path: root/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala

/* NSC -- new Scala compiler
 * Copyright 2005-2006 LAMP/EPFL
 * @author Martin Odersky
 */
// $Id$

package scala.tools.nsc.transform

import symtab._
import Flags._
import collection.mutable.{HashMap, ListBuffer}

abstract class AddInterfaces extends InfoTransform {
  import global._                  // the global environment
  import definitions._             // standard classes and methods
  import posAssigner.atPos         // for filling in tree positions

  /** The phase sets lateINTERFACE for non-interface traits that now become interfaces
   *  It sets lateDEFERRED for formerly concrete methods in such traits
   */
  override def phaseNewFlags: long = lateDEFERRED | lateINTERFACE

  /** Type reference after erasure; to be defined in subclass Erasure */
  def erasedTypeRef(sym: Symbol): Type

  /** A lazily constructed map that associates every non-interface trait with
   *  its implementation class */
  private val implClassMap = new HashMap[Symbol, Symbol]

  /** A lazily constructed map that associates every concrete method in a non-interface
   *  trait that's currently compiled with its corresponding method in the trait's
   *  implementation class.
   */
  private val implMethodMap = new HashMap[Symbol, Symbol]

  override def newPhase(prev: scala.tools.nsc.Phase): StdPhase = {
    implClassMap.clear
    implMethodMap.clear
    super.newPhase(prev)
  }

  /** Is given trait member symbol a member of the trait's interface
   *  after this transform is performed? */
  private def isInterfaceMember(sym: Symbol): boolean = {
    sym.info; // to set lateMETHOD flag if necessary
    (sym.isType ||
     sym.isMethod && !(sym hasFlag (PRIVATE | BRIDGE | LABEL)) &&
     !sym.isConstructor && !sym.isImplOnly)
  }

  /** Does symbol need an implementation method? */
  private def needsImplMethod(sym: Symbol): boolean =
    sym.isMethod && isInterfaceMember(sym) &&
    (!(sym hasFlag (DEFERRED | SUPERACCESSOR)) || (sym hasFlag lateDEFERRED))

  /** Return the implementation class of a trait; create a new one of one does not yet exist */
  def implClass(iface: Symbol): Symbol = implClassMap.get(iface) match {
    case Some(c) => c
    case None =>
      atPhase(currentRun.erasurePhase) {
        val implName = nme.implClassName(iface.name)
        var impl = if (iface.owner.isClass) iface.owner.info.decl(implName) else NoSymbol
        if (impl == NoSymbol) {
          impl = iface.cloneSymbolImpl(iface.owner)
          impl.name = implName
          if (iface.owner.isClass) {
            atPhase(phase.next) {
              val decls = iface.owner.info.decls
              val e = decls.lookupEntry(impl.name)
              if (e == null) {
                decls enter impl
              } else {
                decls.unlink(e)
                decls enter impl
              }
            }
          }
        }
        if (currentRun.compiles(iface)) currentRun.symSource(impl) = iface.sourceFile
        impl setPos iface.pos
        impl.flags = iface.flags & ~(INTERFACE | lateINTERFACE) | IMPLCLASS
        impl setInfo new LazyImplClassType(iface)
        implClassMap(iface) = impl
        if (settings.debug.value) log("generating impl class " + impl + " in " + iface.owner)//debug
        impl
      }
  }

  /** A lazy type to set the info of an implementation class
   *  The parents of an implementation class for trait `iface' are:
   *    - superclass: Object
   *    - mixin classes: mixin classes of `iface' where every non-interface trait
   *                     is mapped to its implementation class, followed by
   *                     `iface' itself.
   *  The declarations of a mixin class are
   *    - for every interface member of `iface' its implemention method, if one is needed.
   *    - every former member of `iface' that is implementation only
   */
  private class LazyImplClassType(iface: Symbol) extends LazyType {

