortedSet.scala
@@ -13,7 +13,6 @@ package collection
 package immutable
 
 import generic._
-import mutable.Builder
 
 /** A subtrait of `collection.SortedSet` which represents sorted sets
  *  which cannot be mutated.
diff --git a/src/library/scala/collection/immutable/Stream.scala b/src/library/scala/collection/immutable/Stream.scala
index aa98b810d4..d92b159f3b 100644
--- a/src/library/scala/collection/immutable/Stream.scala
+++ b/src/library/scala/collection/immutable/Stream.scala
@@ -11,7 +11,7 @@ package collection
 package immutable
 
 import generic._
-import mutable.{Builder, StringBuilder, LazyBuilder, ListBuffer}
+import mutable.{Builder, StringBuilder, LazyBuilder}
 import scala.annotation.tailrec
 import Stream.cons
 import scala.language.implicitConversions
@@ -203,11 +203,9 @@ abstract class Stream[+A] extends AbstractSeq[A]
                              with LinearSeq[A]
                              with GenericTraversableTemplate[A, Stream]
                              with LinearSeqOptimized[A, Stream[A]]
-                             with Serializable {
-self =>
-  override def companion: GenericCompanion[Stream] = Stream
+                             with Serializable { self =>
 
-  import scala.collection.{Traversable, Iterable, Seq, IndexedSeq}
+  override def companion: GenericCompanion[Stream] = Stream
 
   /** Indicates whether or not the `Stream` is empty.
    *
@@ -1091,14 +1089,12 @@ object Stream extends SeqFactory[Stream] {
   /** Creates a new builder for a stream */
   def newBuilder[A]: Builder[A, Stream[A]] = new StreamBuilder[A]
 
-  import scala.collection.{Iterable, Seq, IndexedSeq}
-
   /** A builder for streams
    *  @note This builder is lazy only in the sense that it does not go downs the spine
    *        of traversables that are added as a whole. If more laziness can be achieved,
    *        this builder should be bypassed.
    */
-  class StreamBuilder[A] extends scala.collection.mutable.LazyBuilder[A, Stream[A]] {
+  class StreamBuilder[A] extends LazyBuilder[A, Stream[A]] {
     def result: Stream[A] = parts.toStream flatMap (_.toStream)
   }
 
diff --git a/src/library/scala/collection/immutable/StringLike.scala b/src/library/scala/collection/immutable/StringLike.scala
index 7b3da1e2ea..d92db68912 100644
--- a/src/library/scala/collection/immutable/StringLike.scala
+++ b/src/library/scala/collection/immutable/StringLike.scala
@@ -10,7 +10,7 @@ package scala
 package collection
 package immutable
 
-import mutable.{ ArrayBuilder, Builder }
+import mutable.Builder
 import scala.util.matching.Regex
 import scala.math.ScalaNumber
 import scala.reflect.ClassTag
@@ -208,32 +208,32 @@ self =>
     else "\\" + ch
 
   /** Split this string around the separator character
-   * 
+   *
    * If this string is the empty string, returns an array of strings
    * that contains a single empty string.
-   * 
+   *
    * If this string is not the empty string, returns an array containing
    * the substrings terminated by the start of the string, the end of the
    * string or the separator character, excluding empty trailing substrings
-   * 
-   * If the separator character is a surrogate character, only split on 
+   *
+   * If the separator character is a surrogate character, only split on
    * matching surrogate characters if they are not part of a surrogate pair
-   * 
+   *
    * The behaviour follows, and is implemented in terms of <a href="http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split%28java.lang.String%29">String.split(re: String)</a>
-   * 
-   * 
+   *
+   *
    * @example {{{
    * "a.b".split('.') //returns Array("a", "b")
-   * 
+   *
    * //splitting the empty string always returns the array with a single
    * //empty string
-   * "".split('.') //returns Array("") 
-   * 
+   * "".split('.') //returns Array("")
+   *
    * //only trailing empty substrings are removed
    * "a.".split('.') //returns Array("a")
    * ".a.".split('.') //returns Array("", "a")
    * "..a..".split('.') //returns Array("", "", "a")
-   * 
+   *
    * //all parts are empty and trailing
    * ".".split('.') //returns Array()
    * "..".split('.') //returns Array()
@@ -247,16 +247,16 @@ self =>
    * //well-formed surrogate pairs are not split
    * val highlow = highstring + lowstring
    * highlow.split(high) //returns Array(highlow)
-   * 
+   *
    * //bare surrogate characters are split
    * val bare = "_" + highstring + "_"
    * bare.split(high) //returns Array("_", "_")
-   * 
+   *
    *  }}}
-   * 
+   *
    * @param separator the character used as a delimiter
    */
-  def split(separator: Char): Array[String] = 
+  def split(separator: Char): Array[String] =
     toString.split(escape(separator))
 
 
diff --git a/src/library/scala/collection/mutable/ArrayBuilder.scala b/src/library/scala/collection/mutable/ArrayBuilder.scala
index 6e53824cbe..ac78ab823b 100644
--- a/src/library/scala/collection/mutable/ArrayBuilder.scala
+++ b/src/library/scala/collection/mutable/ArrayBuilder.scala
@@ -11,7 +11,6 @@ package collection
 package mutable
 
 import scala.reflect.ClassTag
-import scala.runtime.ScalaRunTime
 
 /** A builder class for arrays.
  *
diff --git a/src/library/scala/collection/mutable/ArrayOps.scala b/src/library/scala/collection/mutable/ArrayOps.scala
index 2bc41b5802..5144db7de3 100644
--- a/src/library/scala/collection/mutable/ArrayOps.scala
+++ b/src/library/scala/collection/mutable/ArrayOps.scala
@@ -10,7 +10,6 @@ package scala
 package collection
 package mutable
 
-import scala.compat.Platform.arraycopy
 import scala.reflect.ClassTag
 import scala.runtime.ScalaRunTime._
 import parallel.mutable.ParArray
@@ -106,9 +105,9 @@ trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParalleliza
       bb.result()
     }
   }
-  
+
   /** Converts an array of pairs into an array of first elements and an array of second elements.
-   *  
+   *
    *  @tparam T1    the type of the first half of the element pairs
    *  @tparam T2    the type of the second half of the element pairs
    *  @param asPair an implicit conversion which asserts that the element type
@@ -134,9 +133,9 @@ trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParalleliza
     }
     (a1, a2)
   }
-  
+
   /** Converts an array of triples into three arrays, one containing the elements from each position of the triple.
-   *  
+   *
    *  @tparam T1      the type of the first of three elements in the triple
    *  @tparam T2      the type of the second of three elements in the triple
    *  @tparam T3      the type of the third of three elements in the triple
@@ -168,7 +167,7 @@ trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParalleliza
     }
     (a1, a2, a3)
   }
-  
+
 
   def seq = thisCollection
 
diff --git a/src/library/scala/collection/mutable/BitSet.scala b/src/library/scala/collection/mutable/BitSet.scala
index e92d48cfeb..feef694e01 100644
--- a/src/library/scala/collection/mutable/BitSet.scala
+++ b/src/library/scala/collection/mutable/BitSet.scala
@@ -13,7 +13,7 @@ package collection
 package mutable
 
 import generic._
-import BitSetLike.{LogWL, MaxSize, updateArray}
+import BitSetLike.{LogWL, MaxSize}
 
