type_init_formals

Don't type annotate initializing formals.

From Effective Dart:

DON'T type annotate initializing formals.

If a constructor parameter is using this.x to initialize a field, then the type of the parameter is understood to be the same type as the field. If a a constructor parameter is using super.x to forward to a super constructor, then the type of the parameter is understood to be the same as the super constructor parameter.

Type annotating an initializing formal with a different type than that of the field is OK.

BAD:

class Point {
  int x, y;
  Point(int this.x, int this.y);
}

GOOD:

class Point {
  int x, y;
  Point(this.x, this.y);
}

BAD:

class A {
  int a;
  A(this.a);
}

class B extends A {
  B(int super.a);
}

GOOD:

class A {
  int a;
  A(this.a);
}

class B extends A {
  B(super.a);
}

To enable the type_init_formals rule, add type_init_formals under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - type_init_formals

If you're instead using the YAML map syntax to configure linter rules, add type_init_formals: true under linter > rules:

linter:
  rules:
    type_init_formals: true

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2025-01-27. View source or report an issue.