Generic extension method on generic type with LangVersion=preview and Nullable=enable crashes compiler with NullReferenceException in ConstraintsHelper.CheckConstraints when accessing non-existent member of extension method's name on type

[just-ero]

Version Used

Visual Studio Code: 1.91.1, f1e16e1e6214d7c44d078b1f0607b2388f29d729, x64
Compiler: 4.11.0-3.24320.2 (adce315)
C# Extension: v2.38.16
C# Dev Kit Extension: v1.9.2

Steps to Reproduce

1. Open any C# project in Visual Studio Code.
2. Add the following code:

   class Foo<T>;
   static class FooExt
   {
       public static void Bar<T>(this Foo<T> foo)
       {
           foo.Bar = 42;
       }
   }

3. Set LangVersion to preview and Nullable to enable in the project file.
4. Return to the code and observe the crash.

---

Full exception message

[Error - 6:19:22 PM] [LanguageServerHost] System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.CodeAnalysis.CSharp.Symbols.ConstraintsHelper.CheckConstraints(Symbol containingSymbol, CheckConstraintsArgs& args, TypeMap substitution, TypeParameterSymbol typeParameter, TypeWithAnnotations typeArgument, ArrayBuilder`1 diagnosticsBuilder, ArrayBuilder`1 nullabilityDiagnosticsBuilderOpt, ArrayBuilder`1& useSiteDiagnosticsBuilder, HashSet`1 ignoreTypeConstraintsDependentOnTypeParametersOpt) in /_/src/Compilers/CSharp/Portable/Symbols/ConstraintsHelper.cs:line 1062
   at Microsoft.CodeAnalysis.CSharp.Binder.<GetUniqueSignatureFromMethodGroup>g__satisfiesConstraintChecks|545_1(MethodSymbol method) in /_/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs:line 10603
   at Microsoft.CodeAnalysis.CSharp.Binder.GetUniqueSignatureFromMethodGroup(BoundMethodGroup node) in /_/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs:line 10562
   at Microsoft.CodeAnalysis.CSharp.Symbols.FunctionTypeSymbol.GetInternalDelegateType() in /_/src/Compilers/CSharp/Portable/Symbols/FunctionTypeSymbol.cs:line 85
   at Microsoft.CodeAnalysis.CSharp.NullableWalker.ExpressionAndSymbolEqualityComparer.GetHashCode(ValueTuple`2 obj) in /_/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs:line 12477
   at Microsoft.CodeAnalysis.CSharp.NullabilityRewriter.GetUpdatedSymbol[T](BoundNode expr, T sym) in /_/src/Compilers/CSharp/Portable/BoundTree/NullabilityRewriter.cs:line 87
   at Microsoft.CodeAnalysis.CSharp.NullabilityRewriter.VisitMethodGroup(BoundMethodGroup node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 13825
   at Microsoft.CodeAnalysis.CSharp.NullabilityRewriter.VisitBadExpression(BoundBadExpression node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 12397
   at Microsoft.CodeAnalysis.CSharp.NullabilityRewriter.VisitAssignmentOperator(BoundAssignmentOperator node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 12736
   at Microsoft.CodeAnalysis.CSharp.BoundTreeRewriter.VisitExpressionStatement(BoundExpressionStatement node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 11290
   at Microsoft.CodeAnalysis.CSharp.BoundTreeRewriter.DoVisitList[T](ImmutableArray`1 list) in /_/src/Compilers/CSharp/Portable/BoundTree/BoundTreeRewriter.cs:line 39
   at Microsoft.CodeAnalysis.CSharp.NullabilityRewriter.VisitBlock(BoundBlock node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 13284
   at Microsoft.CodeAnalysis.CSharp.BoundTreeRewriter.VisitNonConstructorMethodBody(BoundNonConstructorMethodBody node) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 12137
   at Microsoft.CodeAnalysis.CSharp.NullableWalker.Rewrite(ImmutableDictionary`2 updatedNullabilities, SnapshotManager snapshotManager, BoundNode node, ImmutableDictionary`2& remappedSymbols) in /_/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs:line 1606
   at Microsoft.CodeAnalysis.CSharp.NullableWalker.AnalyzeAndRewrite(CSharpCompilation compilation, Symbol symbol, BoundNode node, Binder binder, VariableState initialState, DiagnosticBag diagnostics, Boolean createSnapshots, SnapshotManager& snapshotManager, ImmutableDictionary`2& remappedSymbols) in /_/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs:line 1486
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.BindMethodBody(MethodSymbol method, TypeCompilationState compilationState, BindingDiagnosticBag diagnostics, Boolean includeInitializersInBody, BoundNode initializersBody, Boolean reportNullableDiagnostics, ImportChain& importChain, Boolean& originalBodyNested, Boolean& prependedDefaultValueTypeConstructorInitializer, InitialState& forSemanticModel) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 1799
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethod(MethodSymbol methodSymbol, Int32 methodOrdinal, ProcessedFieldInitializers& processedInitializers, SynthesizedSubmissionFields previousSubmissionFields, TypeCompilationState compilationState) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 991
