anchor.diff:    Map<String, String> getSuggestedNames(NamingScope scope) {
       if (scope == NamingScope.global) {
         return suggestedGlobalNames;
  +    } else if (scope == NamingScope.instance) {
  +      return suggestedInstanceNames;
       } else {
  -      assert(scope == NamingScope.instance);
  -      return suggestedInstanceNames;
  +      assert(scope == NamingScope.constant);
  +      return const {};
       }
     }
   
  
positive.code:   final Map<String, jsAst.Name> userInstanceOperators =
        new HashMap<String, jsAst.Name>();
  
    Set<String> getUsedNames(NamingScope scope) {
      if (scope == NamingScope.global) {
        return usedGlobalNames;
      } else {
        assert(scope == NamingScope.instance);
        return usedInstanceNames;
      }
    }
  
  
negative.code: 
  enum NamingScope {
    global,
    instance,
    constant
  }