 /** A class for mutable bitsets.
  *
@@ -56,7 +56,7 @@ class BitSet(protected final var elems: Array[Long]) extends AbstractSet[Int]
 
   @deprecatedOverriding("Internal implementation does not admit sensible overriding of this method.", "2.11.0")
   protected def nwords = elems.length
-  
+
   @deprecatedOverriding("Internal implementation does not admit sensible overriding of this method.", "2.11.0")
   protected def word(idx: Int): Long =
     if (idx < nwords) elems(idx) else 0L
@@ -100,7 +100,7 @@ class BitSet(protected final var elems: Array[Long]) extends AbstractSet[Int]
 
   @deprecatedOverriding("Override add to prevent += and add from exhibiting different behavior.", "2.11.0")
   def += (elem: Int): this.type = { add(elem); this }
-  
+
   @deprecatedOverriding("Override add to prevent += and add from exhibiting different behavior.", "2.11.0")
   def -= (elem: Int): this.type = { remove(elem); this }
 
diff --git a/src/library/scala/collection/mutable/BufferLike.scala b/src/library/scala/collection/mutable/BufferLike.scala
index bd9c61ae6a..98c9771a05 100644
--- a/src/library/scala/collection/mutable/BufferLike.scala
+++ b/src/library/scala/collection/mutable/BufferLike.scala
@@ -14,7 +14,7 @@ package mutable
 
 import generic._
 import script._
-import scala.annotation.{migration, bridge}
+import scala.annotation.migration
 
 /** A template trait for buffers of type `Buffer[A]`.
  *
diff --git a/src/library/scala/collection/mutable/ListBuffer.scala b/src/library/scala/collection/mutable/ListBuffer.scala
index eece557fe8..0a483ceb86 100644
--- a/src/library/scala/collection/mutable/ListBuffer.scala
+++ b/src/library/scala/collection/mutable/ListBuffer.scala
@@ -13,7 +13,6 @@ package mutable
 import generic._
 import immutable.{List, Nil, ::}
 import java.io.{ObjectOutputStream, ObjectInputStream}
-import scala.annotation.migration
 
 /** A `Buffer` implementation backed by a list. It provides constant time
  *  prepend and append. Most other operations are linear.
diff --git a/src/library/scala/collection/mutable/MutableList.scala b/src/library/scala/collection/mutable/MutableList.scala
index 646023f469..a333eedb1a 100644
--- a/src/library/scala/collection/mutable/MutableList.scala
+++ b/src/library/scala/collection/mutable/MutableList.scala
@@ -11,7 +11,7 @@ package collection
 package mutable
 
 import generic._
-import immutable.{List, Nil}
+import immutable.List
 
 /**
  *  This class is used internally to represent mutable lists. It is the
diff --git a/src/library/scala/collection/mutable/SynchronizedStack.scala b/src/library/scala/collection/mutable/SynchronizedStack.scala
index bbb6f5a9bb..c77a6fad62 100644
--- a/src/library/scala/collection/mutable/SynchronizedStack.scala
+++ b/src/library/scala/collection/mutable/SynchronizedStack.scala
@@ -27,7 +27,6 @@ package mutable
  */
 @deprecated("Synchronization via selective overriding of methods is inherently unreliable.  Consider java.util.concurrent.LinkedBlockingDequeue instead.", "2.11.0")
 class SynchronizedStack[A] extends Stack[A] {
-  import scala.collection.Traversable
 
   /** Checks if the stack is empty.
    *
diff --git a/src/library/scala/collection/parallel/ParIterableLike.scala b/src/library/scala/collection/parallel/ParIterableLike.scala
index 44df7f7260..2ed7bc075e 100644
--- a/src/library/scala/collection/parallel/ParIterableLike.scala
+++ b/src/library/scala/collection/parallel/ParIterableLike.scala
@@ -9,6 +9,8 @@
 package scala
 package collection.parallel
 
+import scala.language.{ higherKinds, implicitConversions }
+
 import scala.collection.mutable.Builder
 import scala.collection.mutable.ArrayBuffer
 import scala.collection.IterableLike
@@ -21,13 +23,9 @@ import scala.collection.GenIterable
 import scala.collection.GenTraversableOnce
 import scala.collection.GenTraversable
 import immutable.HashMapCombiner
-import scala.reflect.{ClassTag, classTag}
-
-import java.util.concurrent.atomic.AtomicBoolean
+import scala.reflect.ClassTag
 
 import scala.annotation.unchecked.uncheckedVariance
-import scala.annotation.unchecked.uncheckedStable
-import scala.language.{ higherKinds, implicitConversions }
 
 import scala.collection.parallel.ParallelCollectionImplicits._
 
@@ -1284,7 +1282,7 @@ self: ParIterableLike[T, Repr, Sequential] =>
   extends Transformer[Combiner[(U, S), That], Zip[U, S, That]] {
     @volatile var result: Result = null
     def leaf(prev: Option[Result]) = result = pit.zip2combiner[U, S, That](othpit, pbf())
-    protected[this] def newSubtask(p: IterableSplitter[T]) = unsupported
+    protected[this] def newSubtask(p: IterableSplitter[T]) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       val sizes = pits.map(_.remaining)
@@ -1300,7 +1298,7 @@ self: ParIterableLike[T, Repr, Sequential] =>
   extends Transformer[Combiner[(U, S), That], ZipAll[U, S, That]] {
     @volatile var result: Result = null
     def leaf(prev: Option[Result]) = result = pit.zipAll2combiner[U, S, That](othpit, thiselem, thatelem, pbf())
-    protected[this] def newSubtask(p: IterableSplitter[T]) = unsupported
+    protected[this] def newSubtask(p: IterableSplitter[T]) = throw new UnsupportedOperationException
     override def split = if (pit.remaining <= len) {
       val pits = pit.splitWithSignalling
       val sizes = pits.map(_.remaining)
@@ -1322,7 +1320,7 @@ self: ParIterableLike[T, Repr, Sequential] =>
   extends Accessor[Unit, CopyToArray[U, This]] {
     @volatile var result: Unit = ()
     def leaf(prev: Option[Unit]) = pit.copyToArray(array, from, len)
-    protected[this] def newSubtask(p: IterableSplitter[T]) = unsupported
+    protected[this] def newSubtask(p: IterableSplitter[T]) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       for ((p, untilp) <- pits zip pits.scanLeft(0)(_ + _.remaining); if untilp < len) yield {
@@ -1379,7 +1377,7 @@ self: ParIterableLike[T, Repr, Sequential] =>
       val half = howmany / 2
       ScanNode(mergeTrees(trees, from, half), mergeTrees(trees, from + half, howmany - half))
     } else trees(from)
-    protected[this] def newSubtask(pit: IterableSplitter[T]) = unsupported
+    protected[this] def newSubtask(pit: IterableSplitter[T]) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       for ((p, untilp) <- pits zip pits.scanLeft(from)(_ + _.remaining)) yield {
@@ -1416,7 +1414,7 @@ self: ParIterableLike[T, Repr, Sequential] =>
         new FromScanTree(left, z, op, cbf),
         new FromScanTree(right, z, op, cbf)
       )
-      case _ => unsupportedop("Cannot be split further")
+      case _ => throw new UnsupportedOperationException("Cannot be split further")
     }
     def shouldSplitFurther = tree match {
       case ScanNode(_, _) => true
diff --git a/src/library/scala/collection/parallel/ParMap.scala b/src/library/scala/collection/parallel/ParMap.scala
index 9f92e6c1e8..70afe5174b 100644
--- a/src/library/scala/collection/parallel/ParMap.scala
+++ b/src/library/scala/collection/parallel/ParMap.scala
@@ -11,7 +11,6 @@ package collection.parallel
 
