Address reviewers comments

Author: odersky

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

@@ -321,8 +321,8 @@ object Phases {
     private var mySymbolicRefs = false
     private var myLabelsReordered = false
 
-    private var myMembersGroup = 0
-    private var myParentsGroup = 0
+    private var mySameMembersStartId = NoPhaseId
+    private var mySameParentsStartId = NoPhaseId
 
     /** The sequence position of this phase in the given context where 0
      * is reserved for NoPhase and the first real phase is at position 1.
@@ -339,8 +339,11 @@ object Phases {
     final def refChecked = myRefChecked     // Phase is after RefChecks
     final def symbolicRefs = mySymbolicRefs // Phase is after ResolveSuper, newly generated TermRefs should be symbolic
     final def labelsReordered = myLabelsReordered // Phase is after LabelDefs, labels are flattened and owner chains don't mirror this
-    final def membersGroup = myMembersGroup // group id for phases where all symbols have the same non-private members
-    final def parentsGroup = myParentsGroup // group id for phases where all symbols have the same base classes
+
+    final def sameMembersStartId = mySameMembersStartId
+      // id of first phase where all symbols are guaranteed to have the same members as in this phase
+    final def sameParentsStartId = mySameParentsStartId
+      // id of first phase where all symbols are guaranteed to have the same parents as in this phase
 
     protected[Phases] def init(base: ContextBase, start: Int, end:Int): Unit = {
       if (start >= FirstPhaseId)
@@ -352,8 +355,8 @@ object Phases {
       myRefChecked   = prev.getClass == classOf[RefChecks]    || prev.refChecked
       mySymbolicRefs = prev.getClass == classOf[ResolveSuper] || prev.symbolicRefs
       myLabelsReordered = prev.getClass == classOf[LabelDefs] || prev.labelsReordered
-      myMembersGroup = if (changesMembers) prev.membersGroup + 1 else prev.membersGroup
-      myParentsGroup = if (changesParents) prev.parentsGroup + 1 else prev.parentsGroup
+      mySameMembersStartId = if (changesMembers) id else prev.sameMembersStartId
+      mySameParentsStartId = if (changesParents) id else prev.sameMembersStartId
     }
 
     protected[Phases] def init(base: ContextBase, id: Int): Unit = init(base, id, id)

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

@@ -1257,7 +1257,7 @@ object SymDenotations {
     private def baseTypeRefCache(implicit ctx: Context): BaseTypeRefMap = {
       if (myBaseTypeRefCachePeriod != ctx.period &&
           (myBaseTypeRefCachePeriod.runId != ctx.runId ||
-           ctx.phases(myBaseTypeRefCachePeriod.phaseId).parentsGroup != ctx.phase.parentsGroup)) {
+           ctx.phases(myBaseTypeRefCachePeriod.phaseId).sameParentsStartId != ctx.phase.sameParentsStartId)) {
         myBaseTypeRefCache = new BaseTypeRefMap
         myBaseTypeRefCachePeriod = ctx.period
       }
@@ -2027,7 +2027,7 @@ object SymDenotations {
       finally addDependent(onBehalf)
     }
 
-    def sameGroup(p1: Phase, p2: Phase) = p1.membersGroup == p2.membersGroup
+    def sameGroup(p1: Phase, p2: Phase) = p1.sameMembersStartId == p2.sameMembersStartId
   }
 
   private class BaseDataImpl(createdAt: Period) extends InheritedCacheImpl(createdAt) with BaseData {
@@ -2068,7 +2068,7 @@ object SymDenotations {
       finally addDependent(onBehalf)
     }
 
-    def sameGroup(p1: Phase, p2: Phase) = p1.parentsGroup == p2.parentsGroup
+    def sameGroup(p1: Phase, p2: Phase) = p1.sameParentsStartId == p2.sameParentsStartId
   }
 
   class BaseClassSet(val classIds: Array[Int]) extends AnyVal {