From 938eab16f841fee67b2e34c983a7a2a6a5998127 Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Thu, 3 Nov 2011 04:51:52 +0000
Subject: ScalaClassLoader changes.

Lots of fiddling in the interests of a better classloading future.
---
 .../scala/reflect/runtime/JavaToScala.scala        |  19 ++-
 src/compiler/scala/tools/nsc/Global.scala          |   9 +-
 .../tools/nsc/backend/jvm/BytecodeWriters.scala    |   2 +-
 .../scala/tools/nsc/backend/jvm/GenJVM.scala       |   1 -
 .../scala/tools/nsc/interpreter/ByteCode.scala     |   4 +-
 .../scala/tools/nsc/interpreter/ILoop.scala        |   4 +-
 .../scala/tools/nsc/interpreter/IMain.scala        |  13 +-
 .../scala/tools/nsc/interpreter/Line.scala         |  27 ++---
 .../scala/tools/nsc/io/ClassAndJarInfo.scala       |  15 +--
 src/compiler/scala/tools/nsc/io/package.scala      |   5 +-
 src/compiler/scala/tools/nsc/util/ClassPath.scala  |  13 +-
 .../scala/tools/nsc/util/ScalaClassLoader.scala    | 133 +++++++++++++--------
 src/compiler/scala/tools/util/Javap.scala          |   4 +-
 src/compiler/scala/tools/util/SignalManager.scala  |   2 +-
 src/partest/scala/tools/partest/nest/Worker.scala  |   4 +-
 src/scalap/scala/tools/scalap/Decode.scala         |  10 +-
 16 files changed, 155 insertions(+), 110 deletions(-)

(limited to 'src')

diff --git a/src/compiler/scala/reflect/runtime/JavaToScala.scala b/src/compiler/scala/reflect/runtime/JavaToScala.scala
index 18db32c3bb..b8c8718590 100644
--- a/src/compiler/scala/reflect/runtime/JavaToScala.scala
+++ b/src/compiler/scala/reflect/runtime/JavaToScala.scala
@@ -1,7 +1,7 @@
 package scala.reflect
 package runtime
 
-import java.lang.{ Class => jClass, Package => jPackage }
+import java.lang.{ Class => jClass, Package => jPackage, ClassLoader => JClassLoader }
 import java.io.IOException
 import java.lang.reflect.{
   Method => jMethod,
@@ -26,16 +26,6 @@ import internal.Flags._
 import scala.tools.nsc.util.ScalaClassLoader
 import scala.tools.nsc.util.ScalaClassLoader._
 
-class MultiCL(parent: ScalaClassLoader, others: ScalaClassLoader*) extends java.lang.ClassLoader(parent) {
-  override def findClass(name: String): jClass[_] = {
-    for (cl <- others) {
-      try   { return cl.findClass(name) }
-      catch { case _: ClassNotFoundException => () }
-    }
-    super.findClass(name)
-  }
-}
-
 trait JavaToScala extends ConversionUtil { self: SymbolTable =>
 
   import definitions._
@@ -44,11 +34,16 @@ trait JavaToScala extends ConversionUtil { self: SymbolTable =>
     val global: JavaToScala.this.type = self
   }
 
+  protected def defaultReflectiveClassLoader(): JClassLoader =
+    Thread.currentThread.getContextClassLoader
+
   /** Paul: It seems the default class loader does not pick up root classes, whereas the system classloader does.
    *  Can you check with your newly acquired classloader fu whether this implementation makes sense?
    */
   def javaClass(path: String): jClass[_] =
-    jClass.forName(path, false, new MultiCL(getClass.getClassLoader, java.lang.ClassLoader.getSystemClassLoader))
+    javaClass(path, defaultReflectiveClassLoader())
+  def javaClass(path: String, classLoader: JClassLoader): jClass[_] =
+    classLoader.loadClass(path)
 
