Dart crashes on incorrect generic class declaration instead of throwing compile error

[iarkh]

Dart SDK Version: 2.3.1-dev.0.0
OS: Windows 10 64 bit

Dart crashes on the following code example instead of throwing compile time error:

class A<X> {}
class test<X extends num> = A<X>;
main() {}

Analyzer is OK with this.

Please note that dart throws expected error if I change test class declaration to class test<X> = A<X>.

It's not reproducible with dart 2.0 for me (tested 2.0.0-dev.69.5) and is reproducibel with dart 2.2.0 (tested 2.2.0-dev.2.1).

Crashing sample output is:

$> dart test.dart
Crash when compiling null,
at character offset null:
NoSuchMethodError: The method 'buildType' was called on null.
Receiver: null
Tried calling: buildType(Instance of 'KernelLibraryBuilder', null)
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
#1 KernelNamedTypeBuilder.build (package:front_end/src/fasta/kernel/kernel_named_type_builder.dart:57:24)
#2 KernelTypeVariableBuilder.finish (package:front_end/src/fasta/kernel/kernel_type_variable_builder.dart:86:32)
#3 KernelLibraryBuilder.finishTypeVariables (package:front_end/src/fasta/kernel/kernel_library_builder.dart:1247:15)
#4 SourceLoader.finishTypeVariables. (package:front_end/src/fasta/source/source_loader.dart:501:26)
#5 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:367:8)
#6 SourceLoader.finishTypeVariables (package:front_end/src/fasta/source/source_loader.dart:499:14)
#7 KernelTarget.buildOutlines. (package:front_end/src/fasta/kernel/kernel_target.dart:262:14)

#8 withCrashReporting (package:front_end/src/fasta/crash.dart:122:24)

#9 KernelTarget.buildOutlines (package:front_end/src/fasta/kernel/kernel_target.dart:249:12)

#10 IncrementalCompiler.computeDelta. (package:front_end/src/fasta/incremental_compiler.dart:299:52)

#11 CompilerContext.runInContext.. (package:front_end/src/fasta/compiler_context.dart:122:46)
#12 new Future.sync (dart:async/future.dart:224:31)
#13 CompilerContext.runInContext. (package:front_end/src/fasta/compiler_context.dart:122:19)
#14 _rootRun (dart:async/zone.dart:1124:13)
#15 _CustomZone.run (dart:async/zone.dart:1021:19)
#16 _runZoned (dart:async/zone.dart:1516:10)
#17 runZoned (dart:async/zone.dart:1463:12)
#18 CompilerContext.runInContext (package:front_end/src/fasta/compiler_context.dart:121:12)
#19 IncrementalCompiler.computeDelta (package:front_end/src/fasta/incremental_compiler.dart:127:20)

#20 IncrementalCompiler.compile (package:vm/incremental_compiler.dart:48:44)

#21 IncrementalCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:216:28)

#22 Compiler.compile. (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:144:31)

#23 new Future. (dart:async/future.dart:176:37)
#24 _rootRun (dart:async/zone.dart:1120:38)
#25 _CustomZone.run (dart:async/zone.dart:1021:19)
#26 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
#27 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
#28 _rootRun (dart:async/zone.dart:1124:13)
#29 _CustomZone.run (dart:async/zone.dart:1021:19)
#30 _CustomZone.bindCallback. (dart:async/zone.dart:947:23)
#31 Timer._createTimer. (dart:async-patch/timer_patch.dart:21:15)
#32 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
#33 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
#34 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)

#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
#1 KernelNamedTypeBuilder.build (package:front_end/src/fasta/kernel/kernel_named_type_builder.dart:57:24)
#2 KernelTypeVariableBuilder.finish (package:front_end/src/fasta/kernel/kernel_type_variable_builder.dart:86:32)
#3 KernelLibraryBuilder.finishTypeVariables (package:front_end/src/fasta/kernel/kernel_library_builder.dart:1247:15)
#4 SourceLoader.finishTypeVariables. (package:front_end/src/fasta/source/source_loader.dart:501:26)
#5 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:367:8)
#6 SourceLoader.finishTypeVariables (package:front_end/src/fasta/source/source_loader.dart:499:14)
#7 KernelTarget.buildOutlines. (package:front_end/src/fasta/kernel/kernel_target.dart:262:14)

#8 withCrashReporting (package:front_end/src/fasta/crash.dart:122:24)

#9 KernelTarget.buildOutlines (package:front_end/src/fasta/kernel/kernel_target.dart:249:12)

#10 IncrementalCompiler.computeDelta. (package:front_end/src/fasta/incremental_compiler.dart:299:52)

#11 CompilerContext.runInContext.. (package:front_end/src/fasta/compiler_context.dart:122:46)
#12 new Future.sync (dart:async/future.dart:224:31)
#13 CompilerContext.runInContext. (package:front_end/src/fasta/compiler_context.dart:122:19)
#14 _rootRun (dart:async/zone.dart:1124:13)
#15 _CustomZone.run (dart:async/zone.dart:1021:19)
#16 _runZoned (dart:async/zone.dart:1516:10)
#17 runZoned (dart:async/zone.dart:1463:12)
#18 CompilerContext.runInContext (package:front_end/src/fasta/compiler_context.dart:121:12)
#19 IncrementalCompiler.computeDelta (package:front_end/src/fasta/incremental_compiler.dart:127:20)

#20 IncrementalCompiler.compile (package:vm/incremental_compiler.dart:48:44)

#21 IncrementalCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:216:28)

#22 Compiler.compile. (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:144:31)

#23 new Future. (dart:async/future.dart:176:37)
#24 _rootRun (dart:async/zone.dart:1120:38)
#25 _CustomZone.run (dart:async/zone.dart:1021:19)
#26 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
#27 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
#28 _rootRun (dart:async/zone.dart:1124:13)
#29 _CustomZone.run (dart:async/zone.dart:1021:19)
#30 _CustomZone.bindCallback. (dart:async/zone.dart:947:23)
#31 Timer._createTimer. (dart:async-patch/timer_patch.dart:21:15)
#32 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
#33 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
#34 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)