From 2aee8120ee96800ba607e12079b4d3adb639be5c Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 30 Jan 2007 15:40:23 +0000
Subject: added subClasses method to symbols.

---
 src/compiler/scala/tools/nsc/symtab/Symbols.scala     | 14 ++++++++++++++
 src/compiler/scala/tools/nsc/typechecker/Typers.scala | 15 +++++++++------
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/compiler/scala/tools/nsc/symtab/Symbols.scala b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
index dab6870aeb..644544cb2d 100644
--- a/src/compiler/scala/tools/nsc/symtab/Symbols.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
@@ -23,6 +23,7 @@ trait Symbols requires SymbolTable {
   type AttrInfo = Triple[Type, List[Constant], List[Pair[Name,Constant]]]
 
   val emptySymbolArray = new Array[Symbol](0)
+  val emptySymbolSet = Set.empty[Symbol]
   type PositionType;
   def NoPos : PositionType;
   def FirstPos : PositionType;
@@ -867,6 +868,14 @@ trait Symbols requires SymbolTable {
     def isFromClassFile: Boolean =
       (if (isModule) moduleClass else toplevelClass).isFromClassFile
 
+    /** If this is a sealed class, its known subclasses. Otherwise Set.empty */
+    def subClasses: Set[Symbol] = emptySymbolSet
+
+    /** Declare given subclass `sym' of this sealed class */
+    def addSubClass(sym: Symbol) {
+      throw new Error("addSubClass_= inapplicable for " + this)
+    }
+
 
 // ToString -------------------------------------------------------------------
 
@@ -1175,6 +1184,7 @@ trait Symbols requires SymbolTable {
 
     /** The classfile from which this class was loaded. Maybe null. */
     var classFile: AbstractFile = null;
+
     private var source: AbstractFile = null
     override def sourceFile =
       if (owner.isPackageClass) source else super.sourceFile
@@ -1244,6 +1254,10 @@ trait Symbols requires SymbolTable {
     override def sourceModule =
       if (isModuleClass) linkedModuleOfClass else NoSymbol
 
+    private var subClassSet: Set[Symbol] = emptySymbolSet
+    override def subClasses: Set[Symbol] = subClassSet
+    override def addSubClass(sym: Symbol) { subClassSet = subClassSet + sym }
+
     if (util.Statistics.enabled) classSymbolCount = classSymbolCount + 1
   }
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index a90472d56b..e13bc27aff 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -774,9 +774,9 @@ trait Typers requires Analyzer {
       def validateParentClass(parent: Tree, superclazz: Symbol): unit = {
         if (!parent.tpe.isError) {
           val psym = parent.tpe.symbol.initialize
-          if (!psym.isClass)
+          if (!psym.isClass) {
             error(parent.pos, "class type expected")
-          else if (psym != superclazz)
+          } else if (psym != superclazz) {
             if (psym.isTrait) {
               val ps = psym.info.parents
               if (!ps.isEmpty && !superclazz.isSubClass(ps.head.symbol))
@@ -788,11 +788,14 @@ trait Typers requires Analyzer {
             }else {
               error(parent.pos, ""+psym+" needs to be a trait be mixed in")
             }
-          else if (psym hasFlag FINAL)
+          } else if (psym hasFlag FINAL) {
             error(parent.pos, "illegal inheritance from final class")
-          else if (!phase.erasedTypes && psym.isSealed &&
-                   context.unit.source.file != psym.sourceFile)
-            error(parent.pos, "illegal inheritance from sealed "+psym)
+          } else if (psym.isSealed && !phase.erasedTypes) {
+            if (context.unit.source.file != psym.sourceFile)
+              error(parent.pos, "illegal inheritance from sealed "+psym)
+            else
+              psym addSubClass context.owner
+          }
           if (!(selfType <:< parent.tpe.typeOfThis) && !phase.erasedTypes) {
             //Console.println(context.owner);//DEBUG
             //Console.println(context.owner.unsafeTypeParams);//DEBUG
-- 
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