17 files changed, 114 insertions, 27 deletions
diff --git a/src/dotty/tools/dotc/Driver.scala b/src/dotty/tools/dotc/Driver.scala
index fd2b776f8..892e4cf7d 100644
--- a/src/dotty/tools/dotc/Driver.scala
+++ b/src/dotty/tools/dotc/Driver.scala
@@ -2,7 +2,7 @@ package dotty.tools.dotc
 
 import config.CompilerCommand
 import core.Contexts.{Context, ContextBase}
-import core.DotClass
+import util.DotClass
 import reporting._
 
 abstract class Driver extends DotClass {
diff --git a/src/dotty/tools/dotc/ast/Trees.scala b/src/dotty/tools/dotc/ast/Trees.scala
index 13f7d6f18..96a91654d 100644
--- a/src/dotty/tools/dotc/ast/Trees.scala
+++ b/src/dotty/tools/dotc/ast/Trees.scala
@@ -11,7 +11,7 @@ import collection.immutable.IndexedSeq
 import collection.mutable.ListBuffer
 import parsing.Tokens.Token
 import printing.Printer
-import util.Stats
+import util.{Stats, Attachment, DotClass}
 import annotation.unchecked.uncheckedVariance
 
 object Trees {
@@ -29,7 +29,7 @@ object Trees {
 
   /** A base class for things that have positions (currently: modifiers and trees)
    */
-  abstract class Positioned extends DotClass with Product {
+  abstract class Positioned extends Attachment.Container with Product {
 
     private[this] var curPos: Position = _
 
diff --git a/src/dotty/tools/dotc/config/CompilerCommand.scala b/src/dotty/tools/dotc/config/CompilerCommand.scala
index f4c6ea014..ec8b17b0d 100644
--- a/src/dotty/tools/dotc/config/CompilerCommand.scala
+++ b/src/dotty/tools/dotc/config/CompilerCommand.scala
@@ -5,7 +5,7 @@ package config
 import java.io.File
 import Settings._
 import core.Contexts._
-import core.DotClass
+import util.DotClass
 import Properties._
 
 object CompilerCommand extends DotClass {
diff --git a/src/dotty/tools/dotc/core/Denotations.scala b/src/dotty/tools/dotc/core/Denotations.scala
index 19d80db18..5ca53b04e 100644
--- a/src/dotty/tools/dotc/core/Denotations.scala
+++ b/src/dotty/tools/dotc/core/Denotations.scala
@@ -90,7 +90,7 @@ object Denotations {
    *
    *  Then the denotation of `y` is `SingleDenotation(NoSymbol, A | B)`.
    */
-  abstract class Denotation extends DotClass with printing.Showable {
+  abstract class Denotation extends util.DotClass with printing.Showable {
 
     /** The referencing symbol, exists only for non-overloaded denotations */
     def symbol: Symbol
diff --git a/src/dotty/tools/dotc/core/Names.scala b/src/dotty/tools/dotc/core/Names.scala
index 30f82e05e..09fa6cf19 100644
--- a/src/dotty/tools/dotc/core/Names.scala
+++ b/src/dotty/tools/dotc/core/Names.scala
@@ -12,6 +12,7 @@ import collection.generic.CanBuildFrom
 import collection.mutable.{ Builder, StringBuilder }
 import collection.immutable.WrappedString
 import collection.generic.CanBuildFrom
+import util.DotClass
 //import annotation.volatile
 
 object Names {
diff --git a/src/dotty/tools/dotc/core/Periods.scala b/src/dotty/tools/dotc/core/Periods.scala
index 2a38acd15..04eef6aaf 100644
--- a/src/dotty/tools/dotc/core/Periods.scala
+++ b/src/dotty/tools/dotc/core/Periods.scala
@@ -1,6 +1,7 @@
 package dotty.tools.dotc.core
 
 import Contexts._
+import dotty.tools.dotc.util.DotClass
 
 /** Periods are the central "clock" of the compiler.
  *  A period consists of a run id and a phase id.
diff --git a/src/dotty/tools/dotc/core/Phases.scala b/src/dotty/tools/dotc/core/Phases.scala
index 72ebc7129..14cab9821 100644
--- a/src/dotty/tools/dotc/core/Phases.scala
+++ b/src/dotty/tools/dotc/core/Phases.scala
@@ -1,7 +1,9 @@
 package dotty.tools.dotc
 package core
 