 import scala.collection.Map
 import scala.collection.GenMap
-import scala.collection.mutable.Builder
 import scala.collection.generic.ParMapFactory
 import scala.collection.generic.GenericParMapTemplate
 import scala.collection.generic.GenericParMapCompanion
diff --git a/src/library/scala/collection/parallel/ParMapLike.scala b/src/library/scala/collection/parallel/ParMapLike.scala
index 0a671fb085..a3ac388587 100644
--- a/src/library/scala/collection/parallel/ParMapLike.scala
+++ b/src/library/scala/collection/parallel/ParMapLike.scala
@@ -12,10 +12,8 @@ package collection.parallel
 import scala.collection.MapLike
 import scala.collection.GenMapLike
 import scala.collection.Map
-import scala.collection.mutable.Builder
+
 import scala.annotation.unchecked.uncheckedVariance
-import scala.collection.generic.IdleSignalling
-import scala.collection.generic.Signalling
 
 /** A template trait for mutable parallel maps. This trait is to be mixed in
  *  with concrete parallel maps to override the representation type.
diff --git a/src/library/scala/collection/parallel/ParSeqLike.scala b/src/library/scala/collection/parallel/ParSeqLike.scala
index 0b6fec364e..60fa1858e7 100644
--- a/src/library/scala/collection/parallel/ParSeqLike.scala
+++ b/src/library/scala/collection/parallel/ParSeqLike.scala
@@ -9,11 +9,10 @@
 package scala
 package collection.parallel
 
-import scala.collection.{ Parallel, SeqLike, GenSeqLike, GenSeq, GenIterable, Iterator }
+import scala.collection.{ SeqLike, GenSeq, GenIterable, Iterator }
 import scala.collection.generic.DefaultSignalling
 import scala.collection.generic.AtomicIndexFlag
 import scala.collection.generic.CanBuildFrom
-import scala.collection.generic.CanCombineFrom
 import scala.collection.generic.VolatileAbort
 
 import scala.collection.parallel.ParallelCollectionImplicits._
@@ -365,7 +364,7 @@ self =>
         pit.setIndexFlagIfLesser(from)
       }
     }
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       for ((p, untilp) <- pits zip pits.scanLeft(from)(_ + _.remaining)) yield new IndexWhere(pred, untilp, p)
@@ -386,7 +385,7 @@ self =>
         pit.setIndexFlagIfGreater(pos)
       }
     }
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       for ((p, untilp) <- pits zip pits.scanLeft(pos)(_ + _.remaining)) yield new LastIndexWhere(pred, untilp, p)
@@ -420,7 +419,7 @@ self =>
       result = pit.sameElements(otherpit)
       if (!result) pit.abort()
     }
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val fp = pit.remaining / 2
       val sp = pit.remaining - fp
@@ -434,7 +433,7 @@ self =>
   extends Transformer[Combiner[U, That], Updated[U, That]] {
     @volatile var result: Combiner[U, That] = null
     def leaf(prev: Option[Combiner[U, That]]) = result = pit.updated2combiner(pos, elem, pbf())
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val pits = pit.splitWithSignalling
       for ((p, untilp) <- pits zip pits.scanLeft(0)(_ + _.remaining)) yield new Updated(pos - untilp, elem, pbf, p)
@@ -447,7 +446,7 @@ self =>
   extends Transformer[Combiner[(U, S), That], Zip[U, S, That]] {
     @volatile var result: Result = null
     def leaf(prev: Option[Result]) = result = pit.zip2combiner[U, S, That](otherpit, cf())
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val fp = len / 2
       val sp = len - len / 2
@@ -468,7 +467,7 @@ self =>
       result = pit.corresponds(corr)(otherpit)
       if (!result) pit.abort()
     }
-    protected[this] def newSubtask(p: SuperParIterator) = unsupported
+    protected[this] def newSubtask(p: SuperParIterator) = throw new UnsupportedOperationException
     override def split = {
       val fp = pit.remaining / 2
       val sp = pit.remaining - fp
diff --git a/src/library/scala/collection/parallel/RemainsIterator.scala b/src/library/scala/collection/parallel/RemainsIterator.scala
index 7bb278b038..63d63d9ef3 100644
--- a/src/library/scala/collection/parallel/RemainsIterator.scala
+++ b/src/library/scala/collection/parallel/RemainsIterator.scala
@@ -9,13 +9,10 @@
 package scala
 package collection.parallel
 
-import scala.collection.Parallel
 import scala.collection.generic.Signalling
 import scala.collection.generic.DelegatedSignalling
 import scala.collection.generic.IdleSignalling
-import scala.collection.generic.CanCombineFrom
 import scala.collection.mutable.Builder
-import scala.collection.Iterator.empty
 import scala.collection.GenTraversableOnce
 import scala.collection.parallel.immutable.repetition
 
diff --git a/src/library/scala/collection/parallel/immutable/ParMap.scala b/src/library/scala/collection/parallel/immutable/ParMap.scala
index 2956c2a883..65bb2e12c5 100644
--- a/src/library/scala/collection/parallel/immutable/ParMap.scala
+++ b/src/library/scala/collection/parallel/immutable/ParMap.scala
@@ -16,7 +16,6 @@ import scala.collection.generic.GenericParMapCompanion
 import scala.collection.generic.CanCombineFrom
 import scala.collection.parallel.ParMapLike
 import scala.collection.parallel.Combiner
-import scala.collection.GenMapLike
 
 /** A template trait for immutable parallel maps.
  *
diff --git a/src/library/scala/collection/parallel/immutable/ParRange.scala b/src/library/scala/collection/parallel/immutable/ParRange.scala
index ec90de3a7d..8fd5382ce9 100644
--- a/src/library/scala/collection/parallel/immutable/ParRange.scala
+++ b/src/library/scala/collection/parallel/immutable/ParRange.scala
@@ -12,7 +12,6 @@ package collection.parallel.immutable
 import scala.collection.immutable.Range
 import scala.collection.parallel.Combiner
 import scala.collection.parallel.SeqSplitter
-import scala.collection.generic.CanCombineFrom
 import scala.collection.Iterator
 
