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Scala example source code file (Global.scala)

This example Scala source code file (Global.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, collection, compilationunit, compiler, list, none, nsc, phase, pickling, reflection, some, string, symbol, t, unit, utilities

The Global.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala
package tools
package nsc

import java.io.{ File, FileOutputStream, PrintWriter, IOException, FileNotFoundException }
import java.nio.charset.{ Charset, CharsetDecoder, IllegalCharsetNameException, UnsupportedCharsetException }
import java.util.UUID._
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 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 symtab.{ Flags, SymbolTable, SymbolLoaders, SymbolTrackers }
import symtab.classfile.Pickler
import plugins.Plugins
import ast._
import ast.parser._
import typechecker._
import transform.patmat.PatternMatching
import transform._
import backend.icode.{ ICodes, GenICode, ICodeCheckers }
import backend.{ ScalaPrimitives, Platform, JavaPlatform }
import backend.jvm.GenBCode
import backend.jvm.GenASM
import backend.opt.{ Inliners, InlineExceptionHandlers, ConstantOptimization, ClosureElimination, DeadCodeElimination }
import backend.icode.analysis._
import scala.language.postfixOps
import scala.tools.nsc.ast.{TreeGen => AstTreeGen}

class Global(var currentSettings: Settings, var reporter: Reporter)
    extends SymbolTable
    with CompilationUnits
    with Plugins
    with PhaseAssembly
    with Trees
    with Printers
    with DocComments
    with Positions { self =>

  // the mirror --------------------------------------------------

  override def isCompilerUniverse = true
  override val useOffsetPositions = !currentSettings.Yrangepos

  type RuntimeClass = java.lang.Class[_]
  implicit val RuntimeClassTag: ClassTag[RuntimeClass] = ClassTag[RuntimeClass](classOf[RuntimeClass])

  class GlobalMirror extends Roots(NoSymbol) {
    val universe: self.type = self
    def rootLoader: LazyType = new loaders.PackageLoader(classPath)
    override def toString = "compiler mirror"
  }
  implicit val MirrorTag: ClassTag[Mirror] = ClassTag[Mirror](classOf[GlobalMirror])

  lazy val rootMirror: Mirror = {
    val rm = new GlobalMirror
    rm.init()
    rm.asInstanceOf[Mirror]
  }
  def RootClass: ClassSymbol = rootMirror.RootClass
  def EmptyPackageClass: ClassSymbol = rootMirror.EmptyPackageClass

  import definitions.findNamedMember
  def findMemberFromRoot(fullName: Name): Symbol = rootMirror.findMemberFromRoot(fullName)

  // alternate constructors ------------------------------------------

  override def settings = currentSettings

  /** Switch to turn on detailed type logs */
  var printTypings = settings.Ytyperdebug.value

  def this(reporter: Reporter) =
    this(new Settings(err => reporter.error(null, err)), reporter)

  def this(settings: Settings) =
    this(settings, new ConsoleReporter(settings))

  def picklerPhase: Phase = if (currentRun.isDefined) currentRun.picklerPhase else NoPhase

  def erasurePhase: Phase = if (currentRun.isDefined) currentRun.erasurePhase else NoPhase

  // platform specific elements

  protected class GlobalPlatform extends {
    val global: Global.this.type = Global.this
    val settings: Settings = Global.this.settings
  } with JavaPlatform

  type ThisPlatform = JavaPlatform { val global: Global.this.type }
  lazy val platform: ThisPlatform  = new GlobalPlatform

  type PlatformClassPath = ClassPath[AbstractFile]
  type OptClassPath = Option[PlatformClassPath]

  def classPath: PlatformClassPath = platform.classPath

  // sub-components --------------------------------------------------

  /** Tree generation, usually based on existing symbols. */
  override object gen extends {
    val global: Global.this.type = Global.this
  } with AstTreeGen {
    def mkAttributedCast(tree: Tree, pt: Type): Tree =
      typer.typed(mkCast(tree, pt))
  }

  /** A spare instance of TreeBuilder left for backwards compatibility. */
  lazy val treeBuilder: TreeBuilder { val global: Global.this.type } = new TreeBuilder {
    val global: Global.this.type = Global.this;
    def unit = currentUnit
    def source = currentUnit.source
  }

  /** Fold constants */
  object constfold extends {
    val global: Global.this.type = Global.this
  } with ConstantFolder

  /** ICode generator */
  object icodes extends {
    val global: Global.this.type = Global.this
  } with ICodes

  /** Scala primitives, used in genicode */
  object scalaPrimitives extends {
    val global: Global.this.type = Global.this
  } with ScalaPrimitives

  /** Computing pairs of overriding/overridden symbols */
  object overridingPairs extends {
    val global: Global.this.type = Global.this
  } with OverridingPairs

  type SymbolPair = overridingPairs.SymbolPair

  // Optimizer components

  /** ICode analysis for optimization */
  object analysis extends {
    val global: Global.this.type = Global.this
  } with TypeFlowAnalysis

  /** Copy propagation for optimization */
  object copyPropagation extends {
    val global: Global.this.type = Global.this
  } with CopyPropagation

  // Components for collecting and generating output

  /** Some statistics (normally disabled) set with -Ystatistics */
  object statistics extends {
    val global: Global.this.type = Global.this
  } with StatisticsInfo

  /** Print tree in detailed form */
  object nodePrinters extends {
    val global: Global.this.type = Global.this
  } with NodePrinters {
    var lastPrintedPhase: Phase = NoPhase
    var lastPrintedSource: String = ""
    infolevel = InfoLevel.Verbose

    def showUnit(unit: CompilationUnit) {
      print(" // " + unit.source)
      if (unit.body == null) println(": tree is null")
      else {
        val source = util.stringFromWriter(w => newTreePrinter(w) print unit.body)

        // treePrinter show unit.body
        if (lastPrintedSource == source)
          println(": tree is unchanged since " + lastPrintedPhase)
        else {
          lastPrintedPhase = phase.prev // since we're running inside "exitingPhase"
          lastPrintedSource = source
          println("")
          println(source)
          println("")
        }
      }
    }
  }

  def withInfoLevel[T](infolevel: nodePrinters.InfoLevel.Value)(op: => T) = {
    val saved = nodePrinters.infolevel
    try {
      nodePrinters.infolevel = infolevel
      op
    } finally {
      nodePrinters.infolevel = saved
    }
  }

  /** Representing ASTs as graphs */
  object treeBrowsers extends {
    val global: Global.this.type = Global.this
  } with TreeBrowsers

  val nodeToString = nodePrinters.nodeToString
  val treeBrowser = treeBrowsers.create()

  // ------------ Hooks for interactive mode-------------------------

  /** Called every time an AST node is successfully typechecked in typerPhase.
   */
  def signalDone(context: analyzer.Context, old: Tree, result: Tree) {}

  /** Called from parser, which signals hereby that a method definition has been parsed. */
  def signalParseProgress(pos: Position) {}

  /** Register new context; called for every created context
   */
  def registerContext(c: analyzer.Context) {
    lastSeenContext = c
  }

  /** Register top level class (called on entering the class)
   */
  def registerTopLevelSym(sym: Symbol) {}

// ------------------ Reporting -------------------------------------

  // not deprecated yet, but a method called "error" imported into
  // nearly every trait really must go.  For now using globalError.
  def error(msg: String) = globalError(msg)

  override def inform(msg: String)      = inform(NoPosition, msg)
  override def globalError(msg: String) = globalError(NoPosition, msg)
  override def warning(msg: String)     = warning(NoPosition, msg)
  override def deprecationWarning(pos: Position, msg: String) = currentUnit.deprecationWarning(pos, msg)

  def globalError(pos: Position, msg: String) = reporter.error(pos, msg)
  def warning(pos: Position, msg: String)     = if (settings.fatalWarnings) globalError(pos, msg) else reporter.warning(pos, msg)
  def inform(pos: Position, msg: String)      = reporter.echo(pos, msg)

  // Getting in front of Predef's asserts to supplement with more info.
  // This has the happy side effect of masking the one argument forms
  // of assert and require (but for now I've reproduced them here,
  // because there are a million to fix.)
  @inline final def assert(assertion: Boolean, message: => Any) {
    // calling Predef.assert would send a freshly allocated closure wrapping the one received as argument.
    if (!assertion)
      throw new java.lang.AssertionError("assertion failed: "+ supplementErrorMessage("" + message))
  }
  @inline final def assert(assertion: Boolean) {
    assert(assertion, "")
  }
  @inline final def require(requirement: Boolean, message: => Any) {
    // calling Predef.require would send a freshly allocated closure wrapping the one received as argument.
    if (!requirement)
      throw new IllegalArgumentException("requirement failed: "+ supplementErrorMessage("" + message))
  }
  @inline final def require(requirement: Boolean) {
    require(requirement, "")
  }

