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

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author Gilles Dubochet
 */

package scala.tools.nsc
package transform

import symtab._
import Flags._
import scala.collection.{ mutable, immutable }
import scala.collection.mutable.ListBuffer
import scala.tools.nsc.util.FreshNameCreator

/** Translate expressions of the form reflect.Code.lift(exp)
 *  to the lifted "reflect trees" representation of exp.
 *  Also: mutable variables that are accessed from a local function are wrapped in refs.
 *
 *  @author Gilles Dubochet
 *  @author Martin Odersky
 *  @version 2.10
 */
abstract class LiftCode extends Transform with TypingTransformers {

  import global._                  // the global environment
  import definitions._             // standard classes and methods
  import typer.{typed, atOwner}    // methods to type trees

  val symbols: global.type = global

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

  def newTransformer(unit: CompilationUnit): Transformer =
    new Lifter(unit)

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

    /** Set of mutable local variables that are free in some inner method. */
    private val freeMutableVars: mutable.Set[Symbol] = new mutable.HashSet
    private val converted: mutable.Set[Symbol] = new mutable.HashSet // debug

    override def transformUnit(unit: CompilationUnit) {
      freeMutableVars.clear()
      freeLocalsTraverser(unit.body)
      atPhase(phase.next) {
        super.transformUnit(unit)
      }
      for (v <- freeMutableVars)
        assert(converted contains v, "unconverted: "+v+" in "+v.owner+" in unit "+unit)
    }

    override def transform(tree: Tree): Tree = {
      val sym = tree.symbol
      tree match {
        case Apply(lift, List(tree)) if sym == Code_lift =>
          //printTypings = true //debug
          val result = transform(localTyper.typedPos(tree.pos)(codify(tree)))
          //println("transformed = "+result) //debug
          //printTypings = false //debug
          result
        case ValDef(mods, name, tpt, rhs) if (freeMutableVars(sym)) =>
          val tpt1 = TypeTree(sym.tpe) setPos tpt.pos
          /* Creating a constructor argument if one isn't present. */
          val constructorArg = rhs match {
            case EmptyTree => gen.mkZero(atPhase(phase.prev)(sym.tpe))
            case _ => transform(rhs)
          }
          val rhs1 = typer.typedPos(rhs.pos) {
            /*util.errtrace("lifted rhs for "+tree+" in "+unit)*/ (
            Apply(Select(New(TypeTree(sym.tpe)), nme.CONSTRUCTOR), List(constructorArg)))
          }
          sym resetFlag MUTABLE
          sym removeAnnotation VolatileAttr
          converted += sym
          treeCopy.ValDef(tree, mods &~ MUTABLE, name, tpt1, rhs1)
        case Ident(name) if freeMutableVars(sym) =>
          localTyper.typedPos(tree.pos) {
            /*util.errtrace("lifting ")*/(Select(tree setType sym.tpe, nme.elem))
          }
        case _ =>
          super.transform(tree)
      }
    }

    /** todo: Treat embedded Code blocks by merging them into containing block
     *
     */
    class Reifier() {

      private val boundVars: mutable.Set[Symbol] = mutable.Set()

      // todo: review & rework
      // todo replace className by caseName in CaseClass once we have switched to nsc.
      def className(value: AnyRef): String = value match {
        case _ :: _ => "scala.$colon$colon"
        case MethodType(_, _) => "scala.reflect.runtime.Mirror.MethodType"
        case x: Product => "scala.reflect.runtime.Mirror." + x.productPrefix
        case _ => ""
      }

      // todo: review & rework
      def objectName(value: Any): String = value match {
        case Nil => "scala.collection.immutable.Nil"
        case EmptyTree => "scala.reflect.runtime.Mirror.EmptyTree"
        case NoSymbol => "scala.reflect.runtime.Mirror.NoSymbol"
        case definitions.RootClass => "scala.reflect.runtime.Mirror.definitions.RootClass"
        case NoPrefix => "scala.reflect.runtime.Mirror.NoPrefix"
        case NoType => "scala.reflect.runtime.Mirror.NoType"
        case _ => ""
      }

