Implementing `Finalizable` causes unhandled exception in `FrontendCompiler`

[blaugold]

When adding Finalizable to a specific class in my project, I get the following exception when running dart test:

unhandled exception:
Null check operator used on a null value
#0      BinaryPrinter._getVariableIndex (package:kernel/binary/ast_to_binary.dart:83:17)
#1      BinaryPrinter.visitVariableGet (package:kernel/binary/ast_to_binary.dart:1497:17)
#2      VariableGet.accept (package:kernel/ast.dart:4137:44)
#3      BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#4      BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#5      BinaryPrinter.visitArguments (package:kernel/binary/ast_to_binary.dart:1751:5)
#6      Arguments.accept (package:kernel/ast.dart:5119:38)
#7      BinaryPrinter.writeArgumentsNode (package:kernel/binary/ast_to_binary.dart:444:10)
#8      BinaryPrinter.visitStaticInvocation (package:kernel/binary/ast_to_binary.dart:1734:5)
#9      StaticInvocation.accept (package:kernel/ast.dart:6289:44)
#10     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#11     BinaryPrinter.visitExpressionStatement (package:kernel/binary/ast_to_binary.dart:2052:5)
#12     ExpressionStatement.accept (package:kernel/ast.dart:8829:43)
#13     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#14     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#15     BinaryPrinter.visitBlockExpression (package:kernel/binary/ast_to_binary.dart:2017:5)
#16     BlockExpression.accept (package:kernel/ast.dart:8461:44)
#17     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#18     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#19     BinaryPrinter.visitArguments (package:kernel/binary/ast_to_binary.dart:1751:5)
#20     Arguments.accept (package:kernel/ast.dart:5119:38)
#21     BinaryPrinter.writeArgumentsNode (package:kernel/binary/ast_to_binary.dart:444:10)
#22     BinaryPrinter.visitStaticInvocation (package:kernel/binary/ast_to_binary.dart:1734:5)
#23     StaticInvocation.accept (package:kernel/ast.dart:6289:44)
#24     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#25     BinaryPrinter.writeOptionalNode (package:kernel/binary/ast_to_binary.dart:522:7)
#26     BinaryPrinter.writeVariableDeclaration (package:kernel/binary/ast_to_binary.dart:2266:5)
#27     BinaryPrinter.visitLet (package:kernel/binary/ast_to_binary.dart:2006:5)
#28     Let.accept (package:kernel/ast.dart:8390:44)
#29     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#30     BinaryPrinter.visitYieldStatement (package:kernel/binary/ast_to_binary.dart:2246:5)
#31     YieldStatement.accept (package:kernel/ast.dart:10180:43)
#32     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#33     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#34     BinaryPrinter.visitBlock (package:kernel/binary/ast_to_binary.dart:2063:5)
#35     Block.accept (package:kernel/ast.dart:8885:43)
#36     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#37     BinaryPrinter.visitLabeledStatement (package:kernel/binary/ast_to_binary.dart:2096:5)
#38     LabeledStatement.accept (package:kernel/ast.dart:9095:43)
#39     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#40     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#41     BinaryPrinter.visitBlock (package:kernel/binary/ast_to_binary.dart:2063:5)
#42     Block.accept (package:kernel/ast.dart:8885:43)
#43     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#44     BinaryPrinter.visitTryCatch (package:kernel/binary/ast_to_binary.dart:2214:5)
#45     TryCatch.accept (package:kernel/ast.dart:9918:43)
#46     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#47     BinaryPrinter.writeOptionalNode (package:kernel/binary/ast_to_binary.dart:522:7)
#48     BinaryPrinter.visitFunctionNode (package:kernel/binary/ast_to_binary.dart:1481:5)
#49     FunctionNode.accept (package:kernel/ast.dart:3846:38)
#50     BinaryPrinter.writeFunctionNode (package:kernel/binary/ast_to_binary.dart:437:10)
#51     BinaryPrinter.visitFunctionDeclaration (package:kernel/binary/ast_to_binary.dart:2290:5)
#52     FunctionDeclaration.accept (package:kernel/ast.dart:10502:43)
#53     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#54     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:340:7)
#55     BinaryPrinter.visitBlock (package:kernel/binary/ast_to_binary.dart:2063:5)
#56     Block.accept (package:kernel/ast.dart:8885:43)
#57     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:430:10)
#58     BinaryPrinter.writeOptionalNode (package:kernel/binary/ast_to_binary.dart:522:7)
#59     BinaryPrinter.visitFunctionNode (package:kernel/binary/ast_to_binary.dart:1481:5)
#60     FunctionNode.accept (package:kernel/ast.dart:3846:38)
#61     BinaryPrinter.writeFunctionNode (package:kernel/binary/ast_to_binary.dart:437:10)
#62     BinaryPrinter.visitProcedure (package:kernel/binary/ast_to_binary.dart:1312:5)
#63     Procedure.accept (package:kernel/ast.dart:3151:40)
#64     BinaryPrinter.writeProcedureNode (package:kernel/binary/ast_to_binary.dart:458:10)
#65     BinaryPrinter.writeProcedureNodeList (package:kernel/binary/ast_to_binary.dart:349:7)
#66     BinaryPrinter.visitClass (package:kernel/binary/ast_to_binary.dart:1216:5)
#67     Class.accept (package:kernel/ast.dart:1408:38)
#68     BinaryPrinter.writeClassNode (package:kernel/binary/ast_to_binary.dart:472:10)
#69     BinaryPrinter.writeClassNodeList (package:kernel/binary/ast_to_binary.dart:367:7)
#70     BinaryPrinter.visitLibrary (package:kernel/binary/ast_to_binary.dart:1058:5)
#71     Library.accept (package:kernel/ast.dart:565:38)
#72     BinaryPrinter.writeLibraryNode (package:kernel/binary/ast_to_binary.dart:451:10)
#73     BinaryPrinter.writeLibraries (package:kernel/binary/ast_to_binary.dart:756:9)
#74     BinaryPrinter.writeComponentFile.<anonymous closure> (package:kernel/binary/ast_to_binary.dart:595:7)
#75     Timeline.timeSync (dart:developer/timeline.dart:157:22)
#76     BinaryPrinter.writeComponentFile (package:kernel/binary/ast_to_binary.dart:577:14)
#77     IncrementalSerializer.serialize (package:front_end/src/fasta/incremental_serializer.dart:308:13)
#78     IncrementalSerializer.writePackagesToSinkAndTrimComponent (package:front_end/src/fasta/incremental_serializer.dart:158:24)
#79     FrontendCompiler.writeDillFile (file:///opt/s/w/ir/cache/builder/sdk/pkg/frontend_server/lib/frontend_server.dart:728:29)
#80     FrontendCompiler.recompileDelta (file:///opt/s/w/ir/cache/builder/sdk/pkg/frontend_server/lib/frontend_server.dart:838:13)
<asynchronous suspension>

