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 to extend the annotated class is deprecated and will soon be removed. This change will likely be enforced by marking the class with interface, final, or sealed.

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

@Deprecated.extend()
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 directions found in the Deprecation.extend annotation. Otherwise, remove the extends clause.

class D {}