  // Needs to call error to make sure the compile fails.
  override def abort(msg: String): Nothing = {
    error(msg)
    super.abort(msg)
  }

  @inline final def ifDebug(body: => Unit) {
    if (settings.debug)
      body
  }

  override protected def isDeveloper = settings.developer || super.isDeveloper

  /** This is for WARNINGS which should reach the ears of scala developers
   *  whenever they occur, but are not useful for normal users. They should
   *  be precise, explanatory, and infrequent. Please don't use this as a
   *  logging mechanism. !!! is prefixed to all messages issued via this route
   *  to make them visually distinct.
   */
  @inline final override def devWarning(msg: => String): Unit = devWarning(NoPosition, msg)
  @inline final def devWarning(pos: Position, msg: => String) {
    def pos_s = if (pos eq NoPosition) "" else s" [@ $pos]"
    if (isDeveloper)
      warning(pos, "!!! " + msg)
    else
      log(s"!!!$pos_s $msg") // such warnings always at least logged
  }

  def informComplete(msg: String): Unit    = reporter.withoutTruncating(inform(msg))

  def logError(msg: String, t: Throwable): Unit = ()

  override def shouldLogAtThisPhase = settings.log.isSetByUser && (
    (settings.log containsPhase globalPhase) || (settings.log containsPhase phase)
  )
  // Over 200 closure objects are eliminated by inlining this.
  @inline final def log(msg: => AnyRef) {
    if (shouldLogAtThisPhase)
      inform("[log %s%s] %s".format(globalPhase, atPhaseStackMessage, msg))
  }

  @inline final override def debuglog(msg: => String) {
    if (settings.debug)
      log(msg)
  }

  @deprecated("Renamed to reportThrowable", "2.10.1")
  def logThrowable(t: Throwable): Unit = reportThrowable(t)
  def reportThrowable(t: Throwable): Unit = globalError(throwableAsString(t))
  override def throwableAsString(t: Throwable) = util.stackTraceString(t)

// ------------ File interface -----------------------------------------

  private val reader: SourceReader = {
    val defaultEncoding = Properties.sourceEncoding

    def loadCharset(name: String) =
      try Some(Charset.forName(name))
      catch {
        case _: IllegalCharsetNameException =>
          globalError("illegal charset name '" + name + "'")
          None
        case _: UnsupportedCharsetException =>
          globalError("unsupported charset '" + name + "'")
          None
      }

    val charset = ( if (settings.encoding.isSetByUser) Some(settings.encoding.value) else None ) flatMap loadCharset getOrElse {
      settings.encoding.value = defaultEncoding // A mandatory charset
      Charset.forName(defaultEncoding)
    }

    def loadReader(name: String): Option[SourceReader] = {
      def ccon = Class.forName(name).getConstructor(classOf[CharsetDecoder], classOf[Reporter])

      try Some(ccon.newInstance(charset.newDecoder(), reporter).asInstanceOf[SourceReader])
      catch { case ex: Throwable =>
        globalError("exception while trying to instantiate source reader '" + name + "'")
        None
      }
    }

    ( if (settings.sourceReader.isSetByUser) Some(settings.sourceReader.value) else None ) flatMap loadReader getOrElse {
      new SourceReader(charset.newDecoder(), reporter)
    }
  }

  if (settings.verbose || settings.Ylogcp) {
    // Uses the "do not truncate" inform
    informComplete("[search path for source files: " + classPath.sourcepaths.mkString(",") + "]")
    informComplete("[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
  // to create it on that side.  For this one my strategy is a constant def at the file
  // where I need it, and then an override in Global with the setting.
  override protected val etaExpandKeepsStar = settings.etaExpandKeepsStar.value
  // Here comes another one...
  override protected val enableTypeVarExperimentals = settings.Xexperimental.value

  def getSourceFile(f: AbstractFile): BatchSourceFile = new BatchSourceFile(f, reader read f)

  def getSourceFile(name: String): SourceFile = {
    val f = AbstractFile.getFile(name)
    if (f eq null) throw new FileNotFoundException(
      "source file '" + name + "' could not be found")
    getSourceFile(f)
  }

  lazy val loaders = new {
    val global: Global.this.type = Global.this
    val platform: Global.this.platform.type = Global.this.platform
  } with GlobalSymbolLoaders

  /** Returns the mirror that loaded given symbol */
  def mirrorThatLoaded(sym: Symbol): Mirror = rootMirror

// ------------ Phases -------------------------------------------}

  var globalPhase: Phase = NoPhase

  val MaxPhases = 64

  val phaseWithId: Array[Phase] = Array.fill(MaxPhases)(NoPhase)

  abstract class GlobalPhase(prev: Phase) extends Phase(prev) {
    phaseWithId(id) = this

    def run() {
      echoPhaseSummary(this)
      currentRun.units foreach applyPhase
    }

    def apply(unit: CompilationUnit): Unit

    private val isErased = prev.name == "erasure" || prev.erasedTypes
    override def erasedTypes: Boolean = isErased
    private val isFlat = prev.name == "flatten" || prev.flatClasses
    override def flatClasses: Boolean = isFlat
    private val isSpecialized = prev.name == "specialize" || prev.specialized
    override def specialized: Boolean = isSpecialized
    private val isRefChecked = prev.name == "refchecks" || prev.refChecked
    override def refChecked: Boolean = isRefChecked

    /** Is current phase cancelled on this unit? */
    def cancelled(unit: CompilationUnit) = {
      // run the typer only if in `createJavadoc` mode
      val maxJavaPhase = if (createJavadoc) currentRun.typerPhase.id else currentRun.namerPhase.id
      reporter.cancelled || unit.isJava && this.id > maxJavaPhase
    }

    final def applyPhase(unit: CompilationUnit) {
      if ((unit ne null) && unit.exists)
        lastSeenSourceFile = unit.source

      if (settings.debug && (settings.verbose || currentRun.size < 5))
        inform("[running phase " + name + " on " + unit + "]")

      val unit0 = currentUnit
      try {
        currentRun.currentUnit = unit
        if (!cancelled(unit)) {
          currentRun.informUnitStarting(this, unit)
          apply(unit)
        }
        currentRun.advanceUnit()
      } finally {
        //assert(currentUnit == unit)
        currentRun.currentUnit = unit0
      }
    }
  }

  // phaseName = "parser"
  lazy val syntaxAnalyzer = new {
    val global: Global.this.type = Global.this
  } with SyntaxAnalyzer {
    val runsAfter = List[String]()
    val runsRightAfter = None
    override val initial = true
  }

  import syntaxAnalyzer.{ UnitScanner, UnitParser }

  // !!! I think we're overdue for all these phase objects being lazy vals.
  // There's no way for a Global subclass to provide a custom typer
  // despite the existence of a "def newTyper(context: Context): Typer"
  // which is clearly designed for that, because it's defined in
  // Analyzer and Global's "object analyzer" allows no override. For now
  // I only changed analyzer.
  //
  // factory for phases: namer, packageobjects, typer
  lazy val analyzer = new {
    val global: Global.this.type = Global.this
  } with Analyzer

  // phaseName = "patmat"
  object patmat extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("typer")
    val runsRightAfter = None
    // patmat doesn't need to be right after typer, as long as we run before superaccessors
    // (sbt does need to run right after typer, so don't conflict)
  } with PatternMatching

  // phaseName = "superaccessors"
  object superAccessors extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("patmat")
    val runsRightAfter = None
  } with SuperAccessors

  // phaseName = "extmethods"
  object extensionMethods extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("superaccessors")
    val runsRightAfter = None
  } with ExtensionMethods

  // phaseName = "pickler"
  object pickler extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("extmethods")
    val runsRightAfter = None
  } with Pickler

  // phaseName = "refchecks"
  override object refChecks extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("pickler")
    val runsRightAfter = None
  } with RefChecks

  // phaseName = "uncurry"
  override object uncurry extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("refchecks")
    val runsRightAfter = None
  } with UnCurry

  // phaseName = "tailcalls"
  object tailCalls extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("uncurry")
    val runsRightAfter = None
  } with TailCalls

  // phaseName = "explicitouter"
  object explicitOuter extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("tailcalls")
    val runsRightAfter = None
  } with ExplicitOuter

  // phaseName = "specialize"
  object specializeTypes extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("")
    val runsRightAfter = Some("tailcalls")
  } with SpecializeTypes

  // phaseName = "erasure"
  override object erasure extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("explicitouter")
    val runsRightAfter = Some("explicitouter")
  } with Erasure

  // phaseName = "posterasure"
  override object postErasure extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("erasure")
    val runsRightAfter = Some("erasure")
  } with PostErasure

  // phaseName = "lazyvals"
  object lazyVals extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("erasure")
    val runsRightAfter = None
  } with LazyVals