   /** Does `path` correspond to a Java class with that fully qualified name? */
   def isJavaClass(path: String): Boolean =
diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index b798fe71ba..602ff6bf0e 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -1325,10 +1325,11 @@ object Global {
     // !!! The classpath isn't known until the Global is created, which is too
     // late, so we have to duplicate it here.  Classpath is too tightly coupled,
     // it is a construct external to the compiler and should be treated as such.
-    val loader = ScalaClassLoader.fromURLs(new PathResolver(settings).result.asURLs)
-    val name   = settings.globalClass.value
-    val clazz  = Class.forName(name, true, loader)
-    val cons   = clazz.getConstructor(classOf[Settings], classOf[Reporter])
+    val parentLoader = settings.explicitParentLoader getOrElse getClass.getClassLoader
+    val loader       = ScalaClassLoader.fromURLs(new PathResolver(settings).result.asURLs, parentLoader)
+    val name         = settings.globalClass.value
+    val clazz        = Class.forName(name, true, loader)
+    val cons         = clazz.getConstructor(classOf[Settings], classOf[Reporter])
 
     cons.newInstance(settings, reporter).asInstanceOf[Global]
   }
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
index 228d4c6191..5b6e37e4fe 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
@@ -67,7 +67,7 @@ trait BytecodeWriters {
 
     def emitJavap(bytes: Array[Byte], javapFile: io.File) {
       val pw    = javapFile.printWriter()
-      val javap = new Javap(ScalaClassLoader.getSystemLoader(), pw) {
+      val javap = new Javap(ScalaClassLoader.appLoader, pw) {
         override def findBytes(path: String): Array[Byte] = bytes
       }
 
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenJVM.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenJVM.scala
index 1b6b50a793..0bd7109a0d 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenJVM.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenJVM.scala
@@ -12,7 +12,6 @@ import java.nio.ByteBuffer
 import scala.collection.{ mutable, immutable }
 import scala.reflect.internal.pickling.{ PickleFormat, PickleBuffer }
 import scala.tools.reflect.SigParser
-import scala.tools.nsc.util.ScalaClassLoader
 import scala.tools.nsc.symtab._
 import scala.reflect.internal.ClassfileConstants._
 import ch.epfl.lamp.fjbg._
diff --git a/src/compiler/scala/tools/nsc/interpreter/ByteCode.scala b/src/compiler/scala/tools/nsc/interpreter/ByteCode.scala
index 90d8fbb356..3059a8fb10 100644
--- a/src/compiler/scala/tools/nsc/interpreter/ByteCode.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/ByteCode.scala
@@ -9,7 +9,7 @@ package interpreter
 import java.lang.reflect
 import java.util.concurrent.ConcurrentHashMap
 import util.ScalaClassLoader
-import ScalaClassLoader.getSystemLoader
+import ScalaClassLoader.appLoader
 import scala.reflect.NameTransformer._
 
 object ByteCode {
@@ -17,7 +17,7 @@ object ByteCode {
    *  that the compiler will bootstrap, we have to use reflection.
    */
   private lazy val DECODER: Option[AnyRef] =
-    for (clazz <- getSystemLoader.tryToLoadClass[AnyRef]("scala.tools.scalap.Decode$")) yield
+    for (clazz <- appLoader.tryToLoadClass[AnyRef]("scala.tools.scalap.Decode$")) yield
       clazz.getField(MODULE_INSTANCE_NAME).get(null)
 
   private def decoderMethod(name: String, args: JClass*): Option[reflect.Method] = {
diff --git a/src/compiler/scala/tools/nsc/interpreter/ILoop.scala b/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
index 625bf2ae05..1f19740353 100644
--- a/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
@@ -93,11 +93,13 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
   }
 
