/* NSC -- new Scala compiler
 * Copyrights 2005-2011 LAMP/EPFL
 * @author Martin Odersky
 */

package scala.tools.nsc
package transform

import symtab._
import Flags._
import scala.collection._

abstract class CleanUp extends Transform with ast.TreeDSL {
  import global._
  import definitions._
  import CODE._

  /** the following two members override abstract members in Transform */
  val phaseName: String = "cleanup"

  protected def newTransformer(unit: CompilationUnit): Transformer =
    new CleanUpTransformer(unit)

  class CleanUpTransformer(unit: CompilationUnit) extends Transformer {
    private val newStaticMembers      = mutable.Buffer.empty[Tree]
    private val newStaticInits        = mutable.Buffer.empty[Tree]
    private val symbolsStoredAsStatic = mutable.Map.empty[String, Symbol]
    private def clearStatics() {
      newStaticMembers.clear()
      newStaticInits.clear()
      symbolsStoredAsStatic.clear()
    }
    private def savingStatics[T](body: => T): T = {
      val savedNewStaticMembers : mutable.Buffer[Tree] = newStaticMembers.MemberwiseClone()
      val savedNewStaticInits   : mutable.Buffer[Tree] = newStaticInits.MemberwiseClone()
      val savedSymbolsStoredAsStatic : mutable.Map[String, Symbol] = symbolsStoredAsStatic.MemberwiseClone()
      val result = body

      clearStatics()
      newStaticMembers      ++= savedNewStaticMembers
      newStaticInits        ++= savedNewStaticInits
      symbolsStoredAsStatic ++= savedSymbolsStoredAsStatic

      result
    }
    private def transformTemplate(tree: Tree) = {
      val Template(parents, self, body) = tree
      clearStatics()
      val newBody = transformTrees(body)
      val templ   = deriveTemplate(tree)(_ => transformTrees(newStaticMembers.toList) ::: newBody)
      try addStaticInits(templ) // postprocess to include static ctors
      finally clearStatics()
    }
    private def mkTerm(prefix: String): TermName = unit.freshTermName(prefix)

    /** Kludge to provide a safe fix for #4560:
     *  If we generate a reference in an implementation class, we
     *  watch out for embedded This(..) nodes that point to the interface.
     *  These must be wrong. We fix them by setting symbol and type to
     *  the enclosing implementation class instead.
     */
    def safeREF(sym: Symbol) = {
      def fix(tree: Tree): Unit = tree match {
        case Select(qual @ This(_), name) if qual.symbol != currentClass =>
          qual.setSymbol(currentClass).setType(currentClass.tpe)
        case _ =>
      }
      val tree = REF(sym)
      if (currentClass.isImplClass && sym.owner == currentClass) fix(tree)
      tree
    }

    //private val classConstantMeth = new HashMap[String, Symbol]
    //private val symbolStaticFields = new HashMap[String, (Symbol, Tree, Tree)]

    private var localTyper: analyzer.Typer = null

    private object MethodDispatchType extends scala.Enumeration {
      val NO_CACHE, MONO_CACHE, POLY_CACHE = Value
    }
    import MethodDispatchType.{ NO_CACHE, MONO_CACHE, POLY_CACHE }
    private def dispatchType() = settings.refinementMethodDispatch.value match {
      case "no-cache"   => NO_CACHE
      case "mono-cache" => MONO_CACHE
      case "poly-cache" => POLY_CACHE
    }

    def shouldRewriteTry(tree: Try) = {
      val sym = tree.tpe.typeSymbol
      forMSIL && (sym != UnitClass) && (sym != NothingClass)
    }

    private def typedWithPos(pos: Position)(tree: Tree) =
      localTyper.typedPos(pos)(tree)

    /** A value class is defined to be only Java-compatible values: unit is
      * not part of it, as opposed to isValueClass in definitions. scala.Int is
      * a value class, java.lang.Integer is not. */
    def isJavaValueClass(sym: Symbol) = boxedClass contains sym
    def isJavaValueType(tp: Type) = isJavaValueClass(tp.typeSymbol)

