docs: def param_list(self):
          """
          paramlist  : var, paramlist
          paramlist  : var
          paramlist  :
          """
          params = []
          while self.cur_token.type == TokenTypes.VAR:
              params.append(Var(self.cur_token))
              self.eat(TokenTypes.VAR)
              if self.cur_token.type == TokenTypes.COMMA:
                  self.eat(TokenTypes.COMMA)
  
          return FunctionSig(params)