Catch error using catchError in a future and throw another type - https://stackoverflow.com/questions/55596257/catch-error-using-catcherror-in-a-future-and-throw-another-type/55596655#55596655

main.dart

class FirstError { }
class SecondError { }

Future<void> someApi() {
  return Future(() {
    throw FirstError();
  }).catchError((error, stackTrace) {
    print("inner: $error");
    // although `throw SecondError()` has the same effect.
    return Future.error(SecondError());
  });
}

void main() {
  someApi()
    .then((val) { print("success"); })
    .catchError((error, stackTrace) { print("outer: $error"); });
}