    /** Compute the decls of implementation class `implClass',
     *  given the decls `ifaceDecls' of its interface
     */
    def implDecls(implClass: Symbol, ifaceDecls: Scope): Scope = {
      val decls = newScope
      for (val sym <- ifaceDecls.elements) {
        if (isInterfaceMember(sym)) {
          if (needsImplMethod(sym)) {
            val impl = sym.cloneSymbol(implClass).setInfo(sym.info).resetFlag(lateDEFERRED)
            if (currentRun.compiles(implClass)) implMethodMap(sym) = impl
            decls enter impl
            sym setFlag lateDEFERRED
          }
        } else {
          sym.owner = implClass
          // note: OK to destructively modify the owner here,
          // because symbol will not be accessible from outside the sourcefile.
          // mixin constructors are corrected separately; see TermSymbol.owner
          decls enter sym
        }
      }
      decls
    }

    override def complete(sym: Symbol): unit = {
      def implType(tp: Type): Type = tp match {
        case ClassInfoType(parents, decls, _) =>
          //ClassInfoType(mixinToImplClass(parents) ::: List(iface.tpe), implDecls(sym, decls), sym)
          ClassInfoType(
            ObjectClass.tpe :: (parents.tail map mixinToImplClass) ::: List(iface.tpe), //!!!
            implDecls(sym, decls),
            sym)
        case PolyType(tparams, restpe) =>
          PolyType(tparams, implType(restpe))
      }
      sym.setInfo(atPhase(currentRun.erasurePhase)(implType(iface.info)))
    }

    override def load(clazz: Symbol): unit = complete(clazz)
  }

  /** If `tp' refers to a non-interface trait, return a reference to its implementation class.
   *  Otherwise return `tp' itself.
   */
  private def mixinToImplClass(tp: Type): Type = tp match {
    case TypeRef(pre, sym, args) if (sym.needsImplClass) =>
      typeRef(pre, implClass(sym), args)
    case _ =>
      tp
  }

  def transformMixinInfo(tp: Type): Type = tp match {
    case ClassInfoType(parents, decls, clazz) =>
      if (clazz.needsImplClass) {
        clazz setFlag lateINTERFACE
        implClass(clazz) // generate an impl class
      }
      val parents1 =
        if (parents.isEmpty) List()
        else {
          assert(!parents.head.symbol.isTrait || clazz == RepeatedParamClass, clazz);
          if (clazz hasFlag INTERFACE) erasedTypeRef(ObjectClass) :: parents.tail
          else if (clazz.isImplClass || clazz == ArrayClass) parents
          else parents map mixinToImplClass
        }
      val decls1 = decls filter (sym =>
        if (clazz hasFlag INTERFACE) isInterfaceMember(sym)
        else (!sym.isType || sym.isClass))

      //if (!clazz.isPackageClass) System.out.println("Decls of "+clazz+" after explicitOuter = " + decls1);//DEBUG
      //if ((parents1 eq parents) && (decls1 eq decls)) tp
      //else
      ClassInfoType(parents1, decls1, clazz)
    case _ =>
      tp
  }

// Tree transformation --------------------------------------------------------------

  private class ChangeOwnerAndReturnTraverser(oldowner: Symbol, newowner: Symbol)
          extends ChangeOwnerTraverser(oldowner, newowner) {
    override def traverse(tree: Tree): unit = {
      tree match {
        case Return(expr) =>
          if (tree.symbol == oldowner) tree.symbol = newowner
        case _ =>
      }
      super.traverse(tree)
    }
  }

  private def ifaceMemberDef(tree: Tree): Tree =
    if (!tree.isDef || !isInterfaceMember(tree.symbol)) EmptyTree
    else if (needsImplMethod(tree.symbol)) DefDef(tree.symbol, vparamss => EmptyTree)
    else tree

  private def ifaceTemplate(templ: Template): Template =
    copy.Template(templ, templ.parents, templ.body map ifaceMemberDef)

