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Actions.find et.al should return Action<Intent> instead of Action<T>. #180871
Description
This is a TODO extracted from #180435.
In the Action<T extends Intent> class the type parameter T is contravariant since an instance of Action<Intent> should be able to handle any Intent. But currently it means the opposite: an Action<Intent> can handle Intent, but not any Intent subtypes. This is a problem for find but not invoke.
expected behavior:
final class MyIntent extends Intent {}
// Put this widget in the tree.
Actions(
actions: const {
MyIntent: DoNothingAction(),
},
child: ...
),
// Able to find the intent
final intent = Actions.find<Intent>(context, intent: intent);Actual behavior:
crashes because currently Actions.find returns Action<T>. We are able to find Action<U> where T :< U (and verify that in debug mode), but casting the Action<U> to Action<T> would result in a runtime crash.
Options:
- ignore this and wait for contravariance to be added
- change the return type to
Action<Intent> - deprecate
maybeFindandfindand redirect people to invoke.
Activity
loic-sharma commentedon Jan 13, 2026
@LongCatIsLooong would another option be to deprecate
maybeFindandfindin favor of new methods with return typeAction<Intent>?Potential names for the new methods:
Actions.of, maybe acceptable since this does establish a dependencyActions.lookupActions.getFix some type checks in the `Actions` widget (flutter#180883)