Merge pull request #4176 from mpociecha/flat-classpath2

The alternative, flat representation of classpath elements

40 files changed, 1394 insertions, 301 deletions

diff --git a/src/compiler/scala/reflect/macros/contexts/Infrastructure.scala b/src/compiler/scala/reflect/macros/contexts/Infrastructure.scala
index df7aa4d2be..7088058145 100644
--- a/src/compiler/scala/reflect/macros/contexts/Infrastructure.scala
+++ b/src/compiler/scala/reflect/macros/contexts/Infrastructure.scala
@@ -12,5 +12,5 @@ trait Infrastructure {
 
   def compilerSettings: List[String] = universe.settings.recreateArgs
 
-  def classPath: List[java.net.URL] = global.classPath.asURLs
+  def classPath: List[java.net.URL] = global.classPath.asURLs.toList
 }
diff --git a/src/compiler/scala/tools/nsc/ClassPathMemoryConsumptionTester.scala b/src/compiler/scala/tools/nsc/ClassPathMemoryConsumptionTester.scala
new file mode 100644
index 0000000000..2faf6c6272
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/ClassPathMemoryConsumptionTester.scala
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc
+
+import scala.io.StdIn.readLine
+
+/**
+ * Simple application to check out amount of memory used by chosen classpath representation.
+ * It allows us to create many scalac-like calls based on specified parameters, where each main retains Global.
+ * And we need additional tool (e.g. profiler) to measure memory consumption itself.
+ */
+object ClassPathMemoryConsumptionTester {
+
+  private class TestSettings extends Settings {
+    val requiredInstances = IntSetting("-requiredInstances",
+      "Determine how many times classpath should be loaded", 10, Some((1, 10000)), (_: String) => None)
+  }
+
+  private class MainRetainsGlobal extends scala.tools.nsc.MainClass {
+    var retainedGlobal: Global = _
+    override def doCompile(compiler: Global) {
+      retainedGlobal = compiler
+      super.doCompile(compiler)
+    }
+  }
+
+  def main(args: Array[String]): Unit = {
+    if (args contains "-help") usage()
+    else doTest(args)
+  }
+
+  private def doTest(args: Array[String]) = {
+    val settings = loadSettings(args.toList)
+
+    val mains = (1 to settings.requiredInstances.value) map (_ => new MainRetainsGlobal)
+
+    // we need original settings without additional params to be able to use them later
+    val baseArgs = argsWithoutRequiredInstances(args)
+
+    println(s"Loading classpath ${settings.requiredInstances.value} times")
+    val startTime = System.currentTimeMillis()
+
+    mains map (_.process(baseArgs))
+
+    val elapsed = System.currentTimeMillis() - startTime
+    println(s"Operation finished - elapsed $elapsed ms")
+    println("Memory consumption can be now measured")
+
+    var textFromStdIn = ""
+    while (textFromStdIn.toLowerCase != "exit")
+      textFromStdIn = readLine("Type 'exit' to close application: ")
+  }
+
+  /**
+   * Prints usage information
+   */
+  private def usage(): Unit =
+    println( """Use classpath and sourcepath options like in the case of e.g. 'scala' command.
+               | There's also one additional option:
+               | -requiredInstances <int value> Determine how many times classpath should be loaded
+             """.stripMargin.trim)
+
+  private def loadSettings(args: List[String]) = {
+    val settings = new TestSettings()
+    settings.processArguments(args, processAll = true)
+    if (settings.classpath.isDefault)
+      settings.classpath.value = sys.props("java.class.path")
+    settings
+  }
+
+  private def argsWithoutRequiredInstances(args: Array[String]) = {
+    val instancesIndex = args.indexOf("-requiredInstances")
+    if (instancesIndex == -1) args
+    else args.dropRight(args.length - instancesIndex) ++ args.drop(instancesIndex + 2)
+  }
+}
diff --git a/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala b/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
index ad75d02bff..1289d55c37 100644
--- a/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
+++ b/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
@@ -5,10 +5,11 @@
 
 package scala.tools.nsc
 
-import scala.tools.util.PathResolver
+import java.net.URL
+import scala.tools.util.PathResolverFactory
 
 class GenericRunnerSettings(error: String => Unit) extends Settings(error) {
-  def classpathURLs = new PathResolver(this).asURLs
+  def classpathURLs: Seq[URL] = PathResolverFactory.create(this).resultAsURLs
 
   val howtorun =
     ChoiceSetting(
diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index e62dfd00a6..733664c30a 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -14,11 +14,10 @@ import scala.compat.Platform.currentTime
 import scala.collection.{ mutable, immutable }
 import io.{ SourceReader, AbstractFile, Path }
 import reporters.{ Reporter, ConsoleReporter }
-import util.{ ClassPath, MergedClassPath, StatisticsInfo, returning, stackTraceString }
+import util.{ ClassFileLookup, ClassPath, MergedClassPath, StatisticsInfo, returning }
 import scala.reflect.ClassTag
-import scala.reflect.internal.util.{ OffsetPosition, SourceFile, NoSourceFile, BatchSourceFile, ScriptSourceFile }
-import scala.reflect.internal.pickling.{ PickleBuffer, PickleFormat }
-import scala.reflect.io.VirtualFile
+import scala.reflect.internal.util.{ SourceFile, NoSourceFile, BatchSourceFile, ScriptSourceFile }
+import scala.reflect.internal.pickling.PickleBuffer
 import symtab.{ Flags, SymbolTable, SymbolTrackers }
 import symtab.classfile.Pickler
 import plugins.Plugins
@@ -35,6 +34,8 @@ import backend.opt.{ Inliners, InlineExceptionHandlers, ConstantOptimization, Cl
 import backend.icode.analysis._
 import scala.language.postfixOps
 import scala.tools.nsc.ast.{TreeGen => AstTreeGen}
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
 
 class Global(var currentSettings: Settings, var reporter: Reporter)
     extends SymbolTable
@@ -58,7 +59,12 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   class GlobalMirror extends Roots(NoSymbol) {
     val universe: self.type = self
-    def rootLoader: LazyType = new loaders.PackageLoader(classPath)
+    def rootLoader: LazyType = {
+      settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Flat => new loaders.PackageLoaderUsingFlatClassPath(FlatClassPath.RootPackage, flatClassPath)
+        case ClassPathRepresentationType.Recursive => new loaders.PackageLoader(recursiveClassPath)
+      }
+    }
     override def toString = "compiler mirror"
   }
   implicit val MirrorTag: ClassTag[Mirror] = ClassTag[Mirror](classOf[GlobalMirror])
@@ -104,7 +110,14 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
   type PlatformClassPath = ClassPath[AbstractFile]
   type OptClassPath = Option[PlatformClassPath]
 
-  def classPath: PlatformClassPath = platform.classPath
+  def classPath: ClassFileLookup[AbstractFile] = settings.YclasspathImpl.value match {
+    case ClassPathRepresentationType.Flat => flatClassPath
+    case ClassPathRepresentationType.Recursive => recursiveClassPath
+  }
+
+  private def recursiveClassPath: ClassPath[AbstractFile] = platform.classPath
+
+  private def flatClassPath: FlatClassPath = platform.flatClassPath
 
   // sub-components --------------------------------------------------
 
@@ -319,7 +332,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
           None
       }
 
-    val charset = ( if (settings.encoding.isSetByUser) Some(settings.encoding.value) else None ) flatMap loadCharset getOrElse {
+    val charset = settings.encoding.valueSetByUser flatMap loadCharset getOrElse {
       settings.encoding.value = defaultEncoding // A mandatory charset
       Charset.forName(defaultEncoding)
     }
@@ -334,16 +347,16 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
       }
     }
 
-    ( if (settings.sourceReader.isSetByUser) Some(settings.sourceReader.value) else None ) flatMap loadReader getOrElse {
+    settings.sourceReader.valueSetByUser flatMap loadReader getOrElse {
       new SourceReader(charset.newDecoder(), reporter)
     }
   }
 
-  if (settings.verbose || settings.Ylogcp) {
+  if (settings.verbose || settings.Ylogcp)
     reporter.echo(
-      s"[search path for source files: ${classPath.sourcepaths.mkString(",")}]\n"+
-      s"[search path for class files: ${classPath.asClasspathString}")
-  }
+      s"[search path for source files: ${classPath.asSourcePathString}]\n" +
+      s"[search path for class files: ${classPath.asClassPathString}]"
+    )
 
   // The current division between scala.reflect.* and scala.tools.nsc.* is pretty
   // clunky.  It is often difficult to have a setting influence something without having
@@ -846,6 +859,9 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   /** Extend classpath of `platform` and rescan updated packages. */
   def extendCompilerClassPath(urls: URL*): Unit = {
+    if (settings.YclasspathImpl.value == ClassPathRepresentationType.Flat)
+      throw new UnsupportedOperationException("Flat classpath doesn't support extending the compiler classpath")
+
     val newClassPath = platform.classPath.mergeUrlsIntoClassPath(urls: _*)
     platform.currentClassPath = Some(newClassPath)
     // Reload all specified jars into this compiler instance
@@ -881,8 +897,11 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
    *                entries on the classpath.
    */
   def invalidateClassPathEntries(paths: String*): Unit = {
+    if (settings.YclasspathImpl.value == ClassPathRepresentationType.Flat)
+      throw new UnsupportedOperationException("Flat classpath doesn't support the classpath invalidation")
+
     implicit object ClassPathOrdering extends Ordering[PlatformClassPath] {
-      def compare(a:PlatformClassPath, b:PlatformClassPath) = a.asClasspathString compare b.asClasspathString
+      def compare(a:PlatformClassPath, b:PlatformClassPath) = a.asClassPathString compare b.asClassPathString
     }
     val invalidated, failed = new mutable.ListBuffer[ClassSymbol]
     classPath match {
@@ -910,10 +929,10 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
           informProgress(s"classpath updated on entries [${subst.keys mkString ","}]")
           def mkClassPath(elems: Iterable[PlatformClassPath]): PlatformClassPath =
             if (elems.size == 1) elems.head
-            else new MergedClassPath(elems, classPath.context)
+            else new MergedClassPath(elems, recursiveClassPath.context)
           val oldEntries = mkClassPath(subst.keys)
           val newEntries = mkClassPath(subst.values)
-          mergeNewEntries(newEntries, RootClass, Some(classPath), Some(oldEntries), invalidated, failed)
+          mergeNewEntries(newEntries, RootClass, Some(recursiveClassPath), Some(oldEntries), invalidated, failed)
         }
     }
     def show(msg: String, syms: scala.collection.Traversable[Symbol]) =
diff --git a/src/compiler/scala/tools/nsc/ObjectRunner.scala b/src/compiler/scala/tools/nsc/ObjectRunner.scala
index 95264aeda6..7c14f4943f 100644
--- a/src/compiler/scala/tools/nsc/ObjectRunner.scala
+++ b/src/compiler/scala/tools/nsc/ObjectRunner.scala
@@ -18,14 +18,14 @@ trait CommonRunner {
    *  @throws NoSuchMethodException
    *  @throws InvocationTargetException
    */
-  def run(urls: List[URL], objectName: String, arguments: Seq[String]) {
+  def run(urls: Seq[URL], objectName: String, arguments: Seq[String]) {
     (ScalaClassLoader fromURLs urls).run(objectName, arguments)
   }
 
   /** Catches exceptions enumerated by run (in the case of InvocationTargetException,
    *  unwrapping it) and returns it any thrown in Left(x).
    */
-  def runAndCatch(urls: List[URL], objectName: String, arguments: Seq[String]): Either[Throwable, Boolean] = {
+  def runAndCatch(urls: Seq[URL], objectName: String, arguments: Seq[String]): Either[Throwable, Boolean] = {
     try   { run(urls, objectName, arguments) ; Right(true) }
     catch { case e: Throwable => Left(unwrap(e)) }
   }
diff --git a/src/compiler/scala/tools/nsc/PhaseAssembly.scala b/src/compiler/scala/tools/nsc/PhaseAssembly.scala
index cfb4cd23a1..1eb6c9da2c 100644
--- a/src/compiler/scala/tools/nsc/PhaseAssembly.scala
+++ b/src/compiler/scala/tools/nsc/PhaseAssembly.scala
@@ -199,7 +199,7 @@ trait PhaseAssembly {
     // Add all phases in the set to the graph
     val graph = phasesSetToDepGraph(phasesSet)
 
-    val dot = if (settings.genPhaseGraph.isSetByUser) Some(settings.genPhaseGraph.value) else None
+    val dot = settings.genPhaseGraph.valueSetByUser
 
     // Output the phase dependency graph at this stage
     def dump(stage: Int) = dot foreach (n => graphToDotFile(graph, s"$n-$stage.dot"))
diff --git a/src/compiler/scala/tools/nsc/ScriptRunner.scala b/src/compiler/scala/tools/nsc/ScriptRunner.scala
index 7d5c6f6fff..6d24b31531 100644
--- a/src/compiler/scala/tools/nsc/ScriptRunner.scala
+++ b/src/compiler/scala/tools/nsc/ScriptRunner.scala
@@ -8,7 +8,10 @@ package tools.nsc
 
 import io.{ AbstractFile, Directory, File, Path }
 import java.io.IOException
+import scala.tools.nsc.classpath.DirectoryFlatClassPath
 import scala.tools.nsc.reporters.{Reporter,ConsoleReporter}
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.ClassPath.DefaultJavaContext
 import util.Exceptional.unwrap
 