    /** The boxed type if it's a primitive; identity otherwise.
     */
    def toBoxedType(tp: Type) = if (isJavaValueType(tp)) boxedClass(tp.typeSymbol).tpe else tp

    override def transform(tree: Tree): Tree = tree match {

      /* Transforms dynamic calls (i.e. calls to methods that are undefined
       * in the erased type space) to -- dynamically -- unsafe calls using
       * reflection. This is used for structural sub-typing of refinement
       * types, but may be used for other dynamic calls in the future.
       * For 'a.f(b)' it will generate something like:
       * 'a.getClass().
       * '  getMethod("f", Array(classOf[b.type])).
       * '  invoke(a, Array(b))
       * plus all the necessary casting/boxing/etc. machinery required
       * for type-compatibility (see fixResult).
       *
       * USAGE CONTRACT:
       * There are a number of assumptions made on the way a dynamic apply
       * is used. Assumptions relative to type are handled by the erasure
       * phase.
       * - The applied arguments are compatible with AnyRef, which means
       *   that an argument tree typed as AnyVal has already been extended
       *   with the necessary boxing calls. This implies that passed
       *   arguments might not be strictly compatible with the method's
       *   parameter types (a boxed integer while int is expected).
       * - The expected return type is an AnyRef, even when the method's
       *   return type is an AnyVal. This means that the tree containing the
       *   call has already been extended with the necessary unboxing calls
       *   (or is happy with the boxed type).
       * - The type-checker has prevented dynamic applies on methods which
       *   parameter's erased types are not statically known at the call site.
       *   This is necessary to allow dispatching the call to the correct
       *   method (dispatching on parameters is static in Scala). In practice,
       *   this limitation only arises when the called method is defined as a
       *   refinement, where the refinement defines a parameter based on a
       *   type variable. */
      case ad@ApplyDynamic(qual0, params) =>
        if (settings.logReflectiveCalls.value)
          unit.echo(ad.pos, "method invocation uses reflection")

        val typedPos = typedWithPos(ad.pos) _

        assert(ad.symbol.isPublic)
        var qual: Tree = qual0

        /* ### CREATING THE METHOD CACHE ### */

        def addStaticVariableToClass(forName: TermName, forType: Type, forInit: Tree, isFinal: Boolean): Symbol = {
          val flags = PRIVATE | STATIC | SYNTHETIC | (
            if (isFinal) FINAL else 0
          )

          val varSym = currentClass.newVariable(mkTerm("" + forName), ad.pos, flags) setInfoAndEnter forType
          if (!isFinal)
            varSym.addAnnotation(VolatileAttr)

          val varDef = typedPos( VAL(varSym) === forInit )
          newStaticMembers append transform(varDef)

          val varInit = typedPos( safeREF(varSym) === forInit )
          newStaticInits append transform(varInit)

          varSym
        }

        def addStaticMethodToClass(forName: String, forArgsTypes: List[Type], forResultType: Type)
                                  (forBody: Pair[Symbol, List[Symbol]] => Tree): Symbol = {

          val methSym = currentClass.newMethod(mkTerm(forName), ad.pos, STATIC | SYNTHETIC)
          val params  = methSym.newSyntheticValueParams(forArgsTypes)
          methSym setInfoAndEnter MethodType(params, forResultType)

          val methDef = typedPos( DefDef(methSym, forBody(methSym -> params)) )
          newStaticMembers append transform(methDef)

          methSym
        }

        def fromTypesToClassArrayLiteral(paramTypes: List[Type]): Tree =
          ArrayValue(TypeTree(ClassClass.tpe), paramTypes map LIT)

        def theTypeClassArray = arrayType(ClassClass.tpe)

        /* ... */
        def reflectiveMethodCache(method: String, paramTypes: List[Type]): Symbol = dispatchType match {
          case NO_CACHE =>

              /* Implementation of the cache is as follows for method "def xyz(a: A, b: B)":

                var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])

                def reflMethod$Method(forReceiver: JClass[_]): JMethod =
                  forReceiver.getMethod("xyz", reflParams$Cache)

