extension_declares_abstract_member

Extensions can't declare abstract members.

The analyzer produces this diagnostic when an abstract declaration is declared in an extension. Extensions can declare only concrete members.

The following code produces this diagnostic because the method a doesn't have a body:

extension E on String {
  int a();
}

Either provide an implementation for the member or remove it.

Unless stated otherwise, the documentation on this site reflects Dart 3.7.3. Page last updated on 2025-05-08. View source or report an issue.