 /** Parallel ranges.
diff --git a/src/library/scala/collection/parallel/mutable/ParArray.scala b/src/library/scala/collection/parallel/mutable/ParArray.scala
index d0d022db4b..8a2cf2716a 100644
--- a/src/library/scala/collection/parallel/mutable/ParArray.scala
+++ b/src/library/scala/collection/parallel/mutable/ParArray.scala
@@ -18,7 +18,6 @@ import scala.collection.generic.GenericParCompanion
 import scala.collection.generic.CanCombineFrom
 import scala.collection.generic.CanBuildFrom
 import scala.collection.generic.ParFactory
-import scala.collection.generic.Sizing
 import scala.collection.parallel.Combiner
 import scala.collection.parallel.SeqSplitter
 import scala.collection.parallel.ParSeqLike
diff --git a/src/library/scala/collection/parallel/mutable/ResizableParArrayCombiner.scala b/src/library/scala/collection/parallel/mutable/ResizableParArrayCombiner.scala
index 79322c85b1..6883457fef 100644
--- a/src/library/scala/collection/parallel/mutable/ResizableParArrayCombiner.scala
+++ b/src/library/scala/collection/parallel/mutable/ResizableParArrayCombiner.scala
@@ -9,18 +9,10 @@
 package scala
 package collection.parallel.mutable
 
-
-
-import scala.collection.generic.Sizing
 import scala.collection.mutable.ArraySeq
 import scala.collection.mutable.ArrayBuffer
-import scala.collection.parallel.TaskSupport
-import scala.collection.parallel.unsupportedop
-import scala.collection.parallel.Combiner
 import scala.collection.parallel.Task
 
-
-
 /** An array combiner that uses a chain of arraybuffers to store elements. */
 trait ResizableParArrayCombiner[T] extends LazyCombiner[T, ParArray[T], ExposedArrayBuffer[T]] {
 
diff --git a/src/library/scala/collection/parallel/mutable/UnrolledParArrayCombiner.scala b/src/library/scala/collection/parallel/mutable/UnrolledParArrayCombiner.scala
index d1379cde11..5e4572da60 100644
--- a/src/library/scala/collection/parallel/mutable/UnrolledParArrayCombiner.scala
+++ b/src/library/scala/collection/parallel/mutable/UnrolledParArrayCombiner.scala
@@ -9,13 +9,9 @@
 package scala
 package collection.parallel.mutable
 
-import scala.collection.generic.Sizing
 import scala.collection.mutable.ArraySeq
-import scala.collection.mutable.ArrayBuffer
 import scala.collection.mutable.UnrolledBuffer
 import scala.collection.mutable.UnrolledBuffer.Unrolled
-import scala.collection.parallel.TaskSupport
-import scala.collection.parallel.unsupportedop
 import scala.collection.parallel.Combiner
 import scala.collection.parallel.Task
 import scala.reflect.ClassTag
@@ -62,7 +58,7 @@ extends Combiner[T, ParArray[T]] {
     case that: UnrolledParArrayCombiner[t] =>
       buff concat that.buff
       this
-    case _ => unsupportedop("Cannot combine with combiner of different type.")
+    case _ => throw new UnsupportedOperationException("Cannot combine with combiner of different type.")
   }
 
   def size = buff.size
diff --git a/src/library/scala/collection/parallel/package.scala b/src/library/scala/collection/parallel/package.scala
index d77dcb0658..ba64ca505b 100644
--- a/src/library/scala/collection/parallel/package.scala
+++ b/src/library/scala/collection/parallel/package.scala
@@ -35,15 +35,7 @@ package object parallel {
     else sz
   }
 
-  private[parallel] def unsupported = throw new UnsupportedOperationException
-
-  private[parallel] def unsupportedop(msg: String) = throw new UnsupportedOperationException(msg)
-
-  private[parallel] def outofbounds(idx: Int) = throw new IndexOutOfBoundsException(idx.toString)
-
-  private[parallel] def getTaskSupport: TaskSupport = new ExecutionContextTaskSupport
-
-  val defaultTaskSupport: TaskSupport = getTaskSupport
+  val defaultTaskSupport: TaskSupport = new ExecutionContextTaskSupport
 
   def setTaskSupport[Coll](c: Coll, t: TaskSupport): Coll = {
     c match {
@@ -98,7 +90,7 @@ package parallel {
       }
     }
   }
-  
+
   trait FactoryOps[From, Elem, To] {
     trait Otherwise[R] {
       def otherwise(notbody: => R): R
diff --git a/src/library/scala/concurrent/ExecutionContext.scala b/src/library/scala/concurrent/ExecutionContext.scala
index df2d68c9c6..e022b94ea8 100644
--- a/src/library/scala/concurrent/ExecutionContext.scala
+++ b/src/library/scala/concurrent/ExecutionContext.scala
@@ -11,7 +11,6 @@ package scala.concurrent
 
 import java.util.concurrent.{ ExecutorService, Executor }
 import scala.annotation.implicitNotFound
-import scala.util.Try
 
 /**
  * An `ExecutionContext` can execute program logic asynchronously,
@@ -75,7 +74,7 @@ trait ExecutionContext {
   /** Prepares for the execution of a task. Returns the prepared
      *  execution context. The recommended implementation of
      *  `prepare` is to return `this`.
-     * 
+     *
      *  This method should no longer be overridden or called. It was
      *  originally expected that `prepare` would be called by
      *  all libraries that consume ExecutionContexts, in order to
diff --git a/src/library/scala/concurrent/Future.scala b/src/library/scala/concurrent/Future.scala
index c8ababbcab..f49536d351 100644
--- a/src/library/scala/concurrent/Future.scala
+++ b/src/library/scala/concurrent/Future.scala
@@ -10,15 +10,12 @@ package scala.concurrent
 
 import scala.language.higherKinds
 
-import java.util.concurrent.{ CountDownLatch, TimeUnit, Callable }
-import java.util.concurrent.TimeUnit.{ NANOSECONDS => NANOS, MILLISECONDS ⇒ MILLIS }
+import java.util.concurrent.{CountDownLatch, TimeUnit}
 import java.util.concurrent.atomic.AtomicInteger
 
 import scala.util.control.NonFatal
 import scala.util.{Try, Success, Failure}
 import scala.concurrent.duration._
-import scala.annotation.tailrec
-import scala.collection.mutable.Builder
 import scala.collection.generic.CanBuildFrom
 import scala.reflect.ClassTag
 
@@ -215,7 +212,7 @@ trait Future[+T] extends Awaitable[T] {
    *  @param  f  function that transforms a failure of the receiver into a failure of the returned future
    *  @return    a `Future` that will be completed with the transformed value
    */
-  def transform[S](s: T => S, f: Throwable => Throwable)(implicit executor: ExecutionContext): Future[S] = 
+  def transform[S](s: T => S, f: Throwable => Throwable)(implicit executor: ExecutionContext): Future[S] =
     transform {
       case Success(r) => Try(s(r))
       case Failure(t) => Try(throw f(t)) // will throw fatal errors!
@@ -348,7 +345,7 @@ trait Future[+T] extends Awaitable[T] {
    *  @param pf    the `PartialFunction` to apply if this `Future` fails
    *  @return      a `Future` with the successful value of this `Future` or the result of the `PartialFunction`
    */
-  def recover[U >: T](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Future[U] = 
+  def recover[U >: T](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Future[U] =
     transform { _ recover pf }
 