      /** Reify a free reference. The result will be either a mirror reference
       *  to a global value, or else a mirror Literal.
       */
      def reifyFree(tree: Tree): Tree =
        if (tree.symbol.hasFlag(MODULE) && tree.symbol.isStatic)
          reifiedPath(tree.symbol.fullName)
        else
          Apply(termPath("scala.reflect.runtime.Mirror.freeValue"), List(tree))

      /** Reify an arbitary value */
      def reify(value: Any): Tree = {
        //println("reifing "+value) //debug
        /*util.trace("reified "+value+" --> ")*/ {
          value match {
            case tree: DefTree =>
              boundVars += tree.symbol
              reify1(tree)
            case tree @ This(_) if !(boundVars contains tree.symbol) =>
              reifyFree(tree)
            case tree @ Ident(_) if !(boundVars contains tree.symbol) =>
              reifyFree(tree)
            case tree @ TypeTree() if tree.original != null =>
              reify(tree.original)
            // todo: should we also reify inferred types?
            case _ =>
              reify1(value)
          }
        }
      }

      /** Second part of reify */
      def reify1(value: Any): Tree = {
        def treatProduct(c: Product): Tree = {
          val fullname = objectName(c)
          if (fullname.length != 0)
            termPath(fullname)
          else {
            val fullname = className(c)
            if (fullname.length == 0) abort("don't know how to inject " + value + " of class " + value.getClass)
            val injectedArgs = new ListBuffer[Tree]
            for (i <- 0 until c.productArity)
              injectedArgs += reify(c.productElement(i))
            New(typePath(fullname), List(injectedArgs.toList))
          }
        }

        value match {
          case () => Literal(Constant(()))
          case x: String => Literal(Constant(x))
          case x: Boolean => Literal(Constant(x))
          case x: Byte => Literal(Constant(x))
          case x: Short => Literal(Constant(x))
          case x: Char => Literal(Constant(x))
          case x: Int => Literal(Constant(x))
          case x: Long => Literal(Constant(x))
          case x: Float => Literal(Constant(x))
          case x: Double => Literal(Constant(x))
          case x: Name => reifiedName(x)
          case c: Product => treatProduct(c)
          case _ =>
            abort("don't know how to inject " + value + " of class " + value.getClass)
        }
      }

     /** The reified version of given name */
      def reifiedName(name: Name) = {
        val fn = "scala.reflect.runtime.Mirror.new"+(if (name.isTypeName) "TypeName" else "TermName")
        Apply(termPath(fn), List(Literal(Constant(name.toString))))
      }

      /** A reified identifier with given name */
      def reifiedIdent(name: Name) =
        New(typePath("scala.reflect.runtime.Mirror.Ident"), List(List(reifiedName(name))))

      /** A reified selection over given qualifier and name */
      def reifiedSelect(qual: Tree, name: Name) =
        New(typePath("scala.reflect.runtime.Mirror.Select"), List(List(qual, reifiedName(name))))

      /** A reified path that selects definition with given fully qualified name */
      def reifiedPath(fullname: String): Tree = {
        val parts = fullname split "\\."
        val prefixParts = parts.init
        val lastName = parts.last
        if (prefixParts.isEmpty) reifiedIdent(lastName)
        else {
          val prefixTree = ((reifiedIdent(prefixParts.head): Tree) /: prefixParts.tail)(reifiedSelect(_, _))
          reifiedSelect(prefixTree, lastName)
        }
      }

      /** An (unreified) path that refers to definition with given fully qualified name
       *  @param mkName   Creator for last portion of name (either TermName or TypeName)
       */
      private def path(fullname: String, mkName: String => Name): Tree = {
        val parts = fullname split "\\."
        val prefixParts = parts.init
        val lastName = mkName(parts.last)
        if (prefixParts.isEmpty) Ident(lastName)
        else {
          val prefixTree = ((Ident(prefixParts.head): Tree) /: prefixParts.tail)(Select(_, _))
          Select(prefixTree, lastName)
        }
      }

      /** An (unreified) path that refers to term definition with given fully qualified name */
      def termPath(fullname: String) = path(fullname, newTermName)

