“This variable can be final”, “Add const here”, “Implicit dynamic” and many other rules help us be effective developers. And even may prevent critical mistakes in early development stages. These common rules were provided by the Dart team, they are the foundation of product quality. Flutter developers may go even further and add custom rules that will be specific to the team or project. During this talk, I will walk you through the process of creating a custom linter rule in easy and in hard ways.