Your app can break if it relies on the relayout to cause the rebuilding of the
LayoutBuilder rather than on an explicit call to setState. This usually
happens by accident. You meant to add setState, but you forgot because the app
continued functioning as you wanted, and therefore nothing reminded you to add
it.

Migration guide

Look for usages of LayoutBuilder and SliverLayoutBuilder and make sure to
call setState any time the widget state changes.

Code before migration (note the missing setState inside the onPressed
callback):

import

'package:flutter/material.dart'

void

main

()

runApp

MyApp

());

class

MyApp

extends

StatelessWidget

@override

Widget

build

BuildContext