  // phaseName = "lambdalift"
  object lambdaLift extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("lazyvals")
    val runsRightAfter = None
  } with LambdaLift

  // phaseName = "constructors"
  object constructors extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("lambdalift")
    val runsRightAfter = None
  } with Constructors

  // phaseName = "flatten"
  object flatten extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("constructors")
    val runsRightAfter = None
  } with Flatten

  // phaseName = "mixin"
  object mixer extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("flatten", "constructors")
    val runsRightAfter = None
  } with Mixin

  // phaseName = "cleanup"
  object cleanup extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("mixin")
    val runsRightAfter = None
  } with CleanUp

  // phaseName = "delambdafy"
  object delambdafy extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("cleanup")
    val runsRightAfter = None
  } with Delambdafy

  // phaseName = "icode"
  object genicode extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("cleanup")
    val runsRightAfter = None
  } with GenICode

  // phaseName = "inliner"
  object inliner extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("icode")
    val runsRightAfter = None
  } with Inliners

  // phaseName = "inlinehandlers"
  object inlineExceptionHandlers extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("inliner")
    val runsRightAfter = None
  } with InlineExceptionHandlers

  // phaseName = "closelim"
  object closureElimination extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("inlinehandlers")
    val runsRightAfter = None
  } with ClosureElimination

  // phaseName = "constopt"
  object constantOptimization extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("closelim")
    val runsRightAfter = None
  } with ConstantOptimization

  // phaseName = "dce"
  object deadCode extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("closelim")
    val runsRightAfter = None
  } with DeadCodeElimination

  // phaseName = "jvm", ASM-based version
  object genASM extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("dce")
    val runsRightAfter = None
  } with GenASM

  // phaseName = "bcode"
  object genBCode extends {
    val global: Global.this.type = Global.this
    val runsAfter = List("dce")
    val runsRightAfter = None
  } with GenBCode

  // phaseName = "terminal"
  object terminal extends {
    val global: Global.this.type = Global.this
  } with SubComponent {
    val phaseName = "terminal"
    val runsAfter = List("jvm")
    val runsRightAfter = None
    override val terminal = true

    def newPhase(prev: Phase): GlobalPhase = {
      new TerminalPhase(prev)
    }
    private class TerminalPhase(prev: Phase) extends GlobalPhase(prev) {
      def name = phaseName
      def apply(unit: CompilationUnit) {}
    }
  }

  /** The checkers are for validating the compiler data structures
   *  at phase boundaries.
   */

  /** Tree checker */
  object treeChecker extends {
    val global: Global.this.type = Global.this
  } with TreeCheckers

  /** Icode verification */
  object icodeCheckers extends {
    val global: Global.this.type = Global.this
  } with ICodeCheckers

  object icodeChecker extends icodeCheckers.ICodeChecker()

  object typer extends analyzer.Typer(
    analyzer.NoContext.make(EmptyTree, RootClass, newScope)
  )

  /** Add the internal compiler phases to the phases set.
   *  This implementation creates a description map at the same time.
   */
  protected def computeInternalPhases(): Unit = {
    // Note: this fits -Xshow-phases into 80 column width, which it is
    // desirable to preserve.
    val phs = List(
      syntaxAnalyzer          -> "parse source into ASTs, perform simple desugaring",
      analyzer.namerFactory   -> "resolve names, attach symbols to named trees",
      analyzer.packageObjects -> "load package objects",
      analyzer.typerFactory   -> "the meat and potatoes: type the trees",
      patmat                  -> "translate match expressions",
      superAccessors          -> "add super accessors in traits and nested classes",
      extensionMethods        -> "add extension methods for inline classes",
      pickler                 -> "serialize symbol tables",
      refChecks               -> "reference/override checking, translate nested objects",
      uncurry                 -> "uncurry, translate function values to anonymous classes",
      tailCalls               -> "replace tail calls by jumps",
      specializeTypes         -> "@specialized-driven class and method specialization",
      explicitOuter           -> "this refs to outer pointers",
      erasure                 -> "erase types, add interfaces for traits",
      postErasure             -> "clean up erased inline classes",
      lazyVals                -> "allocate bitmaps, translate lazy vals into lazified defs",
      lambdaLift              -> "move nested functions to top level",
      constructors            -> "move field definitions into constructors",
      mixer                   -> "mixin composition",
      delambdafy              -> "remove lambdas",
      cleanup                 -> "platform-specific cleanups, generate reflective calls",
      genicode                -> "generate portable intermediate code",
      inliner                 -> "optimization: do inlining",
      inlineExceptionHandlers -> "optimization: inline exception handlers",
      closureElimination      -> "optimization: eliminate uncalled closures",
      constantOptimization    -> "optimization: optimize null and other constants",
      deadCode                -> "optimization: eliminate dead code",
      terminal                -> "the last phase during a compilation run"
    )

    phs foreach (addToPhasesSet _).tupled
  }
  // This is slightly inelegant but it avoids adding a new member to SubComponent,
  // and attractive -Xshow-phases output is unlikely if the descs span 20 files anyway.
  private val otherPhaseDescriptions = Map(
    "flatten"  -> "eliminate inner classes",
    "jvm"      -> "generate JVM bytecode"
  ) withDefaultValue ""

  protected def computePlatformPhases() = platform.platformPhases foreach { sub =>
    addToPhasesSet(sub, otherPhaseDescriptions(sub.phaseName))
  }

  // sequences the phase assembly
  protected def computePhaseDescriptors: List[SubComponent] = {
    /** Allow phases to opt out of the phase assembly. */
    def cullPhases(phases: List[SubComponent]) = {
      val enabled = if (settings.debug && settings.isInfo) phases else phases filter (_.enabled)
      def isEnabled(q: String) = enabled exists (_.phaseName == q)
      val (satisfied, unhappy) = enabled partition (_.requires forall isEnabled)
      unhappy foreach (u => globalError(s"Phase '${u.phaseName}' requires: ${u.requires filterNot isEnabled}"))
      satisfied   // they're happy now, but they may need an unhappy phase that was booted
    }
    computeInternalPhases()             // Global.scala
    computePlatformPhases()             // backend/Platform.scala
    computePluginPhases()               // plugins/Plugins.scala
    cullPhases(computePhaseAssembly())  // PhaseAssembly.scala
  }

  /* The phase descriptor list. Components that are phase factories. */
  lazy val phaseDescriptors: List[SubComponent] = computePhaseDescriptors

  /* The set of phase objects that is the basis for the compiler phase chain */
  protected lazy val phasesSet     = new mutable.HashSet[SubComponent]
  protected lazy val phasesDescMap = new mutable.HashMap[SubComponent, String] withDefaultValue ""

  protected def addToPhasesSet(sub: SubComponent, descr: String) {
    phasesSet += sub
    phasesDescMap(sub) = descr
  }

  /** The names of the phases. */
  lazy val phaseNames = {
    new Run // force some initialization
    phaseDescriptors map (_.phaseName)
  }

  /** A description of the phases that will run in this configuration, or all if -Ydebug. */
  def phaseDescriptions: String = phaseHelp("description", elliptically = true, phasesDescMap)

  /** Summary of the per-phase values of nextFlags and newFlags, shown under -Xshow-phases -Ydebug. */
  def phaseFlagDescriptions: String = {
    def fmt(ph: SubComponent) = {
      def fstr1 = if (ph.phaseNewFlags == 0L) "" else "[START] " + Flags.flagsToString(ph.phaseNewFlags)
      def fstr2 = if (ph.phaseNextFlags == 0L) "" else "[END] " + Flags.flagsToString(ph.phaseNextFlags)
      if (ph.initial) Flags.flagsToString(Flags.InitialFlags)
      else if (ph.phaseNewFlags != 0L && ph.phaseNextFlags != 0L) fstr1 + " " + fstr2
      else fstr1 + fstr2
    }
    phaseHelp("new flags", elliptically = false, fmt)
  }

  /** Emit a verbose phase table.
   *  The table includes the phase id in the current assembly,
   *  or "oo" to indicate a skipped phase, or "xx" to indicate
   *  a disabled phase.
   *
   *  @param title descriptive header
   *  @param elliptically whether to truncate the description with an ellipsis (...)
   *  @param describe how to describe a component
   */
  def phaseHelp(title: String, elliptically: Boolean, describe: SubComponent => String) = {
    val Limit   = 16    // phase names should not be absurdly long
    val MaxCol  = 80    // because some of us edit on green screens
    val maxName = phaseNames map (_.length) max
    val width   = maxName min Limit
    val maxDesc = MaxCol - (width + 6)  // descriptions not novels
    val fmt     = if (settings.verbose || !elliptically) s"%${maxName}s  %2s  %s%n"
                  else s"%${width}.${width}s  %2s  %.${maxDesc}s%n"

    val line1 = fmt.format("phase name", "id", title)
    val line2 = fmt.format("----------", "--", "-" * title.length)

