Type promotion doesn't work when a closure is used

@johnpryan commented on Apr 8, 2021, 12:12 AM UTC:

Result checkLottery(bool isLucky) {
  String? nullString;
  if (isLucky) {
    nullString = 'You win!';
  }

  if (nullString != null) {
    // Use this to fix:
    // var nonNullString = nullString;
    return () {
      return Result(nullString);
      //            ^ The argument type 'String?' can't be assigned to the parameter type 'String'.
    }();
  }

  return Result('You lose.');
}

@leafpetersen is there already an issue for this? I think this is called out in #44900

DartPad example

This issue was moved by keertip from dart-lang/sdk#45622.

@eernstg commented on Apr 8, 2021, 11:49 AM UTC:

Cf. dart-lang/language#1247.