Be more aggressive invalidating baseTypeRef caches

We might get a wrong baseTypeRef cache when basetypes get
populated while parent type infos of a class are not yet
installed. So at the end of initializing a class type in
namer, we should invalidate the caches of all its base types.
Without the fix, BitSet in the collection strawman fails to
compile.

Author: odersky

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

@@ -1381,12 +1381,15 @@ object SymDenotations {
     /** Invalidate baseTypeRefCache, baseClasses and superClassBits on new run */
     private def checkBasesUpToDate()(implicit ctx: Context) =
       if (baseTypeRefValid != ctx.runId) {
-        baseTypeRefCache = new java.util.HashMap[CachedType, Type]
+        invalidateBaseTypeRefCache()
         myBaseClasses = null
         mySuperClassBits = null
         baseTypeRefValid = ctx.runId
       }
 
+    def invalidateBaseTypeRefCache() =
+      baseTypeRefCache = new java.util.HashMap[CachedType, Type]
+
     private def computeBases(implicit ctx: Context): (List[ClassSymbol], BitSet) = {
       if (myBaseClasses eq Nil) throw CyclicReference(this)
       myBaseClasses = Nil
@@ -1712,18 +1715,23 @@ object SymDenotations {
       /*>|>*/ ctx.debugTraceIndented(s"$tp.baseTypeRef($this)") /*<|<*/ {
         tp match {
           case tp: CachedType =>
-            checkBasesUpToDate()
-            var basetp = baseTypeRefCache get tp
-            if (basetp == null) {
-              baseTypeRefCache.put(tp, NoPrefix)
-              basetp = computeBaseTypeRefOf(tp)
-              if (isCachable(tp)) baseTypeRefCache.put(tp, basetp)
-              else baseTypeRefCache.remove(tp)
-            } else if (basetp == NoPrefix) {
-              baseTypeRefCache.put(tp, null)
-              throw CyclicReference(this)
+            try {
+              checkBasesUpToDate()
+              var basetp = baseTypeRefCache get tp
+              if (basetp == null) {
+                baseTypeRefCache.put(tp, NoPrefix)
+                basetp = computeBaseTypeRefOf(tp)
+                if (isCachable(tp)) baseTypeRefCache.put(tp, basetp)
+                else baseTypeRefCache.remove(tp)
+              } else if (basetp == NoPrefix)
+                throw CyclicReference(this)
+              basetp
+            }
+            catch {
+              case ex: Throwable =>
+                baseTypeRefCache.put(tp, null)
+                throw ex
             }
-            basetp
           case _ =>
             computeBaseTypeRefOf(tp)
         }

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -915,6 +915,7 @@ class Namer { typer: Typer =>
       Checking.checkWellFormed(cls)
       if (isDerivedValueClass(cls)) cls.setFlag(Final)
       cls.info = avoidPrivateLeaks(cls, cls.pos)
+      cls.baseClasses.foreach(_.invalidateBaseTypeRefCache)
     }
   }