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avoid-unrelated-type-casts

v1.0.0
warning
recommended
pro+

Warns about unrelated usages of the as operator and cast method.

Incorrect usages of the as operator can lead to runtime exceptions and unexpected behavior.

Example​

❌ Bad:

class Example {
  final regularString = '';
  final myList = <int>[1, 2, 3];

  final Animal animal = Animal();

  void main() {
    // LINT: Avoid unrelated 'as' cast. Target type has no overlap with the cast type.
    final result = regularString as int;
    // LINT: Avoid unrelated 'as' cast. Target type has no overlap with the cast type.
    final result2 = myList as List<String>;

    // LINT: Avoid unrelated 'as' cast. Target type has no overlap with the cast type.
    final result3 = animal as NotAnimal;

    // LINT: Avoid unrelated 'as' cast. Target type has no overlap with the cast type.
    if (animal case Animal() as NotAnimal) {}
  }
}

class Animal {}

class HomeAnimal extends Animal {}

class NotAnimal {}

✅ Good:

class Example {
  final regularString = '';
  final myList = <int>[1, 2, 3];

  final Animal animal = Animal();

  void main() {
    final result = regularString;
    final result2 = myList;

    final result3 = animal;

    if (animal case Animal() as HomeAnimal) {}
  }
}

Known Limitations​

The rule does not have access to all subclasses and their mixins and therefore in some cases will highlight such usages as incorrect.

class Parent {}

mixin Mixin {}

class Child with Mixin {}

void fn() {
  final list = <Parent>[]; // List of 'Parents'

  for (final item in list) {
    (item as Mixin); // Expected
  }
}

Additional Resources​

Last updated on