break;
      }
       If 
       ass
       pri
      if (parentA.child === parentB.child) {
        let child = parentA.child;
        while (child) {
          if (child === a) {
             We'
            if (isFiberMountedImpl(parentA) !== MOUNTED) {
              throw Error('Unable to find node on an unmounted component.');
            }
            return fiber;
          }
          if (child === b) {
             We'
            if (isFiberMountedImpl(parentA) !== MOUNTED) {
              throw Error('Unable to find node on an unmounted component.');
            }
            return alternate;
          }
          child = child.sibling;
        }
         We 
         way 
        throw Error('Unable to find node on an unmounted component.');
      }
      if (a.return !== b.return) {
         The