    // built-in string precision merely truncates
    import java.util.{ Formattable, FormattableFlags, Formatter }
    def dotfmt(s: String) = new Formattable {
      def elliptically(s: String, max: Int) = (
        if (max < 0 || s.length <= max) s
        else if (max < 4) s.take(max)
        else s.take(max - 3) + "..."
      )
      override def formatTo(formatter: Formatter, flags: Int, width: Int, precision: Int) {
        val p = elliptically(s, precision)
        val w = if (width > 0 && p.length < width) {
          import FormattableFlags.LEFT_JUSTIFY
          val leftly = (flags & LEFT_JUSTIFY) == LEFT_JUSTIFY
          val sb = new StringBuilder
          def pad() = 1 to width - p.length foreach (_ => sb.append(' '))
          if (!leftly) pad()
          sb.append(p)
          if (leftly) pad()
          sb.toString
        } else p
        formatter.out.append(w)
      }
    }

    // phase id in run, or suitable icon
    def idOf(p: SubComponent) = (
      if (settings.skip contains p.phaseName) "oo"   // (currentRun skipPhase p.phaseName)
      else if (!p.enabled) "xx"
      else p.ownPhase.id.toString
    )
    def mkText(p: SubComponent) = {
      val (name, text) = if (elliptically) (dotfmt(p.phaseName), dotfmt(describe(p)))
                         else (p.phaseName, describe(p))
      fmt.format(name, idOf(p), text)
    }
    line1 :: line2 :: (phaseDescriptors map mkText) mkString
  }

  /** Returns List of (phase, value) pairs, including only those
   *  where the value compares unequal to the previous phase's value.
   */
  def afterEachPhase[T](op: => T): List[(Phase, T)] = { // used in tests
    phaseDescriptors.map(_.ownPhase).filterNot(_ eq NoPhase).foldLeft(List[(Phase, T)]()) { (res, ph) =>
      val value = exitingPhase(ph)(op)
      if (res.nonEmpty && res.head._2 == value) res
      else ((ph, value)) :: res
    } reverse
  }

  // ------------ Invalidations ---------------------------------

  /** Is given package class a system package class that cannot be invalidated?
   */
  private def isSystemPackageClass(pkg: Symbol) =
    pkg == RootClass ||
    pkg == definitions.ScalaPackageClass || {
      val pkgname = pkg.fullName
      (pkgname startsWith "scala.") && !(pkgname startsWith "scala.tools")
    }

  /** Invalidates packages that contain classes defined in a classpath entry, and
   *  rescans that entry.
   *  @param paths  Fully qualified names that refer to directories or jar files that are
   *                a entries on the classpath.
   *  First, causes the classpath entry referred to by `path` to be rescanned, so that
   *  any new files or deleted files or changes in subpackages are picked up.
   *  Second, invalidates any packages for which one of the following considitions is met:

   *   - the classpath entry contained during the last compilation run classfiles
   *     that represent a member in the package
   *   - the classpath entry now contains classfiles
   *     that represent a member in the package
   *   - the set of subpackages has changed.
   *
   *  The invalidated packages are reset in their entirety; all member classes and member packages
   *  are re-accessed using the new classpath.
   *  Not invalidated are system packages that the compiler needs to access as parts
   *  of standard definitions. The criterion what is a system package is currently:
   *  any package rooted in "scala", with the exception of packages rooted in "scala.tools".
   *  This can be refined later.
   *  @return A pair consisting of
   *    - a list of invalidated packages
   *    - a list of of packages that should have been invalidated but were not because
   *      they are system packages.
   */
  def invalidateClassPathEntries(paths: String*): (List[ClassSymbol], List[ClassSymbol]) = {
    val invalidated, failed = new mutable.ListBuffer[ClassSymbol]
    classPath match {
      case cp: MergedClassPath[_] =>
        def assoc(path: String): List[(PlatformClassPath, PlatformClassPath)] = {
          val dir = AbstractFile getDirectory path
          val canonical = dir.canonicalPath
          def matchesCanonical(e: ClassPath[_]) = e.origin match {
            case Some(opath) =>
              (AbstractFile getDirectory opath).canonicalPath == canonical
            case None =>
              false
          }
          cp.entries find matchesCanonical match {
            case Some(oldEntry) =>
              List(oldEntry -> cp.context.newClassPath(dir))
            case None =>
              println(s"canonical = $canonical, origins = ${cp.entries map (_.origin)}")
              error(s"cannot invalidate: no entry named $path in classpath $classPath")
              List()
          }
        }
        val subst = Map(paths flatMap assoc: _*)
        if (subst.nonEmpty) {
          platform updateClassPath subst
          informProgress(s"classpath updated on entries [${subst.keys mkString ","}]")
          def mkClassPath(elems: Iterable[PlatformClassPath]): PlatformClassPath =
            if (elems.size == 1) elems.head
            else new MergedClassPath(elems, classPath.context)
          val oldEntries = mkClassPath(subst.keys)
          val newEntries = mkClassPath(subst.values)
          reSync(RootClass, Some(classPath), Some(oldEntries), Some(newEntries), invalidated, failed)
        }
    }
    def show(msg: String, syms: scala.collection.Traversable[Symbol]) =
      if (syms.nonEmpty)
        informProgress(s"$msg: ${syms map (_.fullName) mkString ","}")
    show("invalidated packages", invalidated)
    show("could not invalidate system packages", failed)
    (invalidated.toList, failed.toList)
  }

  /** Re-syncs symbol table with classpath
   *  @param root         The root symbol to be resynced (a package class)
   *  @param allEntries   Optionally, the corresponding package in the complete current classPath
   *  @param oldEntries   Optionally, the corresponding package in the old classPath entries
   *  @param newEntries   Optionally, the corresponding package in the new classPath entries
   *  @param invalidated  A listbuffer collecting the invalidated package classes
   *  @param failed       A listbuffer collecting system package classes which could not be invalidated
   * The resyncing strategy is determined by the absence or presence of classes and packages.
   * If either oldEntries or newEntries contains classes, root is invalidated, provided a corresponding package
   * exists in allEntries, or otherwise is removed.
   * Otherwise, the action is determined by the following matrix, with columns:
   *
   *      old new all sym   action
   *       +   +   +   +    recurse into all child packages of old ++ new
   *       +   -   +   +    invalidate root
   *       +   -   -   +    remove root from its scope
   *       -   +   +   +    invalidate root
   *       -   +   +   -    create and enter root
   *       -   -   *   *    no action
   *
   *  Here, old, new, all mean classpaths and sym means symboltable. + is presence of an
   *  entry in its column, - is absence, * is don't care.
   *
   *  Note that new <= all and old <= sym, so the matrix above covers all possibilities.
   */
  private def reSync(root: ClassSymbol,
             allEntries: OptClassPath, oldEntries: OptClassPath, newEntries: OptClassPath,
             invalidated: mutable.ListBuffer[ClassSymbol], failed: mutable.ListBuffer[ClassSymbol]) {
    ifDebug(informProgress(s"syncing $root, $oldEntries -> $newEntries"))

    val getName: ClassPath[AbstractFile] => String = (_.name)
    def hasClasses(cp: OptClassPath) = cp.isDefined && cp.get.classes.nonEmpty
    def invalidateOrRemove(root: ClassSymbol) = {
      allEntries match {
        case Some(cp) => root setInfo new loaders.PackageLoader(cp)
        case None => root.owner.info.decls unlink root.sourceModule
      }
      invalidated += root
    }
    def packageNames(cp: PlatformClassPath): Set[String] = cp.packages.toSet map getName
    def subPackage(cp: PlatformClassPath, name: String): OptClassPath =
      cp.packages find (cp1 => getName(cp1) == name)

    val classesFound = hasClasses(oldEntries) || hasClasses(newEntries)
    if (classesFound && !isSystemPackageClass(root)) {
      invalidateOrRemove(root)
    } else {
      if (classesFound) {
        if (root.isRoot) invalidateOrRemove(EmptyPackageClass)
        else failed += root
      }
      (oldEntries, newEntries) match {
        case (Some(oldcp) , Some(newcp)) =>
          for (pstr <- packageNames(oldcp) ++ packageNames(newcp)) {
            val pname = newTermName(pstr)
            val pkg = (root.info decl pname) orElse {
              // package was created by external agent, create symbol to track it
              assert(!subPackage(oldcp, pstr).isDefined)
              loaders.enterPackage(root, pstr, new loaders.PackageLoader(allEntries.get))
            }
            reSync(
                pkg.moduleClass.asInstanceOf[ClassSymbol],
                subPackage(allEntries.get, pstr), subPackage(oldcp, pstr), subPackage(newcp, pstr),
                invalidated, failed)
          }
        case (Some(oldcp), None) =>
          invalidateOrRemove(root)
        case (None, Some(newcp)) =>
          invalidateOrRemove(root)
        case (None, None) =>
      }
    }
  }

