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

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

package scala.tools.nsc.transform

import symtab.Flags._
import scala.collection.mutable.HashMap
import scala.tools.nsc.util.HashSet

/*<export>*/
/** - uncurry all symbol and tree types (@see UnCurryPhase)
 *  - for every curried parameter list:  (ps_1) ... (ps_n) ==> (ps_1, ..., ps_n)
 *  - for every curried application: f(args_1)...(args_n) ==> f(args_1, ..., args_n)
 *  - for every type application: f[Ts] ==> f[Ts]() unless followed by parameters
 *  - for every use of a parameterless function: f ==> f()  and  q.f ==> q.f()
 *  - for every def-parameter:  x: => T ==> x: () => T
 *  - for every use of a def-parameter: x ==> x.apply()
 *  - for every argument to a def parameter `x: => T':
 *      if argument is not a reference to a def parameter:
 *        convert argument `e' to (expansion of) `() => e'
 *  - for every repated parameter `x: T*' --> x: Seq[a].
 *  - for every argument list that corresponds to a repeated parameter
 *       (a_1, ..., a_n) => (Seq(a_1, ..., a_n))
 *  - for every argument list that is an escaped sequence
 *       (a_1:_*) => (a_1)g
 *  - convert implicit method types to method types
 *  - convert non-trivial catches in try statements to matches
 *  - convert non-local returns to throws with enclosing try statements.
 */
/*</export>*/
abstract class UnCurry extends InfoTransform with TypingTransformers {
  import global._                  // the global environment
  import definitions._             // standard classes and methods
  import posAssigner.atPos         // for filling in tree positions

  val phaseName: String = "uncurry"

  def newTransformer(unit: CompilationUnit): Transformer = new UnCurryTransformer(unit)
  override def changesBaseClasses = false

// ------ Type transformation --------------------------------------------------------

  private val uncurry: TypeMap = new TypeMap {
    def apply(tp: Type): Type = tp match {
      case MethodType(formals, MethodType(formals1, restpe)) =>
        apply(MethodType(formals ::: formals1, restpe))
      case mt: ImplicitMethodType =>
        apply(MethodType(mt.paramTypes, mt.resultType))
      case PolyType(List(), restpe) =>
        apply(MethodType(List(), restpe))
      case PolyType(tparams, restpe) =>
        PolyType(tparams, apply(MethodType(List(), restpe)))
      case TypeRef(pre, sym, List(arg1, arg2)) if (arg1.symbol == ByNameParamClass) =>
        assert(sym == FunctionClass(1))
        apply(typeRef(pre, definitions.ByNameFunctionClass, List(arg1.typeArgs(0), arg2)))
      case TypeRef(pre, sym, List(arg)) if (sym == ByNameParamClass) =>
        apply(functionType(List(), arg))
      case TypeRef(pre, sym, args) if (sym == RepeatedParamClass) =>
        apply(rawTypeRef(pre, SeqClass, args))
      case _ =>
        mapOver(tp)
    }
  }

  private val uncurryType = new TypeMap {
    def apply(tp: Type): Type = tp match {
      case ClassInfoType(parents, decls, clazz) =>
        val parents1 = List.mapConserve(parents)(uncurry)
        if (parents1 eq parents) tp
        else ClassInfoType(parents1, decls, clazz)
      case PolyType(_, _) =>
        mapOver(tp)
      case _ =>
        tp
    }
  }

  /** - return symbol's transformed type,
   *  - if symbol is a def parameter with transformed type T, return () => T
   */
  def transformInfo(sym: Symbol, tp: Type): Type =
    if (sym.isType) uncurryType(tp) else uncurry(tp)

  class UnCurryTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {

    private var needTryLift = false
    private var inPattern = false
    private var inConstructorFlag = 0L
    private var byNameArgs = new HashSet[Tree](16)

    override def transform(tree: Tree): Tree = try { //debug
      postTransform(mainTransform(tree))
    } catch {
      case ex: Throwable =>
        System.out.println("exception when traversing " + tree)
        throw ex
    }