   /** Creates a new future that will handle any matching throwable that this
@@ -429,7 +426,7 @@ trait Future[+T] extends Awaitable[T] {
    *  @return       a `Future` with the successful result of this or that `Future` or the failure of this `Future` if both fail
    */
   def fallbackTo[U >: T](that: Future[U]): Future[U] =
-    if (this eq that) this 
+    if (this eq that) this
     else {
       implicit val ec = internalExecutor
       recoverWith { case _ => that } recoverWith { case _ => this }
@@ -532,7 +529,7 @@ object Future {
       ready(atMost)
       throw new TimeoutException(s"Future timed out after [$atMost]")
     }
-    
+
     override def onSuccess[U](pf: PartialFunction[Nothing, U])(implicit executor: ExecutionContext): Unit = ()
     override def onFailure[U](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Unit = ()
     override def onComplete[U](f: Try[Nothing] => U)(implicit executor: ExecutionContext): Unit = ()
@@ -597,7 +594,7 @@ object Future {
   *  @return          the `Future` holding the result of the computation
   */
   def apply[T](body: =>T)(implicit @deprecatedName('execctx) executor: ExecutionContext): Future[T] =
-    unit.map(_ => body)    
+    unit.map(_ => body)
 
   /** Simple version of `Future.traverse`. Asynchronously and non-blockingly transforms a `TraversableOnce[Future[A]]`
    *  into a `Future[TraversableOnce[A]]`. Useful for reducing many `Future`s into a single `Future`.
diff --git a/src/library/scala/concurrent/impl/ExecutionContextImpl.scala b/src/library/scala/concurrent/impl/ExecutionContextImpl.scala
index 4cb5f51e62..7bf5cc5729 100644
--- a/src/library/scala/concurrent/impl/ExecutionContextImpl.scala
+++ b/src/library/scala/concurrent/impl/ExecutionContextImpl.scala
@@ -8,10 +8,10 @@
 
 package scala.concurrent.impl
 
-import java.util.concurrent.{ ForkJoinPool, ForkJoinWorkerThread, ForkJoinTask, Callable, Executor, ExecutorService, Executors, ThreadFactory, TimeUnit }
+import java.util.concurrent.{ ForkJoinPool, ForkJoinWorkerThread, ForkJoinTask, Callable, Executor, ExecutorService, ThreadFactory, TimeUnit }
 import java.util.concurrent.atomic.AtomicInteger
 import java.util.Collection
-import scala.concurrent.{ BlockContext, ExecutionContext, Awaitable, CanAwait, ExecutionContextExecutor, ExecutionContextExecutorService }
+import scala.concurrent.{ BlockContext, ExecutionContext, CanAwait, ExecutionContextExecutor, ExecutionContextExecutorService }
 import scala.annotation.tailrec
 
 
diff --git a/src/library/scala/concurrent/impl/Promise.scala b/src/library/scala/concurrent/impl/Promise.scala
index 3538ac6b94..178cd6d912 100644
--- a/src/library/scala/concurrent/impl/Promise.scala
+++ b/src/library/scala/concurrent/impl/Promise.scala
@@ -8,13 +8,13 @@
 
 package scala.concurrent.impl
 
-import scala.concurrent.{ ExecutionContext, CanAwait, OnCompleteRunnable, TimeoutException, ExecutionException, blocking }
+import scala.concurrent.{ ExecutionContext, CanAwait, OnCompleteRunnable, TimeoutException, ExecutionException }
 import scala.concurrent.Future.InternalCallbackExecutor
-import scala.concurrent.duration.{ Duration, Deadline, FiniteDuration, NANOSECONDS }
+import scala.concurrent.duration.{ Duration, FiniteDuration }
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
 import scala.util.{ Try, Success, Failure }
-import java.io.ObjectInputStream
+
 import java.util.concurrent.locks.AbstractQueuedSynchronizer
 import java.util.concurrent.atomic.AtomicReference
 
@@ -393,7 +393,7 @@ private[concurrent] object Promise {
       override def collect[S](pf: PartialFunction[T, S])(implicit executor: ExecutionContext): Future[S] = thisAs[S]
       override def zip[U](that: Future[U]): Future[(T, U)] = thisAs[(T,U)]
       override def zipWith[U, R](that: Future[U])(f: (T, U) => R)(implicit executor: ExecutionContext): Future[R] = thisAs[R]
-      override def fallbackTo[U >: T](that: Future[U]): Future[U] = 
+      override def fallbackTo[U >: T](that: Future[U]): Future[U] =
         if (this eq that) this else that.recoverWith({ case _ => this })(InternalCallbackExecutor)
       override def mapTo[S](implicit tag: ClassTag[S]): Future[S] = thisAs[S]
     }
diff --git a/src/library/scala/io/BufferedSource.scala b/src/library/scala/io/BufferedSource.scala
index 52fa525b24..33b5a1468e 100644
--- a/src/library/scala/io/BufferedSource.scala
+++ b/src/library/scala/io/BufferedSource.scala
@@ -8,11 +8,9 @@
 
 package scala.io
 
-import java.util.Arrays
 import java.io.{ InputStream, BufferedReader, InputStreamReader, PushbackReader }
 import Source.DefaultBufSize
 import scala.collection.{ Iterator, AbstractIterator }
-import scala.collection.mutable.ArrayBuffer
 
 /** This object provides convenience methods to create an iterable
  *  representation of a source file.
diff --git a/src/library/scala/math/BigDecimal.scala b/src/library/scala/math/BigDecimal.scala
index bb337e7a1d..371fd59a93 100644
--- a/src/library/scala/math/BigDecimal.scala
+++ b/src/library/scala/math/BigDecimal.scala
@@ -10,13 +10,12 @@
 package scala
 package math
 
-import java.{ lang => jl }
-import java.math.{ MathContext, BigDecimal => BigDec }
-import scala.collection.immutable.NumericRange
 import scala.language.implicitConversions
 
+import java.math.{ MathContext, BigDecimal => BigDec }
+import scala.collection.immutable.NumericRange
 
-/** 
+/**
  *  @author  Stephane Micheloud
  *  @author  Rex Kerr
  *  @version 1.1
@@ -44,17 +43,17 @@ object BigDecimal {
     val HALF_UP     = Value(RM.HALF_UP.ordinal)
     val HALF_DOWN   = Value(RM.HALF_DOWN.ordinal)
     val HALF_EVEN   = Value(RM.HALF_EVEN.ordinal)
-    val UNNECESSARY = Value(RM.UNNECESSARY.ordinal) 
+    val UNNECESSARY = Value(RM.UNNECESSARY.ordinal)
   }
-  
+
   /** Constructs a `BigDecimal` using the decimal text representation of `Double` value `d`, rounding if necessary. */
   def decimal(d: Double, mc: MathContext): BigDecimal =
     new BigDecimal(new BigDec(java.lang.Double.toString(d), mc), mc)
 