  /** Invalidate contents of setting -Yinvalidate */
  def doInvalidation() = settings.Yinvalidate.value match {
    case "" =>
    case entry => invalidateClassPathEntries(entry)
  }

  // ----------- Runs ---------------------------------------

  private var curRun: Run = null
  private var curRunId = 0

  /** A hook that lets subclasses of `Global` define whether a package or class should be kept loaded for the
   *  next compiler run. If the parameter `sym` is a class or object, and `clearOnNextRun(sym)` returns `true`,
   *  then the symbol is unloaded and reset to its state before the last compiler run. If the parameter `sym` is
   *  a package, and clearOnNextRun(sym)` returns `true`, the package is recursively searched for
   *  classes to drop.
   *
   *  Example: Let's say I want a compiler that drops all classes corresponding to the current project
   *  between runs. Then `keepForNextRun` of a toplevel class or object should return `true` if the
   *  class or object does not form part of the current project, `false` otherwise. For a package,
   *  clearOnNextRun should return `true` if no class in that package forms part of the current project,
   *  `false` otherwise.
   *
   *  @param    sym A class symbol, object symbol, package, or package class.
   */
  @deprecated("use invalidateClassPathEntries instead", "2.10.0")
  def clearOnNextRun(sym: Symbol) = false
    /* To try out clearOnNext run on the scala.tools.nsc project itself
     * replace `false` above with the following code

    settings.Xexperimental.value && { sym.isRoot || {
      sym.fullName match {
        case "scala" | "scala.tools" | "scala.tools.nsc" => true
        case _ => sym.owner.fullName.startsWith("scala.tools.nsc")
      }
    }}

     * Then, fsc -Xexperimental clears the nsc project between successive runs of `fsc`.
     */

  object typeDeconstruct extends {
    val global: Global.this.type = Global.this
  } with typechecker.StructuredTypeStrings

  /** There are common error conditions where when the exception hits
   *  here, currentRun.currentUnit is null.  This robs us of the knowledge
   *  of what file was being compiled when it broke.  Since I really
   *  really want to know, this hack.
   */
  protected var lastSeenSourceFile: SourceFile = NoSourceFile

  /** Let's share a lot more about why we crash all over the place.
   *  People will be very grateful.
   */
  protected var lastSeenContext: analyzer.Context = null

  /** The currently active run
   */
  def currentRun: Run              = curRun
  def currentUnit: CompilationUnit = if (currentRun eq null) NoCompilationUnit else currentRun.currentUnit
  def currentSource: SourceFile    = if (currentUnit.exists) currentUnit.source else lastSeenSourceFile
  def currentFreshNameCreator      = currentUnit.fresh

  def isGlobalInitialized = (
       definitions.isDefinitionsInitialized
    && rootMirror.isMirrorInitialized
  )
  override def isPastTyper = (
       (curRun ne null)
    && isGlobalInitialized // defense against init order issues
    && (globalPhase.id > currentRun.typerPhase.id)
  )

  // TODO - trim these to the absolute minimum.
  @inline final def exitingErasure[T](op: => T): T        = exitingPhase(currentRun.erasurePhase)(op)
  @inline final def exitingPostErasure[T](op: => T): T    = exitingPhase(currentRun.posterasurePhase)(op)
  @inline final def exitingExplicitOuter[T](op: => T): T  = exitingPhase(currentRun.explicitouterPhase)(op)
  @inline final def exitingFlatten[T](op: => T): T        = exitingPhase(currentRun.flattenPhase)(op)
  @inline final def exitingMixin[T](op: => T): T          = exitingPhase(currentRun.mixinPhase)(op)
  @inline final def exitingDelambdafy[T](op: => T): T     = exitingPhase(currentRun.delambdafyPhase)(op)
  @inline final def exitingPickler[T](op: => T): T        = exitingPhase(currentRun.picklerPhase)(op)
  @inline final def exitingRefchecks[T](op: => T): T      = exitingPhase(currentRun.refchecksPhase)(op)
  @inline final def exitingSpecialize[T](op: => T): T     = exitingPhase(currentRun.specializePhase)(op)
  @inline final def exitingTyper[T](op: => T): T          = exitingPhase(currentRun.typerPhase)(op)
  @inline final def exitingUncurry[T](op: => T): T        = exitingPhase(currentRun.uncurryPhase)(op)
  @inline final def enteringErasure[T](op: => T): T       = enteringPhase(currentRun.erasurePhase)(op)
  @inline final def enteringExplicitOuter[T](op: => T): T = enteringPhase(currentRun.explicitouterPhase)(op)
  @inline final def enteringFlatten[T](op: => T): T       = enteringPhase(currentRun.flattenPhase)(op)
  @inline final def enteringIcode[T](op: => T): T         = enteringPhase(currentRun.icodePhase)(op)
  @inline final def enteringMixin[T](op: => T): T         = enteringPhase(currentRun.mixinPhase)(op)
  @inline final def enteringDelambdafy[T](op: => T): T    = enteringPhase(currentRun.delambdafyPhase)(op)
  @inline final def enteringPickler[T](op: => T): T       = enteringPhase(currentRun.picklerPhase)(op)
  @inline final def enteringSpecialize[T](op: => T): T    = enteringPhase(currentRun.specializePhase)(op)
  @inline final def enteringTyper[T](op: => T): T         = enteringPhase(currentRun.typerPhase)(op)
  @inline final def enteringUncurry[T](op: => T): T       = enteringPhase(currentRun.uncurryPhase)(op)

  // Owners which aren't package classes.
  private def ownerChainString(sym: Symbol): String = (
    if (sym == null) ""
    else sym.ownerChain takeWhile (!_.isPackageClass) mkString " -> "
  )

  private def formatExplain(pairs: (String, Any)*): String = (
    pairs.toList collect { case (k, v) if v != null => "%20s: %s".format(k, v) } mkString "\n"
  )

  /** Don't want to introduce new errors trying to report errors,
   *  so swallow exceptions.
   */
  override def supplementErrorMessage(errorMessage: String): String = {
    if (currentRun.supplementedError) errorMessage
    else try {
      currentRun.supplementedError = true
      val tree      = analyzer.lastTreeToTyper
      val sym       = tree.symbol
      val tpe       = tree.tpe
      val site      = lastSeenContext.enclClassOrMethod.owner
      val pos_s     = if (tree.pos.isDefined) s"line ${tree.pos.line} of ${tree.pos.source.file}" else "<unknown>"
      val context_s = try {
        // Taking 3 before, 3 after the fingered line.
        val start = 0 max (tree.pos.line - 3)
        val xs = scala.reflect.io.File(tree.pos.source.file.file).lines drop start take 7
        val strs = xs.zipWithIndex map { case (line, idx) => f"${start + idx}%6d $line" }
        strs.mkString("== Source file context for tree position ==\n\n", "\n", "")
      }
      catch { case t: Exception => devWarning("" + t) ; "<Cannot read source file>" }

      val info1 = formatExplain(
        "while compiling"    -> currentSource.path,
        "during phase"       -> ( if (globalPhase eq phase) phase else "globalPhase=%s, enteringPhase=%s".format(globalPhase, phase) ),
        "library version"    -> scala.util.Properties.versionString,
        "compiler version"   -> Properties.versionString,
        "reconstructed args" -> settings.recreateArgs.mkString(" ")
      )
      val info2 = formatExplain(
        "last tree to typer" -> tree.summaryString,
        "tree position"      -> pos_s,
        "tree tpe"           -> tpe,
        "symbol"             -> Option(sym).fold("null")(_.debugLocationString),
        "symbol definition"  -> Option(sym).fold("null")(s => s.defString + s" (a ${s.shortSymbolClass})"),
        "symbol package"     -> sym.enclosingPackage.fullName,
        "symbol owners"      -> ownerChainString(sym),
        "call site"          -> (site.fullLocationString + " in " + site.enclosingPackage)
      )
      ("\n  " + errorMessage + "\n" + info1) :: info2 :: context_s :: Nil mkString "\n\n"
    }
    catch { case _: Exception | _: TypeError => errorMessage }
  }

  /** The id of the currently active run
   */
  override def currentRunId = curRunId

  def echoPhaseSummary(ph: Phase) = {
    /* Only output a summary message under debug if we aren't echoing each file. */
    if (settings.debug && !(settings.verbose || currentRun.size < 5))
      inform("[running phase " + ph.name + " on " + currentRun.size +  " compilation units]")
  }

