New phase: PrivateToStatic

Make private methods in traits static, so that we do not need
to give a default for them.

Author: odersky

src/dotty/tools/dotc/Compiler.scala

@@ -57,7 +57,8 @@ class Compiler {
            new Constructors),
       List(new LambdaLift,
            new Flatten,
-           new RestoreScopes)
+           new RestoreScopes),
+      List(new PrivateToStatic)
     )
 
   var runId = 1

src/dotty/tools/dotc/ast/tpd.scala

@@ -263,7 +263,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       case _ =>
         false
     }
-    try test
+    try test || tp.symbol.is(JavaStatic)
     catch { // See remark in SymDenotations#accessWithin
       case ex: NotDefinedHere => test(ctx.addMode(Mode.FutureDefsOK))
     }

src/dotty/tools/dotc/core/Flags.scala

@@ -512,6 +512,9 @@ object Flags {
   /** Labeled `private` or `final` */
   final val PrivateOrFinal = Private | Final
 
+  /** A private method */
+  final val PrivateMethod = allOf(Private, Method)
+
   /** A type parameter with synthesized name */
   final val ExpandedTypeParam = allOf(ExpandedName, TypeParam)
 

src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -36,7 +36,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   override def nameString(name: Name): String = name.decode.toString
 
   override protected def simpleNameString(sym: Symbol): String =
-    sym.originalName.decode.toString
+    sym.name.decode.toString
 
   override protected def fullNameOwner(sym: Symbol) = {
     val owner = super.fullNameOwner(sym)
@@ -222,7 +222,9 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         "`" ~ toText(id.name) ~ "`"
       case Ident(name) =>
         tree.typeOpt match {
-          case tp: NamedType if name != nme.WILDCARD => toTextPrefix(tp.prefix) ~ selectionString(tp)
+          case tp: NamedType if name != nme.WILDCARD =>
+            val pre = if (tp.symbol is JavaStatic) tp.prefix.widen else tp.prefix
+            toTextPrefix(pre) ~ selectionString(tp)
           case _ => toText(name)
         }
       case tree @ Select(qual, name) =>

src/dotty/tools/dotc/transform/PrivateToStatic.scala

@@ -0,0 +1,90 @@
+package dotty.tools.dotc
+package transform
+
+import core._
+import DenotTransformers.SymTransformer
+import Contexts.Context
+import Symbols._
+import Scopes._
+import Flags._
+import StdNames._
+import SymDenotations._
+import Types._
+import collection.mutable
+import TreeTransforms._
+import Decorators._
+import ast.Trees._
+import TreeTransforms.TransformerInfo
+
+/** The preceding lambda lift and flatten phases move symbols to different scopes
+ *  and rename them. This miniphase cleans up afterwards and makes sure that all
+ *  class scopes contain the symbols defined in them.
+ */
+class PrivateToStatic extends MiniPhase with SymTransformer { thisTransform =>
+  import ast.tpd._
+  override def phaseName = "privateToStatic"
+  override def relaxedTyping = true
+
+  private val Immovable = Deferred | Accessor | JavaStatic
+
+  def shouldBeStatic(sd: SymDenotation)(implicit ctx: Context) =
+    sd.current(ctx.withPhase(thisTransform)).asInstanceOf[SymDenotation]
+      .is(PrivateMethod, butNot = Immovable) &&
+    (sd.owner.is(Trait) || sd.is(NotJavaPrivate))
+
+  override def transformSym(sd: SymDenotation)(implicit ctx: Context): SymDenotation =
+    if (shouldBeStatic(sd)) {
+      val mt @ MethodType(pnames, ptypes) = sd.info
+      sd.copySymDenotation(
+        initFlags = sd.flags | JavaStatic,
+        info = MethodType(nme.SELF :: pnames, sd.owner.thisType :: ptypes, mt.resultType))
+    }
+    else sd
+
+  val treeTransform = new Transform(NoSymbol)
+
+  class Transform(thisParam: Symbol) extends TreeTransform {
+    def phase = thisTransform
+    override def treeTransformPhase = thisTransform.next
+
+    override def prepareForDefDef(tree: DefDef)(implicit ctx: Context) =
+      if (shouldBeStatic(tree.symbol)) {
+        val selfParam = ctx.newSymbol(tree.symbol, nme.SELF, Param, tree.symbol.owner.thisType, coord = tree.pos)
+        new Transform(selfParam)
+      }
+      else this
+
+    override def transformDefDef(tree: DefDef)(implicit ctx: Context, info: TransformerInfo) =
+      if (shouldBeStatic(tree.symbol)) {
+        val thisParamDef = ValDef(thisParam.asTerm)
+        val vparams :: Nil = tree.vparamss
+        cpy.DefDef(tree)(
+          mods = tree.mods | JavaStatic,
+          vparamss = (thisParamDef :: vparams) :: Nil)
+      }
+      else tree
+
+    override def transformThis(tree: This)(implicit ctx: Context, info: TransformerInfo) =
+      if (shouldBeStatic(ctx.owner.enclosingMethod)) ref(thisParam).withPos(tree.pos)
+      else tree
+
+    override def transformApply(tree: Apply)(implicit ctx: Context, info: TransformerInfo) =
+      tree.fun match {
+        case fun @ Select(qual, name) if shouldBeStatic(fun.symbol) =>
+          println(i"mapping $tree to ${cpy.Ident(fun)(name)} (${qual :: tree.args}%, %)")
+          cpy.Apply(tree)(ref(fun.symbol).withPos(fun.pos), qual :: tree.args)
+        case _ =>
+          tree
+      }
+
+    override def transformClosure(tree: Closure)(implicit ctx: Context, info: TransformerInfo) =
+      tree.meth match {
+        case meth @ Select(qual, name) if shouldBeStatic(meth.symbol) =>
+          cpy.Closure(tree)(
+            env = qual :: tree.env,
+            meth = ref(meth.symbol).withPos(meth.pos))
+        case _ =>
+          tree
+    }
+  }
+}

