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Fasta crashes under specific conditions in anonymous mixin applications #34511

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chloestefantsova opened this issue Sep 18, 2018 · 2 comments
Closed

Fasta crashes under specific conditions in anonymous mixin applications #34511

chloestefantsova opened this issue Sep 18, 2018 · 2 comments
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@chloestefantsova
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area-front-end Use area-front-end for front end / CFE / kernel format related issues. crash Process exits with SIGSEGV, SIGABRT, etc. An unhandled exception is not a crash. P2 A bug or feature request we're likely to work on
Projects
Dart Front End
Milestone
Future

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@chloestefantsova
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Consider the following program:

class A<X, Y> {}

class B<Z> extends Object with A<void Function(Z), int> {}

main() {}

When being compiled with the current repo checkout, it produces the following output:

$ pkg/front_end/tool/fasta compile --strong --dump-ir /tmp/qwerty.dart
library;
import self as self;
import "dart:core" as core;

class A<X extends core::Object = dynamic, Y extends core::Object = dynamic> extends core::Object {
  synthetic constructor •() → void
    : super core::Object::•()
    ;
}
abstract class _B&Object&A extends core::Object implements self::A<(self::B::Z) → void, core::int> {
  synthetic constructor •() → void
    : super core::Object::•()
    ;
}
class B<Z extends core::Object = dynamic> extends self::_B&Object&A {
  synthetic constructor •() → void
    : super core::Object::•()
    ;
}
static method main() → dynamic {}

Unhandled exception:
Type parameter #lib1::B::Z is not indexed
#0      TypeParameterIndexer.[] (package:kernel/binary/ast_to_binary.dart:2055:28)
#1      BinaryPrinter.visitTypeParameterType (package:kernel/binary/ast_to_binary.dart:1678:38)
#2      TypeParameterType.accept (package:kernel/ast.dart:4839:34)
#3      BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:250:10)
#4      BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:242:7)
#5      BinaryPrinter.visitFunctionType (package:kernel/binary/ast_to_binary.dart:1652:7)
#6      FunctionType.accept (package:kernel/ast.dart:4636:34)
#7      BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:250:10)
#8      BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:242:7)
#9      BinaryPrinter.visitSupertype (package:kernel/binary/ast_to_binary.dart:1641:7)
#10     Supertype.accept (package:kernel/ast.dart:4944:26)
#11     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:250:10)
#12     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:242:7)
#13     BinaryPrinter.visitClass (package:kernel/binary/ast_to_binary.dart:768:5)
#14     Class.accept (package:kernel/ast.dart:921:30)
#15     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:250:10)
#16     BinaryPrinter.writeNodeList (package:kernel/binary/ast_to_binary.dart:242:7)
#17     BinaryPrinter.visitLibrary (package:kernel/binary/ast_to_binary.dart:620:5)
#18     Library.accept (package:kernel/ast.dart:409:30)
#19     BinaryPrinter.writeNode (package:kernel/binary/ast_to_binary.dart:250:10)
#20     List.forEach (dart:core-patch/dart:core/growable_array.dart:278)
#21     BinaryPrinter.writeLibraries (package:kernel/binary/ast_to_binary.dart:445:25)
#22     BinaryPrinter.writeComponentFile (package:kernel/binary/ast_to_binary.dart:328:5)
#23     writeComponentToFile (package:front_end/src/fasta/kernel/utils.dart:45:13)
<asynchronous suspension>
#24     CompileTask.compile (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/entry_points.dart:287:13)
<asynchronous suspension>
#25     compile.<anonymous closure>.<anonymous closure> (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/entry_points.dart:214:25)
<asynchronous suspension>
#26     withGlobalOptions.<anonymous closure> (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/command_line.dart:430:13)
#27     CompilerContext.runWithOptions.<anonymous closure> (package:front_end/src/fasta/compiler_context.dart:131:20)
<asynchronous suspension>
#28     CompilerContext.runInContext.<anonymous closure>.<anonymous closure> (package:front_end/src/fasta/compiler_context.dart:120:46)
#29     new Future.sync (dart:async/future.dart:224)
#30     CompilerContext.runInContext.<anonymous closure> (package:front_end/src/fasta/compiler_context.dart:120:19)
#31     _rootRun (dart:async/zone.dart:1124)
#32     _CustomZone.run (dart:async/zone.dart:1021)
#33     _runZoned (dart:async/zone.dart:1516)
#34     runZoned (dart:async/zone.dart:1463)
#35     CompilerContext.runInContext (package:front_end/src/fasta/compiler_context.dart:119:12)
#36     CompilerContext.runWithOptions (package:front_end/src/fasta/compiler_context.dart:129:10)
#37     withGlobalOptions (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/command_line.dart:423:26)
#38     compile.<anonymous closure> (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/entry_points.dart:207:18)
<asynchronous suspension>
#39     runProtectedFromAbort (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/command_line.dart:478:24)
<asynchronous suspension>
#40     compile (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/entry_points.dart:206:16)
<asynchronous suspension>
#41     compileEntryPoint (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/entry_points.dart:72:11)
<asynchronous suspension>
#42     main (file:///usr/local/google/home/dmitryas/dart/sdk/pkg/front_end/tool/_fasta/compile.dart:7:33)
#43     _startIsolate.<anonymous closure> (dart:isolate-patch/dart:isolate/isolate_patch.dart:287)
#44     _RawReceivePortImpl._handleMessage (dart:isolate-patch/dart:isolate/isolate_patch.dart:171)

