invalid_override

'{1}.{0}' ('{2}') isn't a valid override of '{3}.{0}' ('{4}').

The setter '{1}.{0}' ('{2}') isn't a valid override of '{3}.{0}' ('{4}').

The analyzer produces this diagnostic when a member of a class is found that overrides a member from a supertype and the override isn't valid. An override is valid if all of these are true:

• It allows all of the arguments allowed by the overridden member.
• It doesn't require any arguments that aren't required by the overridden member.
• The type of every parameter of the overridden member is assignable to the corresponding parameter of the override.
• The return type of the override is assignable to the return type of the overridden member.

The following code produces this diagnostic because the type of the parameter s (String) isn't assignable to the type of the parameter i (int):

class A {
  void m(int i) {}
}

class B extends A {
  void m(String s) {}
}

If the invalid method is intended to override the method from the superclass, then change it to conform:

class A {
  void m(int i) {}
}

class B extends A {
  void m(int i) {}
}

If it isn't intended to override the method from the superclass, then rename it:

class A {
  void m(int i) {}
}

class B extends A {
  void m2(String s) {}
}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.