  private def implMethodDef(tree: Tree, ifaceMethod: Symbol): Tree =
    implMethodMap.get(ifaceMethod) match {
      case Some(implMethod) =>
        tree.symbol = implMethod
        new ChangeOwnerAndReturnTraverser(ifaceMethod, implMethod)(tree)
      case None =>
        throw new Error("implMethod missing for " + ifaceMethod)
    }

  private def implMemberDef(tree: Tree): Tree =
    if (!tree.isDef || !isInterfaceMember(tree.symbol)) tree
    else if (needsImplMethod(tree.symbol)) implMethodDef(tree, tree.symbol)
    else EmptyTree

  private def implTemplate(clazz: Symbol, templ: Template): Template = atPos(templ.pos) {
    val templ1 = Template(templ.parents, templ.body map implMemberDef)
      .setPos(templ.pos)
      .setSymbol(clazz.newLocalDummy(templ.pos));
    new ChangeOwnerTraverser(templ.symbol.owner, clazz)(
      new ChangeOwnerTraverser(templ.symbol, templ1.symbol)(templ1))
  }

  def implClassDefs(trees: List[Tree]): List[Tree] = {
    val buf = new ListBuffer[Tree]
    for (val tree <- trees)
      tree match {
        case ClassDef(_, _, _, _, impl) =>
          if (tree.symbol.needsImplClass)
            buf += {
              val clazz = implClass(tree.symbol).initialize
              ClassDef(clazz, implTemplate(clazz, impl))
            }
        case _ =>
      }
    buf.toList
  }

  protected val mixinTransformer = new Transformer {
    override def transformStats(stats: List[Tree], exprOwner: Symbol): List[Tree] =
      (super.transformStats(stats, exprOwner) :::
       super.transformStats(implClassDefs(stats), exprOwner))
    override def transform(tree: Tree): Tree = {
      val tree1 = tree match {
        case ClassDef(mods, name, tparams, tpt, impl) =>
          if (tree.symbol.needsImplClass) {
            implClass(tree.symbol).initialize // to force lateDEFERRED flags
            copy.ClassDef(tree, mods | INTERFACE, name, tparams, tpt, ifaceTemplate(impl))
          }
          else tree
        case Template(parents, body) =>
          val parents1 = tree.symbol.owner.info.parents map (t => TypeTree(t) setPos tree.pos)
          copy.Template(tree, parents1, body)
        case This(_) =>
          if (tree.symbol.needsImplClass) {
            val impl = implClass(tree.symbol)
            var owner = currentOwner
            while (owner != tree.symbol && owner != impl) owner = owner.owner;
            if (owner == impl) This(impl) setPos tree.pos
            else tree
          } else tree
        case Super(qual, mix) =>
          val mix1 =
            if (mix == nme.EMPTY.toTypeName) mix
            else {
              val ps = atPhase(currentRun.erasurePhase) {
                tree.symbol.info.parents dropWhile (p => p.symbol.name != mix)
              }
              assert(!ps.isEmpty, tree);
              if (ps.head.symbol.needsImplClass) implClass(ps.head.symbol).name
              else mix
            }
          if (tree.symbol.needsImplClass) Super(implClass(tree.symbol), mix1) setPos tree.pos
          else copy.Super(tree, qual, mix1)
        case _ =>
          tree
      }
      super.transform(tree1)
    }
  }
}
/*
    val ensureNoEscapes = new TypeTraverser {
      def ensureNoEscape(sym: Symbol): unit = {
        if (sym.hasFlag(PRIVATE)) {
          var o = currentOwner;
          while (o != NoSymbol && o != sym.owner && !o.isLocal && !o.hasFlag(PRIVATE))
          o = o.owner
          if (o == sym.owner) sym.makeNotPrivate(base);
        }
      }
      def traverse(t: Type): TypeTraverser = {
        t match {
          case TypeRef(qual, sym, args) =>
            ensureNoEscape(sym)
            mapOver(t)
          case ClassInfoType(parents, decls, clazz) =>
            parents foreach { p => traverse; () }
            traverse(t.typeOfThis)
          case _ =>
            mapOver(t)
        }
        this
      }
    }

*/