Reord of superIds

1) We now keep an association between ClassSymbol and SuperId (instead of TypeRef and SuperId). That's better
   because superId's are deleted anyway after each run, so we gain nothing by keeping a stable ref.
2) hasChildren got dropped. It was too unreliable. The mere fact that someone take's the superId of a class
   does not means that that class has children.

1 files changed, 4 insertions, 8 deletions

diff --git a/src/dotty/tools/dotc/core/Symbols.scala b/src/dotty/tools/dotc/core/Symbols.scala
index a7e59d356..5bba99c9c 100644
--- a/src/dotty/tools/dotc/core/Symbols.scala
+++ b/src/dotty/tools/dotc/core/Symbols.scala
@@ -480,17 +480,16 @@ object Symbols {
 
     override def superId(implicit ctx: Context): Int = {
       val hint = superIdHint
-      val key = this.typeRef
-      if (hint >= 0 && hint <= ctx.lastSuperId && (ctx.classOfId(hint) eq key))
+      if (hint >= 0 && hint <= ctx.lastSuperId && (ctx.classOfId(hint) eq this))
         hint
       else {
-        val id = ctx.superIdOfClass get key match {
+        val id = ctx.superIdOfClass get this match {
           case Some(id) =>
             id
           case None =>
             val id = ctx.nextSuperId
-            ctx.superIdOfClass(key) = id
-            ctx.classOfId(id) = key
+            ctx.superIdOfClass(this) = id
+            ctx.classOfId(id) = this
             id
         }
         superIdHint = id
@@ -498,9 +497,6 @@ object Symbols {
       }
     }
 
-    /** Have we seen a subclass of this class? */
-    def hasChildren = superIdHint >= 0 // dubious, does not survive runs if children are deleted!
-
     override protected def prefixString = "ClassSymbol"
   }