always_specify_types

Specify type annotations.

This rule is available as of Dart 2.0.

This rule has a quick fix available.

Incompatible rules: avoid_types_on_closure_parameters, omit_local_variable_types, omit_obvious_local_variable_types, omit_obvious_property_types

From the style guide for the flutter repo:

DO specify type annotations.

Avoid var when specifying that a type is unknown and short-hands that elide type annotations. Use dynamic if you are being explicit that the type is unknown. Use Object if you are being explicit that you want an object that implements == and hashCode.

BAD:

var foo = 10;
final bar = Bar();
const quux = 20;

GOOD:

int foo = 10;
final Bar bar = Bar();
String baz = 'hello';
const int quux = 20;

NOTE: Using the the @optionalTypeArgs annotation in the meta package, API authors can special-case type parameters whose type needs to be dynamic but whose declaration should be treated as optional. For example, suppose you have a Key object whose type parameter you'd like to treat as optional. Using the @optionalTypeArgs would look like this:

import 'package:meta/meta.dart';

@optionalTypeArgs
class Key<T> {
 ...
}

void main() {
  Key s = Key(); // OK!
}

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

linter:
  rules:
    - always_specify_types

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2024-07-03. View source or report an issue.