Skip to content

avoid-banned-types

Group: Suspicious
Path: lint/suspicious/avoid-banned-types
Default: Off, opt in
Origin: Falcon
Rule: 20 of 512

Ban resolved explicit type annotations, including nested generic arguments. Aliases are expanded; import prefixes and nullability do not change matching. Unknown types are not reported. Match against the declaration's simple name.

Invalid

example.dartdart

class Legacy {}
typedef Alias = Legacy;
Legacy? value;
List<Legacy> values = [];
Alias? alias;

class Wrapper<T> {
  const Wrapper();
}
void genericConstructions() {
  final list = new List<Legacy>.empty();
  final wrapper = const Wrapper<Legacy>();
}

Use the supported alternative.

1class Legacy {}

2typedef Alias = Legacy;

∙

Use the supported alternative.

2typedef Alias = Legacy;

3Legacy? value;

∙

Use the supported alternative.

3Legacy? value;

4List<Legacy> values = [];

∙

Use the supported alternative.

4List<Legacy> values = [];

5Alias? alias;

∙

Use the supported alternative.

10void genericConstructions() {

11 final list = new List<Legacy>.empty();

∙

Use the supported alternative.

11 final list = new List<Legacy>.empty();

12 final wrapper = const Wrapper<Legacy>();

∙

Valid

example.dartdart

class Modern {}
Modern? value;
List<Modern> values = [];
// Unknown types cannot establish a forbidden declaration identity.
Unknown? unknown;

class Legacy {
  const Legacy();
}
class Box<Legacy> {
  Legacy? value;
}
void generic<Legacy>(Legacy value) {
  Legacy? local;
}
void outer() {
  void nested<Legacy>(Legacy value) {}
}
typedef Callback = void Function<Legacy>(Legacy);
void constructors() {
  Legacy();
  new Legacy();
  const Legacy();
}

class Wrapper<T> {
  const Wrapper();
}
void genericConstructions() {
  final list = new List<Modern>.empty();
  final wrapper = const Wrapper<Modern>();
}

Configure avoid-banned-types

Set its severity in falcon.json. See the configuration guide.

falcon.jsonjson

{
  "linter": {
    "rules": {
      "suspicious": {
        "avoid-banned-types": "error"
      }
    }
  }
}

Or silence one occurrence with a suppression comment; the reason is required.

example.dartdart

// falcon-ignore lint/suspicious/avoid-banned-types: <reason>

avoid-barrel-files
Discourage files containing only re-exports, without declarations or parts.
avoid-bitwise-operators-with-booleans
Flags & and | applied to two non-nullable boolean operands.
avoid-commented-out-code
Flags ordinary comments that contain recognizable Dart statements.
avoid-double-slash-imports
Reject repeated path separators in directive URIs (import, export and part).
avoid-dynamicavoid-dynamic
Flags explicit dynamic type annotations.
avoid-empty-elseavoid_empty_elserecommended
Flags an else clause whose body is an empty statement (else ;).
avoid-ignoring-return-valuesavoid-ignoring-return-values
Flags a discarded call whose resolved return type is non-void.
avoid-incorrect-uri
Reject runtime-invalid Uri constructor arguments: conflicting path or query inputs and query parameter values that are neither null, strings nor iterables of strings.