# invalid_deprecated_extend_annotation

> Details about the invalid_deprecated_extend_annotation diagnostic produced by the Dart analyzer.



_The annotation '@Deprecated.extend' can only be applied to extendable classes._

## Description

The analyzer produces this diagnostic when the `@Deprecated.extend`
annotation is applied to a declaration that isn't an extendable class. An
extendable class is one that isn't declared with the `interface`,
`final`, or `sealed` keywords and has at least one public, generative
constructor.

## Example

The following code produces this diagnostic because the annotation is on a
sealed class:

```dart
@[!Deprecated.extend!]()
sealed class C {}
```

## Common fixes

Remove the annotation:

```dart
sealed class C {}
```

