instance_member_access_from_factory

Instance members can't be accessed from a factory constructor.

The analyzer produces this diagnostic when a factory constructor contains an unqualified reference to an instance member. In a generative constructor, the instance of the class is created and initialized before the body of the constructor is executed, so the instance can be bound to this and accessed just like it would be in an instance method. But, in a factory constructor, the instance isn't created before executing the body, so this can't be used to reference it.

The following code produces this diagnostic because x isn't in scope in the factory constructor:

class C {
  int x;
  factory C() {
    return C._(x);
  }
  C._(this.x);
}

Rewrite the code so that it doesn't reference the instance member:

class C {
  int x;
  factory C() {
    return C._(0);
  }
  C._(this.x);
}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.0. Page last updated on 2025-05-08. View source or report an issue.