      /** An (unreified) path that refers to type definition with given fully qualified name */
      def typePath(fullname: String) = path(fullname, newTypeName)
    }

    def codify(tree: Tree): Tree = /*util.trace("codified " + tree + " -> ")*/ {
      val targetType = definitions.CodeClass.primaryConstructor.info.paramTypes.head
      val arg = gen.mkAsInstanceOf(new Reifier().reify(tree), targetType, wrapInApply = false)
      New(TypeTree(appliedType(definitions.CodeClass.typeConstructor, List(tree.tpe))),
        List(List(arg)))
    }

    /**
     * PP: There is apparently some degree of overlap between the CAPTURED
     *  flag and the role being filled here.  I think this is how this was able
     *  to go for so long looking only at DefDef and Ident nodes, as bugs
     *  would only emerge under more complicated conditions such as #3855.
     *  I'll try to figure it all out, but if someone who already knows the
     *  whole story wants to fill it in, that too would be great.
     */
    private val freeLocalsTraverser = new Traverser {
      var currentMethod: Symbol = NoSymbol
      var maybeEscaping = false

      def withEscaping(body: => Unit) {
        val saved = maybeEscaping
        maybeEscaping = true
        try body
        finally maybeEscaping = saved
      }

      override def traverse(tree: Tree) = tree match {
        case DefDef(_, _, _, _, _, _) =>
          val lastMethod = currentMethod
          currentMethod = tree.symbol
          try super.traverse(tree)
          finally currentMethod = lastMethod
        /** A method call with a by-name parameter represents escape. */
        case Apply(fn, args) if fn.symbol.paramss.nonEmpty =>
          traverse(fn)
          (fn.symbol.paramss.head, args).zipped foreach { (param, arg) =>
            if (param.tpe != null && isByNameParamType(param.tpe))
              withEscaping(traverse(arg))
            else
              traverse(arg)
          }
        /** The rhs of a closure represents escape. */
        case Function(vparams, body) =>
          vparams foreach traverse
          withEscaping(traverse(body))

        /**
         * The appearance of an ident outside the method where it was defined or
         *  anytime maybeEscaping is true implies escape.
         */
        case Ident(_) =>
          val sym = tree.symbol
          if (sym.isVariable && sym.owner.isMethod && (maybeEscaping || sym.owner != currentMethod)) {
            freeMutableVars += sym
            val symTpe = sym.tpe
            val symClass = symTpe.typeSymbol
            atPhase(phase.next) {
              def refType(valueRef: Map[Symbol, Symbol], objectRefClass: Symbol) =
                if (isValueClass(symClass)) valueRef(symClass).tpe
                else appliedType(objectRefClass.typeConstructor, List(symTpe))

              sym updateInfo (
                if (sym.hasAnnotation(VolatileAttr)) refType(volatileRefClass, VolatileObjectRefClass)
                else refType(refClass, ObjectRefClass))
            }
          }
        case _ =>
          super.traverse(tree)
      }
    }
  }
}

// case EmptyTree =>
// case LiftPoint(tree) =>
// case PackageDef(pid, stats) =>
// case ClassDef(mods, name, tparams, impl) =>
// case ValDef(mods, name, tpt, rhs) =>
// case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
// case TypeDef(mods, name, tparams, rhs) =>
// case LabelDef(name, params, rhs) =>
// case Template(parents, self, body) =>
// case Block(stats, expr) =>
// case ArrayValue(elemtpt, trees) =>
// case Assign(lhs, rhs) =>
// case If(cond, thenp, elsep) =>
// case Match(selector, cases) =>
// case Return(expr) =>
// case Try(block, catches, finalizer) =>
// case Throw(expr) =>
// case New(tpt) =>
// case Typed(expr, tpt) =>
// case TypeApply(fun, args) =>
// case Apply(fun, args) =>
// case Super(qual, mix) =>
// case This(qual) =>
// case Select(qualifier, selector) =>
// case Ident(name) =>
// case Literal(value) =>
// case TypeTree() =>
// /* Pattern matching */
// case CaseDef(pat, guard, body) =>
// case Alternative(trees) =>
// case Star(elem) =>
// case Bind(name, body) =>