typers.scala

来自「JAVA 语言的函数式编程扩展」· SCALA 代码 · 共 1,553 行 · 第 1/5 页

        case MethodType(formals, restpe) =>
          /*
          if (formals.exists(_.typeSymbol == ByNameParamClass) && formals.length != 1)
            error(pos, "methods with `=>'-parameter can be converted to function values only if they take no other parameters")
          if (formals exists (_.typeSymbol == RepeatedParamClass))
            error(pos, "methods with `*'-parameters cannot be converted to function values");
          */
          if (restpe.isDependent)
            error(pos, "method with dependent type "+tpe+" cannot be converted to function value");
          checkParamsConvertible(pos, restpe)
        case _ =>
      }
    }

    def checkRegPatOK(pos: Position, mode: Int) = 
      if ((mode & REGPATmode) == 0)
        error(pos, "no regular expression pattern allowed here\n"+
              "(regular expression patterns are only allowed in arguments to *-parameters)")

    /** Check that type of given tree does not contain local or private
     *  components.
     */
    object checkNoEscaping extends TypeMap {
      private var owner: Symbol = _
      private var scope: Scope = _
      private var hiddenSymbols: List[Symbol] = _

      /** Check that type <code>tree</code> does not refer to private
       *  components unless itself is wrapped in something private
       *  (<code>owner</code> tells where the type occurs).
       *
       *  @param owner ...
       *  @param tree  ...
       *  @return      ...
       */
      def privates[T <: Tree](owner: Symbol, tree: T): T =
        check(owner, EmptyScope, WildcardType, tree)

      /** Check that type <code>tree</code> does not refer to entities
       *  defined in scope <code>scope</code>.
       *
       *  @param scope ...
       *  @param pt    ...
       *  @param tree  ...
       *  @return      ...
       */
      def locals[T <: Tree](scope: Scope, pt: Type, tree: T): T =
        check(NoSymbol, scope, pt, tree)

      def check[T <: Tree](owner: Symbol, scope: Scope, pt: Type, tree: T): T = {
        this.owner = owner
        this.scope = scope
        hiddenSymbols = List()
        val tp1 = apply(tree.tpe)
        if (hiddenSymbols.isEmpty || inIDE) tree setType tp1 // @S: because arguments of classes are owned by the classes' owner
        else if (hiddenSymbols exists (_.isErroneous)) setError(tree)
        else if (isFullyDefined(pt)) tree setType pt //todo: eliminate
        else if (tp1.typeSymbol.isAnonymousClass) // todo: eliminate
          check(owner, scope, pt, tree setType tp1.typeSymbol.classBound)
        else if (owner == NoSymbol)
          tree setType packSymbols(hiddenSymbols.reverse, tp1)
        else { // privates
          val badSymbol = hiddenSymbols.head
          error(tree.pos,
                (if (badSymbol hasFlag PRIVATE) "private " else "") + badSymbol +
                " escapes its defining scope as part of type "+tree.tpe)
          setError(tree)
        }
      }

      def addHidden(sym: Symbol) =
        if (!(hiddenSymbols contains sym)) hiddenSymbols = sym :: hiddenSymbols

      override def apply(t: Type): Type = {
        def checkNoEscape(sym: Symbol) {
          if (sym.hasFlag(PRIVATE)) {
            var o = owner
            while (o != NoSymbol && o != sym.owner && 
                   !o.isLocal && !o.hasFlag(PRIVATE) &&
                   !o.privateWithin.hasTransOwner(sym.owner))
              o = o.owner
            if (o == sym.owner) addHidden(sym)
          } else if (sym.owner.isTerm && !sym.isTypeParameterOrSkolem) {
            var e = scope.lookupEntry(sym.name)
            var found = false
            while (!found && (e ne null) && e.owner == scope) {
              if (e.sym == sym) {
                found = true
                addHidden(sym)
              } else {
                e = scope.lookupNextEntry(e)
              }
            }
          }
        }
        mapOver(
          t match {
            case TypeRef(_, sym, args) => 
              checkNoEscape(sym)
              if (!hiddenSymbols.isEmpty && hiddenSymbols.head == sym && 
                  sym.isAliasType && sym.typeParams.length == args.length) {
                hiddenSymbols = hiddenSymbols.tail
                t.normalize
              } else t
            case SingleType(_, sym) => 
              checkNoEscape(sym)
              t
            case _ =>
              t
          })
      }
    }

    def reenterValueParams(vparamss: List[List[ValDef]]) {
      for (vparams <- vparamss)
        for (vparam <- vparams)
          vparam.symbol = context.scope enter vparam.symbol
    }

    def reenterTypeParams(tparams: List[TypeDef]): List[Symbol] =
      for (tparam <- tparams) yield {
        tparam.symbol = context.scope enter tparam.symbol
        tparam.symbol.deSkolemize 
      } 

