Find-all-references fails on `SyntaxTree` in VSCode

[333fred]

Version Used: 4.13.0-3.24577.4 (6cc106c), C# ext version v2.59.14 (pre-release)

Steps to Reproduce:

1. Open src/Compilers/Core/Portable/Syntax/SyntaxTree.cs
2. Invoke Find-All-References on the SyntaxTree identifier

Expected Behavior:

References are found.

Actual Behavior:

2024-12-10 17:56:31.700 [info] [Error - 5:56:31 PM] Request textDocument/references failed.
2024-12-10 17:56:31.700 [info]   Message: Object reference not set to an instance of an object.
  Code: -32000 
[object Object]
2024-12-10 17:57:08.113 [info] [Error - 5:57:08 PM] [LanguageServerHost] System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.CodeAnalysis.ChildSyntaxList.CountNodes(GreenNode green) in /_/src/Compilers/Core/Portable/Syntax/ChildSyntaxList.cs:line 42
   at Microsoft.CodeAnalysis.SyntaxNode.DescendantNodesAndTokensIntoTrivia(TextSpan span, Func`2 descendIntoChildren, Boolean includeSelf)+MoveNext()
   at Microsoft.CodeAnalysis.FindSymbols.SyntaxTreeIndex.CreateIndex(ProjectState project, SyntaxNode root, Checksum checksum, CancellationToken _) in /_/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex_Create.cs:line 84
   at Microsoft.CodeAnalysis.FindSymbols.AbstractSyntaxIndex`1.CreateIndexAsync(ProjectState project, DocumentState document, Checksum textChecksum, Checksum textAndDirectivesChecksum, IndexCreator create, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/Shared/AbstractSyntaxIndex.cs:line 142
   at Microsoft.CodeAnalysis.FindSymbols.AbstractSyntaxIndex`1.GetIndexWorkerAsync(SolutionKey solutionKey, ProjectState project, DocumentState document, Boolean loadOnly, IndexReader read, IndexCreator create, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.FindSymbols.AbstractSyntaxIndex`1.GetIndexAsync(SolutionKey solutionKey, ProjectState project, DocumentState document, Boolean loadOnly, IndexReader read, IndexCreator create, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.FindSymbols.AbstractSyntaxIndex`1.GetRequiredIndexAsync(SolutionKey solutionKey, ProjectState project, DocumentState document, IndexReader read, IndexCreator create, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.FindSymbols.Finders.AbstractReferenceFinder`1.GetAllMatchingGlobalAliasNamesAsync(Project project, String name, Int32 arity, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/AbstractReferenceFinder.cs:line 875
   at Microsoft.CodeAnalysis.FindSymbols.Finders.AbstractReferenceFinder`1.GetAllMatchingGlobalAliasNamesAsync(Project project, String name, Int32 arity, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/AbstractReferenceFinder.cs:line 873
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.AddGlobalAliasesAsync(Project project, ImmutableArray`1 allSymbols, PooledDictionary`2 symbolToGlobalAliases, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 352
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.ProcessProjectAsync(Project project, ImmutableArray`1 allSymbols, Action`1 onReferenceFound, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 226
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.ProcessProjectAsync(Project project, ImmutableArray`1 allSymbols, Action`1 onReferenceFound, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 266
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.<>c__DisplayClass13_0.<<PerformSearchAsync>b__0>d.MoveNext() in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 122
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.<>c__57`1.<<ForEachAsync>b__57_0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.PerformSearchAsync(ImmutableArray`1 symbols, Action`1 onReferenceFound, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 117
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.PerformSearchAsync(ImmutableArray`1 symbols, Action`1 onReferenceFound, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 117
   at Microsoft.CodeAnalysis.Shared.Utilities.ProducerConsumer`1.<>c__DisplayClass12_0`2.<<RunChannelAsync>g__ProduceItemsAndWriteToChannelAsync|2>d.MoveNext() in /_/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ProducerConsumer.cs:line 322
