extension_type_inherited_member_conflict

The extension type '{0}' has more than one distinct member named '{1}' from implemented types.

The analyzer produces this diagnostic when an extension type implements two or more other types, and at least two of those types declare a member with the same name.

The following code produces this diagnostic because the extension type C implements both A and B, and both declare a member named m:

class A {
  void m() {}
}

extension type B(A a) {
  void m() {}
}

extension type C(A a) implements A, B {}

If the extension type doesn't need to implement all of the listed types, then remove all but one of the types introducing the conflicting members:

class A {
  void m() {}
}

extension type B(A a) {
  void m() {}
}

extension type C(A a) implements A {}

If the extension type needs to implement all of the listed types but you can rename the members in those types, then give the conflicting members unique names:

class A {
  void m() {}
}

extension type B(A a) {
  void n() {}
}

extension type C(A a) implements A, B {}

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.