 /** An object that runs Scala code in script files.
@@ -112,8 +115,10 @@ class ScriptRunner extends HasCompileSocket {
     }
 
     def hasClassToRun(d: Directory): Boolean = {
-      import util.ClassPath.{ DefaultJavaContext => ctx }
-      val cp = ctx.newClassPath(AbstractFile.getDirectory(d))
+      val cp = settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Recursive => DefaultJavaContext.newClassPath(AbstractFile.getDirectory(d))
+        case ClassPathRepresentationType.Flat => DirectoryFlatClassPath(d.jfile)
+      }
       cp.findClass(mainClass).isDefined
     }
 
diff --git a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
index 4877bd9b80..6bd123c51f 100644
--- a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
+++ b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
@@ -7,7 +7,10 @@ package scala.tools.nsc
 package backend
 
 import io.AbstractFile
-import util.{ClassPath,MergedClassPath,DeltaClassPath}
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.{ ClassPath, DeltaClassPath, MergedClassPath }
+import scala.tools.util.FlatClassPathResolver
 import scala.tools.util.PathResolver
 
 trait JavaPlatform extends Platform {
@@ -19,10 +22,20 @@ trait JavaPlatform extends Platform {
   private[nsc] var currentClassPath: Option[MergedClassPath[AbstractFile]] = None
 
   def classPath: ClassPath[AbstractFile] = {
+    assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Recursive,
+      "To use recursive classpath representation you must enable it with -YclasspathImpl:recursive compiler option.")
+
     if (currentClassPath.isEmpty) currentClassPath = Some(new PathResolver(settings).result)
     currentClassPath.get
   }
 
+  private[nsc] lazy val flatClassPath: FlatClassPath = {
+    assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Flat,
+      "To use flat classpath representation you must enable it with -YclasspathImpl:flat compiler option.")
+
+    new FlatClassPathResolver(settings).result
+  }
+
   /** Update classpath with a substituted subentry */
   def updateClassPath(subst: Map[ClassPath[AbstractFile], ClassPath[AbstractFile]]) =
     currentClassPath = Some(new DeltaClassPath(currentClassPath.get, subst))
diff --git a/src/compiler/scala/tools/nsc/backend/Platform.scala b/src/compiler/scala/tools/nsc/backend/Platform.scala
index 439cc1efb8..c3bc213be1 100644
--- a/src/compiler/scala/tools/nsc/backend/Platform.scala
+++ b/src/compiler/scala/tools/nsc/backend/Platform.scala
@@ -8,6 +8,7 @@ package backend
 
 import util.ClassPath
 import io.AbstractFile
+import scala.tools.nsc.classpath.FlatClassPath
 
 /** The platform dependent pieces of Global.
  */
@@ -15,9 +16,12 @@ trait Platform {
   val symbolTable: symtab.SymbolTable
   import symbolTable._
 
-  /** The compiler classpath. */
+  /** The old, recursive implementation of compiler classpath. */
   def classPath: ClassPath[AbstractFile]
 
+  /** The new implementation of compiler classpath. */
+  private[nsc] def flatClassPath: FlatClassPath
+
   /** Update classpath with a substitution that maps entries to entries */
   def updateClassPath(subst: Map[ClassPath[AbstractFile], ClassPath[AbstractFile]])
 
diff --git a/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala b/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
index bc35a9e7de..10f0c6ee00 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/ICodes.scala
@@ -113,7 +113,8 @@ abstract class ICodes extends AnyRef
       global.loaders.lookupMemberAtTyperPhaseIfPossible(sym, name)
     lazy val symbolTable: global.type = global
     lazy val loaders: global.loaders.type = global.loaders
-    def classPath: util.ClassPath[AbstractFile] = ICodes.this.global.platform.classPath
+
+    def classFileLookup: util.ClassFileLookup[AbstractFile] = global.classPath
   }
 