-import Periods._, Contexts._
+import Periods._
+import Contexts._
+import util.DotClass
 
 trait Phases { self: Context =>
   import Phases._
diff --git a/src/dotty/tools/dotc/core/Symbols.scala b/src/dotty/tools/dotc/core/Symbols.scala
index a574c5ec2..4aa1ef94d 100644
--- a/src/dotty/tools/dotc/core/Symbols.scala
+++ b/src/dotty/tools/dotc/core/Symbols.scala
@@ -4,20 +4,27 @@ package core
 
 import Periods._
 import Transformers._
-import Names._, Scopes._
+import Names._
+import Scopes._
 import Flags._
 import java.lang.AssertionError
 import Decorators._
 import Symbols._
 import Contexts._
-import SymDenotations._, printing.Texts._
+import SymDenotations._
+import printing.Texts._
 import printing.Printer
-import Types._, Annotations._, util.Positions._, StdNames._, NameOps._
+import Types._
+import Annotations._
+import util.Positions._
+import StdNames._
+import NameOps._
 import ast.tpd.{TreeMapper, SharedTree}
 import Denotations.{ Denotation, SingleDenotation, MultiDenotation }
 import collection.mutable
 import io.AbstractFile
 import language.implicitConversions
+import util.DotClass
 
 /** Creation methods for symbols */
 trait Symbols { this: Context =>
diff --git a/src/dotty/tools/dotc/core/Transformers.scala b/src/dotty/tools/dotc/core/Transformers.scala
index ba26c8be8..90df3a274 100644
--- a/src/dotty/tools/dotc/core/Transformers.scala
+++ b/src/dotty/tools/dotc/core/Transformers.scala
@@ -1,8 +1,13 @@
 package dotty.tools.dotc
 package core
 
-import Periods._, SymDenotations._, Contexts._, Types._, Denotations._
+import Periods._
+import SymDenotations._
+import Contexts._
+import Types._
+import Denotations._
 import java.lang.AssertionError
+import dotty.tools.dotc.util.DotClass
 
 trait Transformers
 
diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index 72d8472b6..1d2d4bac9 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -8,8 +8,7 @@ import Decorators._
 import StdNames.{nme, tpnme}
 import collection.mutable
 import printing.Disambiguation.disambiguated
-import util.SimpleMap
-import util.Stats
+import util.{SimpleMap, Stats, DotClass}
 import config.Config
 import config.Printers._
 
diff --git a/src/dotty/tools/dotc/core/TyperState.scala b/src/dotty/tools/dotc/core/TyperState.scala
index 13fbdbe15..e0c7481c8 100644
--- a/src/dotty/tools/dotc/core/TyperState.scala
+++ b/src/dotty/tools/dotc/core/TyperState.scala
@@ -5,7 +5,7 @@ package core
 import Types._
 import Flags._
 import Contexts._
-import util.SimpleMap
+import util.{SimpleMap, DotClass}
 import reporting._
 import printing.{Showable, Printer}
 import printing.Texts._
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 49b57d32f..377b20991 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -16,7 +16,7 @@ import Denotations._
 import Periods._
 import util.Positions.Position
 import util.Stats._
-import util.SimpleMap
+import util.{DotClass, SimpleMap}
 import ast.tpd._, printing.Texts._
 import ast.untpd
 import transform.Erasure
diff --git a/src/dotty/tools/dotc/parsing/Parsers.scala b/src/dotty/tools/dotc/parsing/Parsers.scala
index cf0ab9f62..ceb4ebe42 100644
--- a/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -12,7 +12,8 @@ import core._
 import Flags._
 import Contexts._
 import Names._
-import ast.Trees._, ast.TreeInfo
+import ast.Trees._
+import ast.TreeInfo
 import Decorators._
 import StdNames._
 import util.Positions._
@@ -22,6 +23,7 @@ import NameOps._
 import util.Chars._
 import ScriptParsers._
 import annotation.switch
+import util.DotClass
 
