iterable_contains_unrelated_type

Details
Usage

Invocation of Iterable.contains with references of unrelated types.

This rule is currently deprecated and available as of Dart 2.0.0.

Details

DON’T invoke contains on Iterable with an instance of different type than the parameter type.

Doing this will invoke == on its elements and most likely will return false.

BAD:

void someFunction() {
  var list = <int>[];
  if (list.contains('1')) print('someFunction'); // LINT
}

BAD:

void someFunction3() {
  List<int> list = <int>[];
  if (list.contains('1')) print('someFunction3'); // LINT
}

BAD:

void someFunction8() {
  List<DerivedClass2> list = <DerivedClass2>[];
  DerivedClass3 instance;
  if (list.contains(instance)) print('someFunction8'); // LINT
}

BAD:

abstract class SomeIterable<E> implements Iterable<E> {}

abstract class MyClass implements SomeIterable<int> {
  bool badMethod(String thing) => this.contains(thing); // LINT
}

GOOD:

void someFunction10() {
  var list = [];
  if (list.contains(1)) print('someFunction10'); // OK
}

GOOD:

void someFunction1() {
  var list = <int>[];
  if (list.contains(1)) print('someFunction1'); // OK
}

GOOD:

void someFunction4() {
  List<int> list = <int>[];
  if (list.contains(1)) print('someFunction4'); // OK
}

GOOD:

void someFunction5() {
  List<ClassBase> list = <ClassBase>[];
  DerivedClass1 instance;
  if (list.contains(instance)) print('someFunction5'); // OK
}

abstract class ClassBase {}

class DerivedClass1 extends ClassBase {}

GOOD:

void someFunction6() {
  List<Mixin> list = <Mixin>[];
  DerivedClass2 instance;
  if (list.contains(instance)) print('someFunction6'); // OK
}

abstract class ClassBase {}

abstract class Mixin {}

class DerivedClass2 extends ClassBase with Mixin {}

GOOD:

void someFunction7() {
  List<Mixin> list = <Mixin>[];
  DerivedClass3 instance;
  if (list.contains(instance)) print('someFunction7'); // OK
}

abstract class ClassBase {}

abstract class Mixin {}

class DerivedClass3 extends ClassBase implements Mixin {}

DEPRECATED: This rule is deprecated in favor of collection_methods_unrelated_type. The rule will be removed in a future Dart release.

Usage

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

linter:
  rules:
    - iterable_contains_unrelated_type