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 extending or implementing the annotated class is deprecated and will soon be removed. This change will likely be enforced by marking the class with final or sealed.

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

@Deprecated.subclass()
class C {}

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

import 'package:p/p.dart';
​
class D extends C {}

Follow any specific instructions provided in the @Deprecated.subclass annotation. Otherwise, remove the relevant extends clause or remove the class name from the implements clause:

class D {}