   /** A phase which works on icode. */
diff --git a/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala b/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala
new file mode 100644
index 0000000000..3f06264e3c
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.net.URL
+import scala.annotation.tailrec
+import scala.collection.mutable.ArrayBuffer
+import scala.reflect.io.AbstractFile
+import scala.tools.nsc.util.ClassPath
+import scala.tools.nsc.util.ClassRepresentation
+
+/**
+ * A classpath unifying multiple class- and sourcepath entries.
+ * Flat classpath can obtain entries for classes and sources independently
+ * so it tries to do operations quite optimally - iterating only these collections
+ * which are needed in the given moment and only as far as it's necessary.
+ * @param aggregates classpath instances containing entries which this class processes
+ */
+case class AggregateFlatClassPath(aggregates: Seq[FlatClassPath]) extends FlatClassPath {
+
+  override def findClassFile(className: String): Option[AbstractFile] = {
+    @tailrec
+    def find(aggregates: Seq[FlatClassPath]): Option[AbstractFile] =
+      if (aggregates.nonEmpty) {
+        val classFile = aggregates.head.findClassFile(className)
+        if (classFile.isDefined) classFile
+        else find(aggregates.tail)
+      } else None
+
+    find(aggregates)
+  }
+
+  override def findClass(className: String): Option[ClassRepresentation[AbstractFile]] = {
+    val (pkg, simpleClassName) = PackageNameUtils.separatePkgAndClassNames(className)
+
+    @tailrec
+    def findEntry[T <: ClassRepClassPathEntry](aggregates: Seq[FlatClassPath], getEntries: FlatClassPath => Seq[T]): Option[T] =
+      if (aggregates.nonEmpty) {
+        val entry = getEntries(aggregates.head)
+          .find(_.name == simpleClassName)
+        if (entry.isDefined) entry
+        else findEntry(aggregates.tail, getEntries)
+      } else None
+
+    val classEntry = findEntry(aggregates, classesGetter(pkg))
+    val sourceEntry = findEntry(aggregates, sourcesGetter(pkg))
+
+    mergeClassesAndSources(classEntry.toList, sourceEntry.toList).headOption
+  }
+
+  override def asURLs: Seq[URL] = aggregates.flatMap(_.asURLs)
+
+  override def asClassPathStrings: Seq[String] = aggregates.map(_.asClassPathString).distinct
+
+  override def asSourcePathString: String = ClassPath.join(aggregates map (_.asSourcePathString): _*)
+
+  override private[nsc] def packages(inPackage: String): Seq[PackageEntry] = {
+    val aggregatedPackages = aggregates.flatMap(_.packages(inPackage)).distinct
+    aggregatedPackages
+  }
+
+  override private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] =
+    getDistinctEntries(classesGetter(inPackage))
+
+  override private[nsc] def sources(inPackage: String): Seq[SourceFileEntry] =
+    getDistinctEntries(sourcesGetter(inPackage))
+
+  override private[nsc] def list(inPackage: String): FlatClassPathEntries = {
+    val (packages, classesAndSources) = aggregates.map(_.list(inPackage)).unzip
+    val distinctPackages = packages.flatten.distinct
+    val distinctClassesAndSources = mergeClassesAndSources(classesAndSources: _*)
+    FlatClassPathEntries(distinctPackages, distinctClassesAndSources)
+  }
+
+  /**
+   * Returns only one entry for each name. If there's both a source and a class entry, it
+   * creates an entry containing both of them. If there would be more than one class or source
+   * entries for the same class it always would use the first entry of each type found on a classpath.
+   */
+  private def mergeClassesAndSources(entries: Seq[ClassRepClassPathEntry]*): Seq[ClassRepClassPathEntry] = {
+    // based on the implementation from MergedClassPath
+    var count = 0
+    val indices = collection.mutable.HashMap[String, Int]()
+    val mergedEntries = new ArrayBuffer[ClassRepClassPathEntry](1024)
+
+    for {
+      partOfEntries <- entries
+      entry <- partOfEntries
+    } {
+      val name = entry.name
+      if (indices contains name) {
+        val index = indices(name)
+        val existing = mergedEntries(index)
+
+        if (existing.binary.isEmpty && entry.binary.isDefined)
+          mergedEntries(index) = ClassAndSourceFilesEntry(entry.binary.get, existing.source.get)
+        if (existing.source.isEmpty && entry.source.isDefined)
+          mergedEntries(index) = ClassAndSourceFilesEntry(existing.binary.get, entry.source.get)
+      }
+      else {
+        indices(name) = count
+        mergedEntries += entry
+        count += 1
+      }
+    }
+    mergedEntries.toIndexedSeq
+  }
+
+  private def getDistinctEntries[EntryType <: ClassRepClassPathEntry](getEntries: FlatClassPath => Seq[EntryType]): Seq[EntryType] = {
+    val seenNames = collection.mutable.HashSet[String]()
+    val entriesBuffer = new ArrayBuffer[EntryType](1024)
+    for {
+      cp <- aggregates
+      entry <- getEntries(cp) if !seenNames.contains(entry.name)
+    } {
+      entriesBuffer += entry
+      seenNames += entry.name
+    }
+    entriesBuffer.toIndexedSeq
+  }
+
+  private def classesGetter(pkg: String) = (cp: FlatClassPath) => cp.classes(pkg)
+  private def sourcesGetter(pkg: String) = (cp: FlatClassPath) => cp.sources(pkg)
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/ClassPathFactory.scala b/src/compiler/scala/tools/nsc/classpath/ClassPathFactory.scala
new file mode 100644
index 0000000000..9bf4e3f779
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/ClassPathFactory.scala
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import scala.reflect.io.AbstractFile
+import scala.tools.nsc.util.ClassPath
+
+/**
+ * A trait that contains factory methods for classpath elements of type T.
+ *
+ * The logic has been abstracted from ClassPath#ClassPathContext so it's possible
+ * to have common trait that supports both recursive and flat classpath representations.
+ *
+ * Therefore, we expect that T will be either ClassPath[U] or FlatClassPath.
+ */
+trait ClassPathFactory[T] {
+
+  /**
+   * Create a new classpath based on the abstract file.
+   */
+  def newClassPath(file: AbstractFile): T
+
+  /**
+   * Creators for sub classpaths which preserve this context.
+   */
+  def sourcesInPath(path: String): List[T]
+
+  def expandPath(path: String, expandStar: Boolean = true): List[String] = ClassPath.expandPath(path, expandStar)
+
+  def expandDir(extdir: String): List[String] = ClassPath.expandDir(extdir)
+
+  def contentsOfDirsInPath(path: String): List[T] =
+    for {
+      dir <- expandPath(path, expandStar = false)
+      name <- expandDir(dir)
+      entry <- Option(AbstractFile.getDirectory(name))
+    } yield newClassPath(entry)
+
+  def classesInExpandedPath(path: String): IndexedSeq[T] =
+    classesInPathImpl(path, expand = true).toIndexedSeq
+
+  def classesInPath(path: String) = classesInPathImpl(path, expand = false)
+
+  def classesInManifest(useManifestClassPath: Boolean) =
+    if (useManifestClassPath) ClassPath.manifests.map(url => newClassPath(AbstractFile getResources url))
+    else Nil
+
+  // Internal
+  protected def classesInPathImpl(path: String, expand: Boolean) =
+    for {
+      file <- expandPath(path, expand)
+      dir <- Option(AbstractFile.getDirectory(file))
+    } yield newClassPath(dir)
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/DirectoryFlatClassPath.scala b/src/compiler/scala/tools/nsc/classpath/DirectoryFlatClassPath.scala
new file mode 100644
index 0000000000..81d2f7320f
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/DirectoryFlatClassPath.scala
@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.io.File
+import java.io.FileFilter
+import java.net.URL
+import scala.reflect.io.AbstractFile
+import scala.reflect.io.PlainFile
+import scala.tools.nsc.util.ClassRepresentation
+import FileUtils._
+
+/**
+ * A trait allowing to look for classpath entries of given type in directories.
+ * It provides common logic for classes handling class and source files.
+ * It makes use of the fact that in the case of nested directories it's easy to find a file
+ * when we have a name of a package.
+ */
+trait DirectoryFileLookup[FileEntryType <: ClassRepClassPathEntry] extends FlatClassPath {
+  val dir: File
+  assert(dir != null, "Directory file in DirectoryFileLookup cannot be null")
+
+  override def asURLs: Seq[URL] = Seq(dir.toURI.toURL)
+  override def asClassPathStrings: Seq[String] = Seq(dir.getPath)
+
+  import FlatClassPath.RootPackage
+  private def getDirectory(forPackage: String): Option[File] = {
+    if (forPackage == RootPackage) {
+      Some(dir)
+    } else {
+      val packageDirName = FileUtils.dirPath(forPackage)
+      val packageDir = new File(dir, packageDirName)
+      if (packageDir.exists && packageDir.isDirectory) {
+        Some(packageDir)
+      } else None
+    }
+  }
+
+  override private[nsc] def packages(inPackage: String): Seq[PackageEntry] = {
+    val dirForPackage = getDirectory(inPackage)
+    val nestedDirs: Array[File] = dirForPackage match {
+      case None => Array.empty
+      case Some(directory) => directory.listFiles(DirectoryFileLookup.packageDirectoryFileFilter)
+    }
+    val prefix = PackageNameUtils.packagePrefix(inPackage)
+    val entries = nestedDirs map { file =>
+      PackageEntryImpl(prefix + file.getName)
+    }
+    entries
+  }
+
+  protected def files(inPackage: String): Seq[FileEntryType] = {
+    val dirForPackage = getDirectory(inPackage)
+    val files: Array[File] = dirForPackage match {
+      case None => Array.empty
+      case Some(directory) => directory.listFiles(fileFilter)
+    }
+    val entries = files map { file =>
+      val wrappedFile = new scala.reflect.io.File(file)
+      createFileEntry(new PlainFile(wrappedFile))
+    }
+    entries
+  }
+
+  override private[nsc] def list(inPackage: String): FlatClassPathEntries = {
+    val dirForPackage = getDirectory(inPackage)
+    val files: Array[File] = dirForPackage match {
+      case None => Array.empty
+      case Some(directory) => directory.listFiles()
+    }
+    val packagePrefix = PackageNameUtils.packagePrefix(inPackage)
+    val packageBuf = collection.mutable.ArrayBuffer.empty[PackageEntry]
+    val fileBuf = collection.mutable.ArrayBuffer.empty[FileEntryType]
+    for (file <- files) {
+      if (file.isPackage) {
+        val pkgEntry = PackageEntryImpl(packagePrefix + file.getName)
+        packageBuf += pkgEntry
+      } else if (fileFilter.accept(file)) {
+        val wrappedFile = new scala.reflect.io.File(file)
+        val abstractFile = new PlainFile(wrappedFile)
+        fileBuf += createFileEntry(abstractFile)
+      }
+    }
+    FlatClassPathEntries(packageBuf, fileBuf)
+  }
+
+  protected def createFileEntry(file: AbstractFile): FileEntryType
+  protected def fileFilter: FileFilter
+}
+
+object DirectoryFileLookup {
+
+  private[classpath] object packageDirectoryFileFilter extends FileFilter {
+    override def accept(pathname: File): Boolean = pathname.isPackage
+  }
+}
+
+case class DirectoryFlatClassPath(dir: File)
+  extends DirectoryFileLookup[ClassFileEntryImpl]
+  with NoSourcePaths {
+
+  override def findClass(className: String): Option[ClassRepresentation[AbstractFile]] = findClassFile(className) map ClassFileEntryImpl
+
+  override def findClassFile(className: String): Option[AbstractFile] = {
+    val relativePath = FileUtils.dirPath(className)
+    val classFile = new File(s"$dir/$relativePath.class")
+    if (classFile.exists) {
+      val wrappedClassFile = new scala.reflect.io.File(classFile)
+      val abstractClassFile = new PlainFile(wrappedClassFile)
+      Some(abstractClassFile)
+    } else None
+  }
+
+  override protected def createFileEntry(file: AbstractFile): ClassFileEntryImpl = ClassFileEntryImpl(file)
+  override protected def fileFilter: FileFilter = DirectoryFlatClassPath.classFileFilter
+
+  override private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] = files(inPackage)
+}
+
+object DirectoryFlatClassPath {
+
+  private val classFileFilter = new FileFilter {
+    override def accept(pathname: File): Boolean = pathname.isClass
+  }
+}
+
+case class DirectoryFlatSourcePath(dir: File)
+  extends DirectoryFileLookup[SourceFileEntryImpl]
+  with NoClassPaths {
+
+  override def asSourcePathString: String = asClassPathString
+
+  override protected def createFileEntry(file: AbstractFile): SourceFileEntryImpl = SourceFileEntryImpl(file)
+  override protected def fileFilter: FileFilter = DirectoryFlatSourcePath.sourceFileFilter
+
+  override def findClass(className: String): Option[ClassRepresentation[AbstractFile]] = {
+    findSourceFile(className) map SourceFileEntryImpl
+  }
+
+  private def findSourceFile(className: String): Option[AbstractFile] = {
+    val relativePath = FileUtils.dirPath(className)
+    val sourceFile = Stream("scala", "java")
+      .map(ext => new File(s"$dir/$relativePath.$ext"))
+      .collectFirst { case file if file.exists() => file }
+
+    sourceFile.map { file =>
+      val wrappedSourceFile = new scala.reflect.io.File(file)
+      val abstractSourceFile = new PlainFile(wrappedSourceFile)
+      abstractSourceFile
+    }
+  }
+
+  override private[nsc] def sources(inPackage: String): Seq[SourceFileEntry] = files(inPackage)
+}
+
+object DirectoryFlatSourcePath {
+
+  private val sourceFileFilter = new FileFilter {
+    override def accept(pathname: File): Boolean = endsScalaOrJava(pathname.getName)
+  }
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/FileUtils.scala b/src/compiler/scala/tools/nsc/classpath/FileUtils.scala
new file mode 100644
index 0000000000..ee2528e15c
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/FileUtils.scala
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.io.{ File => JFile }
+import java.net.URL
+import scala.reflect.internal.FatalError
+import scala.reflect.io.AbstractFile
+
+/**
+ * Common methods related to Java files and abstract files used in the context of classpath
+ */
+object FileUtils {
+  implicit class AbstractFileOps(val file: AbstractFile) extends AnyVal {
+    def isPackage: Boolean = file.isDirectory && mayBeValidPackage(file.name)
+
+    def isClass: Boolean = !file.isDirectory && file.hasExtension("class")
+
+    def isScalaOrJavaSource: Boolean = !file.isDirectory && (file.hasExtension("scala") || file.hasExtension("java"))
+
+    // TODO do we need to check also other files using ZipMagicNumber like in scala.tools.nsc.io.Jar.isJarOrZip?
+    def isJarOrZip: Boolean = file.hasExtension("jar") || file.hasExtension("zip")
+
+    /**
+     * Safe method returning a sequence containing one URL representing this file, when underlying file exists,
+     * and returning given default value in other case
+     */
+    def toURLs(default: => Seq[URL] = Seq.empty): Seq[URL] = if (file.file == null) default else Seq(file.toURL)
+  }
+
+  implicit class FileOps(val file: JFile) extends AnyVal {
+    def isPackage: Boolean = file.isDirectory && mayBeValidPackage(file.getName)
+
+    def isClass: Boolean = file.isFile && file.getName.endsWith(".class")
+  }
+
+  def stripSourceExtension(fileName: String): String = {
+    if (endsScala(fileName)) stripClassExtension(fileName)
+    else if (endsJava(fileName)) stripJavaExtension(fileName)
+    else throw new FatalError("Unexpected source file ending: " + fileName)
+  }
+
+  def dirPath(forPackage: String) = forPackage.replace('.', '/')
+
+  def endsClass(fileName: String): Boolean =
+    fileName.length > 6 && fileName.substring(fileName.length - 6) == ".class"
+
+  def endsScalaOrJava(fileName: String): Boolean =
+    endsScala(fileName) || endsJava(fileName)
+
+  def endsJava(fileName: String): Boolean =
+    fileName.length > 5 && fileName.substring(fileName.length - 5) == ".java"
+
+  def endsScala(fileName: String): Boolean =
+    fileName.length > 6 && fileName.substring(fileName.length - 6) == ".scala"
+
+  def stripClassExtension(fileName: String): String =
+    fileName.substring(0, fileName.length - 6) // equivalent of fileName.length - ".class".length
+
+  def stripJavaExtension(fileName: String): String =
+    fileName.substring(0, fileName.length - 5)
+
+  // probably it should match a pattern like [a-z_]{1}[a-z0-9_]* but it cannot be changed
+  // because then some tests in partest don't pass
+  private def mayBeValidPackage(dirName: String): Boolean =
+    (dirName != "META-INF") && (dirName != "") && (dirName.charAt(0) != '.')
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala b/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala
new file mode 100644
index 0000000000..26b5429e23
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import scala.reflect.io.AbstractFile
+import scala.tools.nsc.util.{ ClassFileLookup, ClassPath, ClassRepresentation }
+
+/**
+ * A base trait for the particular flat classpath representation implementations.
+ *
+ * We call this variant of a classpath representation flat because it's possible to
+ * query the whole classpath using just single instance extending this trait.
+ *
+ * This is an alternative design compared to scala.tools.nsc.util.ClassPath
+ */
+trait FlatClassPath extends ClassFileLookup[AbstractFile] {
+  /** Empty string represents root package */
+  private[nsc] def packages(inPackage: String): Seq[PackageEntry]
+  private[nsc] def classes(inPackage: String): Seq[ClassFileEntry]
+  private[nsc] def sources(inPackage: String): Seq[SourceFileEntry]
+
+  /** Allows to get entries for packages and classes merged with sources possibly in one pass. */
+  private[nsc] def list(inPackage: String): FlatClassPathEntries
+
+  // A default implementation which should be overriden, if we can create more efficient
+  // solution for given type of FlatClassPath
+  override def findClass(className: String): Option[ClassRepresentation[AbstractFile]] = {
+    val (pkg, simpleClassName) = PackageNameUtils.separatePkgAndClassNames(className)
+
+    val foundClassFromClassFiles = classes(pkg)
+      .find(_.name == simpleClassName)
+
+    def findClassInSources = sources(pkg)
+      .find(_.name == simpleClassName)
+
+    foundClassFromClassFiles orElse findClassInSources
+  }
+
+  override def asClassPathString: String = ClassPath.join(asClassPathStrings: _*)
+  def asClassPathStrings: Seq[String]
+}
+
+object FlatClassPath {
+  val RootPackage = ""
+}
+
+case class FlatClassPathEntries(packages: Seq[PackageEntry], classesAndSources: Seq[ClassRepClassPathEntry])
+
+object FlatClassPathEntries {
+  import scala.language.implicitConversions
+  // to have working unzip method
+  implicit def entry2Tuple(entry: FlatClassPathEntries) = (entry.packages, entry.classesAndSources)
+}
+
+sealed trait ClassRepClassPathEntry extends ClassRepresentation[AbstractFile]
+
+trait ClassFileEntry extends ClassRepClassPathEntry {
+  def file: AbstractFile
+}
+
+trait SourceFileEntry extends ClassRepClassPathEntry {
+  def file: AbstractFile
+}
+
+trait PackageEntry {
+  def name: String
+}
+
+private[nsc] case class ClassFileEntryImpl(file: AbstractFile) extends ClassFileEntry {
+  override def name = FileUtils.stripClassExtension(file.name) // class name
+
+  override def binary: Option[AbstractFile] = Some(file)
+  override def source: Option[AbstractFile] = None
+}
+
+private[nsc] case class SourceFileEntryImpl(file: AbstractFile) extends SourceFileEntry {
+  override def name = FileUtils.stripSourceExtension(file.name)
+
+  override def binary: Option[AbstractFile] = None
+  override def source: Option[AbstractFile] = Some(file)
+}
+
+private[nsc] case class ClassAndSourceFilesEntry(classFile: AbstractFile, srcFile: AbstractFile) extends ClassRepClassPathEntry {
+  override def name = FileUtils.stripClassExtension(classFile.name)
+
+  override def binary: Option[AbstractFile] = Some(classFile)
+  override def source: Option[AbstractFile] = Some(srcFile)
+}
+
+private[nsc] case class PackageEntryImpl(name: String) extends PackageEntry
+
+private[nsc] trait NoSourcePaths {
+  def asSourcePathString: String = ""
+  private[nsc] def sources(inPackage: String): Seq[SourceFileEntry] = Seq.empty
+}
+
+private[nsc] trait NoClassPaths {
+  def findClassFile(className: String): Option[AbstractFile] = None
+  private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] = Seq.empty
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/FlatClassPathFactory.scala b/src/compiler/scala/tools/nsc/classpath/FlatClassPathFactory.scala
new file mode 100644
index 0000000000..7f67381d4d
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/FlatClassPathFactory.scala
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import scala.tools.nsc.Settings
+import scala.tools.nsc.io.AbstractFile
+import scala.tools.nsc.util.ClassPath
+import FileUtils.AbstractFileOps
+
+/**
+ * Provides factory methods for flat classpath. When creating classpath instances for a given path,
+ * it uses proper type of classpath depending on a types of particular files containing sources or classes.
+ */
+class FlatClassPathFactory(settings: Settings) extends ClassPathFactory[FlatClassPath] {
+
+  override def newClassPath(file: AbstractFile): FlatClassPath =
+    if (file.isJarOrZip)
+      ZipAndJarFlatClassPathFactory.create(file, settings)
+    else if (file.isDirectory)
+      new DirectoryFlatClassPath(file.file)
+    else
+      sys.error(s"Unsupported classpath element: $file")
+
+  override def sourcesInPath(path: String): List[FlatClassPath] =
+    for {
+      file <- expandPath(path, expandStar = false)
+      dir <- Option(AbstractFile getDirectory file)
+    } yield createSourcePath(dir)
+
+  private def createSourcePath(file: AbstractFile): FlatClassPath =
+    if (file.isJarOrZip)
+      ZipAndJarFlatSourcePathFactory.create(file, settings)
+    else if (file.isDirectory)
+      new DirectoryFlatSourcePath(file.file)
+    else
+      sys.error(s"Unsupported sourcepath element: $file")
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/PackageNameUtils.scala b/src/compiler/scala/tools/nsc/classpath/PackageNameUtils.scala
new file mode 100644
index 0000000000..c907d565d2
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/PackageNameUtils.scala
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import scala.tools.nsc.classpath.FlatClassPath.RootPackage
+
+/**
+ * Common methods related to package names represented as String
+ */
+object PackageNameUtils {
+
+  /**
+   * @param fullClassName full class name with package
+   * @return (package, simple class name)
+   */
+  def separatePkgAndClassNames(fullClassName: String): (String, String) = {
+    val lastDotIndex = fullClassName.lastIndexOf('.')
+    if (lastDotIndex == -1)
+      (RootPackage, fullClassName)
+    else
+      (fullClassName.substring(0, lastDotIndex), fullClassName.substring(lastDotIndex + 1))
+  }
+
+  def packagePrefix(inPackage: String): String = if (inPackage == RootPackage) "" else inPackage + "."
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/ZipAndJarFileLookupFactory.scala b/src/compiler/scala/tools/nsc/classpath/ZipAndJarFileLookupFactory.scala
new file mode 100644
index 0000000000..84e21a3ccd
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/ZipAndJarFileLookupFactory.scala
@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.io.File
+import java.net.URL
+import scala.annotation.tailrec
+import scala.reflect.io.{ AbstractFile, FileZipArchive, ManifestResources }
+import scala.tools.nsc.Settings
+import FileUtils._
+
+/**
+ * A trait providing an optional cache for classpath entries obtained from zip and jar files.
+ * It's possible to create such a cache assuming that entries in such files won't change (at
+ * least will be the same each time we'll load classpath during the lifetime of JVM process)
+ * - unlike class and source files in directories, which can be modified and recompiled.
+ * It allows us to e.g. reduce significantly memory used by PresentationCompilers in Scala IDE
+ * when there are a lot of projects having a lot of common dependencies.
+ */
+sealed trait ZipAndJarFileLookupFactory {
+
+  private val cache = collection.mutable.Map.empty[AbstractFile, FlatClassPath]
+
+  def create(zipFile: AbstractFile, settings: Settings): FlatClassPath = {
+    if (settings.YdisableFlatCpCaching) createForZipFile(zipFile)
+    else createUsingCache(zipFile, settings)
+  }
+
+  protected def createForZipFile(zipFile: AbstractFile): FlatClassPath
+
+  private def createUsingCache(zipFile: AbstractFile, settings: Settings): FlatClassPath = cache.synchronized {
+    def newClassPathInstance = {
+      if (settings.verbose || settings.Ylogcp)
+        println(s"$zipFile is not yet in the classpath cache")
+      createForZipFile(zipFile)
+    }
+    cache.getOrElseUpdate(zipFile, newClassPathInstance)
+  }
+}
+
+/**
+ * Manages creation of flat classpath for class files placed in zip and jar files.
+ * It should be the only way of creating them as it provides caching.
+ */
+object ZipAndJarFlatClassPathFactory extends ZipAndJarFileLookupFactory {
+
+  private case class ZipArchiveFlatClassPath(zipFile: File)
+    extends ZipArchiveFileLookup[ClassFileEntryImpl]
+    with NoSourcePaths {
+
+    override def findClassFile(className: String): Option[AbstractFile] = {
+      val (pkg, simpleClassName) = PackageNameUtils.separatePkgAndClassNames(className)
+      classes(pkg).find(_.name == simpleClassName).map(_.file)
+    }
+
+    override private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] = files(inPackage)
+
+    override protected def createFileEntry(file: FileZipArchive#Entry): ClassFileEntryImpl = ClassFileEntryImpl(file)
+    override protected def isRequiredFileType(file: AbstractFile): Boolean = file.isClass
+  }
+
+  /**
+   * This type of classpath is closly related to the support for JSR-223.
+   * Its usage can be observed e.g. when running:
+   * jrunscript -classpath scala-compiler.jar;scala-reflect.jar;scala-library.jar -l scala
+   * with a particularly prepared scala-library.jar. It should have all classes listed in the manifest like e.g. this entry:
+   * Name: scala/Function2$mcFJD$sp.class
+   */
+  private case class ManifestResourcesFlatClassPath(file: ManifestResources)
+    extends FlatClassPath
+    with NoSourcePaths {
+
+    override def findClassFile(className: String): Option[AbstractFile] = {
+      val (pkg, simpleClassName) = PackageNameUtils.separatePkgAndClassNames(className)
+      classes(pkg).find(_.name == simpleClassName).map(_.file)
+    }
+
+    override def asClassPathStrings: Seq[String] = Seq(file.path)
+
+    override def asURLs: Seq[URL] = file.toURLs()
+
+    import ManifestResourcesFlatClassPath.PackageFileInfo
+    import ManifestResourcesFlatClassPath.PackageInfo
+
+    /**
+     * A cache mapping package name to abstract file for package directory and subpackages of given package.
+     *
+     * ManifestResources can iterate through the collections of entries from e.g. remote jar file.
+     * We can't just specify the path to the concrete directory etc. so we can't just 'jump' into
+     * given package, when it's needed. On the other hand we can iterate over entries to get
+     * AbstractFiles, iterate over entries of these files etc.
+     *
+     * Instead of traversing a tree of AbstractFiles once and caching all entries or traversing each time,
+     * when we need subpackages of a given package or its classes, we traverse once and cache only packages.
+     * Classes for given package can be then easily loaded when they are needed.
+     */
+    private lazy val cachedPackages: collection.mutable.HashMap[String, PackageFileInfo] = {
+      val packages = collection.mutable.HashMap[String, PackageFileInfo]()
+
+      def getSubpackages(dir: AbstractFile): List[AbstractFile] =
+        (for (file <- dir if file.isPackage) yield file)(collection.breakOut)
+
+      @tailrec
+      def traverse(packagePrefix: String,
+                   filesForPrefix: List[AbstractFile],
+                   subpackagesQueue: collection.mutable.Queue[PackageInfo]): Unit = filesForPrefix match {
+        case pkgFile :: remainingFiles =>
+          val subpackages = getSubpackages(pkgFile)
+          val fullPkgName = packagePrefix + pkgFile.name
+          packages.put(fullPkgName, PackageFileInfo(pkgFile, subpackages))
+          val newPackagePrefix = fullPkgName + "."
+          subpackagesQueue.enqueue(PackageInfo(newPackagePrefix, subpackages))
+          traverse(packagePrefix, remainingFiles, subpackagesQueue)
+        case Nil if subpackagesQueue.nonEmpty =>
+          val PackageInfo(packagePrefix, filesForPrefix) = subpackagesQueue.dequeue()
+          traverse(packagePrefix, filesForPrefix, subpackagesQueue)
+        case _ =>
+      }
+
+      val subpackages = getSubpackages(file)
+      packages.put(FlatClassPath.RootPackage, PackageFileInfo(file, subpackages))
+      traverse(FlatClassPath.RootPackage, subpackages, collection.mutable.Queue())
+      packages
+    }
+
+    override private[nsc] def packages(inPackage: String): Seq[PackageEntry] = cachedPackages.get(inPackage) match {
+      case None => Seq.empty
+      case Some(PackageFileInfo(_, subpackages)) =>
+        val prefix = PackageNameUtils.packagePrefix(inPackage)
+        subpackages.map(packageFile => PackageEntryImpl(prefix + packageFile.name))
+    }
+
+    override private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] = cachedPackages.get(inPackage) match {
+      case None => Seq.empty
+      case Some(PackageFileInfo(pkg, _)) =>
+        (for (file <- pkg if file.isClass) yield ClassFileEntryImpl(file))(collection.breakOut)
+    }
+
+    override private[nsc] def list(inPackage: String): FlatClassPathEntries = FlatClassPathEntries(packages(inPackage), classes(inPackage))
+  }
+
+  private object ManifestResourcesFlatClassPath {
+    case class PackageFileInfo(packageFile: AbstractFile, subpackages: Seq[AbstractFile])
+    case class PackageInfo(packageName: String, subpackages: List[AbstractFile])
+  }
+
+  override protected def createForZipFile(zipFile: AbstractFile): FlatClassPath =
+    if (zipFile.file == null) createWithoutUnderlyingFile(zipFile)
+    else ZipArchiveFlatClassPath(zipFile.file)
+
+  private def createWithoutUnderlyingFile(zipFile: AbstractFile) = zipFile match {
+    case manifestRes: ManifestResources =>
+      ManifestResourcesFlatClassPath(manifestRes)
+    case _ =>
+      val errorMsg = s"Abstract files which don't have an underlying file and are not ManifestResources are not supported. There was $zipFile"
+      throw new IllegalArgumentException(errorMsg)
+  }
+}
+
+/**
+ * Manages creation of flat classpath for source files placed in zip and jar files.
+ * It should be the only way of creating them as it provides caching.
+ */
+object ZipAndJarFlatSourcePathFactory extends ZipAndJarFileLookupFactory {
+
+  private case class ZipArchiveFlatSourcePath(zipFile: File)
+    extends ZipArchiveFileLookup[SourceFileEntryImpl]
+    with NoClassPaths {
+
+    override def asSourcePathString: String = asClassPathString
+
+    override private[nsc] def sources(inPackage: String): Seq[SourceFileEntry] = files(inPackage)
+
+    override protected def createFileEntry(file: FileZipArchive#Entry): SourceFileEntryImpl = SourceFileEntryImpl(file)
+    override protected def isRequiredFileType(file: AbstractFile): Boolean = file.isScalaOrJavaSource
+  }
+
+  override protected def createForZipFile(zipFile: AbstractFile): FlatClassPath = ZipArchiveFlatSourcePath(zipFile.file)
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/ZipArchiveFileLookup.scala b/src/compiler/scala/tools/nsc/classpath/ZipArchiveFileLookup.scala
new file mode 100644
index 0000000000..1d0de57779
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/ZipArchiveFileLookup.scala
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.io.File
+import java.net.URL
+import scala.collection.Seq
+import scala.reflect.io.AbstractFile
+import scala.reflect.io.FileZipArchive
+import FileUtils.AbstractFileOps
+
+/**
+ * A trait allowing to look for classpath entries of given type in zip and jar files.
+ * It provides common logic for classes handling class and source files.
+ * It's aware of things like e.g. META-INF directory which is correctly skipped.
+ */
+trait ZipArchiveFileLookup[FileEntryType <: ClassRepClassPathEntry] extends FlatClassPath {
+  val zipFile: File
+
+  assert(zipFile != null, "Zip file in ZipArchiveFileLookup cannot be null")
+
+  override def asURLs: Seq[URL] = Seq(zipFile.toURI.toURL)
+  override def asClassPathStrings: Seq[String] = Seq(zipFile.getPath)
+
+  private val archive = new FileZipArchive(zipFile)
+
+  override private[nsc] def packages(inPackage: String): Seq[PackageEntry] = {
+    val prefix = PackageNameUtils.packagePrefix(inPackage)
+    for {
+      dirEntry <- findDirEntry(inPackage).toSeq
+      entry <- dirEntry.iterator if entry.isPackage
+    } yield PackageEntryImpl(prefix + entry.name)
+  }
+
+  protected def files(inPackage: String): Seq[FileEntryType] =
+    for {
+      dirEntry <- findDirEntry(inPackage).toSeq
+      entry <- dirEntry.iterator if isRequiredFileType(entry)
+    } yield createFileEntry(entry)
+
+  override private[nsc] def list(inPackage: String): FlatClassPathEntries = {
+    val foundDirEntry = findDirEntry(inPackage)
+
+    foundDirEntry map { dirEntry =>
+      val pkgBuf = collection.mutable.ArrayBuffer.empty[PackageEntry]
+      val fileBuf = collection.mutable.ArrayBuffer.empty[FileEntryType]
+      val prefix = PackageNameUtils.packagePrefix(inPackage)
+
+      for (entry <- dirEntry.iterator) {
+        if (entry.isPackage)
+          pkgBuf += PackageEntryImpl(prefix + entry.name)
+        else if (isRequiredFileType(entry))
+          fileBuf += createFileEntry(entry)
+      }
+      FlatClassPathEntries(pkgBuf, fileBuf)
+    } getOrElse FlatClassPathEntries(Seq.empty, Seq.empty)
+  }
+
+  private def findDirEntry(pkg: String) = {
+    val dirName = s"${FileUtils.dirPath(pkg)}/"
+    archive.allDirs.get(dirName)
+  }
+
+  protected def createFileEntry(file: FileZipArchive#Entry): FileEntryType
+  protected def isRequiredFileType(file: AbstractFile): Boolean
+}
diff --git a/src/compiler/scala/tools/nsc/plugins/Plugins.scala b/src/compiler/scala/tools/nsc/plugins/Plugins.scala
index 6e3d013e52..4b1805479d 100644
--- a/src/compiler/scala/tools/nsc/plugins/Plugins.scala
+++ b/src/compiler/scala/tools/nsc/plugins/Plugins.scala
@@ -7,7 +7,7 @@
 package scala.tools.nsc
 package plugins
 