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamedType(NamedTypeSymbol containingType) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 530
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.VisitNamedType(NamedTypeSymbol symbol, TypeCompilationState arg) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 420
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamespace(NamespaceSymbol symbol) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 397
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.VisitNamespace(NamespaceSymbol symbol, TypeCompilationState arg) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 374
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamespace(NamespaceSymbol symbol) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 397
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethodBodies(CSharpCompilation compilation, PEModuleBuilder moduleBeingBuiltOpt, Boolean emittingPdb, Boolean hasDeclarationErrors, Boolean emitMethodBodies, BindingDiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 123
   at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.GetDiagnosticsForMethodBodiesInTree(SyntaxTree tree, Nullable`1 span, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs:line 3107
   at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.GetDiagnosticsForSyntaxTree(CompilationStage stage, SyntaxTree syntaxTree, Nullable`1 filterSpanWithinTree, Boolean includeEarlierStages, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs:line 3322
   at Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetCompilationEventsForSingleFileAnalysis(Compilation compilation, AnalysisScope analysisScope, ImmutableArray`1 additionalFiles, Boolean hasAnyActionsRequiringCompilationEvents, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs:line 1019
   at Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.ComputeAnalyzerDiagnosticsAsync(AnalysisScope analysisScope, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs:line 767
   at Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalysisResultCoreAsync(SemanticModel model, Nullable`1 filterSpan, ImmutableArray`1 analyzers, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs:line 654
   at Microsoft.CodeAnalysis.Diagnostics.Extensions.GetAnalysisResultAsync(CompilationWithAnalyzers compilationWithAnalyzers, DocumentAnalysisScope documentAnalysisScope, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs:line 356
   at Microsoft.CodeAnalysis.Diagnostics.Extensions.GetAnalysisResultAsync(CompilationWithAnalyzers compilationWithAnalyzers, DocumentAnalysisScope documentAnalysisScope, Project project, DiagnosticAnalyzerInfoCache analyzerInfoCache, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs:line 323
   at Microsoft.CodeAnalysis.Diagnostics.InProcOrRemoteHostAnalyzerRunner.AnalyzeInProcAsync(DocumentAnalysisScope documentAnalysisScope, Project project, CompilationWithAnalyzers compilationWithAnalyzers, RemoteHostClient client, Boolean logPerformanceInfo, Boolean getTelemetryInfo, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.InProcOrRemoteHostAnalyzerRunner.cs:line 126
   at Microsoft.CodeAnalysis.Diagnostics.InProcOrRemoteHostAnalyzerRunner.<>c__DisplayClass8_0.<<AnalyzeAsync>g__AnalyzeCoreAsync|0>d.MoveNext() in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.InProcOrRemoteHostAnalyzerRunner.cs:line 87
--- End of stack trace from previous location ---
   at Microsoft.CodeAnalysis.Diagnostics.InProcOrRemoteHostAnalyzerRunner.AnalyzeAsync(DocumentAnalysisScope documentAnalysisScope, Project project, CompilationWithAnalyzers compilationWithAnalyzers, Boolean isExplicit, Boolean forceExecuteAllAnalyzers, Boolean logPerformanceInfo, Boolean getTelemetryInfo, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.InProcOrRemoteHostAnalyzerRunner.cs:line 72
   at Microsoft.CodeAnalysis.Diagnostics.DocumentAnalysisExecutor.GetAnalysisResultAsync(DocumentAnalysisScope analysisScope, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs:line 179
   at Microsoft.CodeAnalysis.Diagnostics.DocumentAnalysisExecutor.GetSemanticDiagnosticsAsync(DiagnosticAnalyzer analyzer, Boolean isCompilerAnalyzer, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs:line 282
   at Microsoft.CodeAnalysis.Diagnostics.DocumentAnalysisExecutor.ComputeDiagnosticsAsync(DiagnosticAnalyzer analyzer, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs:line 146
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.LatestDiagnosticsForSpanGetter.ComputeDocumentDiagnosticsForAnalyzerCoreAsync(DiagnosticAnalyzer analyzer, DocumentAnalysisExecutor executor, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 561
