sealed top-level constant

_Sealed const sealed

Annotation marking a class as not allowed as a super-type outside of the current package.

Classes in the same package as the marked class may extend, implement or mix-in the annotated class.

Tools, such as the analyzer, can provide feedback if

• the annotation is associated with anything other than a class,
• the annotation is associated with a class C, and there is a class or mixin D, which extends, implements, mixes in, or constrains to C, and C and D are declared in different packages.

Note: In Dart 3 and later, you can use built-in class modifiers to control what forms of subtyping are allowed outside the current library. To learn more about using class modifiers, check out the Class modifiers documentation.

Implementation

const _Sealed sealed = _Sealed();