              */

              val reflParamsCacheSym: Symbol =
                addStaticVariableToClass(nme.reflParamsCacheName, theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)

              addStaticMethodToClass(nme.reflMethodName, List(ClassClass.tpe), MethodClass.tpe) {
                case Pair(reflMethodSym, List(forReceiverSym)) =>
                  (REF(forReceiverSym) DOT Class_getMethod)(LIT(method), safeREF(reflParamsCacheSym))
              }

            case MONO_CACHE =>

              /* Implementation of the cache is as follows for method "def xyz(a: A, b: B)"
                 (but with a SoftReference wrapping reflClass$Cache, similarly in the poly Cache) :

                var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])

                var reflMethod$Cache: JMethod = null

                var reflClass$Cache: JClass[_] = null

                def reflMethod$Method(forReceiver: JClass[_]): JMethod = {
                  if (reflClass$Cache != forReceiver) {
                    reflMethod$Cache = forReceiver.getMethod("xyz", reflParams$Cache)
                    reflClass$Cache = forReceiver
                  }
                  reflMethod$Cache
                }

              */

              val reflParamsCacheSym: Symbol =
                addStaticVariableToClass(nme.reflParamsCacheName, theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)

              val reflMethodCacheSym: Symbol =
                addStaticVariableToClass(nme.reflMethodCacheName, MethodClass.tpe, NULL, false)

              val reflClassCacheSym: Symbol =
                addStaticVariableToClass(nme.reflClassCacheName, SoftReferenceClass.tpe, NULL, false)

              def isCacheEmpty(receiver: Symbol): Tree =
                reflClassCacheSym.IS_NULL() OR (reflClassCacheSym.GET() OBJ_NE REF(receiver))

              addStaticMethodToClass(nme.reflMethodName, List(ClassClass.tpe), MethodClass.tpe) {
                case Pair(reflMethodSym, List(forReceiverSym)) =>
                  BLOCK(
                    IF (isCacheEmpty(forReceiverSym)) THEN BLOCK(
                      safeREF(reflMethodCacheSym) === ((REF(forReceiverSym) DOT Class_getMethod)(LIT(method), safeREF(reflParamsCacheSym))) ,
                      safeREF(reflClassCacheSym) === gen.mkSoftRef(REF(forReceiverSym)),
                      UNIT
                    ) ENDIF,
                    safeREF(reflMethodCacheSym)
                  )
              }

            case POLY_CACHE =>

              /* Implementation of the cache is as follows for method "def xyz(a: A, b: B)"
                 (SoftReference so that it does not interfere with classloader garbage collection, see ticket
                 #2365 for details):

                var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])

                var reflPoly$Cache: SoftReference[scala.runtime.MethodCache] = new SoftReference(new EmptyMethodCache())

                def reflMethod$Method(forReceiver: JClass[_]): JMethod = {
                  var method: JMethod = reflPoly$Cache.find(forReceiver)
                  if (method != null)
                    return method
                  else {
                    method = ScalaRunTime.ensureAccessible(forReceiver.getMethod("xyz", reflParams$Cache))
                    reflPoly$Cache = new SoftReference(reflPoly$Cache.get.add(forReceiver, method))
                    return method
                  }
                }

              */

              val reflParamsCacheSym: Symbol =
                addStaticVariableToClass(nme.reflParamsCacheName, theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)

              def mkNewPolyCache = gen.mkSoftRef(NEW(TypeTree(EmptyMethodCacheClass.tpe)))
              val reflPolyCacheSym: Symbol = (
                addStaticVariableToClass(nme.reflPolyCacheName, SoftReferenceClass.tpe, mkNewPolyCache, false)
              )
              def getPolyCache = gen.mkCast(fn(safeREF(reflPolyCacheSym), nme.get), MethodCacheClass.tpe)

              addStaticMethodToClass(nme.reflMethodName, List(ClassClass.tpe), MethodClass.tpe)
                { case Pair(reflMethodSym, List(forReceiverSym)) =>
                  val methodSym = reflMethodSym.newVariable(mkTerm("method"), ad.pos) setInfo MethodClass.tpe

