library test;

import 'dart:async';

class MyFuture<T> implements Future<T> {
  MyFuture() {}
  MyFuture.value(x) {}
  dynamic noSuchMethod(invocation) => null;
  MyFuture<S> then<S>(FutureOr<S> f(T x), {Function? onError}) => throw '';
}

Future<int> g1(bool x) async {}
Future<int> g2(bool x) async => x ? 42 : new Future.value(42);
Future<int> g3(bool x) async {}
main() {}