   class ILoopInterpreter extends IMain(settings, out) {
+    outer =>
+
     override lazy val formatting = new Formatting {
       def prompt = ILoop.this.prompt
     }
     override protected def createLineManager(): Line.Manager =
-      if (ReplPropsKludge.noThreadCreation(settings)) null else new Line.Manager {
+      if (ReplPropsKludge.noThreadCreation(settings)) null else new Line.Manager(outer.classLoader) {
         override def onRunaway(line: Line[_]): Unit = {
           val template = """
             |// She's gone rogue, captain! Have to take her out!
diff --git a/src/compiler/scala/tools/nsc/interpreter/IMain.scala b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
index e93d4897ca..b092574eaf 100644
--- a/src/compiler/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
@@ -8,11 +8,7 @@ package interpreter
 
 import Predef.{ println => _, _ }
 import util.{ Set => _, _ }
-import scala.collection.{ mutable, immutable }
 import scala.sys.BooleanProp
-import Exceptional.unwrap
-import ScalaClassLoader.URLClassLoader
-import symtab.Flags
 import io.VirtualDirectory
 import scala.tools.nsc.io.AbstractFile
 import reporters._
@@ -23,7 +19,6 @@ import scala.tools.nsc.util.{ ScalaClassLoader, Exceptional, Indenter }
 import ScalaClassLoader.URLClassLoader
 import Exceptional.unwrap
 import scala.collection.{ mutable, immutable }
-import scala.PartialFunction.{ cond, condOpt }
 import scala.util.control.Exception.{ ultimately }
 import IMain._
 
@@ -257,14 +252,17 @@ class IMain(initialSettings: Settings, protected val out: JPrintWriter) extends
   def setExecutionWrapper(code: String) = _executionWrapper = code
   def clearExecutionWrapper() = _executionWrapper = ""
 
-  lazy val lineManager = createLineManager()
+  private var _lineManager: Line.Manager = createLineManager()
+  def lineManager = _lineManager
 
   /** interpreter settings */
   lazy val isettings = new ISettings(this)
 
   /** Create a line manager.  Overridable.  */
   protected def createLineManager(): Line.Manager =
-    if (ReplPropsKludge.noThreadCreation(settings)) null else new Line.Manager
+    createLineManager(classLoader)
+  protected def createLineManager(loader: ClassLoader): Line.Manager =
+    if (ReplPropsKludge.noThreadCreation(settings)) null else new Line.Manager(loader)
 
   /** Instantiate a compiler.  Overridable. */
   protected def newCompiler(settings: Settings, reporter: Reporter) = {
@@ -298,6 +296,7 @@ class IMain(initialSettings: Settings, protected val out: JPrintWriter) extends
   def resetClassLoader() = {
     repldbg("Setting new classloader: was " + _classLoader)
     _classLoader = makeClassLoader()
+    _lineManager = createLineManager(_classLoader)
   }
   def classLoader: AbstractFileClassLoader = {
     if (_classLoader == null)
diff --git a/src/compiler/scala/tools/nsc/interpreter/Line.scala b/src/compiler/scala/tools/nsc/interpreter/Line.scala
index deaeb913d2..deec9fcc4e 100644
--- a/src/compiler/scala/tools/nsc/interpreter/Line.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/Line.scala
@@ -18,7 +18,7 @@ import Line._
  *  waits on a condition indicating that either the line has
  *  completed or failed.
  */
-class Line[+T](val code: String, body: => T) {
+class Line[+T](val code: String, classLoader: ClassLoader, body: => T) {
   private var _state: State      = Running
   private var _result: Any       = null
   private var _caught: Throwable = null
@@ -37,19 +37,18 @@ class Line[+T](val code: String, body: => T) {
   // private because it should be called by the manager.
   private def cancel() = if (running) setState(Cancelled)
 
-  // This is where the line thread is created and started.
-  private val _thread = io.daemonize {
-    try {
-      _result = body
-      setState(Done)
-    }
-    catch {
-      case x =>
-        _caught = x
-        setState(Threw)
-    }
+  private def runAndSetState[T](body: => T) {
+    var ex: Throwable = null
+
+    try     { _result = body }
+    catch   { case t => ex = t }
+    finally { setState( if (ex == null) Done else Threw ) }
   }
 
