I understand that isolates in Dart run in separate memory spaces and communicate via message passing and I should serialize these objects first before sending them to the isolate, but I found a strange behavior while using the isolate in a closure, here is my example:

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Closure and Isolate Example')),
      body: Center(
        child: ElevatedButton(
          onPressed: () async {
            final a = Text("TEXT");

            await Isolate.spawn((_) {
              print(a);
            }, []);
          },
          child: Text('Run Isolate'),
        ),
      ),
    );
  }
}

This example worked and printed the widget, but if I put this line outside the onPressed

final a = Text("TEXT");

it throws an error:
`E/flutter (25736): <- Instance of 'WidgetsFlutterBinding' (from package:flutter/src/widgets/binding.dart)

E/flutter (25736): <- field this in SemanticsBinding._handleSemanticsActionEvent (from package:flutter/src/widgets/binding.dart)

E/flutter (25736): <- _onSystemFontFamilyChangedZone in Instance of 'PlatformDispatcher' (from dart:ui)

E/flutter (25736): <- platformDispatcher in Instance of 'FlutterView' (from dart:ui)
...

so I can use any object from the closure in the isolate and it will work, no matter how complex this object is, how this happens?