 object Parsers {
 
diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index 776d59542..da90a0ab3 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -9,7 +9,7 @@ import Contexts._, Symbols._, Types._, SymDenotations._, Names._, NameOps._, Fla
 import ast.desugar, ast.desugar._
 import Inferencing._
 import util.Positions._
-import util.SourcePosition
+import util.{Attachment, SourcePosition, DotClass}
 import collection.mutable
 import annotation.tailrec
 import ErrorReporting._
@@ -96,10 +96,15 @@ class Namer { typer: Typer =>
 
   import untpd._
 
+  val TypedAhead = new Attachment.Key[tpd.Tree]
+  val ExpandedTree = new Attachment.Key[Tree]
+  val SymOfTree = new Attachment.Key[Symbol]
+
   /** A partial map from unexpanded member and pattern defs and to their expansions.
    *  Populated during enterSyms, emptied during typer.
    */
-  lazy val expandedTree = new mutable.AnyRefMap[DefTree, Tree] /*{
+  lazy val expandedTree = new mutable.AnyRefMap[DefTree, Tree]
+  /*{
     override def default(tree: DefTree) = tree // can't have defaults on AnyRefMaps :-(
   }*/
 
@@ -113,7 +118,7 @@ class Namer { typer: Typer =>
   /** A map from expanded trees to their typed versions.
    *  Populated when trees are typechecked during completion (using method typedAhead).
    */
-  lazy val typedTree = new mutable.AnyRefMap[Tree, tpd.Tree]
+  // lazy val typedTree = new mutable.AnyRefMap[Tree, tpd.Tree]
 
   /** A map from method symbols to nested typers.
    *  Populated when methods are completed. Emptied when they are typechecked.
@@ -133,9 +138,9 @@ class Namer { typer: Typer =>
   /** The symbol of the given expanded tree. */
   def symbolOfTree(tree: Tree)(implicit ctx: Context): Symbol = {
     val xtree = expanded(tree)
-    typedTree get xtree match {
-      case Some(ttree) => ttree.denot.symbol
-      case _ => symOfTree(xtree)
+    xtree.getAttachment(TypedAhead) match {
+      case Some(ttree) => ttree.symbol
+      case none => symOfTree(xtree)
     }
   }
 
@@ -249,12 +254,14 @@ class Namer { typer: Typer =>
       val expanded = desugar.defTree(mdef)
       typr.println(i"Expansion: $mdef expands to $expanded")
       if (expanded ne mdef) expandedTree(mdef) = expanded
+      // if (expanded ne mdef) mdef.pushAttachment(ExpandedTree(expanded))
     case _ =>
   }
 
   /** The expanded version of this tree, or tree itself if not expanded */
   def expanded(tree: Tree)(implicit ctx: Context): Tree = tree match {
     case ddef: DefTree => expandedTree.getOrElse(ddef, ddef)
+      //ddef.getAttachment(ExpandedTreeKey).orElse(ddef).asInstanceOf[Tree]
     case _ => tree
   }
 
