Compiler crash in pattern matching lowering - Error MSB6006: "csc.exe" exited with code -2146232797. (1, 1)

[TessenR]

Version Used:

Microsoft Visual Studio Professional 2019 Preview
Version 16.10.0 Preview 1.0
VisualStudio.16.Preview/16.10.0-pre.1.0+31025.218
Microsoft .NET Framework
Version 4.8.04084

Steps to Reproduce:

Compile the following code

class Base
{
  public virtual bool IsOk { get { return true; } set { } }
}

class C : Base
{
  public override bool IsOk { set { } }
  public string? Value { get; }

  public string M()
  {
    switch (this)
    {
      case { IsOk: true }:
        return Value;
      default:
        return Value;
    }
  }
}

Expected Behavior:
Either the code compiles or there's a compilation error somewhere in the code (probably on the case { IsOk: true }:)

Actual Behavior:
Error MSB6006: "csc.exe" exited with code -2146232797. (1, 1)

Notes
This example on sharplab.io gives the following exception:

System.NullReferenceException: Object reference not set to an instance of an object.

   at Microsoft.CodeAnalysis.CSharp.SyntheticBoundNodeFactory.Call(BoundExpression receiver, MethodSymbol method, ImmutableArray`1 args) in /_/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs:line 741

   at Microsoft.CodeAnalysis.CSharp.SyntheticBoundNodeFactory.Call(BoundExpression receiver, MethodSymbol method) in /_/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs:line 716

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.PatternLocalRewriter.LowerEvaluation(BoundDagEvaluation evaluation) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.PatternLocalRewriter.cs:line 155

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.DecisionDagRewriter.LowerDecisionDagNode(BoundDecisionDagNode node, BoundDecisionDagNode nextNode) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.DecisionDagRewriter.cs:line 962

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.DecisionDagRewriter.LowerDecisionDagCore(BoundDecisionDag decisionDag) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.DecisionDagRewriter.cs:line 419

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.BaseSwitchLocalRewriter.LowerDecisionDag(BoundDecisionDag decisionDag) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_BasePatternSwitchLocalRewriter.cs:line 70

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.SwitchStatementLocalRewriter.LowerSwitchStatement(BoundSwitchStatement node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_PatternSwitchStatement.cs:line 108

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.SwitchStatementLocalRewriter.Rewrite(LocalRewriter localRewriter, BoundSwitchStatement node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_PatternSwitchStatement.cs:line 32

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitSwitchStatement(BoundSwitchStatement node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_PatternSwitchStatement.cs:line 17

   at Microsoft.CodeAnalysis.CSharp.BoundSwitchStatement.Accept(BoundTreeVisitor visitor) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 3357

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitStatement(BoundStatement node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs:line 193

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitPossibleUsingDeclaration(BoundStatement node, ImmutableArray`1 statements, Int32 statementIndex, Boolean& replacedLocalDeclarations) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Block.cs:line 100

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitStatementSubList(ArrayBuilder`1 builder, ImmutableArray`1 statements, Int32 startIndex) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Block.cs:line 57

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitBlock(BoundBlock node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Block.cs:line 44

   at Microsoft.CodeAnalysis.CSharp.BoundBlock.Accept(BoundTreeVisitor visitor) in /_/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs:line 2867

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.VisitStatement(BoundStatement node) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs:line 193

   at Microsoft.CodeAnalysis.CSharp.LocalRewriter.Rewrite(CSharpCompilation compilation, MethodSymbol method, Int32 methodOrdinal, NamedTypeSymbol containingType, BoundStatement statement, TypeCompilationState compilationState, SynthesizedSubmissionFields previousSubmissionFields, Boolean allowOmissionOfConditionalCalls, Boolean instrumentForDynamicAnalysis, ImmutableArray`1& dynamicAnalysisSpans, DebugDocumentProvider debugDocumentProvider, BindingDiagnosticBag diagnostics, Boolean& sawLambdas, Boolean& sawLocalFunctions, Boolean& sawAwaitInExceptionHandler) in /_/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs:line 137