Note that the issue isn't present if the subclass of an anonymous mixin application is replaced with a named mixin application. That is, the following program compiles without errors:

class A<X, Y> {}

class B<Z> = Object with A<void Function(Z), int>;

main() {}
@chloestefantsova chloestefantsova added area-front-end Use area-front-end for front end / CFE / kernel format related issues. crash Process exits with SIGSEGV, SIGABRT, etc. An unhandled exception is not a crash. labels Sep 18, 2018
@kmillikin kmillikin added the P2 A bug or feature request we're likely to work on label Sep 18, 2018
@kmillikin kmillikin added this to the Dart2.1 milestone Sep 18, 2018
@kmillikin
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It looks like a problem with function types. The test case doesn't need the second type parameter on A, it needs a function type, and it doesn't care if the occurrence of the type parameter is positive or negative.

The code in kernel_library_builder.dart to apply mixins does not handle function types:

      void computeUsedTypeVariables(KernelNamedTypeBuilder type) {
        List<KernelTypeBuilder> typeArguments = type.arguments;
        if (typeArguments != null && typeVariables != null) {
          for (KernelTypeBuilder argument in typeArguments) {
            if (typeVariableNames.contains(argument.name)) {
              usedTypeVariables ??= <String, TypeVariableBuilder>{};
              KernelTypeVariableBuilder freshTypeVariable =
                  (usedTypeVariables[argument.name] ??=
                      addTypeVariable(argument.name, null, charOffset));
              // Notice that [argument] may have been created below as part of
              // [applicationTypeArguments] and have to be rebound now
              // (otherwise it would refer to a type variable in the subclass).
              argument.bind(freshTypeVariable);
            } else {
              if (argument is KernelNamedTypeBuilder) {
                computeUsedTypeVariables(argument);
              }
            }
          }
        }
      }

@kmillikin
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While this is an issue we need to fix, it's not related to the Dart 2.1 release.

@kmillikin kmillikin modified the milestones: Dart2.1, Dart2.2, PostDart2.1 Oct 9, 2018
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@chloestefantsova chloestefantsova

Labels
area-front-end Use area-front-end for front end / CFE / kernel format related issues. crash Process exits with SIGSEGV, SIGABRT, etc. An unhandled exception is not a crash. P2 A bug or feature request we're likely to work on
Projects
Dart Front End
Awaiting triage
Milestone
Future
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@chloestefantsova @kmillikin