No try catch, safe use await in one line.

never_catch.dart

import 'dart:async';

Future<void> main() async {
  final a = await err().noc();
  print(a);
  print(a.runtimeType);
  print(a.hasErr);
  print(a.value);
  print(a.value.runtimeType);
  print(a.error);
  print('==============================');
  final b = await succ().noc();
  print(b);
  print(b.runtimeType);
  print(b.hasErr);
  print(b.value);
  print(b.value.runtimeType);
  print(b.error);
  print('==============================');
  final c = await voidf().noc();
  print(c);
  print(c.runtimeType);
  print(c.hasErr);
  // safe type check. void not any called.
  // print(c.ok);
  // print(c.ok.runtimeType);
  print(c.error);
}

Future<String?> err() async {
  throw UnsupportedError('Unknown error');
}

Future<String> succ() async {
  return 'success';
}

Future<void> voidf() async {
  print('void function.');
}

extension NeverCatchExtension<T> on Future<T> {
  Future<NeverCatch<T>> noc() => noCatch(this);
}

Future<NeverCatch<T>> noCatch<T>(Future<T> future) {
  return future.then<NeverCatch<T>>((T value) {
    return NeverCatch.val(value);
  }).catchError((error, stackTrace) {
    return NeverCatch.cat<T>(error, stackTrace);
  });
}

class NeverCatch<T> {
  NeverCatch._({this.value, this.error, this.stackTrace});

  static NeverCatch<T> val<T>(T value) {
    return NeverCatch._(value: value);
  }

  static NeverCatch<T> cat<T>(Object? error, [StackTrace? stackTrace]) {
    return NeverCatch._(error: error, stackTrace: stackTrace);
  }

  final T? value;
  final Object? error;
  final StackTrace? stackTrace;

  bool get hasErr => error != null;

  @override
  String toString() {
    return 'NeverCatch(value: $value, error: $error, stackTrace: $stackTrace)';
  }
}