    /* Is tree a reference `x' to a call by name parameter that neeeds to be converted to
     * x.apply()? Note that this is not the case if `x' is used as an argument to another
     * call by name parameter.
     */
    def isByNameRef(tree: Tree): boolean =
      tree.isTerm && tree.hasSymbol &&
      tree.symbol.tpe.symbol == ByNameParamClass &&
      !byNameArgs.contains(tree)

    /** Uncurry a type of a tree node.
     *  This function is sensitive to whether or not we are in a pattern -- when in a pattern
     *  additional parameter sections of a case class are skipped.
     */
    def uncurryTreeType(tp: Type): Type = tp match {
      case MethodType(formals, MethodType(formals1, restpe)) if (inPattern) =>
        uncurryTreeType(MethodType(formals, restpe))
      case _ =>
        uncurry(tp)
    }

// ------- Handling non-local returns -------------------------------------------------

    /** The type of a non-local return expression for given method */
    private def nonLocalReturnExceptionType(meth: Symbol) =
      appliedType(
        NonLocalReturnExceptionClass.typeConstructor,
        List(meth.tpe.finalResultType))

    /** A hashmap from method symbols to non-local return keys */
    private val nonLocalReturnKeys = new HashMap[Symbol, Symbol]

    /** Return non-local return key for given method */
    private def nonLocalReturnKey(meth: Symbol) = nonLocalReturnKeys.get(meth) match {
      case Some(k) => k
      case None =>
        val k = meth.newValue(meth.pos, unit.fresh.newName("nonLocalReturnKey"))
          .setFlag(SYNTHETIC).setInfo(ObjectClass.tpe)
        nonLocalReturnKeys(meth) = k
        k
    }

    /** Generate a non-local return throw with given return expression from given method.
     *  I.e. for the method's non-local return key, generate:
     *
     *    throw new NonLocalReturnException(key, expr)
     */
    private def nonLocalReturnThrow(expr: Tree, meth: Symbol) =
      localTyper.typed {
        Throw(
          New(
            TypeTree(nonLocalReturnExceptionType(meth)),
            List(List(Ident(nonLocalReturnKey(meth)), expr))))
      }

    /** Transform (body, key) to:
     *
     *  {
     *    val key = new Object()
     *    try {
     *      body
     *    } catch {
     *      case ex: NonLocalReturnException =>
     *        if (ex.key().eq(key)) ex.value()
     *        else throw ex
     *    }
     *  }
     */
    private def nonLocalReturnTry(body: Tree, key: Symbol, meth: Symbol) = {
      localTyper.typed {
        val extpe = nonLocalReturnExceptionType(meth)
        val ex = meth.newValue(body.pos, nme.ex) setInfo extpe
        val pat = Bind(ex, Typed(Ident(nme.WILDCARD), TypeTree(extpe)))
        val rhs =
          If(
            Apply(
              Select(
                Apply(Select(Ident(ex), "key"), List()),
                Object_eq),
              List(Ident(key))),
            Apply(Select(Ident(ex), "value"), List()),
            Throw(Ident(ex)));
        val keyDef = ValDef(key, New(TypeTree(ObjectClass.tpe), List(List())))
        val tryCatch = Try(body, List(CaseDef(pat, EmptyTree, rhs)), EmptyTree)
        Block(List(keyDef), tryCatch)
      }
    }

// ------ Transforming anonymous functions and by-name-arguments ----------------