tests/pos/CoderTrait.scala

@@ -0,0 +1,63 @@
+import collection.mutable.HashMap
+
+trait CoderTrait {
+
+  val words: List[String]
+
+  (2 -> "ABC",  new ArrowAssoc('3') -> "DEF")
+
+  private val mnemonics = Map(
+      '2' -> "ABC", '3' -> "DEF", '4' -> "GHI", '5' -> "JKL",
+      '6' -> "MNO", '7' -> "PQRS", '8' -> "TUV", '9' -> "WXYZ")
+
+
+  ('1', "1") match {
+    case (digit, str) => true
+    case _ => false
+  }
+
+  /** Invert the mnemonics map to give a map from chars 'A' ... 'Z' to '2' ... '9' */
+  private val charCode0: Map[Char, Char] = mnemonics withFilter {
+    case (digit, str) => true
+    case _ => false
+  } flatMap { x$1 =>
+    x$1 match {
+      case (digit, str) => str map (ltr => ltr -> digit)
+    }
+  }
+
+  private val charCode: Map[Char, Char] =
+    for ((digit, str) <- mnemonics; ltr <- str) yield ltr -> digit
+
+    /** Maps a word to the digit string it can represent */
+  private def wordCode(word: String): String = word map charCode
+
+  /** A map from digit strings to the words that represent them */
+  private val wordsForNum: Map[String, List[String]] =
+    words groupBy wordCode withDefaultValue Nil
+
+  /** All ways to encode a number as a list of words */
+  def encode(number: String): Set[List[String]] =
+    if (number.isEmpty) Set(Nil)
+    else {
+      for {
+        splitPoint <- 1 to number.length
+        word <- wordsForNum(number take splitPoint)
+        rest <- encode(number drop splitPoint)
+      } yield word :: rest
+    }.toSet
+
+  /** Maps a number to a list of all word phrases that can represent it */
+  def translate(number: String): Set[String] = encode(number) map (_ mkString " ")
+
+}
+
+object Coder {
+  def main(args : Array[String]) : Unit = {
+    val coder = new CoderTrait {
+      val words = List("Scala", "sobls", "Python", "Ruby", "C", "A", "rocks", "sucks", "works", "Racka")
+    }
+//    println(coder.wordsForNum)
+    println(coder.translate("7225276257"))
+  }
+}

tests/pos/privates.scala

@@ -0,0 +1,9 @@
+trait Test {
+
+  private val x = 2
+
+  private def foo() = x * x
+
+  private def bar() = foo()
+
+}

tests/pos/traits.scala

@@ -0,0 +1,25 @@
+trait B {
+
+  val z: Int
+
+}
+
+trait T {
+
+  var x = 2
+
+  private var xp = 2
+
+  val y = 3
+
+  private val yp = 3
+
+  val z = 4
+
+  x = 4
+
+  xp = 4
+
+}
+
+class C extends T