   /** Constructs a `BigDecimal` using the decimal text representation of `Double` value `d`. */
   def decimal(d: Double): BigDecimal = decimal(d, defaultMathContext)
-  
-  /** Constructs a `BigDecimal` using the decimal text representation of `Float` value `f`, rounding if necessary. 
+
+  /** Constructs a `BigDecimal` using the decimal text representation of `Float` value `f`, rounding if necessary.
    *  Note that `BigDecimal.decimal(0.1f) != 0.1f` since equality agrees with the `Double` representation, and
    *  `0.1 != 0.1f`.
    */
@@ -66,18 +65,18 @@ object BigDecimal {
    *  `0.1 != 0.1f`.
    */
   def decimal(f: Float): BigDecimal = decimal(f, defaultMathContext)
-  
+
   // This exists solely to avoid conversion from Int/Long to Float, screwing everything up.
   /** Constructs a `BigDecimal` from a `Long`, rounding if necessary.  This is identical to `BigDecimal(l, mc)`. */
   def decimal(l: Long, mc: MathContext): BigDecimal = apply(l, mc)
-  
+
   // This exists solely to avoid conversion from Int/Long to Float, screwing everything up.
   /** Constructs a `BigDecimal` from a `Long`.  This is identical to `BigDecimal(l)`. */
   def decimal(l: Long): BigDecimal = apply(l)
-  
+
   /** Constructs a `BigDecimal` using a `java.math.BigDecimal`, rounding if necessary. */
   def decimal(bd: BigDec, mc: MathContext): BigDecimal = new BigDecimal(bd.round(mc), mc)
-  
+
   /** Constructs a `BigDecimal` by expanding the binary fraction
    *  contained by `Double` value `d` into a decimal representation,
    *  rounding if necessary.  When a `Float` is converted to a
@@ -85,50 +84,50 @@ object BigDecimal {
    *  also works for converted `Float`s.
    */
   def binary(d: Double, mc: MathContext): BigDecimal = new BigDecimal(new BigDec(d, mc), mc)
-  
+
   /** Constructs a `BigDecimal` by expanding the binary fraction
    *  contained by `Double` value `d` into a decimal representation.
    *  Note: this also works correctly on converted `Float`s.
    */
   def binary(d: Double): BigDecimal = binary(d, defaultMathContext)
-  
+
   /** Constructs a `BigDecimal` from a `java.math.BigDecimal`.  The
    *  precision is the default for `BigDecimal` or enough to represent
    *  the `java.math.BigDecimal` exactly, whichever is greater.
    */
   def exact(repr: BigDec): BigDecimal = {
-    val mc = 
+    val mc =
       if (repr.precision <= defaultMathContext.getPrecision) defaultMathContext
       else new MathContext(repr.precision, java.math.RoundingMode.HALF_EVEN)
     new BigDecimal(repr, mc)
   }
-  
+
   /** Constructs a `BigDecimal` by fully expanding the binary fraction
    *  contained by `Double` value `d`, adjusting the precision as
    *  necessary.  Note: this works correctly on converted `Float`s also.
    */
   def exact(d: Double): BigDecimal = exact(new BigDec(d))
-  
+
   /** Constructs a `BigDecimal` that exactly represents a `BigInt`.
    */
   def exact(bi: BigInt): BigDecimal = exact(new BigDec(bi.bigInteger))
-  
+
   /** Constructs a `BigDecimal` that exactly represents a `Long`.  Note that
    *  all creation methods for `BigDecimal` that do not take a `MathContext`
    *  represent a `Long`; this is equivalent to `apply`, `valueOf`, etc..
    */
   def exact(l: Long): BigDecimal = apply(l)
-  
+
   /** Constructs a `BigDecimal` that exactly represents the number
    *  specified in a `String`.
    */
   def exact(s: String): BigDecimal = exact(new BigDec(s))
-  
+
   /** Constructs a `BigDecimal` that exactly represents the number
    *  specified in base 10 in a character array.
    */
  def exact(cs: Array[Char]): BigDecimal = exact(new BigDec(cs))
-  
+
 
   /** Constructs a `BigDecimal` using the java BigDecimal static
    *  valueOf constructor.  Equivalent to `BigDecimal.decimal`.
@@ -137,7 +136,7 @@ object BigDecimal {
    *  @return the constructed `BigDecimal`
    */
   def valueOf(d: Double): BigDecimal = apply(BigDec valueOf d)
-  
+
   /** Constructs a `BigDecimal` using the java BigDecimal static
    *  valueOf constructor, specifying a `MathContext` that is
    *  used for computations but isn't used for rounding.  Use
@@ -151,7 +150,7 @@ object BigDecimal {
    */
   @deprecated("MathContext is not applied to Doubles in valueOf.  Use BigDecimal.decimal to use rounding, or java.math.BigDecimal.valueOf to avoid it.","2.11")
   def valueOf(d: Double, mc: MathContext): BigDecimal = apply(BigDec valueOf d, mc)
-  
+
   /** Constructs a `BigDecimal` using the java BigDecimal static
    *  valueOf constructor.
    *
@@ -159,14 +158,14 @@ object BigDecimal {
    *  @return the constructed `BigDecimal`
    */
   def valueOf(x: Long): BigDecimal = apply(x)
-  
+
   /** Constructs a `BigDecimal` using the java BigDecimal static
    *  valueOf constructor.  This is unlikely to do what you want;
    *  use `valueOf(f.toDouble)` or `decimal(f)` instead.
    */
   @deprecated("Float arguments to valueOf may not do what you wish.  Use decimal or valueOf(f.toDouble).","2.11")
   def valueOf(f: Float): BigDecimal = valueOf(f.toDouble)
-  
+
   /** Constructs a `BigDecimal` using the java BigDecimal static
    *  valueOf constructor.  This is unlikely to do what you want;
    *  use `valueOf(f.toDouble)` or `decimal(f)` instead.
@@ -174,7 +173,7 @@ object BigDecimal {
   @deprecated("Float arguments to valueOf may not do what you wish.  Use decimal or valueOf(f.toDouble).","2.11")
   def valueOf(f: Float, mc: MathContext): BigDecimal = valueOf(f.toDouble, mc)
 
-  
+
   /** Constructs a `BigDecimal` whose value is equal to that of the
    *  specified `Integer` value.
    *
@@ -247,7 +246,7 @@ object BigDecimal {
    *  @return  the constructed `BigDecimal`
    */
   def apply(d: Double): BigDecimal = decimal(d, defaultMathContext)
-  
+
   // note we don't use the static valueOf because it doesn't let us supply
   // a MathContext, but we should be duplicating its logic, modulo caching.
   /** Constructs a `BigDecimal` whose value is equal to that of the
@@ -281,7 +280,7 @@ object BigDecimal {
    *  into a `BigDecimal`.
    */
   def apply(x: String): BigDecimal = exact(x)
-  
+
   /** Translates the decimal String representation of a `BigDecimal`
    *  into a `BigDecimal`, rounding if necessary.
    */
@@ -295,12 +294,12 @@ object BigDecimal {
    *  @return  the constructed `BigDecimal`
    */
   def apply(x: BigInt): BigDecimal = exact(x)
-  
+
   /** Constructs a `BigDecimal` whose value is equal to that of the
    *  specified `BigInt` value, rounding if necessary.
    *
    *  @param x  the specified `BigInt` value
-   *  @param mc the precision and rounding mode for creation of this value and future operations on it   
+   *  @param mc the precision and rounding mode for creation of this value and future operations on it
    *  @return   the constructed `BigDecimal`
    */
   def apply(x: BigInt, mc: MathContext): BigDecimal =
@@ -315,13 +314,13 @@ object BigDecimal {
    */
   def apply(unscaledVal: BigInt, scale: Int): BigDecimal =
     exact(new BigDec(unscaledVal.bigInteger, scale))
-  
+
   /** Constructs a `BigDecimal` whose unscaled value is equal to that
    *  of the specified `BigInt` value.
    *
    *  @param unscaledVal the specified `BigInt` value
    *  @param scale       the scale
-   *  @param mc          the precision and rounding mode for creation of this value and future operations on it   
+   *  @param mc          the precision and rounding mode for creation of this value and future operations on it
    *  @return  the constructed `BigDecimal`
    */
   def apply(unscaledVal: BigInt, scale: Int, mc: MathContext): BigDecimal =
@@ -329,7 +328,7 @@ object BigDecimal {
 
