astonishing-spray-3881

readme.md

astonishing-spray-3881

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main.dart

import 'dart:async';

void main() async {
  // A function marked async will implicitly return a Future.
  future(sync: true).then(print);
  future(sync: false).then(print);
  print('main (sync)');
  
  // clear pending futures
  await Future<void>.delayed(Duration.zero);
  
  // We would expect line 13 to print first if it was synchronous.
  scheduleMicrotask(() => print('microtask'));
  print(await futureOr(sync: true));
  print(await futureOr(sync: false));
  
  // clear pending futures
  await Future<void>.delayed(Duration.zero);
  
  // Treat FutureOr as a sealed class to avoid unnecessary waits
  scheduleMicrotask(() => print('microtask'));
  switch (futureOr(sync: true)) {
    case final String res: print(res);
    case final fut: print(await fut);
  }
}

Future<String> future({required bool sync}) async {
  if (sync) {
    return 'future (sync)';
  }
  await Future<void>.delayed(Duration.zero);
  return 'future (async)';
}

FutureOr<String> futureOr({required bool sync}) {
  if (sync) {
    return 'future (sync)';
  }
  return Future.value('future (async)');
}