+  // This is where the line thread is created and started.
+  private val _thread: Thread =
+    io.newThread(_ setContextClassLoader classLoader)(runAndSetState(body))
+
   def state     = _state
   def thread    = _thread
   def alive     = thread.isAlive
@@ -76,7 +75,7 @@ object Line {
   case object Cancelled extends State
   case object Done extends State
 
-  class Manager {
+  class Manager(classLoader: ClassLoader) {
     /** Override to add behavior for runaway lines.  This method will
      *  be called if a line thread is still running five seconds after
      *  it has been cancelled.
@@ -91,7 +90,7 @@ object Line {
       _current = None
     }
     def set[T](code: String)(body: => T) = {
-      val line = new Line(code, body)
+      val line = new Line(code, classLoader, body)
       _current = Some(line)
       line
     }
diff --git a/src/compiler/scala/tools/nsc/io/ClassAndJarInfo.scala b/src/compiler/scala/tools/nsc/io/ClassAndJarInfo.scala
index 716358a653..d0a0b17494 100644
--- a/src/compiler/scala/tools/nsc/io/ClassAndJarInfo.scala
+++ b/src/compiler/scala/tools/nsc/io/ClassAndJarInfo.scala
@@ -6,7 +6,7 @@
 package scala.tools.nsc
 package io
 
-import java.net.URL
+import java.net.{ URL, URLClassLoader }
 import java.io.IOException
 import collection.JavaConverters._
 
@@ -14,18 +14,20 @@ import collection.JavaConverters._
  *  a given Class object and similar common tasks.
  */
 class ClassAndJarInfo[T: ClassManifest] {
-  val man   = classManifest[T]
-  def clazz = man.erasure
+  val man          = classManifest[T]
+  def clazz        = man.erasure
+  def internalName = clazz.getName.replace('.', '/')
+
+  def resourceURL = new URLClassLoader(Array[URL]()) getResource internalName + ".class"
 
   def baseOfPath(path: String) = path indexOf '!' match {
-    case -1   => path stripSuffix internalClassName
+    case -1   => path stripSuffix internalName + ".class"
     case idx  => path take idx
   }
 
+  def simpleClassName      = clazz.getName split """[$.]""" last
   def classUrl             = clazz getResource simpleClassName + ".class"
   def codeSource           = protectionDomain.getCodeSource()
-  def internalClassName    = internalName + ".class"
-  def internalName         = clazz.getName.replace('.', '/')
   def jarManifest          = (
     try new JManifest(jarManifestUrl.openStream())
     catch { case _: IOException => new JManifest() }
@@ -39,5 +41,4 @@ class ClassAndJarInfo[T: ClassManifest] {
   def rootFromLocation     = Path(locationUrl.toURI.getPath())
   def rootFromResource     = Path(baseOfPath(classUrl.getPath) stripPrefix "file:")
   def rootPossibles        = Iterator(rootFromResource, rootFromLocation)
-  def simpleClassName      = clazz.getName split """[$.]""" last
 }
diff --git a/src/compiler/scala/tools/nsc/io/package.scala b/src/compiler/scala/tools/nsc/io/package.scala
index d0a1d88086..88679e6dce 100644
--- a/src/compiler/scala/tools/nsc/io/package.scala
+++ b/src/compiler/scala/tools/nsc/io/package.scala
@@ -25,9 +25,10 @@ package object io {
   def spawnFn[T](f: () => T): Future[T]       = spawn(f())
 