-import scala.reflect.io.{ File, Path }
+import scala.reflect.io.Path
 import scala.tools.nsc.util.ClassPath
 import scala.tools.util.PathResolver.Defaults
 
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index d6650595eb..18e639b81c 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -202,6 +202,9 @@ trait ScalaSettings extends AbsScalaSettings
   val YmethodInfer    = BooleanSetting    ("-Yinfer-argument-types", "Infer types for arguments of overriden methods.")
   val etaExpandKeepsStar = BooleanSetting ("-Yeta-expand-keeps-star", "Eta-expand varargs methods to T* rather than Seq[T].  This is a temporary option to ease transition.").withDeprecationMessage(removalIn212)
   val inferByName     = BooleanSetting    ("-Yinfer-by-name", "Allow inference of by-name types. This is a temporary option to ease transition. See SI-7899.").withDeprecationMessage(removalIn212)
+  val YclasspathImpl  = ChoiceSetting     ("-YclasspathImpl", "implementation", "Choose classpath scanning method.", List(ClassPathRepresentationType.Recursive, ClassPathRepresentationType.Flat), ClassPathRepresentationType.Recursive)
+  val YdisableFlatCpCaching  = BooleanSetting    ("-YdisableFlatCpCaching", "Do not cache flat classpath representation of classpath elements from jars across compiler instances.")
+
   val YvirtClasses    = false // too embryonic to even expose as a -Y //BooleanSetting    ("-Yvirtual-classes", "Support virtual classes")
   val YdisableUnreachablePrevention = BooleanSetting("-Ydisable-unreachable-prevention", "Disable the prevention of unreachable blocks in code generation.")
   val YnoLoadImplClass = BooleanSetting   ("-Yno-load-impl-class", "Do not load $class.class files.")
@@ -329,3 +332,8 @@ trait ScalaSettings extends AbsScalaSettings
     val Discard = "discard"
   }
 }
+
+object ClassPathRepresentationType {
+  val Flat = "flat"
+  val Recursive = "recursive"
+}
diff --git a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
index 82c2a4d6ed..9af3efbece 100644
--- a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
+++ b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
@@ -6,13 +6,15 @@
 package scala.tools.nsc
 package symtab
 
+import classfile.ClassfileParser
 import java.io.IOException
 import scala.compat.Platform.currentTime
-import scala.tools.nsc.util.{ ClassPath }
-import classfile.ClassfileParser
 import scala.reflect.internal.MissingRequirementError
 import scala.reflect.internal.util.Statistics
 import scala.reflect.io.{ AbstractFile, NoAbstractFile }
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.{ ClassPath, ClassRepresentation }
 
 /** This class ...
  *
@@ -86,8 +88,7 @@ abstract class SymbolLoaders {
       // require yjp.jar at runtime. See SI-2089.
       if (settings.termConflict.isDefault)
         throw new TypeError(
-          root+" contains object and package with same name: "+
-          name+"\none of them needs to be removed from classpath"
+          s"$root contains object and package with same name: $name\none of them needs to be removed from classpath"
         )
       else if (settings.termConflict.value == "package") {
         warning(
@@ -154,7 +155,7 @@ abstract class SymbolLoaders {
 
   /** Initialize toplevel class and module symbols in `owner` from class path representation `classRep`
    */
-  def initializeFromClassPath(owner: Symbol, classRep: ClassPath[AbstractFile]#ClassRep) {
+  def initializeFromClassPath(owner: Symbol, classRep: ClassRepresentation[AbstractFile]) {
     ((classRep.binary, classRep.source) : @unchecked) match {
       case (Some(bin), Some(src))
       if platform.needCompile(bin, src) && !binaryOnly(owner, classRep.name) =>
@@ -250,7 +251,7 @@ abstract class SymbolLoaders {
    * Load contents of a package
    */
   class PackageLoader(classpath: ClassPath[AbstractFile]) extends SymbolLoader with FlagAgnosticCompleter {
-    protected def description = "package loader "+ classpath.name
+    protected def description = s"package loader ${classpath.name}"
 
     protected def doComplete(root: Symbol) {
       assert(root.isPackageClass, root)
@@ -276,6 +277,39 @@ abstract class SymbolLoaders {
     }
   }
 
