docs: private Message resolveMessage(FunctionRef fun) {
          if (fun.getOperand().size() != 5) {
              throw new IllegalArgumentException("Could not resolve call to system operator Message. Expected 5 arguments.");
          }
  
          Message message = of.createMessage()
                  .withSource(fun.getOperand().get(0))
                  .withCondition(fun.getOperand().get(1))
                  .withCode(fun.getOperand().get(2))
                  .withSeverity(fun.getOperand().get(3))
                  .withMessage(fun.getOperand().get(4));
  
          builder.resolveCall("System", "Message", new MessageInvocation(message));
          return message;
      }