   // Create, start, and return a daemon thread
-  def daemonize(body: => Unit): Thread = {
+  def daemonize(body: => Unit): Thread = newThread(_ setDaemon true)(body)
+  def newThread(f: Thread => Unit)(body: => Unit): Thread = {
     val thread = new Thread(runnable(body))
-    thread setDaemon true
+    f(thread)
     thread.start
     thread
   }
diff --git a/src/compiler/scala/tools/nsc/util/ClassPath.scala b/src/compiler/scala/tools/nsc/util/ClassPath.scala
index 1487b42843..1820bd190f 100644
--- a/src/compiler/scala/tools/nsc/util/ClassPath.scala
+++ b/src/compiler/scala/tools/nsc/util/ClassPath.scala
@@ -464,5 +464,16 @@ extends ClassPath[T] {
 class JavaClassPath(
   containers: IndexedSeq[ClassPath[AbstractFile]],
   context: JavaContext)
-extends MergedClassPath[AbstractFile](containers, context) {
+extends MergedClassPath[AbstractFile](containers, context) { }
+
+object JavaClassPath {
+  def fromURLs(urls: Seq[URL], context: JavaContext): JavaClassPath = {
+    val containers = {
+      for (url <- urls ; f = AbstractFile getURL url ; if f != null) yield
+        new DirectoryClassPath(f, context)
+    }
+    new JavaClassPath(containers.toIndexedSeq, context)
+  }
+  def fromURLs(urls: Seq[URL]): JavaClassPath =
+    fromURLs(urls, ClassPath.DefaultJavaContext)
 }
diff --git a/src/compiler/scala/tools/nsc/util/ScalaClassLoader.scala b/src/compiler/scala/tools/nsc/util/ScalaClassLoader.scala
index 07fe254410..d048b75599 100644
--- a/src/compiler/scala/tools/nsc/util/ScalaClassLoader.scala
+++ b/src/compiler/scala/tools/nsc/util/ScalaClassLoader.scala
@@ -6,26 +6,34 @@
 package scala.tools.nsc
 package util
 
-import java.lang.{ ClassLoader => JavaClassLoader }
+import java.lang.{ ClassLoader => JClassLoader }
 import java.lang.reflect.{ Constructor, Modifier, Method }
+import java.io.{ File => JFile }
+import java.net.{ URLClassLoader => JURLClassLoader }
 import java.net.URL
+import scala.reflect.unwrapForHandler
 import ScalaClassLoader._
 import scala.util.control.Exception.{ catching }
+// import Exceptional.unwrap
 
-trait ScalaClassLoader extends JavaClassLoader {
+trait HasClassPath {
+  def classPathURLs: Seq[URL]
+}
+
+/** A wrapper around java.lang.ClassLoader to lower the annoyance
+ *  of java reflection.
+ */
+trait ScalaClassLoader extends JClassLoader {
   /** Override to see classloader activity traced */
   protected def trace: Boolean = false
 
   /** Executing an action with this classloader as context classloader */
   def asContext[T](action: => T): T = {
-    val oldLoader = getContextLoader
-    try {
-      setContextLoader(this)
-      action
-    }
-    finally setContextLoader(oldLoader)
+    val saved = contextLoader
+    try { setContext(this) ; action }
+    finally setContext(saved)
   }
-  def setAsContext() { setContextLoader(this) }
+  def setAsContext() { setContext(this) }
 
   /** Load and link a class with this classloader */
   def tryToLoadClass[T <: AnyRef](path: String): Option[Class[T]] = tryClass(path, false)
@@ -70,68 +78,97 @@ trait ScalaClassLoader extends JavaClassLoader {
     val clsToRun = tryToInitializeClass(objectName) getOrElse (
       throw new ClassNotFoundException(objectName)
     )
-
     val method = clsToRun.getMethod("main", classOf[Array[String]])
     if (!Modifier.isStatic(method.getModifiers))
       throw new NoSuchMethodException(objectName + ".main is not static")
 