                  BLOCK(
                    IF (getPolyCache OBJ_EQ NULL) THEN (safeREF(reflPolyCacheSym) === mkNewPolyCache) ENDIF,
                    VAL(methodSym) === ((getPolyCache DOT methodCache_find)(REF(forReceiverSym))) ,
                    IF (REF(methodSym) OBJ_!= NULL) .
                      THEN (Return(REF(methodSym)))
                    ELSE {
                      def methodSymRHS  = ((REF(forReceiverSym) DOT Class_getMethod)(LIT(method), safeREF(reflParamsCacheSym)))
                      def cacheRHS      = ((getPolyCache DOT methodCache_add)(REF(forReceiverSym), REF(methodSym)))
                      BLOCK(
                        REF(methodSym)        === (REF(ensureAccessibleMethod) APPLY (methodSymRHS)),
                        safeREF(reflPolyCacheSym) === gen.mkSoftRef(cacheRHS),
                        Return(REF(methodSym))
                      )
                    }
                  )
                }
        }

        /* ### HANDLING METHODS NORMALLY COMPILED TO OPERATORS ### */

        def testForName(name: Name): Tree => Tree = t => (
          if (nme.CommonOpNames(name))
            gen.mkMethodCall(getMember(BoxesRunTimeClass, nme.isBoxedNumberOrBoolean), t :: Nil)
          else if (nme.BooleanOpNames(name))
            t IS_OBJ BoxedBooleanClass.tpe
          else
            gen.mkMethodCall(getMember(BoxesRunTimeClass, nme.isBoxedNumber), t :: Nil)
        )

        /** The Tree => Tree function in the return is necessary to prevent the original qual
         *  from being duplicated in the resulting code.  It may be a side-effecting expression,
         *  so all the test logic is routed through gen.evalOnce, which creates a block like
         *    { val x$1 = qual; if (x$1.foo || x$1.bar) f1(x$1) else f2(x$1) }
         *  (If the compiler can verify qual is safe to inline, it will not create the block.)
         */
        def getPrimitiveReplacementForStructuralCall(name: Name): Option[(Symbol, Tree => Tree)] = {
          val methodName = (
            if (params.isEmpty) nme.primitivePostfixMethodName(name)
            else if (params.tail.isEmpty) nme.primitiveInfixMethodName(name)
            else nme.NO_NAME
          )
          if (methodName == nme.NO_NAME) None
          else Some((getMember(BoxesRunTimeClass, methodName), testForName(name)))
        }

        /* ### BOXING PARAMS & UNBOXING RESULTS ### */

        /* Transforms the result of a reflective call (always an AnyRef) to
         * the actual result value (an AnyRef too). The transformation
         * depends on the method's static return type.
         * - for units (void), the reflective call will return null: a new
         *   boxed unit is generated.
         * - otherwise, the value is simply casted to the expected type. This
         *   is enough even for value (int et al.) values as the result of
         *   a dynamic call will box them as a side-effect. */

        /* ### CALLING THE APPLY ### */
        def callAsReflective(paramTypes: List[Type], resType: Type): Tree = {
          gen.evalOnce(qual, currentOwner, unit) { qual1 =>
            /* Some info about the type of the method being called. */
            val methSym       = ad.symbol
            val boxedResType  = toBoxedType(resType)      // Int -> Integer
            val resultSym     = boxedResType.typeSymbol
            // If this is a primitive method type (like '+' in 5+5=10) then the
            // parameter types and the (unboxed) result type should all be primitive types,
            // and the method name should be in the primitive->structural map.
            def isJavaValueMethod = (
              (resType :: paramTypes forall isJavaValueType) && // issue #1110
              (getPrimitiveReplacementForStructuralCall(methSym.name).isDefined)
            )
            // Erasure lets Unit through as Unit, but a method returning Any will have an
            // erased return type of Object and should also allow Unit.
            def isDefinitelyUnit  = (resultSym == UnitClass)
            def isMaybeUnit       = (resultSym == ObjectClass) || isDefinitelyUnit
            // If there's any chance this signature could be met by an Array.
            val isArrayMethodSignature = {
              def typesMatchApply = paramTypes match {
                case List(tp) => tp <:< IntClass.tpe
                case _        => false
              }
              def typesMatchUpdate = paramTypes match {
                case List(tp1, tp2) => (tp1 <:< IntClass.tpe) && isMaybeUnit
                case _              => false
              }

