field_initialized_in_initializer_and_declaration

Fields can't be initialized in the constructor if they are final and were already initialized at their declaration.

The analyzer produces this diagnostic when a final field is initialized in both the declaration of the field and in an initializer in a constructor. Final fields can only be assigned once, so it can't be initialized in both places.

The following code produces this diagnostic because f is :

class C {
  final int f = 0;
  C() : f = 1;
}

If the initialization doesn't depend on any values passed to the constructor, and if all of the constructors need to initialize the field to the same value, then remove the initializer from the constructor:

class C {
  final int f = 0;
  C();
}

If the initialization depends on a value passed to the constructor, or if different constructors need to initialize the field differently, then remove the initializer in the field's declaration:

class C {
  final int f;
  C() : f = 1;
}

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.