Scala example source code file (Duplicators.scala)

This example Scala source code file (Duplicators.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.

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Scala tags/keywords

collection, compiler, context, ident, labeldef, list, nosymbol, nsc, select, symbol, this, tree, type

The Duplicators.scala Scala example source code

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

package scala.tools.nsc
package typechecker

import scala.tools.nsc.symtab.Flags
import scala.collection.{ mutable, immutable }

/** Duplicate trees and re-type check them, taking care to replace
 *  and create fresh symbols for new local definitions.
 *
 *  @author  Iulian Dragos
 *  @version 1.0
 */
abstract class Duplicators extends Analyzer {
  import global._
  import definitions._

  /** Retype the given tree in the given context. Use this method when retyping
   *  a method in a different class. The typer will replace references to the this of
   *  the old class with the new class, and map symbols through the given 'env'. The
   *  environment is a map from type skolems to concrete types (see SpecializedTypes).
   */
  def retyped(context: Context, tree: Tree, oldThis: Symbol, newThis: Symbol, env: scala.collection.Map[Symbol, Type]): Tree = {
    if (oldThis ne newThis) {
      oldClassOwner = oldThis
      newClassOwner = newThis
    } else resetClassOwners()

    envSubstitution = new SubstSkolemsTypeMap(env.keysIterator.toList, env.valuesIterator.toList)
    debuglog("retyped with env: " + env)

    newBodyDuplicator(context).typed(tree)
  }

  protected def newBodyDuplicator(context: Context) = new BodyDuplicator(context)

  /** Return the special typer for duplicate method bodies. */
  override def newTyper(context: Context): Typer =
    newBodyDuplicator(context)

  private def resetClassOwners() {
    oldClassOwner = null
    newClassOwner = null
  }

  private var oldClassOwner: Symbol = _
  private var newClassOwner: Symbol = _
  private var envSubstitution: SubstTypeMap = _

  private class SubstSkolemsTypeMap(from: List[Symbol], to: List[Type]) extends SubstTypeMap(from, to) {
    protected override def matches(sym1: Symbol, sym2: Symbol) =
      if (sym2.isTypeSkolem) sym2.deSkolemize eq sym1
      else sym1 eq sym2
  }

  private val invalidSyms: mutable.Map[Symbol, Tree] = perRunCaches.newMap[Symbol, Tree]()

  /** A typer that creates new symbols for all definitions in the given tree
   *  and updates references to them while re-typechecking. All types in the
   *  tree, except for TypeTrees, are erased prior to type checking. TypeTrees
   *  are fixed by substituting invalid symbols for the new ones.
   */
  class BodyDuplicator(_context: Context) extends Typer(_context) {

    class FixInvalidSyms extends TypeMap {

      def apply(tpe: Type): Type = {
        mapOver(tpe)
      }

      override def mapOver(tpe: Type): Type = tpe match {
        case TypeRef(NoPrefix, sym, args) if sym.isTypeParameterOrSkolem =>
          val sym1 = (
            context.scope lookup sym.name orElse {
              // try harder (look in outer scopes)
              // with virtpatmat, this can happen when the sym is referenced in the scope of a LabelDef but
              // is defined in the scope of an outer DefDef (e.g., in AbstractPartialFunction's andThen)
              BodyDuplicator.super.silent(_ typedType Ident(sym.name)).fold(NoSymbol: Symbol)(_.symbol)
            } filter (_ ne sym)
          )
          if (sym1.exists) {
            debuglog(s"fixing $sym -> $sym1")
            typeRef(NoPrefix, sym1, mapOverArgs(args, sym1.typeParams))
          }
          else super.mapOver(tpe)

        case TypeRef(pre, sym, args) =>
          val newsym = updateSym(sym)
          if (newsym ne sym) {
            debuglog("fixing " + sym + " -> " + newsym)
            typeRef(mapOver(pre), newsym, mapOverArgs(args, newsym.typeParams))
          } else
            super.mapOver(tpe)

        case SingleType(pre, sym) =>
          val sym1 = updateSym(sym)
          if (sym1 ne sym) {
            debuglog("fixing " + sym + " -> " + sym1)
            singleType(mapOver(pre), sym1)
          } else
            super.mapOver(tpe)