              (methSym.name == nme.length && params.isEmpty) ||
              (methSym.name == nme.clone_ && params.isEmpty) ||
              (methSym.name == nme.apply  && typesMatchApply) ||
              (methSym.name == nme.update && typesMatchUpdate)
            }

            /* Some info about the argument at the call site. */
            val qualSym           = qual.tpe.typeSymbol
            val args              = qual1() :: params
            def isDefinitelyArray = (qualSym == ArrayClass)
            def isMaybeArray      = (qualSym == ObjectClass) || isDefinitelyArray
            def isMaybeBoxed      = platform isMaybeBoxed qualSym

            // This is complicated a bit by trying to handle Arrays correctly.
            // Under normal circumstances if the erased return type is Object then
            // we're not going to box it to Unit, but that is the situation with
            // a signature like def f(x: { def update(x: Int, y: Long): Any })
            //
            // However we only want to do that boxing if it has been determined
            // to be an Array and a method returning Unit.  But for this fixResult
            // could be called in one place: instead it is called separately from the
            // unconditional outcomes (genValueCall, genArrayCall, genDefaultCall.)
            def fixResult(tree: Tree, mustBeUnit: Boolean = false) =
              if (mustBeUnit || resultSym == UnitClass) BLOCK(tree, REF(BoxedUnit_UNIT))  // boxed unit
              else if (resultSym == ObjectClass) tree                                     // no cast necessary
              else gen.mkCast(tree, boxedResType)                                         // cast to expected type

            /** Normal non-Array call */
            def genDefaultCall = {
              // reflective method call machinery
              val invokeName  = MethodClass.tpe member nme.invoke_                                  // reflect.Method.invoke(...)
              def cache       = safeREF(reflectiveMethodCache(ad.symbol.name.ToString, paramTypes)) // cache Symbol
              def lookup      = Apply(cache, List(qual1() GETCLASS))                                // get Method object from cache
              def invokeArgs  = ArrayValue(TypeTree(ObjectClass.tpe), params)                       // args for invocation
              def invocation  = (lookup DOT invokeName)(qual1(), invokeArgs)                        // .invoke(qual1, ...)

              // exception catching machinery
              val invokeExc   = currentOwner.newValue(mkTerm(""), ad.pos) setInfo InvocationTargetExceptionClass.tpe
              def catchVar    = Bind(invokeExc, Typed(Ident(nme.WILDCARD), TypeTree(InvocationTargetExceptionClass.tpe)))
              def catchBody   = Throw(Apply(Select(Ident(invokeExc), nme.getCause), Nil))

              // try { method.invoke } catch { case e: InvocationTargetExceptionClass => throw e.getCause() }
              fixResult(TRY (invocation) CATCH { CASE (catchVar) ==> catchBody } ENDTRY)
            }

            /** A possible primitive method call, represented by methods in BoxesRunTime. */
            def genValueCall(operator: Symbol) = fixResult(REF(operator) APPLY args)
            def genValueCallWithTest = {
              getPrimitiveReplacementForStructuralCall(methSym.name) match {
                case Some((operator, test)) =>
                  IF (test(qual1())) THEN genValueCall(operator) ELSE genDefaultCall
                case _ =>
                  genDefaultCall
              }
            }