    /*  Transform a function node (x_1,...,x_n) => body of type FunctionN[T_1, .., T_N, R] to
     *
     *    class $anon() extends Object() with FunctionN[T_1, .., T_N, R] with ScalaObject {
     *      def apply(x_1: T_1, ..., x_N: T_n): R = body
     *    }
     *    new $anon()
     *
     *  transform a function node (x => body) of type PartialFunction[T, R] where
     *    body = x match { case P_i if G_i => E_i }_i=1..n
     *  to:
     *
     *    class $anon() extends Object() with PartialFunction[T, R] with ScalaObject {
     *      def apply(x: T): R = body;
     *      def isDefinedAt(x: T): boolean = x match {
     *        case P_1 if G_1 => true
     *        ...
     *        case P_n if G_n => true
     *        case _ => false
     *      }
     *    }
     *    new $anon()
     *
     *  However, if one of the patterns P_i if G_i is a default pattern, generate instead
     *
     *      def isDefinedAt(x: T): boolean = true
     */
    def transformFunction(fun: Function): Tree = {
      val anonClass = fun.symbol.owner.newAnonymousFunctionClass(fun.pos)
        .setFlag(FINAL | SYNTHETIC | inConstructorFlag)
      val formals = fun.tpe.typeArgs.init
      val restpe = fun.tpe.typeArgs.last
      anonClass setInfo ClassInfoType(
        List(ObjectClass.tpe, fun.tpe, ScalaObjectClass.tpe), newScope, anonClass);
      val applyMethod = anonClass.newMethod(fun.pos, nme.apply)
        .setFlag(FINAL).setInfo(MethodType(formals, restpe));
      anonClass.info.decls enter applyMethod;
      for (val vparam <- fun.vparams) vparam.symbol.owner = applyMethod;
      new ChangeOwnerTraverser(fun.symbol, applyMethod).traverse(fun.body);
      var members = List(
        DefDef(Modifiers(FINAL), nme.apply, List(), List(fun.vparams), TypeTree(restpe), fun.body)
          setSymbol applyMethod);
      if (fun.tpe.symbol == PartialFunctionClass) {
        val isDefinedAtMethod = anonClass.newMethod(fun.pos, nme.isDefinedAt)
          .setFlag(FINAL).setInfo(MethodType(formals, BooleanClass.tpe))
        anonClass.info.decls enter isDefinedAtMethod
        def idbody(idparam: Symbol) = fun.body match {
          case Match(_, cases) =>
            val substParam = new TreeSymSubstituter(List(fun.vparams.head.symbol), List(idparam));
            def transformCase(cdef: CaseDef): CaseDef =
              substParam(
                resetAttrs(
                  CaseDef(cdef.pat.duplicate, cdef.guard.duplicate, Literal(true))))
            if (cases exists treeInfo.isDefaultCase) Literal(true)
            else
              Match(
                Ident(idparam),
                (cases map transformCase) :::
                   List(CaseDef(Ident(nme.WILDCARD), EmptyTree, Literal(false))))
        }
        members = DefDef(isDefinedAtMethod, vparamss => idbody(vparamss.head.head)) :: members;
      }
      localTyper.typed {
        atPos(fun.pos) {
          Block(
            List(ClassDef(anonClass, List(List()), List(List()), members)),
            Typed(
              New(TypeTree(anonClass.tpe), List(List())),
              TypeTree(fun.tpe)))
        }
      }
    }

    def transformArgs(pos: PositionType, args: List[Tree], formals: List[Type]) = {
      if (formals.isEmpty) {
        assert(args.isEmpty); List()
      } else {
        val args1 =
          formals.last match {
            case TypeRef(pre, sym, List(elempt)) if (sym == RepeatedParamClass) =>
              def mkArrayValue(ts: List[Tree]) =
                atPos(pos)(ArrayValue(TypeTree(elempt), ts) setType formals.last);

              if (args.isEmpty)
                List(mkArrayValue(args))
              else {
                val suffix = args.last match {
                  case Typed(arg, Ident(name)) if name == nme.WILDCARD_STAR.toTypeName =>
                    arg setType seqType(arg.tpe)
                  case _ =>
                    mkArrayValue(args.drop(formals.length - 1))
                }
                args.take(formals.length - 1) ::: List(suffix)
              }
            case _ => args
          }
        List.map2(formals, args1) { (formal, arg) =>
          if (formal.symbol != ByNameParamClass) {
            arg
          } else if (isByNameRef(arg)) {
            byNameArgs.addEntry(arg)
            arg setType functionType(List(), arg.tpe)
          } else {
            val fun = localTyper.typed(
              Function(List(), arg) setPos arg.pos).asInstanceOf[Function];
            new ChangeOwnerTraverser(currentOwner, fun.symbol).traverse(arg);
            transformFunction(fun)
          }
        }
      }
    }