    /** The qualifying class of a this or super with prefix <code>qual</code>.
     *
     *  @param tree ...
     *  @param qual ...
     *  @return     ...
     */
    def qualifyingClassContext(tree: Tree, qual: Name): Context = {
      if (qual.isEmpty) {
        if (context.enclClass.owner.isPackageClass) 
          error(tree.pos, tree+" can be used only in a class, object, or template")
        context.enclClass
      } else {
        var c = context.enclClass
        while (c != NoContext && c.owner.name != qual) c = c.outer.enclClass
        if (c == NoContext) error(tree.pos, qual+" is not an enclosing class")
        c
      }
    }

    /** The typer for an expression, depending on where we are. If we are before a superclass 
     *  call, this is a typer over a constructor context; otherwise it is the current typer.
     */  
    def constrTyperIf(inConstr: Boolean): Typer =  
      if (inConstr) newTyper(context.makeConstructorContext) else this

    /** The typer for a label definition. If this is part of a template we
     *  first have to enter the label definition.
     */
    def labelTyper(ldef: LabelDef): Typer = 
      if (ldef.symbol == NoSymbol) { // labeldef is part of template
        val typer1 = newTyper(context.makeNewScope(ldef, context.owner)(LabelScopeKind))
        typer1.enterLabelDef(ldef)
        typer1
      } else this

    final val xtypes = false

    /** Does the context of tree <code>tree</code> require a stable type?
     */
    private def isStableContext(tree: Tree, mode: Int, pt: Type) =  
      isNarrowable(tree.tpe) && ((mode & (EXPRmode | LHSmode)) == EXPRmode) && 
      (xtypes ||
      (pt.isStable ||
       (mode & QUALmode) != 0 && !tree.symbol.isConstant ||
       pt.typeSymbol.isAbstractType && pt.bounds.lo.isStable && !(tree.tpe <:< pt)))

    /** <p>
     *    Post-process an identifier or selection node, performing the following:
     *  </p>
     *  <ol>
     *  <!--(1)--><li>Check that non-function pattern expressions are stable</li>
     *  <!--(2)--><li>Check that packages and static modules are not used as values</li>
     *  <!--(3)--><li>Turn tree type into stable type if possible and required by context.</li>
     *  </ol>
     */
    private def stabilize(tree: Tree, pre: Type, mode: Int, pt: Type): Tree = {
      if (tree.symbol.hasFlag(OVERLOADED) && (mode & FUNmode) == 0)
        inferExprAlternative(tree, pt)
      val sym = tree.symbol
      if (tree.tpe.isError) tree
      else if ((mode & (PATTERNmode | FUNmode)) == PATTERNmode && tree.isTerm) { // (1)
        checkStable(tree)
      } else if ((mode & (EXPRmode | QUALmode)) == EXPRmode && !sym.isValue) { // (2)
        errorTree(tree, sym+" is not a value")
      } else {
        if (sym.isStable && pre.isStable && tree.tpe.typeSymbol != ByNameParamClass &&
            (isStableContext(tree, mode, pt) || sym.isModule && !sym.isMethod))
          tree.setType(singleType(pre, sym))
        else tree
      }
    }

    private def isNarrowable(tpe: Type): Boolean = tpe match {
      case TypeRef(_, _, _) | RefinedType(_, _) => true
      case ExistentialType(_, tpe1) => isNarrowable(tpe1)
      case AnnotatedType(_, tpe1, _) => isNarrowable(tpe1)
      case PolyType(_, tpe1) => isNarrowable(tpe1)
      case _ => !phase.erasedTypes
    } 

    private def stabilizedType(tree: Tree): Type = tree.tpe
/*{
      val sym = tree.symbol
      val res = tree match {
        case Ident(_) if (sym.isStable) =>
          val pre = if (sym.owner.isClass) sym.owner.thisType else NoPrefix 
          singleType(pre, sym)
        case Select(qual, _) if (qual.tpe.isStable && sym.isStable) =>
          singleType(qual.tpe, sym)
        case _ =>
          tree.tpe
      }
      res
    }
*/
    /**
     *  @param tree ...
     *  @param mode ...
     *  @param pt   ...
     *  @return     ...
     */
    def stabilizeFun(tree: Tree, mode: Int, pt: Type): Tree = {
      val sym = tree.symbol
      val pre = tree match {
        case Select(qual, _) => qual.tpe
        case _ => NoPrefix
      }
      if (tree.tpe.isInstanceOf[MethodType] && pre.isStable && sym.tpe.paramTypes.isEmpty &&
          (isStableContext(tree, mode, pt) || sym.isModule))
        tree.setType(MethodType(List(), singleType(pre, sym)))
      else tree
    }