        case ThisType(sym) =>
          val sym1 = updateSym(sym)
          if (sym1 ne sym) {
            debuglog("fixing " + sym + " -> " + sym1)
            ThisType(sym1)
          } else
            super.mapOver(tpe)


        case _ =>
          super.mapOver(tpe)
      }
    }

    /** Fix the given type by replacing invalid symbols with the new ones. */
    def fixType(tpe: Type): Type = {
      val tpe1 = envSubstitution(tpe)
      val tpe2: Type = (new FixInvalidSyms)(tpe1)
      val tpe3 = if (newClassOwner ne null) {
        tpe2.asSeenFrom(newClassOwner.thisType, oldClassOwner)
      } else tpe2
      tpe3
    }

    /** Return the new symbol corresponding to `sym`. */
    private def updateSym(sym: Symbol): Symbol =
      if (invalidSyms.isDefinedAt(sym))
        invalidSyms(sym).symbol
      else
        sym

    private def invalidate(tree: Tree, owner: Symbol = NoSymbol) {
      debuglog(s"attempting to invalidate symbol = ${tree.symbol}")
      if ((tree.isDef || tree.isInstanceOf[Function]) && tree.symbol != NoSymbol) {
        debuglog("invalid " + tree.symbol)
        invalidSyms(tree.symbol) = tree

        tree match {
          case ldef @ LabelDef(name, params, rhs) =>
            debuglog("LabelDef " + name + " sym.info: " + ldef.symbol.info)
            invalidSyms(ldef.symbol) = ldef
          //          breakIf(true, this, ldef, context)
            val newsym = ldef.symbol.cloneSymbol(context.owner)
            newsym.setInfo(fixType(ldef.symbol.info))
            ldef.symbol = newsym
            debuglog("newsym: " + newsym + " info: " + newsym.info)

          case vdef @ ValDef(mods, name, _, rhs) if mods.hasFlag(Flags.LAZY) =>
            debuglog("ValDef " + name + " sym.info: " + vdef.symbol.info)
            invalidSyms(vdef.symbol) = vdef
            val newowner = owner orElse context.owner
            val newsym = vdef.symbol.cloneSymbol(newowner)
            newsym.setInfo(fixType(vdef.symbol.info))
            vdef.symbol = newsym
            debuglog("newsym: " + newsym + " info: " + newsym.info + ", owner: " + newsym.owner + ", " + newsym.owner.isClass)
            if (newsym.owner.isClass) newsym.owner.info.decls enter newsym

          case DefDef(_, name, tparams, vparamss, _, rhs) =>
            // invalidate parameters
            invalidateAll(tparams ::: vparamss.flatten)
            tree.symbol = NoSymbol

          case Function(vparams, _) =>
            // invalidate parameters
            invalidateAll(vparams)
            tree.symbol = NoSymbol

          case _ =>
            tree.symbol = NoSymbol
        }
      }
    }

    private def invalidateAll(stats: List[Tree], owner: Symbol = NoSymbol) {
      stats.foreach(invalidate(_, owner))
    }

    /** Optionally cast this tree into some other type, if required.
     *  Unless overridden, just returns the tree.
     */
    def castType(tree: Tree, pt: Type): Tree = tree

    /** Special typer method for re-type checking trees. It expects a typed tree.
     *  Returns a typed tree that has fresh symbols for all definitions in the original tree.
     *
     *  Each definition tree is visited and its symbol added to the invalidSyms map (except LabelDefs),
     *  then cleared (forcing the namer to create fresh symbols).
     *  All invalid symbols found in trees are cleared (except for LabelDefs), forcing the
     *  typechecker to look for fresh ones in the context.
     *
     *  Type trees are typed by substituting old symbols for new ones (@see fixType).
     *
     *  LabelDefs are not typable from trees alone, unless they have the type ()Unit. Therefore,
     *  their symbols are recreated ad-hoc and their types are fixed inline, instead of letting the
     *  namer/typer handle them, or Idents that refer to them.
     */
    override def typed(tree: Tree, mode: Mode, pt: Type): Tree = {
      debuglog("typing " + tree + ": " + tree.tpe + ", " + tree.getClass)
      val origtreesym = tree.symbol
      if (tree.hasSymbolField && tree.symbol != NoSymbol
          && !tree.symbol.isLabel  // labels cannot be retyped by the type checker as LabelDef has no ValDef/return type trees
          && invalidSyms.isDefinedAt(tree.symbol)) {
        debuglog("removed symbol " + tree.symbol)
        tree.symbol = NoSymbol
      }

