code: void addGuardParameters( Map<String, Expression> parameters, boolean isDefault ) {
          isGuard = true;
          wasDefaultFunction = false;
          guardDefault = isDefault;
          if( parameters != null ) {
              addMixin( null, parameters, null );
          }
      }
docs: Add the parameters of a guard
  
  @param parameters the parameters
  @param isDefault if the default case will be evaluated, in this case the expression "default" in guard is true.