-    asContext(method.invoke(null, Array(arguments.toArray: AnyRef): _*))  // !!! : AnyRef shouldn't be necessary
+    try asContext(method.invoke(null, Array(arguments.toArray: AnyRef): _*)) // !!! : AnyRef shouldn't be necessary
+    catch unwrapForHandler({ case ex => throw ex })
   }
+
+  /** A list comprised of this classloader followed by all its
+   *  (non-null) parent classloaders, if any.
+   */
+  def loaderChain: List[ScalaClassLoader] = this :: (getParent match {
+    case null => Nil
+    case p    => p.loaderChain
+  })
 }
 
+/** Methods for obtaining various classloaders.
+ *      appLoader: the application classloader.  (Also called the java system classloader.)
+ *      extLoader: the extension classloader.
+ *     bootLoader: the boot classloader.
+ *  contextLoader: the context classloader.
+ */
 object ScalaClassLoader {
-  implicit def apply(cl: JavaClassLoader): ScalaClassLoader = {
-    val loader = if (cl == null) JavaClassLoader.getSystemClassLoader() else cl
-    new JavaClassLoader(loader) with ScalaClassLoader
+  /** Returns loaders which are already ScalaClassLoaders unaltered,
+   *  and translates java.net.URLClassLoaders into scala URLClassLoaders.
+   *  Otherwise creates a new wrapper.
+   */
+  implicit def apply(cl: JClassLoader): ScalaClassLoader = cl match {
+    case cl: ScalaClassLoader => cl
+    case cl: JURLClassLoader  => new URLClassLoader(cl.getURLs.toSeq, cl.getParent)
+    case _                    => new JClassLoader(cl) with ScalaClassLoader
+  }
+  def contextLoader = apply(Thread.currentThread.getContextClassLoader)
+  def appLoader     = apply(JClassLoader.getSystemClassLoader)
+  def extLoader     = apply(appLoader.getParent)
+  def bootLoader    = apply(null)
+  def contextChain  = loaderChain(contextLoader)
+
+  def pathToErasure[T: ClassManifest] = pathToClass(classManifest[T].erasure)
+  def pathToClass(clazz: Class[_])    = clazz.getName.replace('.', JFile.separatorChar) + ".class"
+  def locate[T: ClassManifest]        = contextLoader getResource pathToErasure[T]
+
+  /** Tries to guess the classpath by type matching the context classloader
+   *  and its parents, looking for any classloaders which will reveal their
+   *  classpath elements as urls.  It it can't find any, creates a classpath
+   *  from the supplied string.
+   */
+  def guessClassPathString(default: String = ""): String = {
+    val classpathURLs = contextChain flatMap {
+      case x: HasClassPath    => x.classPathURLs
+      case x: JURLClassLoader => x.getURLs.toSeq
+      case _                  => Nil
+    }
+    if (classpathURLs.isEmpty) default
+    else JavaClassPath.fromURLs(classpathURLs).asClasspathString
   }
 
-  class URLClassLoader(urls: Seq[URL], parent: JavaClassLoader)
-      extends java.net.URLClassLoader(urls.toArray, parent)
-      with ScalaClassLoader {
+  def loaderChain(head: JClassLoader) = {
+    def loop(cl: JClassLoader): List[JClassLoader] =
+      if (cl == null) Nil else cl :: loop(cl.getParent)
 
-    private var classloaderURLs = urls.toList
+    loop(head)
+  }
+  def setContext(cl: JClassLoader) =
+    Thread.currentThread.setContextClassLoader(cl)
+
+  class URLClassLoader(urls: Seq[URL], parent: JClassLoader)
+      extends JURLClassLoader(urls.toArray, parent)
+         with ScalaClassLoader
+         with HasClassPath {
+
+    private var classloaderURLs: Seq[URL] = urls
     private def classpathString = ClassPath.fromURLs(urls: _*)
+    def classPathURLs: Seq[URL] = classloaderURLs
+    def classPath: ClassPath[_] = JavaClassPath fromURLs classPathURLs
 
