positional_super_formal_parameter_with_positional_argument

Positional super parameters can't be used when the super constructor invocation has a positional argument.

The analyzer produces this diagnostic when some, but not all, of the positional parameters provided to the constructor of the superclass are using a super parameter.

Positional super parameters are associated with positional parameters in the super constructor by their index. That is, the first super parameter is associated with the first positional parameter in the super constructor, the second with the second, and so on. The same is true for positional arguments. Having both positional super parameters and positional arguments means that there are two values associated with the same parameter in the superclass's constructor, and hence isn't allowed.

The following code produces this diagnostic because the constructor B.new is using a super parameter to pass one of the required positional parameters to the super constructor in A, but is explicitly passing the other in the super constructor invocation:

class A {
  A(int x, int y);
}

class B extends A {
  B(int x, super.y) : super(x);
}

If all the positional parameters can be super parameters, then convert the normal positional parameters to be super parameters:

class A {
  A(int x, int y);
}

class B extends A {
  B(super.x, super.y);
}

If some positional parameters can't be super parameters, then convert the super parameters to be normal parameters:

class A {
  A(int x, int y);
}

class B extends A {
  B(int x, int y) : super(x, y);
}

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.