if-case gives different results in debug and release mode

[Heewookji]

#### General info

- Dart 3.5.4 (stable) (Wed Oct 16 16:18:51 2024 +0000) on "macos_arm64"
- on macos / Version 14.3.1 (Build 23D60)

The code below has different print results depending on debug and release modes.
debug : it is not String null
release: it is String null

void main() {
  TestClass(type: TestType.a).run();
}

enum TestType {
  a,
  b,
}

class TestClass {
  TestClass({
    required this.type,
  });

  final TestType type;

  String? get _subtitle {
    return type == TestType.a ? null : 'test subtitle';
  }

  void run() {
    if (_subtitle case String _) {
      print('it is String $_subtitle');
    } else {
      print('it is not String $_subtitle');
    }
  }
}

[dart-github-bot]

Summary: The if-case statement in the provided code produces different output in debug and release modes. In debug mode, it prints "it is not String null", while in release mode, it prints "it is String null". This discrepancy suggests a potential bug related to type inference or optimization in the if-case statement.

[parlough]

Thanks for opening an issue!

Could you provide more information about what debug and release modes are you talking about? How are you building and running the app to get each result?

[Heewookji]

@parlough
After creating a sample app using flutter create, I ran the main code above using flutter run in debug mode and flutter run --release in release mode. (with android simulator)

[julemand101]

I can reproduce this with normal Dart:

> dart --version
Dart SDK version: 3.5.4 (stable) (Wed Oct 16 16:18:51 2024 +0000) on "windows_x64"

> dart .\bug.dart
it is not String null
> dart compile exe bug.dart
Generated: <hidden>\bug.exe
> .\bug.exe 
it is String null

[julemand101]

Testing with latest beta release, I can no longer reproduce the issue:

dart.exe --version
Dart SDK version: 3.6.0-334.3.beta (beta) (Fri Oct 11 09:25:26 2024 +0000) on "windows_x64"

> dart.exe bug.dart
it is not String null
> dart.exe compile exe bug.dart
Generated: <hidden>\bug.exe
> .\bug.exe
it is not String null

[mraleph]

I think this was fixed by 36054ee