extension_declares_member_of_object

Extensions can't declare members with the same name as a member declared by 'Object'.

The analyzer produces this diagnostic when an extension declaration declares a member with the same name as a member declared in the class Object. Such a member can never be used because the member in Object is always found first.

The following code produces this diagnostic because toString is defined by Object:

extension E on String {
  String toString() => this;
}

Remove the member or rename it so that the name doesn't conflict with the member in Object:

extension E on String {
  String displayString() => this;
}