const newLFLeft = calculateLF(x);
if (newSizeLeft !== x.parent.size_left || newLFLeft !== x.parent.lf_left) {
const lf_delta = newLFLeft - x.parent.lf_left;
x.parent.size_left = newSizeLeft;
x.parent.lf_left = newLFLeft;
updateTreeMetadata(tree, x.parent, delta, lf_delta);
}
}