deprecated_subclass

Subclassing '{0}' is deprecated.

The analyzer produces this diagnostic when a class annotated with @Deprecated.subclass is used in the extends clause of a class declaration, or the implements clause of a class or enum declaration.

This annotation indicates that the ability for classes or enums to extend or implement the annotated class is deprecated, and will soon be removed, perhaps by marking the annotated class with final or sealed.

If the library p defines a class annotated with @Deprecated.subclass:

@Deprecated.subclass()
class C {}

Then, the following code, when in a library other than p, produces this diagnostic:

import 'package:p/p.dart';

class D extends C {}

If the annotation contains a description of how to deal with not being able to subclass the class, then try following those directions.

If the annotation doesn't contain a description, or if the described approach isn't appropriate for your case, then remove the relevant extends clause or remove the class name from the implements clause:

class D {}