CSharpTestEmbeddedLanguageClassifier crashes with index out of range

[jnm2]

Version Used: 17.13.0 Preview 2.1

This is when using [StringSyntax(PredefinedEmbeddedLanguageNames.CSharpTest)] in tests in Roslyn.sln.

StreamJsonRpc.RemoteInvocationException: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')
   at StreamJsonRpc.JsonRpc.<InvokeCoreAsync>d__156`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at Microsoft.CodeAnalysis.Remote.BrokeredServiceConnection`1.<TryInvokeAsync>d__20`1.MoveNext()
RPC server exception:
System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')
      at Microsoft.CodeAnalysis.Collections.Internal.ThrowHelper.ThrowArgumentOutOfRange_IndexMustBeLessException()
      at Microsoft.CodeAnalysis.EmbeddedLanguages.VirtualChars.VirtualCharSequence.ImmutableSegmentedListChunk.get_Item(Int32 index)
      at Microsoft.CodeAnalysis.CSharp.Features.EmbeddedLanguages.CSharpTestEmbeddedLanguageClassifier.RegisterClassifications(EmbeddedLanguageClassificationContext context)
      at Microsoft.CodeAnalysis.Classification.AbstractEmbeddedLanguageClassificationService.Worker.ClassifyToken(SyntaxToken token)
      at Microsoft.CodeAnalysis.Classification.AbstractEmbeddedLanguageClassificationService.Worker.VisitTokens(SyntaxNode node)
      at Microsoft.CodeAnalysis.Classification.AbstractEmbeddedLanguageClassificationService.AddEmbeddedLanguageClassifications(SolutionServices services, Project project, SemanticModel semanticModel, ImmutableArray`1 textSpans, ClassificationOptions options, SegmentedList`1 result, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Classification.AbstractEmbeddedLanguageClassificationService.AddEmbeddedLanguageClassificationsAsync(Document document, ImmutableArray`1 textSpans, ClassificationOptions options, SegmentedList`1 result, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Classification.AbstractClassificationService.AddClassificationsInCurrentProcessAsync(Document document, ImmutableArray`1 textSpans, ClassificationType type, ClassificationOptions options, SegmentedList`1 result, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Classification.AbstractClassificationService.AddClassificationsAsync(Document document, ImmutableArray`1 textSpans, ClassificationOptions options, ClassificationType type, SegmentedList`1 result, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.RemoteSemanticClassificationService.<>c__DisplayClass20_0.<<GetClassificationsAsync>b__0>d.MoveNext()
   --- End of stack trace from previous location ---
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.<>c__DisplayClass7_0`1.<<RunWithSolutionAsync>g__ProcessSolutionAsync|1>d.MoveNext()
   --- End of stack trace from previous location ---
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.RunWithSolutionAsync[T](AssetProvider assetProvider, Checksum solutionChecksum, Boolean updatePrimaryBranch, Func`2 implementation, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.RunWithSolutionAsync[T](AssetProvider assetProvider, Checksum solutionChecksum, Boolean updatePrimaryBranch, Func`2 implementation, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.BrokeredServiceBase.RunWithSolutionAsync[T](Checksum solutionChecksum, Func`2 implementation, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.BrokeredServiceBase.RunServiceImplAsync[T](Func`2 implementation, CancellationToken cancellationToken)