      tree match {
        case ttree @ TypeTree() =>
          // log("fixing tpe: " + tree.tpe + " with sym: " + tree.tpe.typeSymbol)
          ttree modifyType fixType

        case Block(stats, res) =>
          debuglog("invalidating block")
          invalidateAll(stats)
          invalidate(res)
          super.typed(tree.clearType(), mode, pt)

        case ClassDef(_, _, _, tmpl @ Template(parents, _, stats)) =>
          // log("invalidating classdef " + tree)
          tmpl.symbol = tree.symbol.newLocalDummy(tree.pos)
          invalidateAll(stats, tree.symbol)
          super.typed(tree.clearType(), mode, pt)

        case ddef @ DefDef(_, _, _, _, tpt, rhs) =>
          ddef.tpt modifyType fixType
          super.typed(ddef.clearType(), mode, pt)

        case fun: Function =>
          debuglog("Clearing the type and retyping Function: " + fun)
          super.typed(fun.clearType, mode, pt)

        case vdef @ ValDef(mods, name, tpt, rhs) =>
          // log("vdef fixing tpe: " + tree.tpe + " with sym: " + tree.tpe.typeSymbol + " and " + invalidSyms)
          //if (mods.hasFlag(Flags.LAZY)) vdef.symbol.resetFlag(Flags.MUTABLE) // Martin to Iulian: lazy vars can now appear because they are no longer boxed; Please check that deleting this statement is OK.
          vdef.tpt modifyType fixType
          super.typed(vdef.clearType(), mode, pt)

        case ldef @ LabelDef(name, params, rhs) =>
          // log("label def: " + ldef)
          // in case the rhs contains any definitions -- TODO: is this necessary?
          invalidate(rhs)
          ldef.clearType()

          // is this LabelDef generated by tailcalls?
          val isTailLabel = (ldef.params.length >= 1) && (ldef.params.head.name == nme.THIS)

          // the typer does not create the symbols for a LabelDef's params, so unless they were created before we need
          // to do it manually here -- but for the tailcalls-generated labels, ValDefs are created before the LabelDef,
          // so we just need to change the tree to point to the updated symbols
          def newParam(p: Tree): Ident =
            if (isTailLabel)
              Ident(updateSym(p.symbol))
            else {
              val newsym = p.symbol.cloneSymbol //(context.owner) // TODO owner?
              Ident(newsym.setInfo(fixType(p.symbol.info)))
            }

          val params1 = params map newParam
          val rhs1 = (new TreeSubstituter(params map (_.symbol), params1) transform rhs) // TODO: duplicate?

          super.typed(treeCopy.LabelDef(tree, name, params1, rhs1.clearType()), mode, pt)

        case Bind(name, _) =>
          // log("bind: " + tree)
          invalidate(tree)
          super.typed(tree.clearType(), mode, pt)

        case Ident(_) if tree.symbol.isLabel =>
          debuglog("Ident to labeldef " + tree + " switched to ")
          tree.symbol = updateSym(tree.symbol)
          super.typed(tree.clearType(), mode, pt)

        case Ident(_) if (origtreesym ne null) && origtreesym.isLazy =>
          debuglog("Ident to a lazy val " + tree + ", " + tree.symbol + " updated to " + origtreesym)
          tree.symbol = updateSym(origtreesym)
          super.typed(tree.clearType(), mode, pt)