Dart version:

Dart SDK version: 2.17.1 (stable) (Tue May 17 17:58:21 2022 +0000) on "macos_arm64"

Steps to replicate:

git clone https://github.com/cbl-dart/cbl-dart.git --depth 1 -b refactor/finalizable
cd cbl-dart
dart pub global activate melos
melos bs --scope cbl_e2e_tests_standalone_dart
cd packages/cbl_e2e_tests_standalone_dart
dart test

When FfiReplicator is not implementing Finalizable the error goes away.

[blaugold]

Maybe @dcharkes has some insight on this since he implemented Finalizable.

[blaugold]

#49122 looks very similar to this issue, but much easier to reproduce and not specific to Finalizable.

[voledyaev]

I was able to reproduce the same issue in my project and found the root of problem, this could be any async operation with saving a finalizable instance to a variable
Consider this example with async factory method

Future<void> main(List<String> arguments) async {
  // Working without any problem
  await MyFinalizable.create();

  // You'll face BinaryPrinter._getVariableIndex crash if will try to save created instance to the variable
  final myFinalizable = await MyFinalizable.create();

  // Or you even can just try to use await for finalizable, same crash
  final mySecondFinalizable = await MySecondFinalizable();
}

class MyFinalizable implements Finalizable {
  MyFinalizable._();

  static Future<MyFinalizable> create() async {
    // Some initialization...
    await Future.delayed(Duration(seconds: 1));

    return MyFinalizable._();
  }
}

class MySecondFinalizable implements Finalizable {
  MySecondFinalizable();
}

Dart SDK version: 2.17.1 (stable) on "macos_arm64"

[dcharkes]

Fix underway: https://dart-review.googlesource.com/c/sdk/+/246520

[dcharkes]

Thanks @voledyaev for making the minimal repro, that was really useful! 🚀
Thanks for reporting @blaugold.