the Dart compiler exited unexpectedly, if I place a breakpoint inside a certain function

[escamoteur]

Unhandled exception:
FormatException: Invalid radix-10 number (at character 1)
package:functional_listener/functional_listener.dart
functional_listener.dart:1
^

#0      int._handleFormatError (dart:core-patch/integers_patch.dart:126:5)
#1      int._parseRadix (dart:core-patch/integers_patch.dart:152:16)

#2      int._parse (dart:core-patch/integers_patch.dart:98:12)
#3      int.parse (dart:core-patch/integers_patch.dart:60:12)
#4      parseDefinitionTypes (package:front_end/src/api_prototype/expression_compilation_tools.dart:113:36)
#5      createDefinitionsWithTypes (package:front_end/src/api_prototype/expression_compilation_tools.dart:32:7)
#6      IncrementalCompiler.compileExpression (package:vm/incremental_compiler.dart:219:50)
#7      FrontendCompiler.compileExpression (package:frontend_server/frontend_server.dart:981:45)
#8      listenAndCompile.<anonymous closure> (package:frontend_server/frontend_server.dart:1452:26)
#9      _RootZone.runUnaryGuarded (dart:async/zone.dart:1594:10)
#10     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339:11)
#11     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:271:7)
#12     _SinkTransformerStreamSubscription._add (dart:async/stream_transformers.dart:63:11)
#13     _EventSinkWrapper.add (dart:async/stream_transformers.dart:13:11)
#14     _StringAdapterSink.add (dart:convert/string_conversion.dart:228:11)
#15     _LineSplitterSink._addLines (dart:convert/line_splitter.dart:164:13)
#16     _LineSplitterSink.addSlice (dart:convert/line_splitter.dart:131:7)
#17     StringConversionSink.add (dart:convert/string_conversion.dart:39:5)

It only happens when I set a breakpoint inside

if I remove the breakpoint the app doesn't crash.
I also have no idea where I should do an int.parse to get such an exception. also thee reported file as place where it happens doesn't make sense as the listen function only looks like this

  ListenableSubscription listen(
    void Function(T, ListenableSubscription) handler,
  ) {
    final subscription = ListenableSubscription(this);
    subscription.handler = () => handler(this.value, subscription);
    this.addListener(subscription.handler);
    return subscription;
  }

happens on: Flutter (Channel stable, 3.13.1, on Microsoft Windows [Version 10.0.19045.3324], locale de-DE)

[derekxu16]

I created a Flutter app and made the contents of lib/main.dart the following:

import 'package:flutter/material.dart';
import 'package:functional_listener/functional_listener.dart';

class C {
  Object error = 123;
}

void main() {
  final listenable1 = ValueNotifier<C?>(C());
  final listenable2 = ValueNotifier<C>(C());

  final mergedListenable = listenable1.mergeWith([
    listenable2,
  ]);
  final subscription = mergedListenable.listen((x, _) {
    final apiException = x?.error;
    print(apiException);
  });

  listenable1.value = C();

  subscription.cancel();
}

I was able to set a breakpoint on the final apiException = x?.error; line without any problems. I tested on Linux and not Windows though. It would take me a while to get my Windows environment back up-to-date. So first, can you please try this example on Windows? If it works without issue, can you please try writing a minimal reproduction example? It will be hard to fix this bug without one. Thanks!

[escamoteur]

unfortunately I couldn't reproduce it with the example from you. I can still reproduce it in our real app project. Still wondering why it crashes in

#0 int._handleFormatError (dart:core-patch/integers_patch.dart:126:5)

and the stack trace seems to have no connection to my code whatsoever.

Is there anything that I can add to my code to get more details?
Because I have no idea how to reproduce this in a smaller demo project?

[derekxu16]

Since you're using VSCode, can you please follow these instructions and paste the contents of the log here?

[escamoteur]

dart.log

[derekxu16]

Looks like Dart Code is trying to get the value of di, which is making the compiler crash. Is di from a public package or is it something you wrote yourself? And is di the name of a function or the name of a class here?

[escamoteur]

di is a global variable defined in my package watch_it

[escamoteur]

oh, and its a callable class

[mraleph]

/cc @johnniwinther @jensjoha - seems to be related to the expression evaluation.

[johnniwinther]

This might be related to #53453 where the crash also originates from FrontEndCompiler.compileExpression where an invalid definitionTypes value can cause the crash.

@derekxu16 @mraleph Do you know where these values are created?

[johnniwinther]

@aam Do you know where calls to compileExpression comes from when called through Flutter?

I can see the change that added the definitionTypes argument (flutter/flutter@09c0706) but I cannot see any call-site changes other than in tests.