        case Select(th @ This(_), sel) if (oldClassOwner ne null) && (th.symbol == oldClassOwner) =>
          // We use the symbol name instead of the tree name because the symbol
          // may have been name mangled, rendering the tree name obsolete.
          // ...but you can't just do a Select on a name because if the symbol is
          // overloaded, you will crash in the backend.
          val memberByName  = newClassOwner.thisType.member(tree.symbol.name)
          def nameSelection = Select(This(newClassOwner), tree.symbol.name)
          val newTree = (
            if (memberByName.isOverloaded) {
              // Find the types of the overload alternatives as seen in the new class,
              // and filter the list down to those which match the old type (after
              // fixing the old type so it is seen as if from the new class.)
              val typeInNewClass = fixType(oldClassOwner.info memberType tree.symbol)
              val alts           = memberByName.alternatives
              val memberTypes    = alts map (newClassOwner.info memberType _)
              val memberString   = memberByName.defString
              alts zip memberTypes filter (_._2 =:= typeInNewClass) match {
                case ((alt, tpe)) :: Nil =>
                  log(s"Arrested overloaded type in Duplicators, narrowing to ${alt.defStringSeenAs(tpe)}\n  Overload was: $memberString")
                  Select(This(newClassOwner), alt)
                case xs =>
                  alts filter (alt => (alt.paramss corresponds tree.symbol.paramss)(_.size == _.size)) match {
                    case alt :: Nil =>
                      log(s"Resorted to parameter list arity to disambiguate to $alt\n  Overload was: $memberString")
                      Select(This(newClassOwner), alt)
                    case _ =>
                      log(s"Could not disambiguate $memberTypes. Attempting name-based selection, but we may crash later.")
                      nameSelection
                  }
              }
            }
            else nameSelection
          )
          super.typed(atPos(tree.pos)(newTree), mode, pt)

        case This(_) if (oldClassOwner ne null) && (tree.symbol == oldClassOwner) =>
//          val tree1 = Typed(This(newClassOwner), TypeTree(fixType(tree.tpe.widen)))
          // log("selection on this: " + tree)
          val tree1 = This(newClassOwner)
          // log("tree1: " + tree1)
          debuglog("mapped " + tree + " to " + tree1)
          super.typedPos(tree.pos, mode, pt)(tree1)

        case This(_) =>
          debuglog("selection on this, plain: " + tree)
          tree.symbol = updateSym(tree.symbol)
          val ntree = castType(tree, pt)
          val tree1 = super.typed(ntree, mode, pt)
          // log("plain this typed to: " + tree1)
          tree1
/* no longer needed, because Super now contains a This(...)
        case Super(qual, mix) if (oldClassOwner ne null) && (tree.symbol == oldClassOwner) =>
          val tree1 = Super(qual, mix)
          log("changed " + tree + " to " + tree1)
          super.typed(atPos(tree.pos)(tree1))
*/
        case Match(scrut, cases) =>
          val scrut1   = typedByValueExpr(scrut)
          val scrutTpe = scrut1.tpe.widen
          val cases1 = {
            if (scrutTpe.isFinalType) cases filter {
              case CaseDef(Bind(_, pat @ Typed(_, tpt)), EmptyTree, body) =>
                // the typed pattern is not incompatible with the scrutinee type
                scrutTpe matchesPattern fixType(tpt.tpe)
              case CaseDef(Typed(_, tpt), EmptyTree, body) =>
                // the typed pattern is not incompatible with the scrutinee type
                scrutTpe matchesPattern fixType(tpt.tpe)
              case _ => true
            }
            // Without this, AnyRef specializations crash on patterns like
            //   case _: Boolean => ...
            // Not at all sure this is safe.
            else if (scrutTpe <:< AnyRefTpe)
              cases filterNot (_.pat.tpe <:< AnyValTpe)
            else
              cases
          }

          super.typed(atPos(tree.pos)(Match(scrut, cases1)), mode, pt)

        case EmptyTree =>
          // no need to do anything, in particular, don't set the type to null, EmptyTree.tpe_= asserts
          tree

        case _ =>
          debuglog("Duplicators default case: " + tree.summaryString)
          debuglog(" ---> " + tree)
          if (tree.hasSymbolField && tree.symbol.safeOwner == AnyClass)
            tree.symbol = NoSymbol // maybe we can find a more specific member in a subclass of Any (see AnyVal members, like ==)

          val ntree = castType(tree, pt)
          super.typed(ntree, mode, pt)
      }
    }

  }
}