   /** Constructs a `BigDecimal` from a `java.math.BigDecimal`. */
   def apply(bd: BigDec): BigDecimal = apply(bd, defaultMathContext)
-  
+
   @deprecated("This method appears to round a java.math.BigDecimal but actually doesn't.  Use new BigDecimal(bd, mc) instead for no rounding, or BigDecimal.decimal(bd, mc) for rounding.", "2.11")
   def apply(bd: BigDec, mc: MathContext): BigDecimal = new BigDecimal(bd, mc)
 
@@ -402,7 +401,7 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
   def this(bigDecimal: BigDec) = this(bigDecimal, BigDecimal.defaultMathContext)
   import BigDecimal.RoundingMode._
   import BigDecimal.{decimal, binary, exact}
-  
+
   if (bigDecimal eq null) throw new IllegalArgumentException("null value for BigDecimal")
   if (mc eq null) throw new IllegalArgumentException("null MathContext for BigDecimal")
 
@@ -423,7 +422,7 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
         scala.util.hashing.MurmurHash3.mixLast( temp.scaleByPowerOfTen(temp.scale).toBigInteger.hashCode, temp.scale )
       }
   }
-  
+
   /** Returns the hash code for this BigDecimal.
    *  Note that this does not merely use the underlying java object's
    *  `hashCode` because we compare `BigDecimal`s with `compareTo`
@@ -444,15 +443,15 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
    */
   override def equals (that: Any): Boolean = that match {
     case that: BigDecimal     => this equals that
-    case that: BigInt         => 
-      that.bitLength > (precision-scale-2)*BigDecimal.deci2binary && 
+    case that: BigInt         =>
+      that.bitLength > (precision-scale-2)*BigDecimal.deci2binary &&
       this.toBigIntExact.exists(that equals _)
-    case that: Double         => 
+    case that: Double         =>
       !that.isInfinity && {
         val d = toDouble
         !d.isInfinity && d == that && equals(decimal(d))
       }
-    case that: Float          => 
+    case that: Float          =>
       !that.isInfinity && {
         val f = toFloat
         !f.isInfinity && f == that && equals(decimal(f.toDouble))
@@ -482,43 +481,43 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
     val d = toDouble
     !d.isInfinity && bigDecimal.compareTo(new BigDec(d)) == 0
   }
-  
+
   /** Tests whether this `BigDecimal` holds the decimal representation of a `Double`. */
   def isDecimalDouble = {
     val d = toDouble
     !d.isInfinity && equals(decimal(d))
   }
-  
+
   /** Tests whether this `BigDecimal` holds the decimal representation of a `Float`. */
   def isDecimalFloat = {
     val f = toFloat
     !f.isInfinity && equals(decimal(f))
   }
-  
+
   /** Tests whether this `BigDecimal` holds, to within precision, the binary representation of a `Double`. */
   def isBinaryDouble = {
     val d = toDouble
     !d.isInfinity && equals(binary(d,mc))
   }
-  
+
   /** Tests whether this `BigDecimal` holds, to within precision, the binary representation of a `Float`. */
   def isBinaryFloat = {
     val f = toFloat
     !f.isInfinity && equals(binary(f,mc))
   }
-  
+
   /** Tests whether this `BigDecimal` holds the exact expansion of a `Double`'s binary fractional form into base 10. */
   def isExactDouble = {
     val d = toDouble
     !d.isInfinity && equals(exact(d))
   }
-  
+
   /** Tests whether this `BigDecimal` holds the exact expansion of a `Float`'s binary fractional form into base 10. */
   def isExactFloat = {
     val f = toFloat
     !f.isInfinity && equals(exact(f.toDouble))
   }
-  
+
 
   private def noArithmeticException(body: => Unit): Boolean = {
     try   { body ; true }
@@ -526,9 +525,9 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
   }
 
   def isWhole() = scale <= 0 || bigDecimal.stripTrailingZeros.scale <= 0
-  
+
   def underlying = bigDecimal
-  
+
 
   /** Compares this BigDecimal with the specified BigDecimal for equality.
    */
@@ -589,14 +588,14 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
     case x if x <= 0 => this
     case _           => that
   }
-  
+
   /** Returns the maximum of this and that, or this if the two are equal
    */
   def max (that: BigDecimal): BigDecimal = (this compare that) match {
     case x if x >= 0 => this
     case _           => that
   }
-  
+
   /** Remainder after dividing this by that.
    */
   def remainder (that: BigDecimal): BigDecimal = new BigDecimal(this.bigDecimal remainder that.bigDecimal, mc)
@@ -635,7 +634,7 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
     val r = this.bigDecimal round mc
     if (r eq bigDecimal) this else new BigDecimal(r, this.mc)
   }
-  
+
   /** Returns a `BigDecimal` rounded according to its own `MathContext` */
   def rounded: BigDecimal = {
     val r = bigDecimal round mc
@@ -657,7 +656,7 @@ extends ScalaNumber with ScalaNumericConversions with Serializable {
   /** Returns a `BigDecimal` whose scale is the specified value, and whose value is
    *  numerically equal to this BigDecimal's.
    */
-  def setScale(scale: Int): BigDecimal = 
+  def setScale(scale: Int): BigDecimal =
     if (this.scale == scale) this
     else new BigDecimal(this.bigDecimal setScale scale, mc)
 
diff --git a/src/library/scala/runtime/AbstractPartialFunction.scala b/src/library/scala/runtime/AbstractPartialFunction.scala
index 986cd0390f..630966d0d4 100644
--- a/src/library/scala/runtime/AbstractPartialFunction.scala
+++ b/src/library/scala/runtime/AbstractPartialFunction.scala
@@ -9,8 +9,6 @@
 package scala
 package runtime
 
-import scala.annotation.unspecialized
-
 /** `AbstractPartialFunction` reformulates all operations of its supertrait `PartialFunction`
  *  in terms of `isDefinedAt` and `applyOrElse`.
  *
diff --git a/src/library/scala/runtime/ScalaNumberProxy.scala b/src/library/scala/runtime/ScalaNumberProxy.scala
index 5e4da24c0d..9b4899aef6 100644
--- a/src/library/scala/runtime/ScalaNumberProxy.scala
+++ b/src/library/scala/runtime/ScalaNumberProxy.scala
@@ -9,8 +9,8 @@
 package scala
 package runtime
 
-import scala.collection.{ mutable, immutable }
-import scala.math.{ ScalaNumericConversions, ScalaNumericAnyConversions }
+import scala.collection.immutable
+import scala.math.ScalaNumericAnyConversions
 import immutable.NumericRange
 import Proxy.Typed
 
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 026d5edd29..1195f95093 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -9,16 +9,14 @@
 package scala
 package runtime
 