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.LatestDiagnosticsForSpanGetter.ComputeDocumentDiagnosticsCoreAsync(DocumentAnalysisExecutor executor, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 547
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.LatestDiagnosticsForSpanGetter.ComputeDocumentDiagnosticsAsync(ImmutableArray`1 analyzersWithState, AnalysisKind kind, Nullable`1 span, ArrayBuilder`1 builder, Boolean incrementalAnalysis, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 438
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.LatestDiagnosticsForSpanGetter.TryGetAsync(ArrayBuilder`1 list, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 274
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.TryAppendDiagnosticsForSpanAsync(TextDocument document, Nullable`1 range, ArrayBuilder`1 result, Func`2 shouldIncludeDiagnostic, Boolean includeSuppressedDiagnostics, Boolean includeCompilerDiagnostics, ICodeActionRequestPriorityProvider priorityProvider, Boolean blockForData, DiagnosticKind diagnosticKinds, Boolean isExplicit, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 34
   at Microsoft.CodeAnalysis.Diagnostics.EngineV2.DiagnosticIncrementalAnalyzer.GetDiagnosticsForSpanAsync(TextDocument document, Nullable`1 range, Func`2 shouldIncludeDiagnostic, Boolean includeSuppressedDiagnostics, Boolean includeCompilerDiagnostics, ICodeActionRequestPriorityProvider priorityProvider, Boolean blockForData, DiagnosticKind diagnosticKinds, Boolean isExplicit, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs:line 50
   at Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzerService.GetDiagnosticsForSpanAsync(TextDocument document, Nullable`1 range, Func`2 shouldIncludeDiagnostic, Boolean includeCompilerDiagnostics, Boolean includeSuppressedDiagnostics, ICodeActionRequestPriorityProvider priorityProvider, DiagnosticKind diagnosticKinds, Boolean isExplicit, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/Diagnostics/DiagnosticAnalyzerService.cs:line 112
   at Microsoft.CodeAnalysis.CodeFixes.CodeFixService.StreamFixesAsync(TextDocument document, TextSpan range, ICodeActionRequestPriorityProvider priorityProvider, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)+MoveNext() in /_/src/LanguageServer/Protocol/Features/CodeFixes/CodeFixService.cs:line 197
   at Microsoft.CodeAnalysis.CodeFixes.CodeFixService.StreamFixesAsync(TextDocument document, TextSpan range, ICodeActionRequestPriorityProvider priorityProvider, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
   at Microsoft.CodeAnalysis.Shared.Extensions.IAsyncEnumerableExtensions.ToImmutableArrayAsync[T](IAsyncEnumerable`1 values, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Extensions/IAsyncEnumerableExtensions.cs:line 39
   at Microsoft.CodeAnalysis.Shared.Extensions.IAsyncEnumerableExtensions.ToImmutableArrayAsync[T](IAsyncEnumerable`1 values, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Extensions/IAsyncEnumerableExtensions.cs:line 39
   at Microsoft.CodeAnalysis.UnifiedSuggestions.UnifiedSuggestedActionsSource.GetFilterAndOrderCodeFixesAsync(Workspace workspace, ICodeFixService codeFixService, TextDocument document, TextSpan selection, ICodeActionRequestPriorityProvider priorityProvider, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Features/UnifiedSuggestions/UnifiedSuggestedActionsSource.cs:line 49
   at Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions.CodeActionHelpers.GetActionSetsAsync(TextDocument document, CodeActionOptionsProvider fallbackOptions, ICodeFixService codeFixService, ICodeRefactoringService codeRefactoringService, Range selection, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Handler/CodeActions/CodeActionHelpers.cs:line 395
   at Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions.CodeActionHelpers.GetVSCodeActionsAsync(CodeActionParams request, TextDocument document, CodeActionOptionsProvider fallbackOptions, ICodeFixService codeFixService, ICodeRefactoringService codeRefactoringService, Boolean hasVsLspCapability, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Handler/CodeActions/CodeActionHelpers.cs:line 40
   at Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActionsHandler.HandleRequestAsync(CodeActionParams request, RequestContext context, CancellationToken cancellationToken) in /_/src/LanguageServer/Protocol/Handler/CodeActions/CodeActionsHandler.cs:line 59
   at Microsoft.CommonLanguageServerProtocol.Framework.QueueItem`3.StartRequestAsync(TRequestContext context, IMethodHandler handler, CancellationToken cancellationToken)