deprecated_extend

Extending '{0}' is deprecated.

The analyzer produces this diagnostic when a class annotated with @Deprecated.extend is used in the extends clause of a class declaration.

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

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

@Deprecated.extend()
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 {}

Follow any directions found in the Deprecation.extend annotation, or just remove the extends clause.

class D {}