            /** A native Array call. */
            def genArrayCall = fixResult(
              methSym.name match {
                case nme.length => REF(boxMethod(IntClass)) APPLY (REF(arrayLengthMethod) APPLY args)
                case nme.update => REF(arrayUpdateMethod) APPLY List(args(0), (REF(unboxMethod(IntClass)) APPLY args(1)), args(2))
                case nme.apply  => REF(arrayApplyMethod) APPLY List(args(0), (REF(unboxMethod(IntClass)) APPLY args(1)))
                case nme.clone_ => REF(arrayCloneMethod) APPLY List(args(0))
              },
              mustBeUnit = methSym.name == nme.update
            )

            /** A conditional Array call, when we can't determine statically if the argument is
             *  an Array, but the structural type method signature is consistent with an Array method
             *  so we have to generate both kinds of code.
             */
            def genArrayCallWithTest =
              IF ((qual1() GETCLASS()) DOT nme.isArray) THEN genArrayCall ELSE genDefaultCall

            localTyper typed (
              if (isMaybeBoxed && isJavaValueMethod) genValueCallWithTest
              else if (isArrayMethodSignature && isDefinitelyArray) genArrayCall
              else if (isArrayMethodSignature && isMaybeArray) genArrayCallWithTest
              else genDefaultCall
            )
          }
        }

        if (settings.refinementMethodDispatch.value == "invoke-dynamic") {
/*          val guardCallSite: Tree = {
            val cachedClass = addStaticVariableToClass("cachedClass", definitions.ClassClass.tpe, EmptyTree)
            val tmpVar = currentOwner.newVariable(ad.pos, unit.freshTermName(ad.pos, "x")).setInfo(definitions.AnyRefClass.tpe)
            atPos(ad.pos)(Block(List(
              ValDef(tmpVar, transform(qual))),
              If(Apply(Select(gen.mkAttributedRef(cachedClass), nme.EQ), List(getClass(Ident(tmpVar)))),
                 Block(List(Assign(gen.mkAttributedRef(cachedClass), getClass(Ident(tmpVar)))),
                       treeCopy.ApplyDynamic(ad, Ident(tmpVar), transformTrees(params))),
                 EmptyTree)))
          }
          //println(guardCallSite)
*/
          localTyper.typed(treeCopy.ApplyDynamic(ad, transform(qual), transformTrees(params)))
        }
        else {

          /* ### BODY OF THE TRANSFORMATION -> remember we're in case ad@ApplyDynamic(qual, params) ### */

          /* This creates the tree that does the reflective call (see general comment
           * on the apply-dynamic tree for its format). This tree is simply composed
           * of three successive calls, first to getClass on the callee, then to
           * getMethod on the class, then to invoke on the method.
           * - getMethod needs an array of classes for choosing one amongst many
           *   overloaded versions of the method. This is provided by paramTypeClasses
           *   and must be done on the static type as Scala's dispatching is static on
           *   the parameters.
           * - invoke needs an array of AnyRefs that are the method's arguments. The
           *   erasure phase guarantees that any parameter passed to a dynamic apply
           *   is compatible (through boxing). Boxed ints et al. is what invoke expects
           *   when the applied method expects ints, hence no change needed there.
           * - in the end, the result of invoke must be fixed, again to deal with arrays.
           *   This is provided by fixResult. fixResult will cast the invocation's result
           *   to the method's return type, which is generally ok, except when this type
           *   is a value type (int et al.) in which case it must cast to the boxed version
           *   because invoke only returns object and erasure made sure the result is
           *   expected to be an AnyRef. */
          val t: Tree = ad.symbol.tpe match {
            case MethodType(mparams, resType) =>
              assert(params.length == mparams.length, mparams)

              typedPos {
                val sym = currentOwner.newValue(mkTerm("qual"), ad.pos) setInfo qual0.tpe
                qual = safeREF(sym)

                BLOCK(
                  VAL(sym) === qual0,
                  callAsReflective(mparams map (_.tpe), resType)
                )
              }
          }

