'NullReferenceException' occurs when getting 'Microsoft.CodeAnalysis.TypeInfo'

[VasilievSerg]

When using Microsoft.CodeAnalysis libraries, I faced a problem that when calling GetTypeInfo (extension method for SemanticModel), NullReferenceException occurs. The node for which a character is requested – ConstantPatternSyntax.

The used version is Microsoft.CodeAnalysis: 3.0.19.17001

Stack trace:

at Microsoft.CodeAnalysis.CSharp.ConversionsBase.ClassifyImplicitBuiltInConversionSlow(TypeSymbol source, TypeSymbol destination, HashSet`1& useSiteDiagnostics) in /_/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs:line 552
 at Microsoft.CodeAnalysis.CSharp.ConversionsBase.ClassifyBuiltInConversion(TypeSymbol source, TypeSymbol destination, HashSet`1& useSiteDiagnostics) in /_/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs:line 404
 at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoForNode(BoundNode lowestBoundNode, BoundNode highestBoundNode, BoundNode boundNodeForSyntacticParent) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs:line 2043
 at Microsoft.CodeAnalysis.CSharp.MemberSemanticModel.GetTypeInfoWorker(CSharpSyntaxNode node, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs:line 1142
 at Microsoft.CodeAnalysis.CSharp.SyntaxTreeSemanticModel.GetTypeInfoWorker(CSharpSyntaxNode node, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/SyntaxTreeSemanticModel.cs:line 310
 at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfo(PatternSyntax pattern, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs:line 844
 at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoFromNode(SyntaxNode node, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs:line 4644
 at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoCore(SyntaxNode node, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs:line 4713
 at Microsoft.CodeAnalysis.ModelExtensions.GetTypeInfo(SemanticModel semanticModel, SyntaxNode node, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/Compilation/Extensions.cs:line 60

It also seems like the problem is reproduced in Visual Studio.

Visual Studio version: 16.0.2

class C1<T1, T2>
{
    void foo()
    {
        T1 val = default;
        if (val is null)
        {

        }
    }
}

If in this code you try to get TypeSymbol from ConstantPatternExpression (null) through Syntax Visualizer, Visual Studio will restart. In Event Viewer you can find a corresponding recording with description:

Application: devenv.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
   at Microsoft.CodeAnalysis.CSharp.ConversionsBase.ClassifyImplicitBuiltInConversionSlow(Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol, Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol, System.Collections.Generic.HashSet`1<Microsoft.CodeAnalysis.DiagnosticInfo> ByRef)
   at Microsoft.CodeAnalysis.CSharp.ConversionsBase.ClassifyBuiltInConversion(Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol, Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol, System.Collections.Generic.HashSet`1<Microsoft.CodeAnalysis.DiagnosticInfo> ByRef)
   at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoForNode(Microsoft.CodeAnalysis.CSharp.BoundNode, Microsoft.CodeAnalysis.CSharp.BoundNode, Microsoft.CodeAnalysis.CSharp.BoundNode)
   at Microsoft.CodeAnalysis.CSharp.MemberSemanticModel.GetTypeInfoWorker(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode, System.Threading.CancellationToken)
   at Microsoft.CodeAnalysis.CSharp.SyntaxTreeSemanticModel.GetTypeInfoWorker(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode, System.Threading.CancellationToken)
   at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfo(Microsoft.CodeAnalysis.CSharp.Syntax.PatternSyntax, System.Threading.CancellationToken)
   at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoFromNode(Microsoft.CodeAnalysis.SyntaxNode, System.Threading.CancellationToken)
   at Microsoft.CodeAnalysis.CSharp.CSharpSemanticModel.GetTypeInfoCore(Microsoft.CodeAnalysis.SyntaxNode, System.Threading.CancellationToken)
   at Roslyn.SyntaxVisualizer.Control.SyntaxVisualizerControl.TypeSymbolDetailsMenuItem_Click(System.Object, System.Windows.RoutedEventArgs)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(System.Object, System.Windows.RoutedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(System.Object, System.Windows.RoutedEventArgs, Boolean)
   at System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject, System.Windows.RoutedEventArgs)
   at System.Windows.UIElement.RaiseEvent(System.Windows.RoutedEventArgs)
   at System.Windows.Controls.MenuItem.InvokeClickAfterRender(System.Object)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(System.Object)
   at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(System.Object)
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at MS.Internal.CulturePreservingExecutionContext.Run(MS.Internal.CulturePreservingExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
   at MS.Win32.HwndWrapper.WndProc(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(System.Object)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority, System.TimeSpan, System.Delegate, System.Object, Int32)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr, Int32, IntPtr, IntPtr)

[jcouv]

Tagging @agocke
This is likely related to an issue he just fixed (PR #35249)

[jcouv]

@VasilievSerg Would you be able to try this in 16.1 or later? I think this was fixed there already. Thanks

[ghost]

Closing this issue as we've seen no reply to the request for more information. If you are able to get the requested information, please add it to the issue and we will retriage it.