Roslyn: [Bug] This program breaks the C# compiler

[netogallo]

I have a program that causes the compiler to fail with error "-2146232797", see the program attached below. I don't know if this program should compile or not, but in any case, it should at least throw a meaningful error indicating why the compilation failed.

namespace AsyncBug
{
    class Program
    {
        private class SomeClass
        {
            public bool Method(int value)
            {
                Console.WriteLine($"Boom! {value}");
                return true;
            }
        }

        private Task<SomeClass> Danger()
        {
            return Task.FromResult(new SomeClass());
        }

        private async void Killer()
        {
            new int[5].Select((await Danger()).Method);
        }

        static void Main(string[] args)
        {
        }
    }
}

[hmemcpy]

Cool, this throws The method or operation is not implemented. on TryRoslyn

Full stack trace

The method or operation is not implemented.
   at Microsoft.CodeAnalysis.CSharp.BoundNode.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitExpressionWithoutStackGuard(BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.BoundTreeVisitor.VisitExpressionWithStackGuard(Int32& recursionDepth, BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitConversion(BoundConversion node)
   at Microsoft.CodeAnalysis.CSharp.BoundConversion.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitExpressionWithoutStackGuard(BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.BoundTreeVisitor.VisitExpressionWithStackGuard(Int32& recursionDepth, BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitArguments(ImmutableArray`1 arguments, ImmutableArray`1 refKindsOpt, MethodSymbol method)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitCall(BoundCall node)
   at Microsoft.CodeAnalysis.CSharp.BoundCall.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitExpressionWithoutStackGuard(BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.BoundTreeVisitor.VisitExpressionWithStackGuard(BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.BoundTreeVisitor.VisitExpressionWithStackGuard(Int32& recursionDepth, BoundExpression node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitExpressionStatement(BoundExpressionStatement node)
   at Microsoft.CodeAnalysis.CSharp.BoundExpressionStatement.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitStatement(BoundStatement statement)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitSequencePoint(BoundSequencePoint node)
   at Microsoft.CodeAnalysis.CSharp.BoundSequencePoint.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitStatement(BoundStatement statement)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitBlock(BoundBlock node)
   at Microsoft.CodeAnalysis.CSharp.DataFlowPass.VisitBlock(BoundBlock node)
   at Microsoft.CodeAnalysis.CSharp.BoundBlock.Accept(BoundTreeVisitor visitor)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitWithStackGuard(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.VisitAlways(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Visit(BoundNode node)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Scan(Boolean& badRegion)
   at Microsoft.CodeAnalysis.CSharp.DataFlowPass.Scan(Boolean& badRegion)
   at Microsoft.CodeAnalysis.CSharp.PreciseAbstractFlowPass`1.Analyze(Boolean& badRegion)
   at Microsoft.CodeAnalysis.CSharp.DataFlowPass.Analyze(Boolean& badRegion, DiagnosticBag diagnostics)
   at Microsoft.CodeAnalysis.CSharp.UnassignedVariablesWalker.Analyze(CSharpCompilation compilation, Symbol member, BoundNode node, Boolean convertInsufficientExecutionStackExceptionToCancelledByStackGuardException)
   at Microsoft.CodeAnalysis.CSharp.IteratorAndAsyncCaptureWalker.Analyze(CSharpCompilation compilation, MethodSymbol method, BoundNode node, DiagnosticBag diagnostics)
   at Microsoft.CodeAnalysis.CSharp.StateMachineRewriter.Rewrite()
   at Microsoft.CodeAnalysis.CSharp.AsyncRewriter.Rewrite(BoundStatement body, MethodSymbol method, Int32 methodOrdinal, VariableSlotAllocator slotAllocatorOpt, TypeCompilationState compilationState, DiagnosticBag diagnostics, AsyncStateMachine& stateMachineType)
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.LowerBodyOrInitializer(MethodSymbol method, Int32 methodOrdinal, BoundStatement body, SynthesizedSubmissionFields previousSubmissionFields, TypeCompilationState compilationState, DiagnosticBag diagnostics, VariableSlotAllocator& lazyVariableSlotAllocator, ArrayBuilder`1 lambdaDebugInfoBuilder, ArrayBuilder`1 closureDebugInfoBuilder, StateMachineTypeSymbol& stateMachineTypeOpt)
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethod(MethodSymbol methodSymbol, Int32 methodOrdinal, ProcessedFieldInitializers& processedInitializers, SynthesizedSubmissionFields previousSubmissionFields, TypeCompilationState compilationState)
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileNamedType(NamedTypeSymbol containingType)
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.<>c__DisplayClass20_0.<CompileNamedTypeAsTask>b__0()
   at Roslyn.Utilities.UICultureUtilities.<>c__DisplayClass5_0.<WithCurrentUICulture>b__0()
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.WaitForWorkers()
   at Microsoft.CodeAnalysis.CSharp.MethodCompiler.CompileMethodBodies(CSharpCompilation compilation, PEModuleBuilder moduleBeingBuiltOpt, Boolean generateDebugInfo, Boolean hasDeclarationErrors, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.CompileImpl(CommonPEModuleBuilder moduleBuilder, Stream win32Resources, Stream xmlDocStream, Boolean emittingPdb, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Compilation.Compile(CommonPEModuleBuilder moduleBuilder, Stream win32Resources, Stream xmlDocStream, Boolean emittingPdb, DiagnosticBag diagnostics, Predicate`1 filterOpt, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Compilation.Emit(EmitStreamProvider peStreamProvider, EmitStreamProvider pdbStreamProvider, EmitStreamProvider xmlDocumentationStreamProvider, EmitStreamProvider win32ResourcesStreamProvider, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CompilationTestData testData, Func`1 getHostDiagnostics, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CompilationTestData testData, Func`1 getHostDiagnostics, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CancellationToken cancellationToken)
   at TryRoslyn.Core.Processing.CodeProcessor.Process(String code, ProcessingOptions options)
   at TryRoslyn.Web.Api.Controllers.RoslynController.Compilation(CompilationArguments arguments)
   at lambda_method(Closure , Object , Object[] )
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.Tracers.HttpControllerTracer.<ExecuteAsyncCore>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Tracing.ITraceWriterExtensions.<TraceBeginEndAsyncCore>d__18`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()

[alrz]

Simpler program to reproduce,

Func<Type> f = (await Task.FromResult(1)).GetType; // boom

var x = await Task.FromResult(1);
Func<Type> f = x.GetType; // ok