// ------ The tree transformers --------------------------------------------------------

    def mainTransform(tree: Tree): Tree = {

      def withNeedLift(needLift: Boolean)(f: => Tree): Tree = {
        val savedNeedTryLift = needTryLift
        needTryLift = needLift
        val t = f
        needTryLift = savedNeedTryLift
        t
      }

      def withInConstructorFlag(inConstructorFlag: long)(f: => Tree): Tree = {
        val savedInConstructorFlag = this.inConstructorFlag
        this.inConstructorFlag = inConstructorFlag
        val t = f
        this.inConstructorFlag = savedInConstructorFlag
        t
      }

      tree match {
        case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
          withNeedLift(false) {
            if (tree.symbol.isConstructor) {
              atOwner(tree.symbol) {
                val rhs1 = rhs match {
                  case Block(stat :: stats, expr) =>
                    copy.Block(
                      rhs,
                      withInConstructorFlag(INCONSTRUCTOR) { transform(stat) } :: transformTrees(stats),
                      transform(expr));
                  case _ =>
                    withInConstructorFlag(INCONSTRUCTOR) { transform(rhs) }
                }
                copy.DefDef(
                  tree, mods, name, transformAbsTypeDefs(tparams),
                  transformValDefss(vparamss), transform(tpt), rhs1)
              }
            } else {
              super.transform(tree)
            }
          }

        case ValDef(_, _, _, rhs)
          if (!tree.symbol.owner.isSourceMethod) =>
            withNeedLift(true) { super.transform(tree) }

        case Apply(Select(Block(List(), Function(vparams, body)), nme.apply), args) =>
          // perform beta-reduction; this helps keep view applications small
          withNeedLift(true) {
            mainTransform(new TreeSubstituter(vparams map (.symbol), args).transform(body))
          }

        case Apply(Select(Function(vparams, body), nme.apply), args) =>
          // perform beta-reduction; this helps keep view applications small
          withNeedLift(true) {
            mainTransform(new TreeSubstituter(vparams map (.symbol), args).transform(body))
          }

        case Apply(fn, args) =>
          if (settings.noassertions.value &&
              fn.symbol != null &&
              (fn.symbol.name == nme.assert_ || fn.symbol.name == nme.assume_) &&
              fn.symbol.owner == PredefModule.moduleClass) {
            Literal(()).setPos(tree.pos).setType(UnitClass.tpe)
          } else {
            withNeedLift(true) {
              val formals = fn.tpe.paramTypes;
              copy.Apply(tree, transform(fn), transformTrees(transformArgs(tree.pos, args, formals)))
            }
          }

        case Assign(Select(_, _), _) =>
          withNeedLift(true) { super.transform(tree) }

        case Try(block, catches, finalizer) =>
          if (needTryLift) {
            if (settings.debug.value)
              log("lifting try at: " + unit.position(tree.pos));

            val sym = currentOwner.newMethod(tree.pos, unit.fresh.newName("liftedTry"));
            sym.setInfo(MethodType(List(), tree.tpe));
            new ChangeOwnerTraverser(currentOwner, sym).traverse(tree);

            transform(localTyper.typed(atPos(tree.pos)(
              Block(List(DefDef(sym, List(List()), tree)),
                    Apply(Ident(sym), Nil)))))
          } else
            super.transform(tree)

        case CaseDef(pat, guard, body) =>
          inPattern = true
          val pat1 = transform(pat)
          inPattern = false
          copy.CaseDef(tree, pat1, transform(guard), transform(body))