  /** Collects for certain classes of warnings during this run. */
  class ConditionalWarning(what: String, option: Settings#BooleanSetting) {
    val warnings = mutable.LinkedHashMap[Position, String]()
    def warn(pos: Position, msg: String) =
      if (option) reporter.warning(pos, msg)
      else if (!(warnings contains pos)) warnings += ((pos, msg))
    def summarize() =
      if (warnings.nonEmpty && (option.isDefault || settings.fatalWarnings))
        warning("there were %d %s warning(s); re-run with %s for details".format(warnings.size, what, option.name))
  }

  def newSourceFile(code: String, filename: String = "<console>") =
    new BatchSourceFile(filename, code)

  def newCompilationUnit(code: String, filename: String = "<console>") =
    new CompilationUnit(newSourceFile(code, filename))

  def newUnitScanner(unit: CompilationUnit): UnitScanner =
    new UnitScanner(unit)

  def newUnitParser(unit: CompilationUnit): UnitParser =
    new UnitParser(unit)

  def newUnitParser(code: String, filename: String = "<console>"): UnitParser =
    newUnitParser(newCompilationUnit(code, filename))

  /** A Run is a single execution of the compiler on a set of units.
   */
  class Run extends RunContextApi {
    /** Have been running into too many init order issues with Run
     *  during erroneous conditions.  Moved all these vals up to the
     *  top of the file so at least they're not trivially null.
     */
    var isDefined = false
    /** The currently compiled unit; set from GlobalPhase */
    var currentUnit: CompilationUnit = NoCompilationUnit

    // This change broke sbt; I gave it the thrilling name of uncheckedWarnings0 so
    // as to recover uncheckedWarnings for its ever-fragile compiler interface.
    val deprecationWarnings0 = new ConditionalWarning("deprecation", settings.deprecation)
    val uncheckedWarnings0 = new ConditionalWarning("unchecked", settings.unchecked)
    val featureWarnings = new ConditionalWarning("feature", settings.feature)
    val inlinerWarnings = new ConditionalWarning("inliner", settings.YinlinerWarnings)
    val allConditionalWarnings = List(deprecationWarnings0, uncheckedWarnings0, featureWarnings, inlinerWarnings)

    def uncheckedWarnings: List[(Position, String)] = uncheckedWarnings0.warnings.toList // used in sbt
    def deprecationWarnings: List[(Position, String)] = deprecationWarnings0.warnings.toList // used in sbt

    var reportedFeature = Set[Symbol]()

    /** Has any macro expansion used a fallback during this run? */
    var seenMacroExpansionsFallingBack = false

    /** Have we already supplemented the error message of a compiler crash? */
    private[nsc] final var supplementedError = false

    private class SyncedCompilationBuffer { self =>
      private val underlying = new mutable.ArrayBuffer[CompilationUnit]
      def size = synchronized { underlying.size }
      def +=(cu: CompilationUnit): this.type = { synchronized { underlying += cu }; this }
      def head: CompilationUnit = synchronized{ underlying.head }
      def apply(i: Int): CompilationUnit = synchronized { underlying(i) }
      def iterator: Iterator[CompilationUnit] = new collection.AbstractIterator[CompilationUnit] {
        private var used = 0
        def hasNext = self.synchronized{ used < underlying.size }
        def next = self.synchronized {
          if (!hasNext) throw new NoSuchElementException("next on empty Iterator")
          used += 1
          underlying(used-1)
        }
      }
      def toList: List[CompilationUnit] = synchronized{ underlying.toList }
    }

    private val unitbuf = new SyncedCompilationBuffer

    val compiledFiles   = new mutable.HashSet[String]

    /** A map from compiled top-level symbols to their source files */
    val symSource = new mutable.HashMap[Symbol, AbstractFile]

    /** A map from compiled top-level symbols to their picklers */
    val symData = new mutable.HashMap[Symbol, PickleBuffer]

    private var phasec: Int  = 0   // phases completed
    private var unitc: Int   = 0   // units completed this phase

    def size = unitbuf.size
    override def toString = "scalac Run for:\n  " + compiledFiles.toList.sorted.mkString("\n  ")

    // Calculate where to stop based on settings -Ystop-before or -Ystop-after.
    // The result is the phase to stop at BEFORE running it.
    private lazy val stopPhaseSetting = {
      def isBefore(pd: SubComponent) = settings.stopBefore contains pd.phaseName
      phaseDescriptors sliding 2 collectFirst {
        case xs if xs exists isBefore
                => (xs find isBefore).get
        case xs if settings.stopAfter contains xs.head.phaseName
                => xs.last
      }
    }
    /** Should we stop right before entering the given phase? */
    protected def stopPhase(name: String) = stopPhaseSetting exists (_.phaseName == name)
    /** Should we skip the given phase? */
    protected def skipPhase(name: String) = settings.skip contains name

    private val firstPhase = {
      // Initialization.  definitions.init requires phase != NoPhase
      import scala.reflect.internal.SomePhase
      curRunId += 1
      curRun = this
      phase = SomePhase
      phaseWithId(phase.id) = phase
      definitions.init()

      // the components to use, omitting those named by -Yskip and stopping at the -Ystop phase
      val components = {
        // stop on a dime, but this test fails if pd is after the stop phase
        def unstoppable(pd: SubComponent) = {
          val stoppable = stopPhase(pd.phaseName)
          if (stoppable && pd.initial) {
            globalError(s"Cannot stop before initial phase '${pd.phaseName}'.")
            true
          } else
            !stoppable
        }
        // skip a component for -Yskip or if not enabled
        def skippable(pd: SubComponent) = {
          val skippable = skipPhase(pd.phaseName)
          if (skippable && (pd.initial || pd.terminal)) {
            globalError(s"Cannot skip an initial or terminal phase '${pd.phaseName}'.")
            false
          } else
            skippable || !pd.enabled
        }
        val phs = phaseDescriptors takeWhile unstoppable filterNot skippable
        // Ensure there is a terminal phase at the end, since -Ystop may have limited the phases.
        if (phs.isEmpty || !phs.last.terminal) {
          val t = if (phaseDescriptors.last.terminal) phaseDescriptors.last else terminal
          phs :+ t
        } else phs
      }
      // Create phases and link them together. We supply the previous, and the ctor sets prev.next.
      val last  = components.foldLeft(NoPhase: Phase)((prev, c) => c newPhase prev)
      // rewind (Iterator.iterate(last)(_.prev) dropWhile (_.prev ne NoPhase)).next
      val first = { var p = last ; while (p.prev ne NoPhase) p = p.prev ; p }
      val ss    = settings

      // As a final courtesy, see if the settings make any sense at all.
      // If a setting selects no phase, it's a mistake. If a name prefix
      // doesn't select a unique phase, that might be surprising too.
      def checkPhaseSettings(including: Boolean, specs: Seq[String]*) = {
        def isRange(s: String) = s.forall(c => c.isDigit || c == '-')
        def isSpecial(s: String) = (s == "all" || isRange(s))
        val setting = new ss.PhasesSetting("fake","fake")
        for (p <- specs.flatten.to[Set]) {
          setting.value = List(p)
          val count = (
            if (including) first.iterator count (setting containsPhase _)
            else phaseDescriptors count (setting contains _.phaseName)
          )
          if (count == 0) warning(s"'$p' specifies no phase")
          if (count > 1 && !isSpecial(p)) warning(s"'$p' selects $count phases")
          if (!including && isSpecial(p)) globalError(s"-Yskip and -Ystop values must name phases: '$p'")
          setting.clear()
        }
      }
      // phases that are excluded; for historical reasons, these settings only select by phase name
      val exclusions = List(ss.stopBefore, ss.stopAfter, ss.skip)
      val inclusions = ss.visibleSettings collect {
        case s: ss.PhasesSetting if !(exclusions contains s) => s.value
      }
      checkPhaseSettings(including = true, inclusions.toSeq: _*)
      checkPhaseSettings(including = false, exclusions map (_.value): _*)

      phase = first   //parserPhase
      first
    }

    /** Reset all classes contained in current project, as determined by
     *  the clearOnNextRun hook
     */
    @deprecated("use invalidateClassPathEntries instead", "2.10.0")
    def resetProjectClasses(root: Symbol): Unit = try {
      def unlink(sym: Symbol) =
        if (sym != NoSymbol) root.info.decls.unlink(sym)
      if (settings.verbose) inform("[reset] recursing in "+root)
      val toReload = mutable.Set[String]()
      for (sym <- root.info.decls) {
        if (sym.isInitialized && clearOnNextRun(sym))
          if (sym.hasPackageFlag) {
            resetProjectClasses(sym.moduleClass)
            openPackageModule(sym.moduleClass)
          } else {
            unlink(sym)
            unlink(root.info.decls.lookup(
              if (sym.isTerm) sym.name.toTypeName else sym.name.toTermName))
            toReload += sym.fullName
              // note: toReload could be set twice with the same name
              // but reinit must happen only once per name. That's why
              // the following classPath.findClass { ... } code cannot be moved here.
          }
      }
      for (fullname <- toReload)
        classPath.findClass(fullname) match {
          case Some(classRep) =>
            if (settings.verbose) inform("[reset] reinit "+fullname)
            loaders.initializeFromClassPath(root, classRep)
          case _ =>
        }
    } catch {
      case ex: Throwable =>
        // this handler should not be nessasary, but it seems that `fsc`
        // eats exceptions if they appear here. Need to find out the cause for
        // this and fix it.
        inform("[reset] exception happened: "+ex)
        ex.printStackTrace()
        throw ex
    }