     /** Override to widen to public */
     override def addURL(url: URL) = {
-      classloaderURLs +:= url
+      classloaderURLs :+= url
       super.addURL(url)
     }
-    override def run(objectName: String, arguments: Seq[String]) {
-      try super.run(objectName, arguments)
-      catch { case x: ClassNotFoundException  =>
-        throw new ClassNotFoundException(objectName +
-          " (args = %s, classpath = %s)".format(arguments mkString ", ", classpathString))
-      }
-    }
     override def toString = urls.mkString("URLClassLoader(\n  ", "\n  ", "\n)\n")
   }
 
-  def setContextLoader(cl: JavaClassLoader) = Thread.currentThread.setContextClassLoader(cl)
-  def getContextLoader() = Thread.currentThread.getContextClassLoader()
-  def getSystemLoader(): ScalaClassLoader = ScalaClassLoader(null)
-  def defaultParentClassLoader() = findExtClassLoader()
-
-  def fromURLs(urls: Seq[URL], parent: ClassLoader = defaultParentClassLoader()): URLClassLoader =
-    new URLClassLoader(urls.toList, parent)
+  def fromURLs(urls: Seq[URL], parent: ClassLoader = null): URLClassLoader =
+    new URLClassLoader(urls, parent)
 
   /** True if supplied class exists in supplied path */
   def classExists(urls: Seq[URL], name: String): Boolean =
-    (fromURLs(urls) tryToLoadClass name).isDefined
-
-  // we cannot use the app classloader here or we get what looks to
-  // be classloader deadlock, but if we pass null we bypass the extension
-  // classloader and our extensions, so we search the hierarchy to find
-  // the classloader whose parent is null.  Resolves bug #857.
-  def findExtClassLoader(): JavaClassLoader = {
-    def search(cl: JavaClassLoader): JavaClassLoader = {
-      if (cl == null) null
-      else if (cl.getParent == null) cl
-      else search(cl.getParent)
-    }
-
-    search(getContextLoader())
-  }
+    fromURLs(urls) tryToLoadClass name isDefined
 
   /** Finding what jar a clazz or instance came from */
   def origin(x: Any): Option[URL] = originOfClass(x.getClass)
diff --git a/src/compiler/scala/tools/util/Javap.scala b/src/compiler/scala/tools/util/Javap.scala
index 04033e913d..94de5588dd 100644
--- a/src/compiler/scala/tools/util/Javap.scala
+++ b/src/compiler/scala/tools/util/Javap.scala
@@ -14,7 +14,7 @@ import scala.tools.nsc.io.{ File, NullPrintStream }
 import Javap._
 
 class Javap(
-  val loader: ScalaClassLoader = ScalaClassLoader.getSystemLoader(),
+  val loader: ScalaClassLoader = ScalaClassLoader.appLoader,
   val printWriter: PrintWriter = new PrintWriter(System.out, true)
 ) {
 
@@ -79,7 +79,7 @@ object Javap {
   val Env     = "sun.tools.javap.JavapEnvironment"
   val Printer = "sun.tools.javap.JavapPrinter"
 
-  def isAvailable(cl: ScalaClassLoader = ScalaClassLoader.getSystemLoader()) =
+  def isAvailable(cl: ScalaClassLoader = ScalaClassLoader.appLoader) =
     cl.tryToInitializeClass[AnyRef](Env).isDefined
 