          /* For testing purposes, the dynamic application's condition
           * can be printed-out in great detail. Remove? */
          if (settings.debug.value) {
            def paramsToString(xs: Any*) = xs map (_.ToString) mkString ", "
            val mstr = ad.symbol.tpe match {
              case MethodType(mparams, resType) =>
                """|  with
                   |  - declared parameter types: '%s'
                   |  - passed argument types:    '%s'
                   |  - result type:              '%s'""" .
                  stripMargin.format(
                     paramsToString(mparams),
                     paramsToString(params),
                     resType.ToString
                  )
              case _ => ""
            }
            log(
              """Dynamically application '%s.%s(%s)' %s - resulting code: '%s'""".format(
                qual, ad.symbol.name, paramsToString(params), mstr, t
              )
            )
          }

          /* We return the dynamic call tree, after making sure no other
           * clean-up transformation are to be applied on it. */
          transform(t)
        }
        /* ### END OF DYNAMIC APPLY TRANSFORM ### */

      /* Some cleanup transformations add members to templates (classes, traits, etc).
       * When inside a template (i.e. the body of one of its members), two maps
       * (newStaticMembers and newStaticInits) are available in the tree transformer. Any mapping from
       * a symbol to a MemberDef (DefDef, ValDef, etc.) that is in newStaticMembers once the
       * transformation of the template is finished will be added as a member to the
       * template. Any mapping from a symbol to a tree that is in newStaticInits, will be added
       * as a statement of the form "symbol = tree" to the beginning of the default
       * constructor. */
      case Template(parents, self, body) =>
        localTyper = typer.atOwner(tree, currentClass)
        if (forMSIL) savingStatics( transformTemplate(tree) )
        else transformTemplate(tree)

      case Literal(c) if (c.tag == ClassTag) && !forMSIL=>
        val tpe = c.typeValue
        typedWithPos(tree.pos) {
          if (isValueClass(tpe.typeSymbol)) {
            if (tpe.typeSymbol == UnitClass)
              REF(BoxedUnit_TYPE)
            else
              Select(REF(boxedModule(tpe.typeSymbol)), nme.TYPE_)
          }

          else tree
        }

      /* MSIL requires that the stack is empty at the end of a try-block.
       * Hence, we here rewrite all try blocks with a result != {Unit, All} such that they
       * store their result in a local variable. The catch blocks are adjusted as well.
       * The try tree is subsituted by a block whose result expression is read of that variable. */
      case theTry @ Try(block, catches, finalizer) if shouldRewriteTry(theTry) =>
        val tpe = theTry.tpe.widen
        val tempVar = currentOwner.newVariable(mkTerm(nme.EXCEPTION_RESULT_PREFIX), theTry.pos).setInfo(tpe)
        def assignBlock(rhs: Tree) = super.transform(BLOCK(Ident(tempVar) === transform(rhs)))

        val newBlock    = assignBlock(block)
        val newCatches  = for (CaseDef(pattern, guard, body) <- catches) yield
          (CASE(super.transform(pattern)) IF (super.transform(guard))) ==> assignBlock(body)
        val newTry      = Try(newBlock, newCatches, super.transform(finalizer))

        typedWithPos(theTry.pos)(BLOCK(VAL(tempVar) === EmptyTree, newTry, Ident(tempVar)))

     /*
      * This transformation should identify Scala symbol invocations in the tree and replace them
      * with references to a static member. Also, whenever a class has at least a single symbol invocation
      * somewhere in its methods, a new static member should be created and initialized for that symbol.
      * For instance, say we have a Scala class:
      *
      * class Cls {
      *   // ...
      *   def someSymbol = `symbolic
      *   // ...
      * }
      *
      * After transformation, this class looks like this:
      *
      * class Cls {
      *   private "static" val <some_name>$symbolic = Symbol("symbolic")
      *   // ...
      *   def someSymbol = <some_name>$symbolic
      *   // ...
      * }
      *
      * The reasoning behind this transformation is the following. Symbols get interned - they are stored
      * in a global map which is protected with a lock. The reason for this is making equality checks
      * quicker. But calling Symbol.apply, although it does return a unique symbol, accesses a locked object,
      * making symbol access slow. To solve this, the unique symbol from the global symbol map in Symbol
      * is accessed only once during class loading, and after that, the unique symbol is in the static
      * member. Hence, it is cheap to both reach the unique symbol and do equality checks on it.
      *
      * And, finally, be advised - scala symbol literal and the Symbol class of the compiler
      * have little in common.
      */
      case Apply(fn, (arg @ Literal(Constant(symname: String))) :: Nil) if fn.symbol == Symbol_apply =>
        // add the symbol name to a map if it's not there already
        val rhs = gen.mkMethodCall(Symbol_apply, arg :: Nil)
        val staticFieldSym = getSymbolStaticField(tree.pos, symname, rhs, tree)
        // create a reference to a static field
        val ntree = typedWithPos(tree.pos)(safeREF(staticFieldSym))
        super.transform(ntree)