    // --------------- Miscellania -------------------------------

    /** Progress tracking.  Measured in "progress units" which are 1 per
     *  compilation unit per phase completed.
     *
     *  @param    current   number of "progress units" completed
     *  @param    total     total number of "progress units" in run
     */
    def progress(current: Int, total: Int) {}

    /**
     * For subclasses to override. Called when `phase` is about to be run on `unit`.
     * Variables are passed explicitly to indicate that `globalPhase` and `currentUnit` have been set.
     */
    def informUnitStarting(phase: Phase, unit: CompilationUnit) { }

    /** take note that phase is completed
     *  (for progress reporting)
     */
    def advancePhase() {
      unitc = 0
      phasec += 1
      refreshProgress()
    }
    /** take note that a phase on a unit is completed
     *  (for progress reporting)
     */
    def advanceUnit() {
      unitc += 1
      refreshProgress()
    }

    def cancel() { reporter.cancelled = true }

    private def currentProgress   = (phasec * size) + unitc
    private def totalProgress     = (phaseDescriptors.size - 1) * size // -1: drops terminal phase
    private def refreshProgress() = if (size > 0) progress(currentProgress, totalProgress)

    // ----- finding phases --------------------------------------------

    def phaseNamed(name: String): Phase =
      findOrElse(firstPhase.iterator)(_.name == name)(NoPhase)

    /** All phases as of 3/2012 here for handiness; the ones in
     *  active use uncommented.
     */
    val parserPhase                  = phaseNamed("parser")
    val namerPhase                   = phaseNamed("namer")
    // val packageobjectsPhase          = phaseNamed("packageobjects")
    val typerPhase                   = phaseNamed("typer")
    // val inlineclassesPhase           = phaseNamed("inlineclasses")
    // val superaccessorsPhase          = phaseNamed("superaccessors")
    val picklerPhase                 = phaseNamed("pickler")
    val refchecksPhase               = phaseNamed("refchecks")
    // val selectiveanfPhase            = phaseNamed("selectiveanf")
    // val selectivecpsPhase            = phaseNamed("selectivecps")
    val uncurryPhase                 = phaseNamed("uncurry")
    // val tailcallsPhase               = phaseNamed("tailcalls")
    val specializePhase              = phaseNamed("specialize")
    val explicitouterPhase           = phaseNamed("explicitouter")
    val erasurePhase                 = phaseNamed("erasure")
    val posterasurePhase             = phaseNamed("posterasure")
    // val lazyvalsPhase                = phaseNamed("lazyvals")
    // val lambdaliftPhase              = phaseNamed("lambdalift")
    // val constructorsPhase            = phaseNamed("constructors")
    val flattenPhase                 = phaseNamed("flatten")
    val mixinPhase                   = phaseNamed("mixin")
    val delambdafyPhase              = phaseNamed("delambdafy")
    val cleanupPhase                 = phaseNamed("cleanup")
    val icodePhase                   = phaseNamed("icode")
    val inlinerPhase                 = phaseNamed("inliner")
    val inlineExceptionHandlersPhase = phaseNamed("inlinehandlers")
    val closelimPhase                = phaseNamed("closelim")
    val dcePhase                     = phaseNamed("dce")
    // val jvmPhase                     = phaseNamed("jvm")

    def runIsAt(ph: Phase)   = globalPhase.id == ph.id
    def runIsAtOptimiz       = {
      runIsAt(inlinerPhase)                 || // listing phases in full for robustness when -Ystop-after has been given.
      runIsAt(inlineExceptionHandlersPhase) ||
      runIsAt(closelimPhase)                ||
      runIsAt(dcePhase)
    }

    isDefined = true

    // ----------- Units and top-level classes and objects --------


    /** add unit to be compiled in this run */
    private def addUnit(unit: CompilationUnit) {
      unitbuf += unit
      compiledFiles += unit.source.file.path
    }
    private def checkDeprecatedSettings(unit: CompilationUnit) {
      // issue warnings for any usage of deprecated settings
      settings.userSetSettings filter (_.isDeprecated) foreach { s =>
        unit.deprecationWarning(NoPosition, s.name + " is deprecated: " + s.deprecationMessage.get)
      }
      if (settings.target.value.contains("jvm-1.5"))
        unit.deprecationWarning(NoPosition, settings.target.name + ":" + settings.target.value + " is deprecated: use target for Java 1.6 or above.")
    }

    /* An iterator returning all the units being compiled in this run */
    /* !!! Note: changing this to unitbuf.toList.iterator breaks a bunch
       of tests in tests/res.  This is bad, it means the resident compiler
       relies on an iterator of a mutable data structure reflecting changes
       made to the underlying structure.
     */
    def units: Iterator[CompilationUnit] = unitbuf.iterator

    def registerPickle(sym: Symbol): Unit = ()

    /** does this run compile given class, module, or case factory? */
    // NOTE: Early initialized members temporarily typechecked before the enclosing class, see typedPrimaryConstrBody!
    //       Here we work around that wrinkle by claiming that a top-level, early-initialized member is compiled in
    //       *every* run. This approximation works because this method is exclusively called with `this` == `currentRun`.
    def compiles(sym: Symbol): Boolean =
      if (sym == NoSymbol) false
      else if (symSource.isDefinedAt(sym)) true
      else if (sym.isTopLevel && sym.isEarlyInitialized) true
      else if (!sym.isTopLevel) compiles(sym.enclosingTopLevelClass)
      else if (sym.isModuleClass) compiles(sym.sourceModule)
      else false

    /** Is this run allowed to redefine the given symbol? Usually this is true
     *  if the run does not already compile `sym`, but for interactive mode
     *  we have a more liberal interpretation.
     */
    def canRedefine(sym: Symbol) = !compiles(sym)

    // --------------- Compilation methods ----------------------------

    protected def runCheckers() {
      val toCheck  = globalPhase.prev
      val canCheck = toCheck.checkable
      val fmt      = if (canCheck) "[Now checking: %s]" else "[Not checkable: %s]"

      inform(fmt format toCheck.name)

      if (canCheck) {
        phase = globalPhase
        if (globalPhase.id >= icodePhase.id) icodeChecker.checkICodes()
        else treeChecker.checkTrees()
      }
    }

    private def showMembers() = {
      // Allows for syntax like scalac -Xshow-class Random@erasure,typer
      def splitClassAndPhase(str: String, term: Boolean): Name = {
        def mkName(s: String) = if (term) newTermName(s) else newTypeName(s)
        (str indexOf '@') match {
          case -1   => mkName(str)
          case idx  =>
            val phasePart = str drop (idx + 1)
            settings.Yshow.tryToSetColon(phasePart split ',' toList)
            mkName(str take idx)
        }
      }
      if (settings.Xshowcls.isSetByUser)
        showDef(splitClassAndPhase(settings.Xshowcls.value, term = false), declsOnly = false, globalPhase)

      if (settings.Xshowobj.isSetByUser)
        showDef(splitClassAndPhase(settings.Xshowobj.value, term = true), declsOnly = false, globalPhase)
    }

    // Similarly, this will only be created under -Yshow-syms.
    object trackerFactory extends SymbolTrackers {
      val global: Global.this.type = Global.this
      lazy val trackers = currentRun.units.toList map (x => SymbolTracker(x))
      def snapshot() = {
        inform("\n[[symbol layout at end of " + phase + "]]")
        exitingPhase(phase) {
          trackers foreach { t =>
            t.snapshot()
            inform(t.show("Heading from " + phase.prev.name + " to " + phase.name))
          }
        }
      }
    }

    def reportCompileErrors() {
      if (!reporter.hasErrors && reporter.hasWarnings && settings.fatalWarnings)
        globalError("No warnings can be incurred under -Xfatal-warnings.")

      if (reporter.hasErrors) {
        for ((sym, file) <- symSource.iterator) {
          sym.reset(new loaders.SourcefileLoader(file))
          if (sym.isTerm)
            sym.moduleClass reset loaders.moduleClassLoader
        }
      }
      else {
        allConditionalWarnings foreach (_.summarize())

        if (seenMacroExpansionsFallingBack)
          warning("some macros could not be expanded and code fell back to overridden methods;"+
                  "\nrecompiling with generated classfiles on the classpath might help.")
        // todo: migrationWarnings
      }
    }

