Create OverloadedSymbol and OverloadedDenotation

Will be needed to represent overloaded TermRefs

Author: odersky

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

@@ -1848,18 +1848,21 @@ object SymDenotations {
     }
   }
 
-  class NoDenotation extends SymDenotation(
-    NoSymbol, NoSymbol, "<none>".toTermName, Permanent, NoType) {
+  class NoDenotation(sym: Symbol, name: Name, override val isTerm: Boolean)
+  extends SymDenotation(sym, NoSymbol, name, Permanent, NoType) {
     override def exists = false
-    override def isTerm = false
     override def isType = false
     override def owner: Symbol = throw new AssertionError("NoDenotation.owner")
     override def computeAsSeenFrom(pre: Type)(implicit ctx: Context): SingleDenotation = this
     override def mapInfo(f: Type => Type)(implicit ctx: Context): SingleDenotation = this
     validFor = Period.allInRun(NoRunId)
   }
 
-  @sharable val NoDenotation = new NoDenotation
+  @sharable val NoDenotation =
+    new NoDenotation(NoSymbol, "<none>".toTermName, isTerm = false)
+
+  @sharable val OverloadedDenotation =
+    new NoDenotation(OverloadedSymbol, "<overloaded>".toTermName, isTerm = true)
 
   // ---- Completion --------------------------------------------------------
 

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

@@ -643,12 +643,20 @@ object Symbols {
     denot = underlying.denot
   }
 
-  @sharable object NoSymbol extends Symbol(NoCoord, 0) {
-    denot = NoDenotation
+  class NonExistingSymbol extends Symbol(NoCoord, 0) {
     override def associatedFile(implicit ctx: Context): AbstractFile = NoSource.file
     override def recomputeDenot(lastd: SymDenotation)(implicit ctx: Context): SymDenotation = NoDenotation
   }
 
+  @sharable object NoSymbol extends NonExistingSymbol {
+    denot = NoDenotation
+  }
+
+  @sharable object OverloadedSymbol extends NonExistingSymbol {
+    denot = OverloadedDenotation
+    type ThisName = TermName
+  }
+
   implicit class Copier[N <: Name](sym: Symbol { type ThisName = N })(implicit ctx: Context) {
     /** Copy a symbol, overriding selective fields */
     def copy(