flutter has a bool cost kDebugMode
and this example
https://github.com/flutter/flutter/blob/6e49cce18f26c24027f92dabf903ef51baa43250/examples/api/lib/widgets/framework/error_widget.0.dart

uses assertion to run a specific code in debug only
this works fine but new comers might does not know that assert works only on debug
using the const (kDebugMode) will make it more clear
since the example is about the error handling not about assert use cases