Invalide fullName cache when name changes

Also: use "_$" instead of "~" as filler when taking the full name
of a term member. If the term member is symbolic (e.g. +) the
filler name would be misinterpreted as a symbolic name "~+", so would
be mangled as "$tilde$plus$ instead of "~$plus".

Author: odersky

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

@@ -135,7 +135,7 @@ object SymDenotations {
     def name = myName
 
     /** Update the name; only called when unpickling top-level classes */
-    def name_=(n: Name) = myName = n
+    private[core] def name_=(n: Name) = myName = n
 
     /** The owner of the symbol; overridden in NoDenotation */
     def owner: Symbol = ownerIfExists
@@ -403,7 +403,7 @@ object SymDenotations {
         var encl = owner
         while (!encl.isClass && !encl.isPackageObject) {
           encl = encl.owner
-          filler += "~"
+          filler += "_$"
         }
         var prefix = encl.fullNameSeparated(kind)
         if (kind.separator == "$")
@@ -505,7 +505,7 @@ object SymDenotations {
      *  step for creating Refinement types.
      */
     final def isRefinementClass(implicit ctx: Context): Boolean =
-      name.decode == tpnme.REFINE_CLASS
+      name == tpnme.REFINE_CLASS
 
     /** Is this symbol a package object or its module class? */
     def isPackageObject(implicit ctx: Context): Boolean = {
@@ -1260,6 +1260,11 @@ object SymDenotations {
       myTypeParams
     }
 
+    override private[core] def name_=(n: Name) = {
+      fullNameCache = SimpleMap.Empty
+      super.name_=(n)
+    }
+
     override protected[dotc] final def info_=(tp: Type) = {
       super.info_=(tp)
       myTypeParams = null // changing the info might change decls, and with it typeParams