   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.LowerBodyOrInitializer(MethodSymbol method, Int32 methodOrdinal, BoundStatement body, SynthesizedSubmissionFields previousSubmissionFields, TypeCompilationState compilationState, Boolean instrumentForDynamicAnalysis, DebugDocumentProvider debugDocumentProvider, ImmutableArray`1& dynamicAnalysisSpans, BindingDiagnosticBag diagnostics, VariableSlotAllocator& lazyVariableSlotAllocator, ArrayBuilder`1 lambdaDebugInfoBuilder, ArrayBuilder`1 closureDebugInfoBuilder, StateMachineTypeSymbol& stateMachineTypeOpt) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 1431

   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 917

   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamedType(NamedTypeSymbol containingType) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 524

   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.<>c__DisplayClass23_0.<CompileNamedTypeAsync>b__0() in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 420

   at Roslyn.Utilities.UICultureUtilities.<>c__DisplayClass5_0.<WithCurrentUICulture>b__0() in /_/src/Compilers/Core/Portable/InternalUtilities/UICultureUtilities.cs:line 141

   at System.Threading.Tasks.Task.InnerInvoke()

   at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)

   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

--- End of stack trace from previous location ---

   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)

--- End of stack trace from previous location ---

   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.WaitForWorkers() in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 329

   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethodBodies(CSharpCompilation compilation, PEModuleBuilder moduleBeingBuiltOpt, Boolean emittingPdb, Boolean emitTestCoverageData, Boolean hasDeclarationErrors, Boolean emitMethodBodies, BindingDiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs:line 128

   at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.CompileMethods(CommonPEModuleBuilder moduleBuilder, Boolean emittingPdb, Boolean emitMetadataOnly, Boolean emitTestCoverageData, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken) in /_/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs:line 3091

   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream metadataPEStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, Boolean useRawWin32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, Stream sourceLinkStream, IEnumerable`1 embeddedTexts, Nullable`1 pdbOptionsBlobReader, CompilationTestData testData, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/Compilation/Compilation.cs:line 2617

   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, Boolean useRawWin32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, Stream sourceLinkStream, IEnumerable`1 embeddedTexts, Stream metadataPEStream, Nullable`1 pdbOptionsBlobReader, CancellationToken cancellationToken) in /_/src/Compilers/Core/Portable/Compilation/Compilation.cs:line 2569

   at SharpLab.Server.Compilation.Compiler.TryCompileToStreamAsync(MemoryStream assemblyStream, MemoryStream symbolStream, IWorkSession session, IList`1 diagnostics, CancellationToken cancellationToken) in D:\a\SharpLab\SharpLab\!roslyn-branches\dotnet-main\sharplab\source\Server\Compilation\Compiler.cs:line 31

   at SharpLab.Server.MirrorSharp.SlowUpdate.ProcessAsync(IWorkSession session, IList`1 diagnostics, CancellationToken cancellationToken) in D:\a\SharpLab\SharpLab\!roslyn-branches\dotnet-main\sharplab\source\Server\MirrorSharp\SlowUpdate.cs:line 110

   at MirrorSharp.Internal.Handlers.SlowUpdateHandler.ExecuteAsync(AsyncData data, WorkSession session, ICommandResultSender sender, CancellationToken cancellationToken)

   at MirrorSharp.Internal.Connection.ReceiveAndProcessInternalAsync(CancellationToken cancellationToken)

   at MirrorSharp.Internal.Connection.ReceiveAndProcessAsync(CancellationToken cancellationToken)

[RikkiGibson]

Very likely that we are not correctly obtaining the get accessor symbol for the property.

[RikkiGibson]

I think an analogous bug exists for list patterns when an indexer lacks an override of a get accessor. I will add it to #51289.

I think this test should be added, although I could be wrong about the details, and of course a baseline needs to be included:

        [Fact, WorkItem(51801, "https://github.com/dotnet/roslyn/issues/51801")]
        public void IndexerOverrideLacksAccessor()
        {
            var source = @"
#nullable enable

class Base
{
  public virtual object this[int i] { get { return 1; } set { } }
}

class C : Base
{
  public override object this[int i] { set { } }
  public int Length => 1;

  public string Value { get; }

  public string M()
  {
    switch (this)
    {
      case [1]:
        return Value;
      default:
        return Value;
    }   
  }
}
";
            var verifier = CompileAndVerify(source);
            verifier.VerifyIL("C.M", @"");