Get rid of Frozen flag

No longer needed because we have proper cache invalidation now

Author: odersky

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

@@ -817,7 +817,6 @@ object Denotations {
                 next match {
                   case next: ClassDenotation =>
                     assert(!next.is(Package), s"illegal transformation of package denotation by transformer ${ctx.withPhase(transformer).phase}")
-                    next.resetFlag(Frozen)
                   case _ =>
                 }
                 next.insertAfter(cur)

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

@@ -375,9 +375,6 @@ object Flags {
   /** Denotation is in train of being loaded and completed, used to catch cyclic dependencies */
   final val Touched = commonFlag(48, "<touched>")
 
-  /** Class is not allowed to accept new members because fingerprint of subclass has been taken */
-  final val Frozen = commonFlag(49, "<frozen>")
-
   /** An error symbol */
   final val Erroneous = commonFlag(50, "<is-error>")
 
@@ -450,7 +447,7 @@ object Flags {
     Module | Package | Deferred | MethodOrHKCommon | Param | ParamAccessor |
     Scala2ExistentialCommon | Mutable.toCommonFlags | Touched | JavaStatic |
     CovariantOrOuter | ContravariantOrLabel | CaseAccessorOrBaseTypeArg |
-    Fresh | Frozen | Erroneous | ImplicitCommon | Permanent | Synthetic |
+    Fresh | Erroneous | ImplicitCommon | Permanent | Synthetic |
     SuperAccessorOrScala2x | Inline
 
   /** Flags guaranteed to be set upon symbol creation, or, if symbol is a top-level

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

@@ -1168,7 +1168,7 @@ object SymDenotations {
       privateWithin: Symbol = null,
       annotations: List[Annotation] = null)(implicit ctx: Context) =
     { // simulate default parameters, while also passing implicit context ctx to the default values
-      val initFlags1 = (if (initFlags != UndefinedFlags) initFlags else this.flags) &~ Frozen
+      val initFlags1 = (if (initFlags != UndefinedFlags) initFlags else this.flags)
       val info1 = if (info != null) info else this.info
       if (ctx.isAfterTyper && changedClassParents(info, info1, completersMatter = false))
         assert(ctx.phase.changesParents, i"undeclared parent change at ${ctx.phase} for $this, was: $info, now: $info1")
@@ -1483,17 +1483,7 @@ object SymDenotations {
 
     /** Enter a symbol in given `scope` without potentially replacing the old copy. */
     def enterNoReplace(sym: Symbol, scope: MutableScope)(implicit ctx: Context): Unit = {
-      def isUsecase = ctx.docCtx.isDefined && sym.name.show.takeRight(4) == "$doc"
-      require(
-          (sym.denot.flagsUNSAFE is Private) ||
-          !(this is Frozen) ||
-          (scope ne this.unforcedDecls) ||
-          sym.hasAnnotation(defn.ScalaStaticAnnot) ||
-          sym.name.is(InlineAccessorName) ||
-          isUsecase, i"trying to enter $sym in $this, frozen = ${this is Frozen}")
-
       scope.enter(sym)
-
       if (myMemberCache != null) myMemberCache.invalidate(sym.name)
       if (!sym.flagsUNSAFE.is(Private)) invalidateMemberNamesCache()
     }
@@ -1503,7 +1493,6 @@ object SymDenotations {
      *  @pre `prev` and `replacement` have the same name.
      */
     def replace(prev: Symbol, replacement: Symbol)(implicit ctx: Context): Unit = {
-      require(!(this is Frozen))
       unforcedDecls.openForMutations.replace(prev, replacement)
       if (myMemberCache != null) myMemberCache.invalidate(replacement.name)
     }
@@ -1513,7 +1502,6 @@ object SymDenotations {
      *  someone does a findMember on a subclass.
      */
     def delete(sym: Symbol)(implicit ctx: Context) = {
-      require(!(this is Frozen))
       info.decls.openForMutations.unlink(sym)
       if (myMemberCache != null) myMemberCache.invalidate(sym.name)
       if (!sym.flagsUNSAFE.is(Private)) invalidateMemberNamesCache()

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

@@ -343,7 +343,7 @@ trait Symbols { this: Context =>
         copy.denot = odenot.copySymDenotation(
           symbol = copy,
           owner = ttmap1.mapOwner(odenot.owner),
-          initFlags = odenot.flags &~ (Frozen | Touched) | Fresh,
+          initFlags = odenot.flags &~ Touched | Fresh,
           info = completer,
           privateWithin = ttmap1.mapOwner(odenot.privateWithin), // since this refers to outer symbols, need not include copies (from->to) in ownermap here.
           annotations = odenot.annotations)