subtype_of_sealed_class

The class '{0}' shouldn't be extended, mixed in, or implemented because it's sealed.

The analyzer produces this diagnostic when a sealed class (one that either has the sealed annotation or inherits or mixes in a sealed class) is referenced in either the extends, implements, or with clause of a class or mixin declaration if the declaration isn't in the same package as the sealed class.

Given a library in a package other than the package being analyzed that contains the following:

import 'package:meta/meta.dart';

class A {}

@sealed
class B {}

The following code produces this diagnostic because C, which isn't in the same package as B, is extending the sealed class B:

import 'package:a/a.dart';

class C extends B {}

If the class doesn't need to be a subtype of the sealed class, then change the declaration so that it isn't:

import 'package:a/a.dart';

class B extends A {}

除非另有说明，文档之所提及适用于 Dart 3.7.3 版本，本页面最后更新时间: 2025-05-08。 查看文档源码 或者 报告页面问题。