SI-7624 Fix -feature warnings and build with -feature

I added a language.existential import to LazyCombiner.scala which
should not be necessary, but causes a spurious warning otherwise:

    scala/src/library/scala/collection/parallel/mutable/LazyCombiner.scala:33:
    warning: the existential type
        scala.collection.parallel.mutable.LazyCombiner[_$1,_$2,_$3] forSome {
          type _$1; type _$2; type _$3 <: scala.collection.generic.Growable[_$1] with scala.collection.generic.Sizing },
    which cannot be expressed by wildcards, should be enabled by making the implicit value scala.language.existentials visible.
    if (other.isInstanceOf[LazyCombiner[_, _, _]]) {
                       ^

I created ticket SI-7750 to track this issue.

Author: soc

build.xml

@@ -395,7 +395,7 @@ TODO:
     <property name="scalac.args"           value=""/>
     <property name="javac.args"            value=""/>
 
-    <property name="scalac.args.always"    value="" />
+    <property name="scalac.args.always"    value="-feature" />
     <property name="scalac.args.optimise"  value=""/> <!-- scalac.args.optimise is selectively overridden in certain antcall tasks. -->
     <property name="scalac.args.all"       value="${scalac.args.always} ${scalac.args} ${scalac.args.optimise}"/>
     <property name="scalac.args.locker"    value="${scalac.args.all}"/>

src/compiler/scala/tools/nsc/typechecker/Contexts.scala

@@ -1340,6 +1340,7 @@ trait Contexts { self: Analyzer =>
 }
 
 object ContextMode {
+  import scala.language.implicitConversions
   private implicit def liftIntBitsToContextState(bits: Int): ContextMode = apply(bits)
   def apply(bits: Int): ContextMode = new ContextMode(bits)
   final val NOmode: ContextMode                   = 0

src/compiler/scala/tools/nsc/typechecker/Infer.scala

@@ -700,7 +700,7 @@ trait Infer extends Checkable {
         tp nonPrivateMember nme.apply match {
           case NoSymbol                                 => tp
           case sym if !sym.isOverloaded && sym.isPublic => OverloadedType(tp, sym.alternatives)
-          case sym                                      => OverloadedType(tp, sym filter (_.isPublic) alternatives)
+          case sym                                      => OverloadedType(tp, sym.filter(_.isPublic).alternatives)
         }
     }
 

src/library/scala/collection/parallel/mutable/LazyCombiner.scala

@@ -30,6 +30,7 @@ trait LazyCombiner[Elem, +To, Buff <: Growable[Elem] with Sizing] extends Combin
   def result: To = allocateAndCopy
   def clear() = { chain.clear() }
   def combine[N <: Elem, NewTo >: To](other: Combiner[N, NewTo]): Combiner[N, NewTo] = if (this ne other) {
+    import language.existentials // FIXME: See SI-7750
     if (other.isInstanceOf[LazyCombiner[_, _, _]]) {
       val that = other.asInstanceOf[LazyCombiner[Elem, To, Buff]]
       newLazyCombiner(chain ++= that.chain)

src/reflect/scala/reflect/internal/Kinds.scala

@@ -233,7 +233,7 @@ trait Kinds {
 
   /**
    * The data structure describing the kind of a given type.
-   * 
+   *
    * Proper types are represented using ProperTypeKind.
    *
    * Type constructors are reprented using TypeConKind.
@@ -251,7 +251,7 @@ trait Kinds {
      * it uses prescribed letters for each level: A, F, X, Y, Z.
      */
     def scalaNotation: String
-    
+
     /** Kind notation used in http://adriaanm.github.com/files/higher.pdf.
      * Proper types are expressed as *.
      * Type constructors are expressed * -> *(lo, hi) -(+)-> *.
@@ -261,13 +261,13 @@ trait Kinds {
     /** Contains bounds either as part of itself or its arguments.
      */
     def hasBounds: Boolean = !bounds.isEmptyBounds
-    
+
     private[internal] def buildState(sym: Symbol, v: Variance)(s: StringState): StringState
   }
   object Kind {
     private[internal] sealed trait ScalaNotation
     private[internal] sealed case class Head(order: Int, n: Option[Int], alias: Option[String]) extends ScalaNotation {
-      override def toString: String = { 
+      override def toString: String = {
         alias getOrElse {
           typeAlias(order) + n.map(_.toString).getOrElse("")
         }
@@ -285,7 +285,7 @@ trait Kinds {
     }
     private[internal] sealed case class Text(value: String) extends ScalaNotation {
       override def toString: String = value
-    } 
+    }
     private[internal] case class StringState(tokens: Seq[ScalaNotation]) {
       override def toString: String = tokens.mkString
       def append(value: String): StringState = StringState(tokens :+ Text(value))
@@ -310,7 +310,7 @@ trait Kinds {
             ts map {
               case Head(`o`, _, a) => Head(o, None, a)
               case t               => t
-            } 
+            }
           else ts
         })
       }
@@ -332,7 +332,7 @@ trait Kinds {
     val order = 0
     private[internal] def buildState(sym: Symbol, v: Variance)(s: StringState): StringState = {
       s.append(v.symbolicString).appendHead(order, sym).append(bounds.scalaNotation(_.toString))
-    } 
+    }
     def scalaNotation: String = Kind.Head(order, None, None) + bounds.scalaNotation(_.toString)
     def starNotation: String = "*" + bounds.starNotation(_.toString)
   }
@@ -344,7 +344,7 @@ trait Kinds {
 
