1. export default function memo<Props>(
    2.   type: React$ElementType,
    3.   compare?: (oldProps: Props, newProps: Props) => boolean,
    4. ) {
    5.   // 根据传入的比较函数来决定是否 rerender
    6.   return {
    7.     $$typeof: REACT_MEMO_TYPE,
    8.     type,
    9.     compare: compare === undefined ? null : compare,
    10.   };
    11. }