      // This transform replaces Array(Predef.wrapArray(Array(...)), <manifest>)
      // with just Array(...)
      case Apply(appMeth, List(Apply(wrapRefArrayMeth, List(array)), _))
      if (wrapRefArrayMeth.symbol == Predef_wrapRefArray &&
          appMeth.symbol == ArrayModule_overloadedApply.suchThat {
            _.tpe.resultType.dealias.typeSymbol == ObjectClass
          }) =>
        super.transform(array)

      case _ =>
        super.transform(tree)
    }

    /* Returns the symbol and the tree for the symbol field interning a reference to a symbol 'synmname'.
     * If it doesn't exist, i.e. the symbol is encountered the first time,
     * it creates a new static field definition and initialization and returns it.
     */
    private def getSymbolStaticField(pos: Position, symname: String, rhs: Tree, tree: Tree): Symbol = {
      symbolsStoredAsStatic.getOrElseUpdate(symname, {
        val theTyper = typer.atOwner(tree, currentClass)

        // create a symbol for the static field
        val stfieldSym = (
          currentClass.newVariable(mkTerm("symbol$"), pos, PRIVATE | STATIC | SYNTHETIC | FINAL)
            setInfo SymbolClass.tpe
        )
        currentClass.info.decls enter stfieldSym

        // create field definition and initialization
        val stfieldDef  = theTyper.typedPos(pos)(VAL(stfieldSym) === rhs)
        val stfieldInit = theTyper.typedPos(pos)(safeREF(stfieldSym) === rhs)

        // add field definition to new defs
        newStaticMembers append stfieldDef
        newStaticInits append stfieldInit

        stfieldSym
      })
    }

    /* finds the static ctor DefDef tree within the template if it exists. */
    private def findStaticCtor(template: Template): Option[Tree] =
      template.body find {
        case defdef @ DefDef(_, nme.CONSTRUCTOR, _, _, _, _) => defdef.symbol.hasStaticFlag
        case _ => false
      }

    /* changes the template for the class so that it contains a static constructor with symbol fields inits,
     * augments an existing static ctor if one already existed.
     */
    private def addStaticInits(template: Template): Template = {
      if (newStaticInits.isEmpty)
        template
      else {
        val newCtor = findStaticCtor(template) match {
          // in case there already were static ctors - augment existing ones
          // currently, however, static ctors aren't being generated anywhere else
          case Some(ctor @ DefDef(_,_,_,_,_,_)) =>
            // modify existing static ctor
            deriveDefDef(ctor) {
              case block @ Block(stats, expr) =>
                // need to add inits to existing block
                treeCopy.Block(block, newStaticInits.toList ::: stats, expr)
              case term: TermTree =>
                // need to create a new block with inits and the old term
                treeCopy.Block(term, newStaticInits.toList, term)
            }
          case None =>
            // create new static ctor
            val staticCtorSym  = currentClass.newStaticConstructor(template.pos)
            val rhs            = Block(newStaticInits.toList, Literal(Constant(())))

            localTyper.typedPos(template.pos)(DefDef(staticCtorSym, rhs))
        }
        deriveTemplate(template)(newCtor :: _)
      }
    }

  } // CleanUpTransformer

}
