Repository: flutter
Issue: Debugger disconnects
Labels: tool,a: quality,a: debugging,a: annoyance,P2,team-tool,triaged-tool


## Steps to Reproduce

 At some random point this happens and debugger exists.

## Logs

```
Unhandled exception:
Unimplemented clone for Kernel expression: SpreadElement
#0      CloneVisitor.defaultExpression (package:kernel/clone.dart:567:5)
#1      ControlFlowElement.accept (package:front_end/src/fasta/kernel/collections.dart:53:44)
#2      CloneVisitor.clone (package:kernel/clone.dart:73:34)
#3      MappedListIterable.elementAt (dart:_internal/iterable.dart:415:29)
#4      ListIterable.toList (dart:_internal/iterable.dart:219:19)
#5      CloneVisitor.visitListLiteral (package:kernel/clone.dart:255:56)
#6      ListLiteral.accept (package:kernel/ast.dart:3811:36)
#7      CloneVisitor.cloneOptional (package:kernel/clone.dart:83:29)
#8      CloneVisitor.visitReturnStatement (package:kernel/clone.dart:400:32)
#9      ReturnStatement.accept (package:kernel/ast.dart:4577:35)
#10     CloneVisitor.cloneOptional (package:kernel/clone.dart:83:29)
#11     CloneVisitor.cloneFunctionNodeBody (package:kernel/clone.dart:530:14)
#12     CloneVisitor.visitFunctionNode (package:kernel/clone.dart:540:29)
#13     FunctionNode.accept (package:kernel/ast.dart:2322:30)
#14     CloneVisitor.clone (package:kernel/clone.dart:73:34)
#15     CloneVisitor.visitProcedure (package:kernel/clone.dart:457:48)
#16     Procedure.accept (package:kernel/ast.dart:1984:32)
#17     createExpressionEvaluationComponent (package:front_end/src/fasta/kernel/utils.dart:112:27)
#18     FrontendCompiler.compileExpression (package:vm/frontend_server.dart:582:29)
<asynchronous suspension>
#19     _FlutterFrontendCompiler.compileExpression (package:frontend_server/server.dart:60:22)
#20     listenAndCompile.<anonymous closure> (package:vm/frontend_server.dart:866:20)
<asynchronous suspension>
#21     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#22     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#23     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#24     _SinkTransformerStreamSubscription._add (dart:async/stream_transformers.dart:68:11)
#25     _EventSinkWrapper.add (dart:async/stream_transformers.dart:15:11)
#26     _StringAdapterSink.add (dart:convert/string_conversion.dart:236:11)
#27     _LineSplitterSink._addLines (dart:convert/line_splitter.dart:150:13)
#28     _LineSplitterSink.addSlice (dart:convert/line_splitter.dart:125:5)
#29     StringConversionSinkMixin.add (dart:convert/string_conversion.dart:163:5)
#30     _SinkTransformerStreamSubscription._handleData (dart:async/stream_transformers.dart:120:24)
#31     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#32     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#33     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#34     _SinkTransformerStreamSubscription._add (dart:async/stream_transformers.dart:68:11)
#35     _EventSinkWrapper.add (dart:async/stream_transformers.dart:15:11)
#36     _StringAdapterSink.add (dart:convert/string_conversion.dart:236:11)
#37     _StringAdapterSink.addSlice (dart:convert/string_conversion.dart:241:7)
#38     _Utf8ConversionSink.addSlice (dart:convert/string_conversion.dart:312:20)
#39     _Utf8ConversionSink.add (dart:convert/string_conversion.dart:305:5)
#40     _ConverterStreamEventSink.add (dart:convert/chunked_conversion.dart:72:18)
#41     _SinkTransformerStreamSubscription._handleData (dart:async/stream_transformers.dart:120:24)
#42     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#43     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#44     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#45     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:764:19)
#46     _StreamController._add (dart:async/stream_controller.dart:640:7)
#47     _StreamController.add (dart:async/stream_controller.dart:586:5)
#48     _Socket._onData (dart:io-patch/socket_patch.dart:1791:41)
#49     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#50     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#51     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#52     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:764:19)
#53     _StreamController._add (dart:async/stream_controller.dart:640:7)
#54     _StreamController.add (dart:async/stream_controller.dart:586:5)
#55     new _RawSocket.<anonymous closure> (dart:io-patch/socket_patch.dart:1339:33)
#56     _NativeSocket.issueReadEvent.issue (dart:io-patch/socket_patch.dart:860:14)
#57     _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
#58     _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
#59     _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:116:13)
#60     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:173:5)
the Dart compiler exited unexpectedly.
the Dart compiler exited unexpectedly.
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
[✓] Flutter (Channel beta, v1.9.1+hotfix.4, on Mac OS X 10.14.6 18G87, locale en-US)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 11.0)
[✓] Android Studio (version 3.5)
[!] IntelliJ IDEA Ultimate Edition (version 2018.1.2)
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    ✗ Dart plugin not installed; this adds Dart specific functionality.
[✓] Connected device (2 available)

! Doctor found issues in 1 category.
```