Why Build failed after migration to flutter 3.3.0?

Question

lib/src/domain/application/bloc/app/app_bloc.freezed.dart:87:23:

Error: The class 'InitAppUseCase' can't be used as a mixin because it extends a class other than 'Object'.

class _$_InitApp with InitAppUseCase implements _InitApp {

user_5243472 · Answer

if you are using abstract class as mixin:

abstract class InitAppUseCase extend SomeMixin{...}

then try to use 'implements' instead of 'extends'. if you use mixin then use 'on':

mixin InitAppUseCase on SomClass{...}

before flutter 3.3.0 you could fix it with:

analyzer:
  strong-mode: true
  errors:
    mixin_inherits_from_not_object: ignore

but looks like it not work after update. more info Dart 2 Mixin Declarations