   class TypeConKind(val bounds: TypeBounds, val args: Seq[TypeConKind.Argument]) extends Kind {
     import Kind.StringState
-    val order = (args map {_.kind.order} max) + 1
+    val order = (args map (_.kind.order)).max + 1
     def description: String =
       if (order == 1) "This is a type constructor: a 1st-order-kinded type."
       else  "This is a type constructor that takes type constructor(s): a higher-kinded type."
@@ -389,7 +389,7 @@ trait Kinds {
    */
   object inferKind {
     import TypeConKind.Argument
-    
+
     abstract class InferKind {
       protected def infer(tpe: Type, owner: Symbol, topLevel: Boolean): Kind
       protected def infer(sym: Symbol, topLevel: Boolean): Kind = infer(sym.tpeHK, sym.owner, topLevel)
@@ -398,7 +398,7 @@ trait Kinds {
     }
 
     def apply(pre: Type): InferKind = new InferKind {
-      protected def infer(tpe: Type, owner: Symbol, topLevel: Boolean): Kind = {        
+      protected def infer(tpe: Type, owner: Symbol, topLevel: Boolean): Kind = {
         val bounds = if (topLevel) TypeBounds.empty
                      else tpe.asSeenFrom(pre, owner).bounds
         if(!tpe.isHigherKinded) ProperTypeKind(bounds)

src/reflect/scala/reflect/internal/transform/Erasure.scala

@@ -60,7 +60,7 @@ trait Erasure {
    */
   protected def unboundedGenericArrayLevel(tp: Type): Int = tp match {
     case GenericArray(level, core) if !(core <:< AnyRefTpe) => level
-    case RefinedType(ps, _) if ps.nonEmpty                  => logResult(s"Unbounded generic level for $tp is")(ps map unboundedGenericArrayLevel max)
+    case RefinedType(ps, _) if ps.nonEmpty                  => logResult(s"Unbounded generic level for $tp is")((ps map unboundedGenericArrayLevel).max)
     case _                                                  => 0
   }
 

src/reflect/scala/reflect/internal/util/ScalaClassLoader.scala

@@ -44,7 +44,7 @@ trait ScalaClassLoader extends JClassLoader {
 
   /** Create an instance of a class with this classloader */
   def create(path: String): AnyRef =
-    tryToInitializeClass[AnyRef](path) map (_.newInstance()) orNull
+    tryToInitializeClass[AnyRef](path).map(_.newInstance()).orNull
 
   /** The actual bytes for a class file, or an empty array if it can't be found. */
   def classBytes(className: String): Array[Byte] = classAsStream(className) match {
@@ -116,7 +116,7 @@ object ScalaClassLoader {
 
   /** True if supplied class exists in supplied path */
   def classExists(urls: Seq[URL], name: String): Boolean =
-    fromURLs(urls) tryToLoadClass name isDefined
+    (fromURLs(urls) tryToLoadClass name).isDefined
 
   /** Finding what jar a clazz or instance came from */
   def originOfClass(x: Class[_]): Option[URL] =

src/reflect/scala/reflect/internal/util/TriState.scala

@@ -3,6 +3,8 @@ package reflect
 package internal
 package util
 
+import scala.language.implicitConversions
+
 import TriState._
 
 /** A simple true/false/unknown value, for those days when

src/scaladoc/scala/tools/nsc/doc/model/ModelFactory.scala

@@ -305,10 +305,9 @@ class ModelFactory(val global: Global, val settings: doc.Settings) {
       else None
     }
 
+    private def templateAndType(ancestor: Symbol): (TemplateImpl, TypeEntity) = (makeTemplate(ancestor), makeType(reprSymbol.info.baseType(ancestor), this))
     lazy val (linearizationTemplates, linearizationTypes) =
-      reprSymbol.ancestors map { ancestor =>
-        (makeTemplate(ancestor), makeType(reprSymbol.info.baseType(ancestor), this))
-      } unzip
+      (reprSymbol.ancestors map templateAndType).unzip
 
     /* Subclass cache */
     private lazy val subClassesCache = (
@@ -321,7 +320,7 @@ class ModelFactory(val global: Global, val settings: doc.Settings) {
     }
     def directSubClasses = if (subClassesCache == null) Nil else subClassesCache.toList
 
-    /* Implcitly convertible class cache */
+    /* Implicitly convertible class cache */
     private var implicitlyConvertibleClassesCache: mutable.ListBuffer[(DocTemplateImpl, ImplicitConversionImpl)] = null
     def registerImplicitlyConvertibleClass(dtpl: DocTemplateImpl, conv: ImplicitConversionImpl): Unit = {
       if (implicitlyConvertibleClassesCache == null)
@@ -841,7 +840,7 @@ class ModelFactory(val global: Global, val settings: doc.Settings) {
                 def value = tree
               }
             }
-          case None => 
+          case None =>
             argTrees map { tree =>
               new ValueArgument {
                 def parameter = None

src/xml/scala/xml/Elem.scala

@@ -37,6 +37,7 @@ object Elem {
   }
 
   import scala.sys.process._
+  import scala.language.implicitConversions
   /** Implicitly convert a [[scala.xml.Elem]] into a
     * [[scala.sys.process.ProcessBuilder]]. This is done by obtaining the text
     * elements of the element, trimming spaces, and then converting the result