always_specify_types

Specify type annotations.

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 @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!
}

The always_specify_types rule is incompatible with the following rules:

• avoid_types_on_closure_parameters
• omit_local_variable_types
• omit_obvious_local_variable_types
• omit_obvious_property_types

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

If you're instead using the YAML map syntax to configure linter rules, add always_specify_types: true under linter > rules:

linter:
  rules:
    always_specify_types: true

Unless stated otherwise, the documentation on this site reflects Dart 3.7.0. Page last updated on 2025-01-27. View source or report an issue.