code: public static void throwException(CodeBuilder b, Class type, String message) {
          TypeDesc desc = TypeDesc.forClass(type);
          b.newObject(desc);
          b.dup();
          if (message == null) {
              b.invokeConstructor(desc, null);
          } else {
              b.loadConstant(message);
              b.invokeConstructor(desc, new TypeDesc[] {TypeDesc.STRING});
          }
          b.throwObject();
      }
docs: Generate code to throw an exception with an optional message.
  @param b {@link CodeBuilder} to which to add code
  @param type type of the object to throw
  @param message optional message to provide to the constructor