extension_type_constructor_with_super_formal_parameter

Extension type constructors can't declare super formal parameters.

The analyzer produces this diagnostic when a constructor in an extension type has a super parameter. Super parameters aren't valid because extension types don't have a superclass.

The following code produces this diagnostic because the named constructor n contains a super parameter:

extension type E(int i) {
  E.n(this.i, super.foo);
}

If you need the parameter, replace the super parameter with a normal parameter:

extension type E(int i) {
  E.n(this.i, String foo);
}

If you don't need the parameter, remove the super parameter:

extension type E(int i) {
  E.n(this.i);
}

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.