+  /**
+   * Loads contents of a package
+   */
+  class PackageLoaderUsingFlatClassPath(packageName: String, classPath: FlatClassPath) extends SymbolLoader with FlagAgnosticCompleter {
+    protected def description = {
+      val shownPackageName = if (packageName == FlatClassPath.RootPackage) "<root package>" else packageName
+      s"package loader $shownPackageName"
+    }
+
+    protected def doComplete(root: Symbol) {
+      assert(root.isPackageClass, root)
+      root.setInfo(new PackageClassInfoType(newScope, root))
+
+      val classPathEntries = classPath.list(packageName)
+
+      if (!root.isRoot)
+        for (entry <- classPathEntries.classesAndSources) initializeFromClassPath(root, entry)
+      if (!root.isEmptyPackageClass) {
+        for (pkg <- classPathEntries.packages) {
+          val fullName = pkg.name
+
+          val name =
+            if (packageName == FlatClassPath.RootPackage) fullName
+            else fullName.substring(packageName.length + 1)
+          val packageLoader = new PackageLoaderUsingFlatClassPath(fullName, classPath)
+          enterPackage(root, name, packageLoader)
+        }
+
+        openPackageModule(root)
+      }
+    }
+  }
+
   class ClassfileLoader(val classfile: AbstractFile) extends SymbolLoader with FlagAssigningCompleter {
     private object classfileParser extends {
       val symbolTable: SymbolLoaders.this.symbolTable.type = SymbolLoaders.this.symbolTable
@@ -293,8 +327,13 @@ abstract class SymbolLoaders {
        *
        */
       private type SymbolLoadersRefined = SymbolLoaders { val symbolTable: classfileParser.symbolTable.type }
+
       val loaders = SymbolLoaders.this.asInstanceOf[SymbolLoadersRefined]
-      val classPath = platform.classPath
+
+      override def classFileLookup: util.ClassFileLookup[AbstractFile] = settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Recursive => platform.classPath
+        case ClassPathRepresentationType.Flat => platform.flatClassPath
+      }
     }
 
     protected def description = "class file "+ classfile.toString
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index 14be8374b9..1abbdb50b0 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -16,8 +16,7 @@ import scala.annotation.switch
 import scala.reflect.internal.{ JavaAccFlags }
 import scala.reflect.internal.pickling.{PickleBuffer, ByteCodecs}
 import scala.tools.nsc.io.AbstractFile
-
-import util.ClassPath
+import scala.tools.nsc.util.ClassFileLookup
 
 /** This abstract class implements a class file parser.
  *
@@ -43,8 +42,8 @@ abstract class ClassfileParser {
    */
   protected def lookupMemberAtTyperPhaseIfPossible(sym: Symbol, name: Name): Symbol
 
-  /** The compiler classpath. */
-  def classPath: ClassPath[AbstractFile]
+  /** The way of the class file lookup used by the compiler. */
+  def classFileLookup: ClassFileLookup[AbstractFile]
 
   import definitions._
   import scala.reflect.internal.ClassfileConstants._
@@ -352,7 +351,7 @@ abstract class ClassfileParser {
   }
 
   private def loadClassSymbol(name: Name): Symbol = {
-    val file = classPath findClassFile ("" +name) getOrElse {
+    val file = classFileLookup findClassFile name.toString getOrElse {
       // SI-5593 Scaladoc's current strategy is to visit all packages in search of user code that can be documented
       // therefore, it will rummage through the classpath triggering errors whenever it encounters package objects
       // that are not in their correct place (see bug for details)
@@ -1047,8 +1046,8 @@ abstract class ClassfileParser {
     for (entry <- innerClasses.entries) {
       // create a new class member for immediate inner classes
       if (entry.outerName == currentClass) {
-        val file = classPath.findClassFile(entry.externalName.toString) getOrElse {
-          throw new AssertionError(entry.externalName)
+        val file = classFileLookup.findClassFile(entry.externalName.toString) getOrElse {
+          throw new AssertionError(s"Class file for ${entry.externalName} not found")
         }
         enterClassAndModule(entry, file)
       }
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
index cbe427775a..bd1fa4e707 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
@@ -130,7 +130,7 @@ abstract class ICodeReader extends ClassfileParser {
     log("ICodeReader reading " + cls)
     val name = cls.javaClassName
 
-    classPath.findClassFile(name) match {
+    classFileLookup.findClassFile(name) match {
       case Some(classFile) => parse(classFile, cls)
       case _               => MissingRequirementError.notFound("Could not find bytecode for " + cls)
     }
diff --git a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
index 2b7c6cca2c..f786ffb8f3 100644
--- a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
+++ b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
@@ -8,6 +8,7 @@ package transform
 
 import symtab._
 import Flags._
+import scala.tools.nsc.util.ClassPath
 
 abstract class AddInterfaces extends InfoTransform { self: Erasure =>
   import global._                  // the global environment
@@ -67,25 +68,30 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
     val implName  = tpnme.implClassName(iface.name)
     val implFlags = (iface.flags & ~(INTERFACE | lateINTERFACE)) | IMPLCLASS
 
-    val impl0 = (
+    val impl0 = {
       if (!inClass) NoSymbol
-      else iface.owner.info.decl(implName) match {
-        case NoSymbol => NoSymbol
-        case implSym  =>
-          // Unlink a pre-existing symbol only if the implementation class is
-          // visible on the compilation classpath.  In general this is true under
-          // -optimise and not otherwise, but the classpath can use arbitrary
-          // logic so the classpath must be queried.
-          if (classPath.context.isValidName(implName + ".class")) {
-            iface.owner.info.decls unlink implSym
-            NoSymbol
-          }
-          else {
-            log(s"not unlinking $iface's existing implClass ${implSym.name} because it is not on the classpath.")
-            implSym
-          }
+      else {
+        val typeInfo = iface.owner.info
+        typeInfo.decl(implName) match {
+          case NoSymbol => NoSymbol
+          case implSym =>
+            // Unlink a pre-existing symbol only if the implementation class is
+            // visible on the compilation classpath. In general this is true under
+            // -optimise and not otherwise, but the classpath can use arbitrary
+            // logic so the classpath must be queried.
+            // TODO this is not taken into account by flat classpath yet
+            classPath match {
+              case cp: ClassPath[_] if !cp.context.isValidName(implName + ".class") =>
+                log(s"not unlinking $iface's existing implClass ${implSym.name} because it is not on the classpath.")
+                implSym
+              case _ =>
+                typeInfo.decls unlink implSym
+                NoSymbol
+            }
+        }
       }
-    )
+    }
+
     val impl = impl0 orElse {
       val impl = iface.owner.newImplClass(implName, iface.pos, implFlags)
       if (iface.thisSym != iface) {
@@ -345,6 +351,7 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
           while (owner != sym && owner != impl) owner = owner.owner;
           if (owner == impl) This(impl) setPos tree.pos
           else tree
+        //TODO what about this commented out code?
 /* !!!
         case Super(qual, mix) =>
           val mix1 = mix
diff --git a/src/compiler/scala/tools/nsc/util/ClassFileLookup.scala b/src/compiler/scala/tools/nsc/util/ClassFileLookup.scala
new file mode 100644
index 0000000000..4451651229
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/util/ClassFileLookup.scala
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.util
+
+import scala.tools.nsc.io.AbstractFile
+import java.net.URL
+
+/**
+ * Simple interface that allows us to abstract over how class file lookup is performed
+ * in different classpath representations.
+ */
+// TODO at the end, after the possible removal of the old classpath representation, this class shouldn't be generic
+// T should be just changed to AbstractFile
+trait ClassFileLookup[T] {
+  def findClassFile(name: String): Option[AbstractFile]
+
+  /**
+   * It returns both classes from class file and source files (as our base ClassRepresentation).
+   * So note that it's not so strictly related to findClassFile.
+   */
+  def findClass(name: String): Option[ClassRepresentation[T]]
+
+  /**
+   * A sequence of URLs representing this classpath.
+   */
+  def asURLs: Seq[URL]
+
+  /** The whole classpath in the form of one String.
+    */
+  def asClassPathString: String
+
+  // for compatibility purposes
+  @deprecated("Use asClassPathString instead of this one", "2.11.5")
+  def asClasspathString: String = asClassPathString
+
+  /** The whole sourcepath in the form of one String.
+    */
+  def asSourcePathString: String
+}
+
+/**
+ * Represents classes which can be loaded with a ClassfileLoader and/or SourcefileLoader.
+ */
+// TODO at the end, after the possible removal of the old classpath implementation, this class shouldn't be generic
+// T should be just changed to AbstractFile
+trait ClassRepresentation[T] {
+  def binary: Option[T]
+  def source: Option[AbstractFile]
+
+  def name: String
+}
+
+object ClassRepresentation {
+  def unapply[T](classRep: ClassRepresentation[T]): Option[(Option[T], Option[AbstractFile])] =
+    Some((classRep.binary, classRep.source))
+}
diff --git a/src/compiler/scala/tools/nsc/util/ClassPath.scala b/src/compiler/scala/tools/nsc/util/ClassPath.scala
index e78dee5eee..8d4d07759f 100644
--- a/src/compiler/scala/tools/nsc/util/ClassPath.scala
+++ b/src/compiler/scala/tools/nsc/util/ClassPath.scala
@@ -7,16 +7,18 @@
 package scala.tools.nsc
 package util
 
+import io.{ AbstractFile, Directory, File, Jar }
+import java.net.MalformedURLException
 import java.net.URL
+import java.util.regex.PatternSyntaxException
 import scala.collection.{ mutable, immutable }
-import io.{ File, Directory, Path, Jar, AbstractFile }
 import scala.reflect.internal.util.StringOps.splitWhere
-import Jar.isJarOrZip
+import scala.tools.nsc.classpath.FileUtils
+
 import File.pathSeparator
-import scala.collection.convert.WrapAsScala.enumerationAsScalaIterator
-import java.net.MalformedURLException
-import java.util.regex.PatternSyntaxException
-import scala.reflect.runtime.ReflectionUtils
+import FileUtils.endsClass
+import FileUtils.endsScalaOrJava
+import Jar.isJarOrZip
 
 /** <p>
  *    This module provides star expansion of '-classpath' option arguments, behaves the same as
@@ -89,7 +91,7 @@ object ClassPath {
   /** A class modeling aspects of a ClassPath which should be
    *  propagated to any classpaths it creates.
    */
-  abstract class ClassPathContext[T] {
+  abstract class ClassPathContext[T] extends classpath.ClassPathFactory[ClassPath[T]] {
     /** A filter which can be used to exclude entities from the classpath
      *  based on their name.
      */
@@ -99,75 +101,47 @@ object ClassPath {
      */
     def validClassFile(name: String)  = endsClass(name) && isValidName(name)
     def validPackage(name: String)    = (name != "META-INF") && (name != "") && (name.charAt(0) != '.')
-    def validSourceFile(name: String) = endsScala(name) || endsJava(name)
+    def validSourceFile(name: String) = endsScalaOrJava(name)
 
     /** From the representation to its identifier.
      */
     def toBinaryName(rep: T): String
 
-    /** Create a new classpath based on the abstract file.
-     */
-    def newClassPath(file: AbstractFile): ClassPath[T]
-
-    /** Creators for sub classpaths which preserve this context.
-     */
     def sourcesInPath(path: String): List[ClassPath[T]] =
       for (file <- expandPath(path, expandStar = false) ; dir <- Option(AbstractFile getDirectory file)) yield
         new SourcePath[T](dir, this)
-
-    def contentsOfDirsInPath(path: String): List[ClassPath[T]] =
-      for (dir <- expandPath(path, expandStar = false) ; name <- expandDir(dir) ; entry <- Option(AbstractFile getDirectory name)) yield
-        newClassPath(entry)
-
-    def classesInExpandedPath(path: String): IndexedSeq[ClassPath[T]] =
-      classesInPathImpl(path, expand = true).toIndexedSeq
-
-    def classesInPath(path: String) = classesInPathImpl(path, expand = false)
-
-    // Internal
-    private def classesInPathImpl(path: String, expand: Boolean) =
-      for (file <- expandPath(path, expand) ; dir <- Option(AbstractFile getDirectory file)) yield
-        newClassPath(dir)
-
-    def classesInManifest(used: Boolean) =
-      if (used) for (url <- manifests) yield newClassPath(AbstractFile getResources url) else Nil
   }
 
-  def manifests = Thread.currentThread().getContextClassLoader().getResources("META-INF/MANIFEST.MF").filter(_.getProtocol() == "jar").toList
+  def manifests: List[java.net.URL] = {
+    import scala.collection.convert.WrapAsScala.enumerationAsScalaIterator
+    Thread.currentThread().getContextClassLoader()
+      .getResources("META-INF/MANIFEST.MF")
+      .filter(_.getProtocol == "jar").toList
+  }
 
   class JavaContext extends ClassPathContext[AbstractFile] {
     def toBinaryName(rep: AbstractFile) = {
       val name = rep.name
       assert(endsClass(name), name)
-      name.substring(0, name.length - 6)
+      FileUtils.stripClassExtension(name)
     }
+
     def newClassPath(dir: AbstractFile) = new DirectoryClassPath(dir, this)
   }
 
   object DefaultJavaContext extends JavaContext
 
-  private def endsClass(s: String) = s.length > 6 && s.substring(s.length - 6) == ".class"
-  private def endsScala(s: String) = s.length > 6 && s.substring(s.length - 6) == ".scala"
-  private def endsJava(s: String)  = s.length > 5 && s.substring(s.length - 5) == ".java"
-
   /** From the source file to its identifier.
    */
-  def toSourceName(f: AbstractFile): String = {
-    val name = f.name
-
-    if (endsScala(name)) name.substring(0, name.length - 6)
-    else if (endsJava(name)) name.substring(0, name.length - 5)
-    else throw new FatalError("Unexpected source file ending: " + name)
-  }
+  def toSourceName(f: AbstractFile): String = FileUtils.stripSourceExtension(f.name)
 }
+
 import ClassPath._
 
 /**
  * Represents a package which contains classes and other packages
  */
-abstract class ClassPath[T] {
-  type AnyClassRep = ClassPath[T]#ClassRep
-
+abstract class ClassPath[T] extends ClassFileLookup[T] {
   /**
    * The short name of the package (without prefix)
    */
@@ -179,21 +153,13 @@ abstract class ClassPath[T] {
    */
   def origin: Option[String] = None
 