   // "documentation"
diff --git a/src/compiler/scala/tools/util/SignalManager.scala b/src/compiler/scala/tools/util/SignalManager.scala
index 19b5348a43..e93297386a 100644
--- a/src/compiler/scala/tools/util/SignalManager.scala
+++ b/src/compiler/scala/tools/util/SignalManager.scala
@@ -32,7 +32,7 @@ import scala.util.Random
  *  }}}
  */
 class SignalManager(classLoader: ScalaClassLoader) {
-  def this() = this(ScalaClassLoader.getSystemLoader)
+  def this() = this(ScalaClassLoader.appLoader)
   private val illegalArgHandler: PartialFunction[Throwable, Boolean] = {
     case x if unwrap(x).isInstanceOf[IllegalArgumentException] => false
   }
diff --git a/src/partest/scala/tools/partest/nest/Worker.scala b/src/partest/scala/tools/partest/nest/Worker.scala
index 45902229eb..711e3f0935 100644
--- a/src/partest/scala/tools/partest/nest/Worker.scala
+++ b/src/partest/scala/tools/partest/nest/Worker.scala
@@ -400,8 +400,8 @@ class Worker(val fileManager: FileManager, params: TestRunParams) extends Actor
    */
   def runTests(files: List[File])(topcont: Map[String, Int] => Unit) {
     val compileMgr = new CompileManager(fileManager)
-    if (kind == "scalacheck") fileManager.CLASSPATH += File.pathSeparator + PathSettings.scalaCheck
-
+    // if (kind == "scalacheck")
+    fileManager.CLASSPATH += File.pathSeparator + PathSettings.scalaCheck
     filesRemaining = files
 
     // You don't default "succeeded" to true.
diff --git a/src/scalap/scala/tools/scalap/Decode.scala b/src/scalap/scala/tools/scalap/Decode.scala
index b4f93bccd4..4e12075541 100644
--- a/src/scalap/scala/tools/scalap/Decode.scala
+++ b/src/scalap/scala/tools/scalap/Decode.scala
@@ -11,7 +11,7 @@ package scala.tools.scalap
 
 import scala.tools.scalap.scalax.rules.scalasig._
 import scala.tools.nsc.util.ScalaClassLoader
-import scala.tools.nsc.util.ScalaClassLoader.getSystemLoader
+import scala.tools.nsc.util.ScalaClassLoader.appLoader
 import scala.reflect.internal.pickling.ByteCodecs
 
 import ClassFileParser.{ ConstValueIndex, Annotation }
@@ -31,7 +31,7 @@ object Decode {
   /** Return the classfile bytes representing the scala sig classfile attribute.
    *  This has been obsoleted by the switch to annotations.
    */
-  def scalaSigBytes(name: String): Option[Array[Byte]] = scalaSigBytes(name, getSystemLoader())
+  def scalaSigBytes(name: String): Option[Array[Byte]] = scalaSigBytes(name, appLoader)
   def scalaSigBytes(name: String, classLoader: ScalaClassLoader): Option[Array[Byte]] = {
     val bytes = classLoader.classBytes(name)
     val reader = new ByteArrayReader(bytes)
@@ -41,7 +41,7 @@ object Decode {
 
   /** Return the bytes representing the annotation
    */
-  def scalaSigAnnotationBytes(name: String): Option[Array[Byte]] = scalaSigAnnotationBytes(name, getSystemLoader())
+  def scalaSigAnnotationBytes(name: String): Option[Array[Byte]] = scalaSigAnnotationBytes(name, appLoader)
   def scalaSigAnnotationBytes(name: String, classLoader: ScalaClassLoader): Option[Array[Byte]] = {
     val bytes     = classLoader.classBytes(name)
     val byteCode  = ByteCode(bytes)
@@ -67,7 +67,7 @@ object Decode {
     }
 
     for {
-      clazz <- getSystemLoader.tryToLoadClass[AnyRef](outer)
+      clazz <- appLoader.tryToLoadClass[AnyRef](outer)
       ssig <- ScalaSigParser.parse(clazz)
     }
     yield {
@@ -89,7 +89,7 @@ object Decode {
    */
   private[scala] def typeAliases(pkg: String) = {
     for {
-      clazz <- getSystemLoader.tryToLoadClass[AnyRef](pkg + ".package")
+      clazz <- appLoader.tryToLoadClass[AnyRef](pkg + ".package")
       ssig <- ScalaSigParser.parse(clazz)
     }
     yield {
-- 
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