Use union type for TypeOrSymbol

Author: odersky

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -939,7 +939,7 @@ object SymDenotations {
       if (this.is(ModuleClass))
         myInfo match {
           case ClassInfo(_, _, _, _, selfType) =>
-            def sourceOfSelf(tp: TypeOrSymbol): Symbol = tp match {
+            def sourceOfSelf(tp: TypeOrSymbol): Symbol = (tp: @unchecked) match {
               case tp: TermRef => tp.symbol
               case tp: Symbol => sourceOfSelf(tp.info)
               case tp: RefinedType => sourceOfSelf(tp.parent)

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3940,7 +3940,7 @@ object Types {
 
   // ------ ClassInfo, Type Bounds --------------------------------------------------
 
-  type TypeOrSymbol = AnyRef /* should be: Type | Symbol */
+  type TypeOrSymbol = Type | Symbol
 
   /** Roughly: the info of a class during a period.
    *  @param prefix       The prefix on which parents, decls, and selfType need to be rebased.
@@ -4618,7 +4618,7 @@ object Types {
     override def mapClassInfo(tp: ClassInfo): ClassInfo = {
       val prefix1 = this(tp.prefix)
       val parents1 = tp.parents mapConserve this
-      val selfInfo1 = tp.selfInfo match {
+      val selfInfo1: TypeOrSymbol = tp.selfInfo match {
         case selfInfo: Type => this(selfInfo)
         case selfInfo => selfInfo
       }

compiler/src/dotty/tools/dotc/printing/Formatting.scala

@@ -86,7 +86,7 @@ object Formatting {
       }
   }
 
-  private def wrapNonSensical(arg: Any /* Type | Symbol */, str: String)(implicit ctx: Context): String = {
+  private def wrapNonSensical(arg: Any, str: String)(implicit ctx: Context): String = {
     import MessageContainer._
     def isSensical(arg: Any): Boolean = arg match {
       case tpe: Type =>

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -102,7 +102,7 @@ trait NamerContextOps { this: Context =>
   }
 
   /** A new context for the interior of a class */
-  def inClassContext(selfInfo: AnyRef /* Should be Type | Symbol*/): Context = {
+  def inClassContext(selfInfo: TypeOrSymbol): Context = {
     val localCtx: Context = ctx.fresh.setNewScope
     selfInfo match {
       case sym: Symbol if sym.exists && sym.name != nme.WILDCARD => localCtx.scope.openForMutations.enter(sym)