-  /** A list of URLs representing this classpath.
-   */
-  def asURLs: List[URL]
-
-  /** The whole classpath in the form of one String.
-   */
-  def asClasspathString: String
-
   /** Info which should be propagated to any sub-classpaths.
    */
   def context: ClassPathContext[T]
 
   /** Lists of entities.
    */
-  def classes: IndexedSeq[AnyClassRep]
+  def classes: IndexedSeq[ClassRepresentation[T]]
   def packages: IndexedSeq[ClassPath[T]]
   def sourcepaths: IndexedSeq[AbstractFile]
 
@@ -217,7 +183,7 @@ abstract class ClassPath[T] {
   /**
    * Represents classes which can be loaded with a ClassfileLoader and/or SourcefileLoader.
    */
-  case class ClassRep(binary: Option[T], source: Option[AbstractFile]) {
+  case class ClassRep(binary: Option[T], source: Option[AbstractFile]) extends ClassRepresentation[T] {
     def name: String = binary match {
       case Some(x)  => context.toBinaryName(x)
       case _        =>
@@ -236,25 +202,27 @@ abstract class ClassPath[T] {
    * Find a ClassRep given a class name of the form "package.subpackage.ClassName".
    * Does not support nested classes on .NET
    */
-  def findClass(name: String): Option[AnyClassRep] =
+  override def findClass(name: String): Option[ClassRepresentation[T]] =
     splitWhere(name, _ == '.', doDropIndex = true) match {
       case Some((pkg, rest)) =>
         val rep = packages find (_.name == pkg) flatMap (_ findClass rest)
         rep map {
-          case x: ClassRep  => x
+          case x: ClassRepresentation[T] => x
           case x            => throw new FatalError("Unexpected ClassRep '%s' found searching for name '%s'".format(x, name))
         }
       case _ =>
         classes find (_.name == name)
     }
 
-  def findClassFile(name: String): Option[AbstractFile] =
+  override def findClassFile(name: String): Option[AbstractFile] =
     findClass(name) match {
-      case Some(ClassRep(Some(x: AbstractFile), _)) => Some(x)
+      case Some(ClassRepresentation(Some(x: AbstractFile), _)) => Some(x)
       case _                                        => None
     }
 
-  def sortString = join(split(asClasspathString).sorted: _*)
+  override def asSourcePathString: String = sourcepaths.mkString(pathSeparator)
+
+  def sortString = join(split(asClassPathString).sorted: _*)
   override def equals(that: Any) = that match {
     case x: ClassPath[_]  => this.sortString == x.sortString
     case _                => false
@@ -266,10 +234,12 @@ abstract class ClassPath[T] {
  * A Classpath containing source files
  */
 class SourcePath[T](dir: AbstractFile, val context: ClassPathContext[T]) extends ClassPath[T] {
+  import FileUtils.AbstractFileOps
+
   def name = dir.name
   override def origin = dir.underlyingSource map (_.path)
-  def asURLs = if (dir.file == null) Nil else List(dir.toURL)
-  def asClasspathString = dir.path
+  def asURLs = dir.toURLs()
+  def asClassPathString = dir.path
   val sourcepaths: IndexedSeq[AbstractFile] = IndexedSeq(dir)
 
   private def traverse() = {
@@ -292,10 +262,12 @@ class SourcePath[T](dir: AbstractFile, val context: ClassPathContext[T]) extends
  * A directory (or a .jar file) containing classfiles and packages
  */
 class DirectoryClassPath(val dir: AbstractFile, val context: ClassPathContext[AbstractFile]) extends ClassPath[AbstractFile] {
+  import FileUtils.AbstractFileOps
+
   def name = dir.name
   override def origin = dir.underlyingSource map (_.path)
-  def asURLs = if (dir.file == null) List(new URL(name)) else List(dir.toURL)
-  def asClasspathString = dir.path
+  def asURLs = dir.toURLs(default = Seq(new URL(name)))
+  def asClassPathString = dir.path
   val sourcepaths: IndexedSeq[AbstractFile] = IndexedSeq()
 
   // calculates (packages, classes) in one traversal.
@@ -342,6 +314,7 @@ class MergedClassPath[T](
   override val entries: IndexedSeq[ClassPath[T]],
   val context: ClassPathContext[T])
 extends ClassPath[T] {
+
   def this(entries: TraversableOnce[ClassPath[T]], context: ClassPathContext[T]) =
     this(entries.toIndexedSeq, context)
 
@@ -350,12 +323,12 @@ extends ClassPath[T] {
   lazy val sourcepaths: IndexedSeq[AbstractFile] = entries flatMap (_.sourcepaths)
 
   override def origin = Some(entries map (x => x.origin getOrElse x.name) mkString ("Merged(", ", ", ")"))
-  override def asClasspathString: String = join(entries map (_.asClasspathString) : _*)
+  override def asClassPathString: String = join(entries map (_.asClassPathString) : _*)
 
-  lazy val classes: IndexedSeq[AnyClassRep] = {
+  lazy val classes: IndexedSeq[ClassRepresentation[T]] = {
     var count   = 0
     val indices = mutable.HashMap[String, Int]()
-    val cls     = new mutable.ArrayBuffer[AnyClassRep](1024)
+    val cls     = new mutable.ArrayBuffer[ClassRepresentation[T]](1024)
 
     for (e <- entries; c <- e.classes) {
       val name = c.name
@@ -364,9 +337,9 @@ extends ClassPath[T] {
         val existing = cls(idx)
 
         if (existing.binary.isEmpty && c.binary.isDefined)
-          cls(idx) = existing.copy(binary = c.binary)
+          cls(idx) = ClassRep(binary = c.binary, source = existing.source)
         if (existing.source.isEmpty && c.source.isDefined)
-          cls(idx) = existing.copy(source = c.source)
+          cls(idx) = ClassRep(binary = existing.binary, source = c.source)
       }
       else {
         indices(name) = count
@@ -404,10 +377,12 @@ extends ClassPath[T] {
     }
     new MergedClassPath[T](newEntries, context)
   }
+
   def show() {
     println("ClassPath %s has %d entries and results in:\n".format(name, entries.size))
-    asClasspathString split ':' foreach (x => println("  " + x))
+    asClassPathString split ':' foreach (x => println("  " + x))
   }
+
   override def toString() = "merged classpath "+ entries.mkString("(", "\n", ")")
 }
 
diff --git a/src/compiler/scala/tools/reflect/ReflectMain.scala b/src/compiler/scala/tools/reflect/ReflectMain.scala
index 3ae21b6b98..8d8418945a 100644
--- a/src/compiler/scala/tools/reflect/ReflectMain.scala
+++ b/src/compiler/scala/tools/reflect/ReflectMain.scala
@@ -1,17 +1,17 @@
 package scala.tools
 package reflect
 
+import scala.reflect.internal.util.ScalaClassLoader
 import scala.tools.nsc.Driver
 import scala.tools.nsc.Global
 import scala.tools.nsc.Settings
-import scala.tools.nsc.util.ScalaClassLoader
-import scala.tools.util.PathResolver
+import scala.tools.util.PathResolverFactory
 
 object ReflectMain extends Driver {
 
   private def classloaderFromSettings(settings: Settings) = {
-    val classpath = new PathResolver(settings).result
-    ScalaClassLoader.fromURLs(classpath.asURLs, getClass.getClassLoader)
+    val classPathURLs = PathResolverFactory.create(settings).resultAsURLs
+    ScalaClassLoader.fromURLs(classPathURLs, getClass.getClassLoader)
   }
 
   override def newCompiler(): Global = new ReflectGlobal(settings, reporter, classloaderFromSettings(settings))
diff --git a/src/compiler/scala/tools/util/PathResolver.scala b/src/compiler/scala/tools/util/PathResolver.scala
index 5526660509..8e5b1e0a5c 100644
--- a/src/compiler/scala/tools/util/PathResolver.scala
+++ b/src/compiler/scala/tools/util/PathResolver.scala
@@ -7,14 +7,17 @@ package scala
 package tools
 package util
 
+import java.net.URL
 import scala.tools.reflect.WrappedProperties.AccessControl
-import scala.tools.nsc.{ Settings }
-import scala.tools.nsc.util.{ ClassPath, JavaClassPath }
+import scala.tools.nsc.Settings
+import scala.tools.nsc.util.{ ClassFileLookup, ClassPath, JavaClassPath }
 import scala.reflect.io.{ File, Directory, Path, AbstractFile }
 import scala.reflect.runtime.ReflectionUtils
 import ClassPath.{ JavaContext, DefaultJavaContext, join, split }
 import PartialFunction.condOpt
 import scala.language.postfixOps
+import scala.tools.nsc.classpath.{ AggregateFlatClassPath, ClassPathFactory, FlatClassPath, FlatClassPathFactory }
+import scala.tools.nsc.settings.ClassPathRepresentationType
 
 // Loosely based on the draft specification at:
 // https://wiki.scala-lang.org/display/SIW/Classpath
@@ -48,9 +51,8 @@ object PathResolver {
   /** Values found solely by inspecting environment or property variables.
    */
   object Environment {
-    private def searchForBootClasspath = (
+    private def searchForBootClasspath =
       systemProperties find (_._1 endsWith ".boot.class.path") map (_._2) getOrElse ""
-    )
 
     /** Environment variables which java pays attention to so it
      *  seems we do as well.
@@ -104,7 +106,7 @@ object PathResolver {
       else if (scalaLibAsDir.isDirectory) scalaLibAsDir.path
       else ""
 
-    // XXX It must be time for someone to figure out what all these things
+    // TODO It must be time for someone to figure out what all these things
     // are intended to do.  This is disabled here because it was causing all
     // the scala jars to end up on the classpath twice: one on the boot
     // classpath as set up by the runner (or regular classpath under -nobootcp)
@@ -170,39 +172,48 @@ object PathResolver {
       !ReflectionUtils.scalacShouldntLoadClassfile(name)
   }
 
-  // called from scalap
+  @deprecated("This method is no longer used be scalap and will be deleted", "2.11.5")
   def fromPathString(path: String, context: JavaContext = DefaultJavaContext): JavaClassPath = {
     val s = new Settings()
     s.classpath.value = path
-    new PathResolver(s, context) result
+    new PathResolver(s, context).result
   }
 
   /** With no arguments, show the interesting values in Environment and Defaults.
    *  If there are arguments, show those in Calculated as if those options had been
    *  given to a scala runner.
    */
-  def main(args: Array[String]): Unit = {
+  def main(args: Array[String]): Unit =
     if (args.isEmpty) {
       println(Environment)
       println(Defaults)
-    }
-    else {
+    } else {
       val settings = new Settings()
       val rest = settings.processArguments(args.toList, processAll = false)._2
-      val pr = new PathResolver(settings)
-      println(" COMMAND: 'scala %s'".format(args.mkString(" ")))
+      val pr = PathResolverFactory.create(settings)
+      println("COMMAND: 'scala %s'".format(args.mkString(" ")))
       println("RESIDUAL: 'scala %s'\n".format(rest.mkString(" ")))
-      pr.result.show()
+
+      pr.result match {
+        case cp: JavaClassPath =>
+          cp.show()
+        case cp: AggregateFlatClassPath =>
+          println(s"ClassPath has ${cp.aggregates.size} entries and results in:\n${cp.asClassPathStrings}")
+      }
     }
-  }
 }
 
-class PathResolver(settings: Settings, context: JavaContext) {
-  import PathResolver.{ Defaults, Environment, AsLines, MkLines, ppcp }
+trait PathResolverResult {
+  def result: ClassFileLookup[AbstractFile]
 
-  def this(settings: Settings) = this(settings,
-      if (settings.YnoLoadImplClass) PathResolver.NoImplClassJavaContext
-      else DefaultJavaContext)
+  def resultAsURLs: Seq[URL] = result.asURLs
+}
+
+abstract class PathResolverBase[BaseClassPathType <: ClassFileLookup[AbstractFile], ResultClassPathType <: BaseClassPathType]
+(settings: Settings, classPathFactory: ClassPathFactory[BaseClassPathType])
+  extends PathResolverResult {
+
+  import PathResolver.{ AsLines, Defaults, ppcp }
 
   private def cmdLineOrElse(name: String, alt: String) = {
     (commandLineFor(name) match {
@@ -232,6 +243,7 @@ class PathResolver(settings: Settings, context: JavaContext) {
     def javaUserClassPath   = if (useJavaClassPath) Defaults.javaUserClassPath else ""
     def scalaBootClassPath  = cmdLineOrElse("bootclasspath", Defaults.scalaBootClassPath)
     def scalaExtDirs        = cmdLineOrElse("extdirs", Defaults.scalaExtDirs)
+
     /** Scaladoc doesn't need any bootstrapping, otherwise will create errors such as:
      * [scaladoc] ../scala-trunk/src/reflect/scala/reflect/macros/Reifiers.scala:89: error: object api is not a member of package reflect
      * [scaladoc] case class ReificationException(val pos: reflect.api.PositionApi, val msg: String) extends Throwable(msg)
@@ -250,16 +262,14 @@ class PathResolver(settings: Settings, context: JavaContext) {
      *  - Otherwise, if CLASSPATH is set, it is that
      *  - If neither of those, then "." is used.
      */
-    def userClassPath = (
-      if (!settings.classpath.isDefault)
-        settings.classpath.value
+    def userClassPath =
+      if (!settings.classpath.isDefault) settings.classpath.value
       else sys.env.getOrElse("CLASSPATH", ".")
-    )
 