    /** Caching member symbols that are def-s in Defintions because they might change from Run to Run. */
    val runDefinitions: definitions.RunDefinitions = new definitions.RunDefinitions

    /** Compile list of source files,
     *  unless there is a problem already,
     *  such as a plugin was passed a bad option.
     */
    def compileSources(sources: List[SourceFile]) = if (!reporter.hasErrors) {

      def checkDeprecations() = {
        checkDeprecatedSettings(newCompilationUnit(""))
        reportCompileErrors()
      }

      val units = sources map scripted map (new CompilationUnit(_))

      units match {
        case Nil => checkDeprecations()   // nothing to compile, report deprecated options
        case _   => compileUnits(units, firstPhase)
      }
    }

    def compileUnits(units: List[CompilationUnit], fromPhase: Phase): Unit =
      compileUnitsInternal(units, fromPhase)

    private def compileUnitsInternal(units: List[CompilationUnit], fromPhase: Phase) {
      doInvalidation()

      units foreach addUnit
      val startTime = currentTime

      reporter.reset()
      checkDeprecatedSettings(unitbuf.head)
      globalPhase = fromPhase

     while (globalPhase.hasNext && !reporter.hasErrors) {
        val startTime = currentTime
        phase = globalPhase
        globalPhase.run()

        // progress update
        informTime(globalPhase.description, startTime)
        val shouldWriteIcode = (
             (settings.writeICode.isSetByUser && (settings.writeICode containsPhase globalPhase))
          || (!settings.Xprint.doAllPhases && (settings.Xprint containsPhase globalPhase) && runIsAtOptimiz)
        )
        if (shouldWriteIcode) {
          // Write *.icode files when -Xprint-icode or -Xprint:<some-optimiz-phase> was given.
          writeICode()
        } else if ((settings.Xprint containsPhase globalPhase) || settings.printLate && runIsAt(cleanupPhase)) {
          // print trees
          if (settings.Xshowtrees || settings.XshowtreesCompact || settings.XshowtreesStringified) nodePrinters.printAll()
          else printAllUnits()
        }

        // print the symbols presently attached to AST nodes
        if (settings.Yshowsyms)
          trackerFactory.snapshot()

        // print members
        if (settings.Yshow containsPhase globalPhase)
          showMembers()

        // browse trees with swing tree viewer
        if (settings.browse containsPhase globalPhase)
          treeBrowser browse (phase.name, units)

        // move the pointer
        globalPhase = globalPhase.next

        // run tree/icode checkers
        if (settings.check containsPhase globalPhase.prev)
          runCheckers()

        // output collected statistics
        if (settings.Ystatistics)
          statistics.print(phase)

        advancePhase()
      }

      if (traceSymbolActivity)
        units map (_.body) foreach (traceSymbols recordSymbolsInTree _)

      // In case no phase was specified for -Xshow-class/object, show it now for sure.
      if (settings.Yshow.isDefault)
        showMembers()

      reportCompileErrors()
      symSource.keys foreach (x => resetPackageClass(x.owner))
      informTime("total", startTime)

      // Clear any sets or maps created via perRunCaches.
      perRunCaches.clearAll()

      // Reset project
      if (!stopPhase("namer")) {
        enteringPhase(namerPhase) {
          resetProjectClasses(RootClass)
        }
      }
    }

    /** Compile list of abstract files. */
    def compileFiles(files: List[AbstractFile]) {
      try compileSources(files map getSourceFile)
      catch { case ex: IOException => globalError(ex.getMessage()) }
    }

    /** Compile list of files given by their names */
    def compile(filenames: List[String]) {
      try {
        val sources: List[SourceFile] =
          if (settings.script.isSetByUser && filenames.size > 1) returning(Nil)(_ => globalError("can only compile one script at a time"))
          else filenames map getSourceFile

        compileSources(sources)
      }
      catch { case ex: IOException => globalError(ex.getMessage()) }
    }

    /** If this compilation is scripted, convert the source to a script source. */
    private def scripted(s: SourceFile) = s match {
      case b: BatchSourceFile if settings.script.isSetByUser => ScriptSourceFile(b)
      case _ => s
    }

    /** Compile abstract file until `globalPhase`, but at least
     *  to phase "namer".
     */
    def compileLate(file: AbstractFile) {
      if (!compiledFiles(file.path))
        compileLate(new CompilationUnit(scripted(getSourceFile(file))))
    }

    /** Compile abstract file until `globalPhase`, but at least to phase "namer".
     */
    def compileLate(unit: CompilationUnit) {
      addUnit(unit)

      if (firstPhase ne null) { // we might get here during initialization, is a source is newer than the binary
        val maxId = math.max(globalPhase.id, typerPhase.id)
        firstPhase.iterator takeWhile (_.id < maxId) foreach (ph =>
          enteringPhase(ph)(ph.asInstanceOf[GlobalPhase] applyPhase unit))
        refreshProgress()
      }
    }

    /** Reset package class to state at typer (not sure what this
     *  is needed for?)
     */
    private def resetPackageClass(pclazz: Symbol) {
      enteringPhase(firstPhase) {
        pclazz.setInfo(enteringPhase(typerPhase)(pclazz.info))
      }
      if (!pclazz.isRoot) resetPackageClass(pclazz.owner)
    }
  } // class Run

  def printAllUnits() {
    print("[[syntax trees at end of %25s]]".format(phase))
    exitingPhase(phase)(currentRun.units foreach { unit =>
      nodePrinters showUnit unit
    })
  }

  /** We resolve the class/object ambiguity by passing a type/term name.
   */
  def showDef(fullName: Name, declsOnly: Boolean, ph: Phase) = {
    val boringOwners = Set[Symbol](definitions.AnyClass, definitions.AnyRefClass, definitions.ObjectClass)
    def phased[T](body: => T): T = exitingPhase(ph)(body)
    def boringMember(sym: Symbol) = boringOwners(sym.owner)
    def symString(sym: Symbol) = if (sym.isTerm) sym.defString else sym.toString

    def members(sym: Symbol) = phased(sym.info.members filterNot boringMember map symString)
    def decls(sym: Symbol)   = phased(sym.info.decls.toList map symString)
    def bases(sym: Symbol)   = phased(sym.info.baseClasses map (x => x.kindString + " " + x.fullName))

    // make the type/term selections walking from the root.
    val syms = findMemberFromRoot(fullName) match {
      // The name as given was not found, so we'll sift through every symbol in
      // the run looking for plausible matches.
      case NoSymbol => phased(currentRun.symSource.keys map (sym => findNamedMember(fullName, sym)) filterNot (_ == NoSymbol) toList)
      // The name as given matched, so show only that.
      case sym      => List(sym)
    }

    syms foreach { sym =>
      val name        = "\n<<-- %s %s after phase '%s' -->>".format(sym.kindString, sym.fullName, ph.name)
      val baseClasses = bases(sym).mkString("Base classes:\n  ", "\n  ", "")
      val contents =
        if (declsOnly) decls(sym).mkString("Declarations:\n  ", "\n  ", "")
        else members(sym).mkString("Members (excluding Any/AnyRef unless overridden):\n  ", "\n  ", "")

      inform(List(name, baseClasses, contents) mkString "\n\n")
    }
  }

  def getFile(source: AbstractFile, segments: Array[String], suffix: String): File = {
    val outDir = Path(
      settings.outputDirs.outputDirFor(source).path match {
        case ""   => "."
        case path => path
      }
    )
    val dir      = segments.init.foldLeft(outDir)(_ / _).createDirectory()
    new File(dir.path, segments.last + suffix)
  }

  /** Returns the file with the given suffix for the given class. Used for icode writing. */
  def getFile(clazz: Symbol, suffix: String): File = getFile(clazz.sourceFile, clazz.fullName split '.', suffix)

  private def writeICode() {
    val printer = new icodes.TextPrinter(null, icodes.linearizer)
    icodes.classes.values.foreach((cls) => {
      val moduleSfx = if (cls.symbol.hasModuleFlag) "$" else ""
      val phaseSfx  = if (settings.debug) phase else "" // only for debugging, appending the full phasename breaks windows build
      val file      = getFile(cls.symbol, s"$moduleSfx$phaseSfx.icode")

      try {
        val stream = new FileOutputStream(file)
        printer.setWriter(new PrintWriter(stream, true))
        printer.printClass(cls)
        informProgress("wrote " + file)
      } catch {
        case ex: IOException =>
          if (settings.debug) ex.printStackTrace()
        globalError("could not write file " + file)
      }
    })
  }
  def createJavadoc    = false
}

object Global {
  def apply(settings: Settings, reporter: Reporter): Global = new Global(settings, reporter)
}

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