falcon

Rules / Style / type-init-formals

type-init-formals

lint/style/type-init-formals
recommended
Same as type_init_formals · Dart lints

Flags a redundant type annotation on an initializing formal or super parameter.

In C(int this.x) or C(int super.x) the parameter's type is already fixed by the field (or super-parameter) it initializes, so restating it is redundant and risks drifting out of sync with the field's declared type. Detection runs over the raw source because the parser only records a field/super formal when the token is literally this/super with no preceding type. To stay conservative the rule flags only a this./super. immediately preceded by a bare type identifier — a shape that in valid Dart occurs solely in a constructor parameter list — and skips non-type words such as final, covariant, return, and await.

Invalid

example.dartdart
// Type annotations on initializing formals and super parameters.
class A {
  int x;
  double y;
  A(int this.x, double this.y);
}

class Base {
  final int a;
  Base(this.a);
}

class Derived extends Base {
  Derived(int super.a);
}

class C {
  String name;
  num size;
  C(String this.name);
  C.sized(num this.size);
}

class D {
  bool flag;
  D(bool this.flag);
}
Don't type annotate initializing formals.
4 double y;
5 A(int this.x, double this.y);
Don't type annotate initializing formals.
4 double y;
5 A(int this.x, double this.y);
Don't type annotate initializing formals.
13class Derived extends Base {
14 Derived(int super.a);
Don't type annotate initializing formals.
19 num size;
20 C(String this.name);
Don't type annotate initializing formals.
20 C(String this.name);
21 C.sized(num this.size);
Don't type annotate initializing formals.
25 bool flag;
26 D(bool this.flag);

Valid

example.dartdart
// Initializing formals and super parameters without a redundant type.
class A {
  int x;
  double y;
  A(this.x, this.y);
}

class Base {
  final int a;
  Base(this.a);
}

class Derived extends Base {
  Derived(super.a);
}

class C {
  String name;
  num size;
  C(this.name);
  C.sized(this.size);
  void use() {
    print(this.name);
    return this.size.isNaN ? null : null;
  }
}

class D {
  bool flag;
  D(this.flag);
}

How to configure

Set the severity of type-init-formals in your falcon.json:

falcon.jsonjson
{
  "linter": {
    "rules": {
      "style": {
        "type-init-formals": "error"
      }
    }
  }
}

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