-    import context._
+    import classPathFactory._
 
     // Assemble the elements!
-    def basis = List[Traversable[ClassPath[AbstractFile]]](
+    def basis = List[Traversable[BaseClassPathType]](
       classesInPath(javaBootClassPath),             // 1. The Java bootstrap class path.
       contentsOfDirsInPath(javaExtDirs),            // 2. The Java extension class path.
       classesInExpandedPath(javaUserClassPath),     // 3. The Java application class path.
@@ -278,7 +288,7 @@ class PathResolver(settings: Settings, context: JavaContext) {
       |  javaBootClassPath    = ${ppcp(javaBootClassPath)}
       |  javaExtDirs          = ${ppcp(javaExtDirs)}
       |  javaUserClassPath    = ${ppcp(javaUserClassPath)}
-      |    useJavaClassPath   = $useJavaClassPath
+      |  useJavaClassPath     = $useJavaClassPath
       |  scalaBootClassPath   = ${ppcp(scalaBootClassPath)}
       |  scalaExtDirs         = ${ppcp(scalaExtDirs)}
       |  userClassPath        = ${ppcp(userClassPath)}
@@ -288,8 +298,10 @@ class PathResolver(settings: Settings, context: JavaContext) {
 
   def containers = Calculated.containers
 
-  lazy val result = {
-    val cp = new JavaClassPath(containers.toIndexedSeq, context)
+  import PathResolver.MkLines
+
+  def result: ResultClassPathType = {
+    val cp = computeResult()
     if (settings.Ylogcp) {
       Console print f"Classpath built from ${settings.toConciseString} %n"
       Console print s"Defaults: ${PathResolver.Defaults}"
@@ -301,5 +313,37 @@ class PathResolver(settings: Settings, context: JavaContext) {
     cp
   }
 
-  def asURLs = result.asURLs
+  @deprecated("Use resultAsURLs instead of this one", "2.11.5")
+  def asURLs: List[URL] = resultAsURLs.toList
+
+  protected def computeResult(): ResultClassPathType
+}
+
+class PathResolver(settings: Settings, context: JavaContext)
+  extends PathResolverBase[ClassPath[AbstractFile], JavaClassPath](settings, context) {
+
+  def this(settings: Settings) =
+    this(settings,
+      if (settings.YnoLoadImplClass) PathResolver.NoImplClassJavaContext
+      else DefaultJavaContext)
+
+  override protected def computeResult(): JavaClassPath =
+    new JavaClassPath(containers.toIndexedSeq, context)
+}
+
+class FlatClassPathResolver(settings: Settings, flatClassPathFactory: ClassPathFactory[FlatClassPath])
+  extends PathResolverBase[FlatClassPath, AggregateFlatClassPath](settings, flatClassPathFactory) {
+
+  def this(settings: Settings) = this(settings, new FlatClassPathFactory(settings))
+
+  override protected def computeResult(): AggregateFlatClassPath = AggregateFlatClassPath(containers.toIndexedSeq)
+}
+
+object PathResolverFactory {
+
+  def create(settings: Settings): PathResolverResult =
+    settings.YclasspathImpl.value match {
+      case ClassPathRepresentationType.Flat => new FlatClassPathResolver(settings)
+      case ClassPathRepresentationType.Recursive => new PathResolver(settings)
+    }
 }
diff --git a/src/interactive/scala/tools/nsc/interactive/Global.scala b/src/interactive/scala/tools/nsc/interactive/Global.scala
index 7df809b6ff..5d00141e6a 100644
--- a/src/interactive/scala/tools/nsc/interactive/Global.scala
+++ b/src/interactive/scala/tools/nsc/interactive/Global.scala
@@ -128,8 +128,8 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
     else NullLogger
 
   import log.logreplay
-  debugLog("logger: " + log.getClass + " writing to " + (new java.io.File(logName)).getAbsolutePath)
-  debugLog("classpath: "+classPath)
+  debugLog(s"logger: ${log.getClass} writing to ${(new java.io.File(logName)).getAbsolutePath}")
+  debugLog(s"classpath: $classPath")
 
   private var curTime = System.nanoTime
   private def timeStep = {
diff --git a/src/partest-extras/scala/tools/partest/BytecodeTest.scala b/src/partest-extras/scala/tools/partest/BytecodeTest.scala
index 3261cada37..37ef4684ef 100644
--- a/src/partest-extras/scala/tools/partest/BytecodeTest.scala
+++ b/src/partest-extras/scala/tools/partest/BytecodeTest.scala
@@ -116,10 +116,8 @@ abstract class BytecodeTest {
       sys.error(s"Didn't find method '$name' in class '${classNode.name}'")
 
   protected def loadClassNode(name: String, skipDebugInfo: Boolean = true): ClassNode = {
-    val classBytes: InputStream = (for {
-      classRep <- classpath.findClass(name)
-      binary <- classRep.binary
-    } yield binary.input) getOrElse sys.error(s"failed to load class '$name'; classpath = $classpath")
+    val classBytes: InputStream = classpath.findClassFile(name).map(_.input)
+      .getOrElse(sys.error(s"failed to load class '$name'; classpath = $classpath"))
 
     val cr = new ClassReader(classBytes)
     val cn = new ClassNode()
diff --git a/src/reflect/scala/reflect/internal/SymbolTable.scala b/src/reflect/scala/reflect/internal/SymbolTable.scala
index ed5c68fe82..01e4cdf367 100644
--- a/src/reflect/scala/reflect/internal/SymbolTable.scala
+++ b/src/reflect/scala/reflect/internal/SymbolTable.scala
@@ -338,7 +338,6 @@ abstract class SymbolTable extends macros.Universe
       case _ => false
     }
     if (pkgModule.isModule && !fromSource) {
-      // println("open "+pkgModule)//DEBUG
       openPackageModule(pkgModule, pkgClass)
     }
   }
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index c665f2b91a..8e86e6fad9 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -181,7 +181,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     type AccessBoundaryType = Symbol
     type AnnotationType     = AnnotationInfo
 
-    // TODO - don't allow names to be renamed in this unstructured a fashion.
+    // TODO - don't allow names to be renamed in this unstructured fashion.
     // Rename as little as possible.  Enforce invariants on all renames.
     type TypeOfClonedSymbol >: Null <: Symbol { type NameType = Symbol.this.NameType }
 
@@ -1461,11 +1461,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     def info: Type = try {
       var cnt = 0
       while (validTo == NoPeriod) {
-        //if (settings.debug.value) System.out.println("completing " + this);//DEBUG
         assert(infos ne null, this.name)
         assert(infos.prev eq null, this.name)
         val tp = infos.info
-        //if (settings.debug.value) System.out.println("completing " + this.rawname + tp.getClass());//debug
 
         if ((_rawflags & LOCKED) != 0L) { // rolled out once for performance
           lock {
@@ -1474,6 +1472,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
           }
         } else {
           _rawflags |= LOCKED
+          // TODO another commented out lines - this should be solved in one way or another
 //          activeLocks += 1
  //         lockedSyms += this
         }
diff --git a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
index a494c7f0d0..38893d8db3 100644
--- a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
+++ b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
@@ -31,6 +31,9 @@ abstract class MutableSettings extends AbsSettings {
       v = arg
       postSetHook()
     }
+
+    /** Returns Some(value) in the case of a value set by user and None otherwise. */
+    def valueSetByUser: Option[T] = if (isSetByUser) Some(value) else None
   }
 
   def Xexperimental: BooleanSetting
diff --git a/src/reflect/scala/reflect/io/VirtualFile.scala b/src/reflect/scala/reflect/io/VirtualFile.scala
index 45f38db745..1cb4f2fe6f 100644
--- a/src/reflect/scala/reflect/io/VirtualFile.scala
+++ b/src/reflect/scala/reflect/io/VirtualFile.scala
@@ -75,10 +75,10 @@ class VirtualFile(val name: String, override val path: String) extends AbstractF
   }
 
   /** Does this abstract file denote an existing file? */
-  def create() { unsupported() }
+  def create(): Unit = unsupported()
 
   /** Delete the underlying file or directory (recursively). */
-  def delete() { unsupported() }
+  def delete(): Unit = unsupported()
 
   /**
    * Returns the abstract file in this abstract directory with the
diff --git a/src/reflect/scala/reflect/io/ZipArchive.scala b/src/reflect/scala/reflect/io/ZipArchive.scala
index 8260189459..0c63acb86c 100644
--- a/src/reflect/scala/reflect/io/ZipArchive.scala
+++ b/src/reflect/scala/reflect/io/ZipArchive.scala
@@ -74,12 +74,6 @@ abstract class ZipArchive(override val file: JFile) extends AbstractFile with Eq
   def container = unsupported()
   def absolute  = unsupported()
 
-  private def walkIterator(its: Iterator[AbstractFile]): Iterator[AbstractFile] = {
-    its flatMap { f =>
-      if (f.isDirectory) walkIterator(f.iterator)
-      else Iterator(f)
-    }
-  }
   /** ''Note:  This library is considered experimental and should not be used unless you know what you are doing.'' */
   sealed abstract class Entry(path: String) extends VirtualFile(baseName(path), path) {
     // have to keep this name for compat with sbt's compiler-interface
@@ -87,6 +81,7 @@ abstract class ZipArchive(override val file: JFile) extends AbstractFile with Eq
     override def underlyingSource = Some(self)
     override def toString = self.path + "(" + path + ")"
   }
+
   /** ''Note:  This library is considered experimental and should not be used unless you know what you are doing.'' */
   class DirEntry(path: String) extends Entry(path) {
     val entries = mutable.HashMap[String, Entry]()
@@ -125,14 +120,15 @@ abstract class ZipArchive(override val file: JFile) extends AbstractFile with Eq
 }
 /** ''Note:  This library is considered experimental and should not be used unless you know what you are doing.'' */
 final class FileZipArchive(file: JFile) extends ZipArchive(file) {
-  def iterator: Iterator[Entry] = {
+  lazy val (root, allDirs) = {
+    val root = new DirEntry("/")
+    val dirs = mutable.HashMap[String, DirEntry]("/" -> root)
     val zipFile = try {
       new ZipFile(file)
     } catch {
       case ioe: IOException => throw new IOException("Error accessing " + file.getPath, ioe)
     }
-    val root    = new DirEntry("/")
-    val dirs    = mutable.HashMap[String, DirEntry]("/" -> root)
+
     val enum    = zipFile.entries()
 
     while (enum.hasMoreElements) {
@@ -150,11 +146,11 @@ final class FileZipArchive(file: JFile) extends ZipArchive(file) {
         dir.entries(f.name) = f
       }
     }
-
-    try root.iterator
-    finally dirs.clear()
+    (root, dirs)
   }
 
+  def iterator: Iterator[Entry] = root.iterator
+
   def name         = file.getName
   def path         = file.getPath
   def input        = File(file).inputStream()
@@ -244,11 +240,9 @@ final class ManifestResources(val url: URL) extends ZipArchive(null) {
     val manifest = new Manifest(input)
     val iter     = manifest.getEntries().keySet().iterator().filter(_.endsWith(".class")).map(new ZipEntry(_))
 
-    while (iter.hasNext) {
-      val zipEntry = iter.next()
+    for (zipEntry <- iter) {
       val dir = getDir(dirs, zipEntry)
-      if (zipEntry.isDirectory) dir
-      else {
+      if (!zipEntry.isDirectory) {
         class FileEntry() extends Entry(zipEntry.getName) {
           override def lastModified = zipEntry.getTime()
           override def input        = resourceInputStream(path)
@@ -284,14 +278,14 @@ final class ManifestResources(val url: URL) extends ZipArchive(null) {
   private def resourceInputStream(path: String): InputStream = {
     new FilterInputStream(null) {
       override def read(): Int = {
-        if(in == null) in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path);
+        if(in == null) in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path)
         if(in == null) throw new RuntimeException(path + " not found")
-        super.read();
+        super.read()
       }
 
       override def close(): Unit = {
-        super.close();
-        in = null;
+        super.close()
+        in = null
       }
     }
   }
diff --git a/src/repl/scala/tools/nsc/interpreter/ILoop.scala b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
index ee1dea4dc1..4fd5768b79 100644
--- a/src/repl/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
@@ -618,8 +618,8 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     if (f.exists) {
       addedClasspath = ClassPath.join(addedClasspath, f.path)
       intp.addUrlsToClassPath(f.toURI.toURL)
-      echo("Added '%s' to classpath.".format(f.path, intp.global.classPath.asClasspathString))
-      repldbg("Added '%s'.  Your new classpath is:\n\"%s\"".format(f.path, intp.global.classPath.asClasspathString))
+      echo("Added '%s' to classpath.".format(f.path, intp.global.classPath.asClassPathString))
+      repldbg("Added '%s'.  Your new classpath is:\n\"%s\"".format(f.path, intp.global.classPath.asClassPathString))
     }
     else echo("The path '" + f + "' doesn't seem to exist.")
   }
@@ -663,8 +663,8 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     else {
       addedClasspath = ClassPath.join(addedClasspath, f.path)
       intp.addUrlsToClassPath(f.toURI.toURL)
-      echo("Added '%s' to classpath.".format(f.path, intp.global.classPath.asClasspathString))
-      repldbg("Added '%s'.  Your new classpath is:\n\"%s\"".format(f.path, intp.global.classPath.asClasspathString))
+      echo("Added '%s' to classpath.".format(f.path, intp.global.classPath.asClassPathString))
+      repldbg("Added '%s'.  Your new classpath is:\n\"%s\"".format(f.path, intp.global.classPath.asClassPathString))
     }
   }
 
diff --git a/src/repl/scala/tools/nsc/interpreter/IMain.scala b/src/repl/scala/tools/nsc/interpreter/IMain.scala
index b990e401ec..f9f7388363 100644
--- a/src/repl/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/repl/scala/tools/nsc/interpreter/IMain.scala
@@ -15,7 +15,7 @@ import scala.concurrent.{ Future, ExecutionContext }
 import scala.reflect.runtime.{ universe => ru }
 import scala.reflect.{ ClassTag, classTag }
 import scala.reflect.internal.util.{ BatchSourceFile, SourceFile }
-import scala.tools.util.PathResolver
+import scala.tools.util.PathResolverFactory
 import scala.tools.nsc.io.AbstractFile
 import scala.tools.nsc.typechecker.{ TypeStrings, StructuredTypeStrings }
 import scala.tools.nsc.util.{ ScalaClassLoader, stringFromReader, stringFromWriter, StackTraceOps, ClassPath, MergedClassPath }
@@ -90,7 +90,7 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
 
   def compilerClasspath: Seq[java.net.URL] = (
     if (isInitializeComplete) global.classPath.asURLs
-    else new PathResolver(settings).result.asURLs  // the compiler's classpath
+    else PathResolverFactory.create(settings).resultAsURLs  // the compiler's classpath
   )
   def settings = initialSettings
   // Run the code body with the given boolean settings flipped to true.
@@ -1282,9 +1282,11 @@ object IMain {
 
     def getProgram(statements: String*): String = null
 
-    def getScriptEngine: ScriptEngine = new IMain(this, new Settings() {
-      usemanifestcp.value = true
-    })
+    def getScriptEngine: ScriptEngine = {
+      val settings = new Settings()
+      settings.usemanifestcp.value = true
+      new IMain(this, settings)
+    }
   }
 
