[Flutter] type '(int) => void' is not a subtype of type '(Object) => void'

I checked all my generics are all OK. Inheritance seems ok. Type inference seems ok. No compiler error. I don't have any hard type casting. Everything is seems strongly typed.

class ModelField {}

class DropdownField<V> extends ModelField {
final void Function(V value) setValue;

final List<V> options;

DropdownField({
required this.setValue,
required this.options,
});
}

void _buildDropdownField<V>(DropdownField<V> field) {
final options = field.options;
final data = options.first;

field.setValue(data); // error Here
}

void _renderField(ModelField field) {
/// from server
// if field is StringField, else if field is DateField, ... else
if (field is DropdownField<Object>) {
// print('field is DropdownField<dynamic, dynamic>');
_buildDropdownField(field);
}
}

void main() {
final field =
DropdownField<int>(setValue: (value) => print(value), options: [1, 2, 3]);

_renderField(field);
}


But when I run:

Unhandled exception:
type '(int) => void' is not a subtype of type '(Object) => void'
#0 _buildDropdownField (package:shared_core/weird_dart/generic_promotion.dart:18:9)
#1 _renderField (package:shared_core/weird_dart/generic_promotion.dart:26:5)
#2 main (package:shared_core/weird_dart/generic_promotion.dart:34:3)
#3 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19)
#4 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)


How can int not be a subtype of Object???

I am so confused (or Dart is) I hope it's me. But this error occurs only at run time.

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