@@ -445,15 +452,13 @@ class Namer { typer: Typer =>
   /** Typecheck tree during completion, and remember result in typedtree map */
   private def typedAheadImpl(tree: Tree, pt: Type)(implicit ctx: Context): tpd.Tree = {
     val xtree = expanded(tree)
-    typedTree.get(xtree) match {
+    xtree.getAttachment(TypedAhead) match {
       case Some(ttree) => ttree
       case none =>
         val ttree = typer.typed(tree, pt)
-        typedTree(xtree) = ttree
+        xtree.pushAttachment(TypedAhead, ttree)
         ttree
     }
-    // was: typedTree.getOrElseUpdate(expanded(tree), typer.typed(tree, pt))
-    // but this fails for AnyRefMap with an ArrayIndexOutOfBounds exception in getOrElseUpdate
   }
 
   def typedAheadType(tree: Tree, pt: Type = WildcardType)(implicit ctx: Context): tpd.Tree =
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 697441ca1..e68109c9b 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -964,7 +964,7 @@ class Typer extends Namer with Applications with Implicits {
   def typedUnadapted(initTree: untpd.Tree, pt: Type = WildcardType)(implicit ctx: Context): Tree = {
 
     val xtree = expanded(initTree)
-    typedTree remove xtree match {
+    xtree.removeAttachment(TypedAhead) match {
       case Some(ttree) => ttree
       case none =>
         val sym = symOfTree.getOrElse(xtree, NoSymbol)
diff --git a/src/dotty/tools/dotc/util/Attachment.scala b/src/dotty/tools/dotc/util/Attachment.scala
new file mode 100644
index 000000000..dc9602df3
--- /dev/null
+++ b/src/dotty/tools/dotc/util/Attachment.scala
@@ -0,0 +1,65 @@
+package dotty.tools.dotc.util
+
+/** A class inheriting from Attachment.Container supports
+ *  adding, removing and lookup of attachments. Attachments are typed key/value pairs.
+ */
+object Attachment {
+
+  class Key[+V]
+
+  val NullKey = new Key[Null]
+
+  abstract class AttachmentLink[+V] extends DotClass {
+    private[Attachment] def key: Key[V]
+    private[Attachment] def value: V
+    private[Attachment] var next: Link[_]
+
+    def getAttachment[V](key: Key[V]): Option[V] =
+      if (this.key eq key) Some(this.value.asInstanceOf[V])
+      else if (next == null) None
+      else next.getAttachment(key)
+
+    def pushAttachment[V](key: Key[V], value: V): Unit = {
+      assert(!getAttachment(key).isDefined)
+      next = new Link(key, value, next)
+    }
+
+    def putAttachment[V](key: Key[V], value: V): Option[V] = {
+      if (next == null) {
+        next = new Link(key, value, null)
+        None
+      }
+      else if (next.key eq key) {
+        val nx = next
+        next = new Link(key, value, nx.next)
+        Some(nx.value.asInstanceOf[V])
+      }
+      else next.putAttachment(key, value)
+    }
+
+    def removeAttachment[V](key: Key[V]): Option[V] = {
+      if (next == null)
+        None
+      else if (next.key eq key) {
+        val nx = next
+        next = nx.next
+        Some(nx.value.asInstanceOf[V])
+      }
+      else next.removeAttachment(key)
+    }
+
+    def allAttachments: List[Any] =
+      if (next == null) Nil else next.allAttachments
+  }
+
+  private[Attachment] class Link[+V](val key: Key[V], val value: V, var next: Link[_])
+      extends AttachmentLink[V] {
+    override def allAttachments: List[Any] = value :: super.allAttachments
+  }
+
+  class Container extends AttachmentLink[Null] {
+    private[Attachment] def key = NullKey
+    private[Attachment] def value: Null = unsupported("value")
+    private[Attachment] var next: Link[_] = null
+  }
+}
+\ No newline at end of file
diff --git a/src/dotty/tools/dotc/core/DotClass.scala b/src/dotty/tools/dotc/util/DotClass.scala
index f74a4ba81..7839fc37d 100644
--- a/src/dotty/tools/dotc/core/DotClass.scala
+++ b/src/dotty/tools/dotc/util/DotClass.scala
@@ -1,4 +1,4 @@
-package dotty.tools.dotc.core
+package dotty.tools.dotc.util
 
 /** Adds standard functionality to a class.
  *  For now: Just the `unsupported` method.