        case fun @ Function(_, _) =>
          mainTransform(transformFunction(fun))

        case Template(_, _) =>
          withInConstructorFlag(0) { super.transform(tree) }

        case _ =>
          val tree1 = super.transform(tree)
          if (isByNameRef(tree1))
            localTyper.typed(atPos(tree1.pos)(
              Apply(Select(tree1 setType functionType(List(), tree1.tpe), nme.apply), List())))
          else tree1;
      }
    } setType uncurryTreeType(tree.tpe)

    def postTransform(tree: Tree): Tree = atPhase(phase.next) {
      def applyUnary(tree: Tree): Tree =
        if (tree.symbol.isMethod && (!tree.tpe.isInstanceOf[PolyType] || tree.tpe.typeParams.isEmpty)) {
          if (!tree.tpe.isInstanceOf[MethodType]) tree.tpe = MethodType(List(), tree.tpe);
          atPos(tree.pos)(Apply(tree, List()) setType tree.tpe.resultType)
        } else if (tree.isType && !tree.isInstanceOf[TypeTree]) {
          TypeTree(tree.tpe) setPos tree.pos
        } else {
          tree
        }
      tree match {
        case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
          val rhs1 = nonLocalReturnKeys.get(tree.symbol) match {
            case None => rhs
            case Some(k) => atPos(rhs.pos)(nonLocalReturnTry(rhs, k, tree.symbol))
          }
          copy.DefDef(tree, mods, name, tparams, List(List.flatten(vparamss)), tpt, rhs1)
        case Try(body, catches, finalizer) =>
          if (catches forall treeInfo.isCatchCase) tree
          else {
            val exname = unit.fresh.newName("ex$")
            val cases =
              if ((catches exists treeInfo.isDefaultCase) || (catches.last match {  // bq: handle try { } catch { ... case ex:Throwable => ...}
                    case CaseDef(Typed(Ident(nme.WILDCARD), tpt), EmptyTree, _) if (tpt.tpe =:= ThrowableClass.tpe) =>
                      true
                    case CaseDef(Bind(_, Typed(Ident(nme.WILDCARD), tpt)), EmptyTree, _) if (tpt.tpe =:= ThrowableClass.tpe) =>
                      true
                    case _ =>
                      false
                  })) catches
              else catches ::: List(CaseDef(Ident(nme.WILDCARD), EmptyTree, Throw(Ident(exname))));
            val catchall =
              atPos(tree.pos) {
                CaseDef(
                  Bind(exname, Ident(nme.WILDCARD)),
                  EmptyTree,
                  Match(Ident(exname), cases))
              }
            if (settings.debug.value) log("rewrote try: " + catches + " ==> " + catchall);
            val catches1 = localTyper.typedCases(
              tree, List(catchall), ThrowableClass.tpe, WildcardType);
            copy.Try(tree, body, catches1, finalizer)
          }
        case Apply(Apply(fn, args), args1) =>
          copy.Apply(tree, fn, args ::: args1)
        case Ident(name) =>
          if (name == nme.WILDCARD_STAR.toTypeName)
            unit.error(tree.pos, " argument does not correspond to `*'-parameter");
          applyUnary(tree);
        case Select(qual, name) =>
          /* Function1.apply to ByNameFunction.apply if qualifier is a ByNameFunction */
          if (qual.tpe.symbol == ByNameFunctionClass) {
            assert(tree.symbol.name == nme.apply && tree.symbol.owner == FunctionClass(1), tree.symbol)
            tree.symbol = getMember(ByNameFunctionClass, nme.apply)
          }
          applyUnary(tree)
        case TypeApply(_, _) =>
          applyUnary(tree)
        case Return(expr) if (tree.symbol != currentOwner.enclMethod) =>
          if (settings.debug.value) log("non local return in "+tree.symbol+" from "+currentOwner.enclMethod)
          atPos(tree.pos)(nonLocalReturnThrow(expr, tree.symbol))
        case _ =>
          tree
      }
    }
  }
}