--- End of stack trace from previous location ---
   at Microsoft.CodeAnalysis.Shared.Utilities.ProducerConsumer`1.RunChannelAsync[TArgs,TResult](ProducerConsumerOptions options, Func`4 produceItems, Func`4 consumeItems, TArgs args, CancellationToken cancellationToken) in /_/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ProducerConsumer.cs:line 301
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.FindReferencesAsync(ImmutableArray`1 symbols, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 69
   at Microsoft.CodeAnalysis.FindSymbols.FindReferencesSearchEngine.FindReferencesAsync(ImmutableArray`1 symbols, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.cs:line 78
   at Microsoft.CodeAnalysis.FindSymbols.SymbolFinder.FindReferencesAsync(ISymbol symbol, Solution solution, IStreamingFindReferencesProgress progress, IImmutableSet`1 documents, FindReferencesSearchOptions options, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_FindReferences_Current.cs:line 64
   at Microsoft.CodeAnalysis.FindUsages.AbstractFindUsagesService.FindReferencesAsync(IFindUsagesContext context, ISymbol symbol, Project project, FindReferencesSearchOptions searchOptions, OptionsProvider`1 classificationOptions, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/FindUsages/AbstractFindUsagesService_FindReferences.cs:line 151
   at Microsoft.CodeAnalysis.FindUsages.AbstractFindUsagesService.FindSymbolReferencesAsync(IFindUsagesContext context, ISymbol symbol, Project project, OptionsProvider`1 classificationOptions, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/FindUsages/AbstractFindUsagesService_FindReferences.cs:line 121
   at Microsoft.CodeAnalysis.FindUsages.AbstractFindUsagesService.FindSymbolReferencesAsync(IFindUsagesContext context, Document document, Int32 position, OptionsProvider`1 classificationOptions, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/FindUsages/AbstractFindUsagesService_FindReferences.cs:line 99
   at Microsoft.CodeAnalysis.FindUsages.AbstractFindUsagesService.FindLiteralOrSymbolReferencesAsync(IFindUsagesContext context, Document document, Int32 position, OptionsProvider`1 classificationOptions, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/FindUsages/AbstractFindUsagesService_FindReferences.cs:line 61
   at Microsoft.CodeAnalysis.LanguageServer.Handler.FindAllReferencesHandler.FindReferencesAsync(IProgress`1 progress, Workspace workspace, Document document, LinePosition linePosition, Boolean supportsVSExtensions, IGlobalOptionService globalOptions, IMetadataAsSourceFileService metadataAsSourceFileService, IAsynchronousOperationListener asyncListener, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Handler/References/FindAllReferencesHandler.cs:line 88
   at Microsoft.CodeAnalysis.LanguageServer.Handler.FindAllReferencesHandler.HandleRequestAsync(VSInternalReferenceParams referenceParams, RequestContext context, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Handler/References/FindAllReferencesHandler.cs:line 64
   at Microsoft.CommonLanguageServerProtocol.Framework.QueueItem`1.StartRequestAsync[TRequest,TResponse](TRequest request, TRequestContext context, IMethodHandler handler, String language, CancellationToken cancellationToken)

[333fred]

FYI @dibarbet

[333fred]

Even weirder: when I make a subsequent Find-All-Refs call, I get mixed results:

The Find-All-Refs call was on https://github.com/dotnet/roslyn/blob/main/src/Compilers/CSharp/Portable/Errors/DiagnosticInfoWithSymbols.cs#L14, on Symbols.

[CyrusNajmabadi]

    at Microsoft.CodeAnalysis.ChildSyntaxList.CountNodes(GreenNode green) in /_/src/Compilers/Core/Portable/Syntax/ChildSyntaxList.cs:line 42
   at Microsoft.CodeAnalysis.SyntaxNode.DescendantNodesAndTokensIntoTrivia(TextSpan span, Func`2 descendIntoChildren, Boolean includeSelf)+MoveNext()

Well that seems bad. Someone on compiler needs to see how we can have a tree we can't walk the descendant nodes/tokens of without crashing :(