   // The two name forms this is catching are the two sides of this assignment:
diff --git a/src/scalap/scala/tools/scalap/Arguments.scala b/src/scalap/scala/tools/scalap/Arguments.scala
index c375a5bac4..de9c30b8af 100644
--- a/src/scalap/scala/tools/scalap/Arguments.scala
+++ b/src/scalap/scala/tools/scalap/Arguments.scala
@@ -9,7 +9,7 @@
 package scala.tools.scalap
 
 import scala.collection.mutable
-import mutable.{ Buffer, ListBuffer }
+import mutable.ListBuffer
 
 object Arguments {
   case class Parser(optionPrefix: Char) {
@@ -47,7 +47,7 @@ object Arguments {
     }
 
     def parseBinding(str: String, separator: Char): (String, String) = (str indexOf separator) match {
-      case -1   => argumentError("missing '" + separator + "' in binding '" + str + "'") ; ("", "")
+      case -1   => argumentError(s"missing '$separator' in binding '$str'") ; ("", "")
       case idx  => ((str take idx).trim, (str drop (idx + 1)).trim)
     }
 
@@ -71,7 +71,7 @@ object Arguments {
             i += 1
           } else if (optionalArgs contains args(i)) {
             if ((i + 1) == args.length) {
-              argumentError("missing argument for '" + args(i) + "'")
+              argumentError(s"missing argument for '${args(i)}'")
               i += 1
             } else {
               res.addArgument(args(i), args(i + 1))
@@ -79,11 +79,11 @@ object Arguments {
             }
           } else if (optionalBindings contains args(i)) {
             if ((i + 1) == args.length) {
-              argumentError("missing argument for '" + args(i) + "'")
+              argumentError(s"missing argument for '${args(i)}'")
               i += 1
             } else {
               res.addBinding(args(i),
-                parseBinding(args(i + 1), optionalBindings(args(i))));
+                parseBinding(args(i + 1), optionalBindings(args(i))))
               i += 2
             }
           } else {
@@ -92,23 +92,23 @@ object Arguments {
             while ((i == j) && iter.hasNext) {
               val prefix = iter.next
               if (args(i) startsWith prefix) {
-                res.addPrefixed(prefix, args(i).substring(prefix.length()).trim());
+                res.addPrefixed(prefix, args(i).substring(prefix.length()).trim())
                 i += 1
               }
             }
             if (i == j) {
-              val iter = prefixedBindings.keysIterator;
+              val iter = prefixedBindings.keysIterator
               while ((i == j) && iter.hasNext) {
                 val prefix = iter.next
                 if (args(i) startsWith prefix) {
                   val arg = args(i).substring(prefix.length()).trim()
                   i = i + 1
                   res.addBinding(prefix,
-                    parseBinding(arg, prefixedBindings(prefix)));
+                    parseBinding(arg, prefixedBindings(prefix)))
                 }
               }
               if (i == j) {
-                argumentError("unknown option '" + args(i) + "'")
+                argumentError(s"unknown option '${args(i)}'")
                 i = i + 1
               }
             }
@@ -119,7 +119,7 @@ object Arguments {
 
   def parse(options: String*)(args: Array[String]): Arguments = {
     val parser = new Parser('-')
-    options foreach (parser withOption _)
+    options foreach parser.withOption
     parser parse args
   }
 }
@@ -142,7 +142,7 @@ class Arguments {
     if (key.length > 0)
       bindings.getOrElseUpdate(tag, new mutable.HashMap)(key) = value
 
-  def addBinding(tag: String, binding: Tuple2[String, String]): Unit =
+  def addBinding(tag: String, binding: (String, String)): Unit =
     addBinding(tag, binding._1, binding._2)
 
   def addOther(arg: String): Unit = others += arg
diff --git a/src/scalap/scala/tools/scalap/Main.scala b/src/scalap/scala/tools/scalap/Main.scala
index c72f416a89..7c554d196c 100644
--- a/src/scalap/scala/tools/scalap/Main.scala
+++ b/src/scalap/scala/tools/scalap/Main.scala
@@ -10,11 +10,16 @@ package tools.scalap
 
 import java.io.{ PrintStream, OutputStreamWriter, ByteArrayOutputStream }
 import scala.reflect.NameTransformer
-import scalax.rules.scalasig._
-import scala.tools.nsc.util.{ ClassPath, JavaClassPath }
-import scala.tools.util.PathResolver
-import ClassPath.DefaultJavaContext
+import scala.tools.nsc.Settings
+import scala.tools.nsc.classpath.AggregateFlatClassPath
+import scala.tools.nsc.classpath.FlatClassPathFactory
 import scala.tools.nsc.io.AbstractFile
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.ClassFileLookup
+import scala.tools.nsc.util.ClassPath.DefaultJavaContext
+import scala.tools.nsc.util.JavaClassPath
+import scala.tools.util.PathResolverFactory
+import scalax.rules.scalasig._
 
 /**The main object used to execute scalap on the command-line.
  *
@@ -42,12 +47,12 @@ class Main {
    *
    * @param clazz the class file to be processed.
    */
-  def processJavaClassFile(clazz: Classfile) {
+  def processJavaClassFile(clazz: Classfile): Unit = {
     // construct a new output stream writer
     val out = new OutputStreamWriter(Console.out)
     val writer = new JavaWriter(clazz, out)
     // print the class
-    writer.printClass
+    writer.printClass()
     out.flush()
   }
 
@@ -60,21 +65,20 @@ class Main {
 
     syms.head.parent match {
       // Partial match
-      case Some(p) if (p.name != "<empty>") => {
+      case Some(p) if p.name != "<empty>" =>
         val path = p.path
         if (!isPackageObject) {
-          stream.print("package ");
-          stream.print(path);
+          stream.print("package ")
+          stream.print(path)
           stream.print("\n")
         } else {
           val i = path.lastIndexOf(".")
           if (i > 0) {
-            stream.print("package ");
+            stream.print("package ")
             stream.print(path.substring(0, i))
             stream.print("\n")
           }
         }
-      }
       case _ =>
     }
     // Print classes
@@ -96,7 +100,7 @@ class Main {
   /** Executes scalap with the given arguments and classpath for the
    *  class denoted by `classname`.
    */
-  def process(args: Arguments, path: ClassPath[AbstractFile])(classname: String): Unit = {
+  def process(args: Arguments, path: ClassFileLookup[AbstractFile])(classname: String): Unit = {
     // find the classfile
     val encName = classname match {
       case "scala.AnyRef" => "java.lang.Object"
@@ -106,92 +110,115 @@ class Main {
         // we can afford allocations because this is not a performance critical code
         classname.split('.').map(NameTransformer.encode).mkString(".")
     }
-    val cls = path.findClass(encName)
-    if (cls.isDefined && cls.get.binary.isDefined) {
-      val cfile = cls.get.binary.get
-      if (verbose) {
-        Console.println(Console.BOLD + "FILENAME" + Console.RESET + " = " + cfile.path)
-      }
-      val bytes = cfile.toByteArray
-      if (isScalaFile(bytes)) {
-        Console.println(decompileScala(bytes, isPackageObjectFile(encName)))
-      } else {
-        // construct a reader for the classfile content
-        val reader = new ByteArrayReader(cfile.toByteArray)
-        // parse the classfile
-        val clazz = new Classfile(reader)
-        processJavaClassFile(clazz)
-      }
-      // if the class corresponds to the artificial class scala.Any.
-      // (see member list in class scala.tool.nsc.symtab.Definitions)
-    }
-    else
-      Console.println("class/object " + classname + " not found.")
-  }
 
-  object EmptyClasspath extends ClassPath[AbstractFile] {
-    /**
-     * The short name of the package (without prefix)
-     */
-    def name              = ""
-    def asURLs            = Nil
-    def asClasspathString = ""
-
-    val context     = DefaultJavaContext
-    val classes     = IndexedSeq()
-    val packages    = IndexedSeq()
-    val sourcepaths = IndexedSeq()
+    path.findClassFile(encName) match {
+      case Some(classFile) =>
+        if (verbose) {
+          Console.println(Console.BOLD + "FILENAME" + Console.RESET + " = " + classFile.path)
+        }
+        val bytes = classFile.toByteArray
+        if (isScalaFile(bytes)) {
+          Console.println(decompileScala(bytes, isPackageObjectFile(encName)))
+        } else {
+          // construct a reader for the classfile content
+          val reader = new ByteArrayReader(classFile.toByteArray)
+          // parse the classfile
+          val clazz = new Classfile(reader)
+          processJavaClassFile(clazz)
+        }
+        // if the class corresponds to the artificial class scala.Any.
+        // (see member list in class scala.tool.nsc.symtab.Definitions)
+      case _ =>
+        Console.println(s"class/object $classname not found.")
+    }
   }
 }
 
 object Main extends Main {
+
+  private object opts {
+    val cp = "-cp"
+    val help = "-help"
+    val classpath = "-classpath"
+    val showPrivateDefs = "-private"
+    val verbose = "-verbose"
+    val version = "-version"
+
+    val classPathImplType = "-YclasspathImpl"
+    val disableFlatClassPathCaching = "-YdisableFlatCpCaching"
+    val logClassPath = "-Ylog-classpath"
+  }
+
   /** Prints usage information for scalap. */
-  def usage() {
-    Console println """
+  def usage(): Unit = {
+    Console println s"""
       |Usage: scalap {<option>} <name>
       |where <name> is fully-qualified class name or <package_name>.package for package objects
       |and <option> is
-      |  -private           print private definitions
-      |  -verbose           print out additional information
-      |  -version           print out the version number of scalap
-      |  -help              display this usage message
-      |  -classpath <path>  specify where to find user class files
-      |  -cp <path>         specify where to find user class files
+      |  ${opts.showPrivateDefs}           print private definitions
+      |  ${opts.verbose}           print out additional information
+      |  ${opts.version}           print out the version number of scalap
+      |  ${opts.help}              display this usage message
+      |  ${opts.classpath} <path>  specify where to find user class files
+      |  ${opts.cp} <path>         specify where to find user class files
     """.stripMargin.trim
   }
 
-  def main(args: Array[String]) {
-    // print usage information if there is no command-line argument
-    if (args.isEmpty)
-      return usage()
-
-    val arguments = Arguments.Parser('-')
-            .withOption("-private")
-            .withOption("-verbose")
-            .withOption("-version")
-            .withOption("-help")
-            .withOptionalArg("-classpath")
-            .withOptionalArg("-cp")
-            .parse(args);
-
-    if (arguments contains "-version")
-      Console.println(versionMsg)
-    if (arguments contains "-help")
-      usage()
-
-    verbose       = arguments contains "-verbose"
-    printPrivates = arguments contains "-private"
-    // construct a custom class path
-    val cparg = List("-classpath", "-cp") map (arguments getArgument _) reduceLeft (_ orElse _)
-    val path = cparg match {
-      case Some(cp) => new JavaClassPath(DefaultJavaContext.classesInExpandedPath(cp), DefaultJavaContext)
-      case _        => PathResolver.fromPathString(".") // include '.' in the default classpath SI-6669
+  def main(args: Array[String]): Unit =
+  // print usage information if there is no command-line argument
+    if (args.isEmpty) usage()
+    else {
+      val arguments = parseArguments(args)
+
+      if (arguments contains opts.version)
+        Console.println(versionMsg)
+      if (arguments contains opts.help)
+        usage()
+
+      verbose = arguments contains opts.verbose
+      printPrivates = arguments contains opts.showPrivateDefs
+      // construct a custom class path
+      val cpArg = List(opts.classpath, opts.cp) map arguments.getArgument reduceLeft (_ orElse _)
+
+      val settings = new Settings()
+
+      arguments getArgument opts.classPathImplType foreach settings.YclasspathImpl.tryToSetFromPropertyValue
+      settings.YdisableFlatCpCaching.value = arguments contains opts.disableFlatClassPathCaching
+      settings.Ylogcp.value = arguments contains opts.logClassPath
+
+      val path = createClassPath(cpArg, settings)
+
+      // print the classpath if output is verbose
+      if (verbose)
+        Console.println(Console.BOLD + "CLASSPATH" + Console.RESET + " = " + path.asClassPathString)
+
+      // process all given classes
+      arguments.getOthers foreach process(arguments, path)
     }
-    // print the classpath if output is verbose
-    if (verbose)
-      Console.println(Console.BOLD + "CLASSPATH" + Console.RESET + " = " + path)
 
-    // process all given classes
-    arguments.getOthers foreach process(arguments, path)
+  private def parseArguments(args: Array[String]) =
+    Arguments.Parser('-')
+      .withOption(opts.showPrivateDefs)
+      .withOption(opts.verbose)
+      .withOption(opts.version)
+      .withOption(opts.help)
+      .withOptionalArg(opts.classpath)
+      .withOptionalArg(opts.cp)
+      // TODO three temporary, hidden options to be able to test different classpath representations
+      .withOptionalArg(opts.classPathImplType)
+      .withOption(opts.disableFlatClassPathCaching)
+      .withOption(opts.logClassPath)
+      .parse(args)
+
+  private def createClassPath(cpArg: Option[String], settings: Settings) = cpArg match {
+    case Some(cp) => settings.YclasspathImpl.value match {
+      case ClassPathRepresentationType.Flat =>
+        AggregateFlatClassPath(new FlatClassPathFactory(settings).classesInExpandedPath(cp))
+      case ClassPathRepresentationType.Recursive =>
+        new JavaClassPath(DefaultJavaContext.classesInExpandedPath(cp), DefaultJavaContext)
+    }
+    case _ =>
+      settings.classpath.value = "." // include '.' in the default classpath SI-6669
+      PathResolverFactory.create(settings).result
   }
 }