Destructuring record that contains Finalizable throws "Attempt to execute code removed by Dart AOT compiler (TFA)"

[blaugold]

This tracker is for issues related to:

• Dart VM

Executing the following program (see this repository for a full repro) causes "Attempt to execute code removed by Dart AOT compiler (TFA)" to be thrown:

import 'package:cbl/cbl.dart';
import 'package:cbl_dart/cbl_dart.dart';

void main() async {
  await CouchbaseLiteDart.init(edition: Edition.enterprise);

  final db = Database.openSync('db');

  final replicatorConfiguration = ReplicatorConfiguration(
    target: UrlEndpoint(Uri.parse('ws://localhost:4984/db')),
  )..addCollection(db.defaultCollection);

  final replicator = await Replicator.createSync(replicatorConfiguration);

  await replicator.close();
  await db.close();
}

Unhandled exception:
Attempt to execute code removed by Dart AOT compiler (TFA)
#0      FfiReplicator.create (package:cbl/src/replication/ffi_replicator.dart)
#1      SyncReplicator.create (package:cbl/src/replication/replicator.dart:278)
#2      Replicator.createSync (package:cbl/src/replication/replicator.dart:147)
#3      main (file:///Users/terwesten/dev/repo_cbl_code_removed_tfa/main.dart:14)
<asynchronous suspension>

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#### General info

- Dart 3.3.0-219.0.dev (dev) (Mon Dec 11 20:03:47 2023 -0800) on "macos_arm64"
- on macos / Version 14.2 (Build 23C64)
- locale is en-US

#### Project info

- sdk constraint: '^3.2.0'
- dependencies: cbl, cbl_dart
- dev_dependencies: 

#### Process info

| Memory |  CPU | Elapsed time | Command line                                                                    |
| -----: | ---: | -----------: | ------------------------------------------------------------------------------- |
|  71 MB | 0.0% |        09:38 | dart devtools --machine --allow-embedding --port 9199                           |
| 588 MB | 0.0% |        09:38 | dart language-server --protocol=lsp --client-id=VS-Code --client-version=3.78.2 |
| 456 MB | 0.0% |        08:16 | dart language-server --protocol=lsp --client-id=VS-Code --client-version=3.78.2 |
| 150 MB | 0.0% |        09:38 | flutter_tools.snapshot daemon  

[blaugold]

Actually, here is a minimal reproducible example:

import 'dart:ffi';

void main() {
  final (a, _) = b();
  print(a);
}

class A implements Finalizable {}

(A, bool) b() => (A(), true);

Unhandled exception:
Attempt to execute code removed by Dart AOT compiler (TFA)
#0      main (file:///Users/terwesten/dev/repo_cbl_code_removed_tfa/simple.dart)
#1      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297)
#2      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184)

[blaugold]

/cc @dcharkes

[dcharkes]

I suspect we have another corner case with the finalizable transform, some previous corner cases:

• Dart Compiler removes declaration of Finalizable class #52596
• Awaiting for a Future returning a class that implements Finalizable in a for-in loop causes a crash #51538

Let me investigate what the compiler makes of this.

static method main() → void {
  final hoisted has-declared-initializer self::A a;
  {
    final synthesized(self::A, core::bool) #0#0 = self::b();
    a = block {
      final synthesized self::A :expressionValueWrappedFinalizable = #0#0.$1{self::A};
      _in::reachabilityFence(a);
    } =>:expressionValueWrappedFinalizable;
  }
  core::print(a);
  _in::reachabilityFence(a);
}

Gets turned into

static method main() → void {
  final hoisted has-declared-initializer self::A a;
  {
    final synthesized(self::A, core::bool) #0#0 = [@vm.inferred-type.metadata=dart.core::_Record] self::b();
    a = block {
      final synthesized self::A :expressionValueWrappedFinalizable = #0#0.$1{self::A};
      throw "Attempt to execute code removed by Dart AOT compiler (TFA)";
    } =>:expressionValueWrappedFinalizable;
  }
  core::print(a);
  _in::reachabilityFence(a);
}

Basically, we have a fence on the variable before it get's projected out from the record.

final hoisted has-declared-initializer self::A a; This should be treated in the same way as a late variable as we did in https://dart-review.googlesource.com/c/sdk/+/287460:

static method main() → void {
  self::A? :a:finalizableValue;
  final hoisted has-declared-initializer self::A a;
  {
    final synthesized(self::A, core::bool) #0#0 = [@vm.inferred-type.metadata=dart.core::_Record] self::b();
    :a:finalizableValue = a = block {
      final synthesized self::A :expressionValueWrappedFinalizable = #0#0.$1{self::A};
      _in::reachabilityFence(:a:finalizableValue);
    } =>:expressionValueWrappedFinalizable;
  }
  core::print(a);
  _in::reachabilityFence(:a:finalizableValue);
}

[dcharkes]

Fix: https://dart-review.googlesource.com/c/sdk/+/343180

Thanks for reporting @blaugold !

[a-siva]

@dcharkes Can this be closed ?

[dcharkes]

I'd like someone from the VM team to review the fix and land it first.