code: private function parseObjectField($isConst)
      {
          $start = $this->lexer->token;
          $name  = $this->parseName();
  
          $this->expect(Token::COLON);
  
          return new ObjectFieldNode([
              'name'  => $name,
              'value' => $this->parseValueLiteral($isConst),
              'loc'   => $this->loc($start),
          ]);
      }
docs: @param bool $isConst
  
  @return ObjectFieldNode