code: private static ConstantValueExpression asCVE(AbstractExpression expr) {
          return expr instanceof ConstantValueExpression ? (ConstantValueExpression) expr :
                  ((ParameterValueExpression) expr).getOriginalValue();
      }
docs: Convert a ConstantValueExpression or ParameterValueExpression into a ConstantValueExpression.
  \pre argument must be either of the two.
  @param expr expression to be casted
  @return casted ConstantValueExpression