    /** The member with given name of given qualifier tree */
    def member(qual: Tree, name: Name) = qual.tpe match {
      case ThisType(clazz) if (context.enclClass.owner.hasTransOwner(clazz)) =>
        qual.tpe.member(name)
      case _  =>
        if (phase.next.erasedTypes) qual.tpe.member(name)
        else qual.tpe.nonLocalMember(name)
    }      

    def silent(op: Typer => Tree): AnyRef /* in fact, TypeError or Tree */ = try {
      if (context.reportGeneralErrors) {
        val context1 = context.makeSilent(context.reportAmbiguousErrors)
        context1.undetparams = context.undetparams
        context1.savedTypeBounds = context.savedTypeBounds
        val typer1 = newTyper(context1)
        val result = op(typer1)
        context.undetparams = context1.undetparams
        context.savedTypeBounds = context1.savedTypeBounds
        result
      } else {
        op(this)
      }
    } catch {
      case ex: CyclicReference => throw ex
      case ex: TypeError => ex
    }

    /** Perform the following adaptations of expression, pattern or type `tree' wrt to 
     *  given mode `mode' and given prototype `pt':
     *  (0) Convert expressions with constant types to literals
     *  (1) Resolve overloading, unless mode contains FUNmode 
     *  (2) Apply parameterless functions
     *  (3) Apply polymorphic types to fresh instances of their type parameters and
     *      store these instances in context.undetparams, 
     *      unless followed by explicit type application.
     *  (4) Do the following to unapplied methods used as values:
     *  (4.1) If the method has only implicit parameters pass implicit arguments
     *  (4.2) otherwise, if `pt' is a function type and method is not a constructor,
     *        convert to function by eta-expansion,
     *  (4.3) otherwise, if the method is nullary with a result type compatible to `pt'
     *        and it is not a constructor, apply it to ()
     *  otherwise issue an error
     *  (5) Convert constructors in a pattern as follows:
     *  (5.1) If constructor refers to a case class factory, set tree's type to the unique
     *        instance of its primary constructor that is a subtype of the expected type.
     *  (5.2) If constructor refers to an exractor, convert to application of
     *        unapply or unapplySeq method.
     *
     *  (6) Convert all other types to TypeTree nodes.
     *  (7) When in TYPEmode but not FUNmode or HKmode, check that types are fully parameterized
     *      (7.1) In HKmode, higher-kinded types are allowed, but they must have the expected kind-arity
     *  (8) When in both EXPRmode and FUNmode, add apply method calls to values of object type.
     *  (9) If there are undetermined type variables and not POLYmode, infer expression instance
     *  Then, if tree's type is not a subtype of expected type, try the following adaptations:
     *  (10) If the expected type is Byte, Short or Char, and the expression
     *      is an integer fitting in the range of that type, convert it to that type. 
     *  (11) Widen numeric literals to their expected type, if necessary
     *  (12) When in mode EXPRmode, convert E to { E; () } if expected type is scala.Unit.
     *  (13) When in mode EXPRmode, apply a view
     *  If all this fails, error
     */
    protected def adapt(tree: Tree, mode: Int, pt: Type): Tree = tree.tpe match {
      case ct @ ConstantType(value) if ((mode & (TYPEmode | FUNmode)) == 0 && (ct <:< pt) && !inIDE) => // (0)
        copy.Literal(tree, value)
      case OverloadedType(pre, alts) if ((mode & FUNmode) == 0) => // (1)
        inferExprAlternative(tree, pt)
        adapt(tree, mode, pt)
      case PolyType(List(), restpe) => // (2)
        adapt(tree setType restpe, mode, pt)
      case TypeRef(_, sym, List(arg))
      if ((mode & EXPRmode) != 0 && sym == ByNameParamClass) => // (2)
        adapt(tree setType arg, mode, pt)
      case tr @ TypeRef(_, sym, _)