-import scala.collection.{ Seq, IndexedSeq, TraversableView, AbstractIterator, GenIterable }
+import scala.collection.{ TraversableView, AbstractIterator, GenIterable }
 import scala.collection.mutable.WrappedArray
-import scala.collection.immutable.{ StringLike, NumericRange, List, Stream, Nil, :: }
+import scala.collection.immutable.{ StringLike, NumericRange }
 import scala.collection.generic.{ Sorted, IsTraversableLike }
 import scala.reflect.{ ClassTag, classTag }
-import scala.util.control.ControlThrowable
 import java.lang.{ Class => jClass }
 
-import java.lang.Double.doubleToLongBits
-import java.lang.reflect.{ Modifier, Method => JMethod }
+import java.lang.reflect.{ Method => JMethod }
 
 /** The object ScalaRunTime provides support methods required by
  *  the scala runtime.  All these methods should be considered
diff --git a/src/library/scala/runtime/SeqCharSequence.scala b/src/library/scala/runtime/SeqCharSequence.scala
index 74e67bb9e7..293bf950db 100644
--- a/src/library/scala/runtime/SeqCharSequence.scala
+++ b/src/library/scala/runtime/SeqCharSequence.scala
@@ -9,8 +9,6 @@
 package scala
 package runtime
 
-import java.util.Arrays.copyOfRange
-
 @deprecated("Use Predef.SeqCharSequence", "2.11.0")
 final class SeqCharSequence(val xs: scala.collection.IndexedSeq[Char]) extends CharSequence {
   def length: Int                                     = xs.length
diff --git a/src/library/scala/util/Sorting.scala b/src/library/scala/util/Sorting.scala
index b4f965f69b..3bda7c0d39 100644
--- a/src/library/scala/util/Sorting.scala
+++ b/src/library/scala/util/Sorting.scala
@@ -45,7 +45,7 @@ object Sorting {
 
   /** Sort an array of Floats using `java.util.Arrays.sort`. */
   def quickSort(a: Array[Float]): Unit  = java.util.Arrays.sort(a)
-  
+
   private final val qsortThreshold = 16
 
   /** Sort array `a` with quicksort, using the Ordering on its elements.
@@ -57,9 +57,9 @@ object Sorting {
     def inner(a: Array[K], i0: Int, iN: Int, ord: Ordering[K]): Unit = {
       if (iN - i0 < qsortThreshold) insertionSort(a, i0, iN, ord)
       else {
-        var iK = (i0 + iN) >>> 1    // Unsigned div by 2
+        val iK = (i0 + iN) >>> 1    // Unsigned div by 2
         // Find index of median of first, central, and last elements
-        var pL = 
+        var pL =
           if (ord.compare(a(i0), a(iN - 1)) <= 0)
             if (ord.compare(a(i0), a(iK)) < 0)
               if (ord.compare(a(iN - 1), a(iK)) < 0) iN - 1 else iK
@@ -140,9 +140,9 @@ object Sorting {
     }
     inner(a, 0, a.length, implicitly[Ordering[K]])
   }
-  
+
   private final val mergeThreshold = 32
-  
+
   // Ordering[T] might be slow especially for boxed primitives, so use binary search variant of insertion sort
   // Caller must pass iN >= i0 or math will fail.  Also, i0 >= 0.
   private def insertionSort[@specialized T](a: Array[T], i0: Int, iN: Int, ord: Ordering[T]): Unit = {
@@ -176,7 +176,7 @@ object Sorting {
       m += 1
     }
   }
-  
+
   // Caller is required to pass iN >= i0, else math will fail.  Also, i0 >= 0.
   private def mergeSort[@specialized T: ClassTag](a: Array[T], i0: Int, iN: Int, ord: Ordering[T], scratch: Array[T] = null): Unit = {
     if (iN - i0 < mergeThreshold) insertionSort(a, i0, iN, ord)
@@ -188,7 +188,7 @@ object Sorting {
       mergeSorted(a, i0, iK, iN, ord, sc)
     }
   }
-  
+
   // Must have 0 <= i0 < iK < iN
   private def mergeSorted[@specialized T](a: Array[T], i0: Int, iK: Int, iN: Int, ord: Ordering[T], scratch: Array[T]): Unit = {
     // Check to make sure we're not already in order
@@ -212,7 +212,7 @@ object Sorting {
       // Don't need to finish a(i) because it's already in place, k = i
     }
   }
-  
+
   // Why would you even do this?
   private def booleanSort(a: Array[Boolean]): Unit = {
     var i = 0
@@ -235,7 +235,7 @@ object Sorting {
   // TODO: add upper bound: T <: AnyRef, propagate to callers below (not binary compatible)
   // Maybe also rename all these methods to `sort`.
   @inline private def sort[T](a: Array[T], ord: Ordering[T]): Unit = a match {
-    case _: Array[AnyRef]  => 
+    case _: Array[AnyRef]  =>
       // Note that runtime matches are covariant, so could actually be any Array[T] s.t. T is not primitive (even boxed value classes)
       if (a.length > 1 && (ord eq null)) throw new NullPointerException("Ordering")
       java.util.Arrays.sort(a, ord)
diff --git a/src/library/scala/util/Try.scala b/src/library/scala/util/Try.scala
index b1b9965614..84d170249d 100644
--- a/src/library/scala/util/Try.scala
+++ b/src/library/scala/util/Try.scala
@@ -9,7 +9,6 @@
 package scala
 package util
 
-import scala.collection.Seq
 import scala.util.control.NonFatal
 import scala.language.implicitConversions
 
@@ -218,12 +217,12 @@ final case class Failure[+T](exception: Throwable) extends Try[T] {
   override def isSuccess: Boolean = false
   override def get: T = throw exception
   override def getOrElse[U >: T](default: => U): U = default
-  override def orElse[U >: T](default: => Try[U]): Try[U] = 
+  override def orElse[U >: T](default: => Try[U]): Try[U] =
     try default catch { case NonFatal(e) => Failure(e) }
   override def flatMap[U](f: T => Try[U]): Try[U] = this.asInstanceOf[Try[U]]
   override def flatten[U](implicit ev: T <:< Try[U]): Try[U] = this.asInstanceOf[Try[U]]
   override def foreach[U](f: T => U): Unit = ()
-  override def transform[U](s: T => Try[U], f: Throwable => Try[U]): Try[U] = 
+  override def transform[U](s: T => Try[U], f: Throwable => Try[U]): Try[U] =
     try f(exception) catch { case NonFatal(e) => Failure(e) }
   override def map[U](f: T => U): Try[U] = this.asInstanceOf[Try[U]]
   override def collect[U](pf: PartialFunction[T, U]): Try[U] = this.asInstanceOf[Try[U]]
diff --git a/src/library/scala/util/control/Exception.scala b/src/library/scala/util/control/Exception.scala
index 24c297a2fc..702d3b5e5e 100644
--- a/src/library/scala/util/control/Exception.scala
+++ b/src/library/scala/util/control/Exception.scala
@@ -10,9 +10,7 @@ package scala
 package util
 package control
 
-import scala.collection.immutable.List
 import scala.reflect.{ ClassTag, classTag }
-import java.lang.reflect.InvocationTargetException
 import scala.language.implicitConversions