I think I was bringing up sig help. VS just disappeared. I pulled this out of the event log:
Application: devenv.exe
Framework Version: v4.0.30319
Description: The application requested process termination through System.Environment.FailFast(string message).
Message: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: position
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.ChildThatContainsPosition(Int32 position)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.FindTokenInternal(Int32 position)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.FindToken(Int32 position, Boolean findInsideTrivia)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.FindToken(Int32 position, Func`2 findInsideTrivia)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.FindToken(Int32 position, Boolean findInsideTrivia)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode.FindTokenCore(Int32 position, Boolean findInsideTrivia)
at Microsoft.CodeAnalysis.Shared.Utilities.FindTokenHelper.GetInitialToken[TRoot](SyntaxNode root, Int32 position, Boolean includeSkipped, Boolean includeDirectives, Boolean includeDocumentationComments)
at Microsoft.CodeAnalysis.Shared.Utilities.FindTokenHelper.FindTokenOnLeftOfPosition[TRoot](SyntaxNode root, Int32 position, Func`3 skippedTokenFinder, Boolean includeSkipped, Boolean includeDirectives, Boolean includeDocumentationComments)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxFactsService.FindTokenOnLeftOfPosition(SyntaxNode node, Int32 position, Boolean includeSkipped, Boolean includeDirectives, Boolean includeDocumentationComments)
at Microsoft.CodeAnalysis.Editor.SignatureHelp.CommonSignatureHelpUtilities.TryGetSyntax[TSyntax](SyntaxNode root, Int32 position, ISyntaxFactsService syntaxFacts, SignatureHelpTriggerReason triggerReason, Func`2 isTriggerToken, Func`3 isArgumentListToken, CancellationToken cancellationToken, TSyntax& expression)
at Microsoft.CodeAnalysis.Editor.CSharp.SignatureHelp.AttributeSignatureHelpProvider.TryGetAttributeExpression(SyntaxNode root, Int32 position, ISyntaxFactsService syntaxFacts, SignatureHelpTriggerReason triggerReason, CancellationToken cancellationToken, AttributeSyntax& attribute)
at Microsoft.CodeAnalysis.Editor.CSharp.SignatureHelp.AttributeSignatureHelpProvider.<GetItemsWorkerAsync>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 Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.AbstractSignatureHelpProvider.<GetItemsAsync>d__15.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 Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller.Session.<ComputeItemsAsync>d__10.MoveNext()
Stack:
at System.Environment.FailFast(System.String, System.Exception)
at Microsoft.CodeAnalysis.FailFast.OnFatalException(System.Exception)
at Microsoft.CodeAnalysis.ErrorReporting.FatalError.Report(System.Exception, System.Action`1<System.Exception>)
at Microsoft.CodeAnalysis.ErrorReporting.FatalError.ReportUnlessCanceled(System.Exception)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<ComputeItemsAsync>d__10.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<ComputeItemsAsync>d__10.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Start[[Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<ComputeItemsAsync>d__10, Microsoft.CodeAnalysis.EditorFeatures, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]](ComputeItemsAsync>d__10 ByRef)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session.ComputeItemsAsync(System.Collections.Generic.IList`1<Microsoft.CodeAnalysis.Editor.ISignatureHelpProvider>, Microsoft.VisualStudio.Text.SnapshotPoint, Microsoft.CodeAnalysis.Editor.SignatureHelpTriggerInfo, Microsoft.CodeAnalysis.Document, System.Threading.CancellationToken)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<ComputeModelInBackgroundAsync>d__5.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Start[[Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<ComputeModelInBackgroundAsync>d__5, Microsoft.CodeAnalysis.EditorFeatures, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]](ComputeModelInBackgroundAsync>d__5 ByRef)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session.ComputeModelInBackgroundAsync(Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Model, System.Collections.Generic.IList`1<Microsoft.CodeAnalysis.Editor.ISignatureHelpProvider>, System.Collections.Generic.IList`1<Microsoft.CodeAnalysis.Editor.ISignatureHelpProvider>, Microsoft.VisualStudio.Text.SnapshotPoint, Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.DisconnectedBufferGraph, Microsoft.CodeAnalysis.Editor.SignatureHelpTriggerInfo, System.Threading.CancellationToken)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Controller+Session+<>c__DisplayClass4_0.<ComputeModel>b__0(Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp.Model, System.Threading.CancellationToken)
at Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.ModelComputation`1+<>c__DisplayClass17_0[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].<ChainTaskAndNotifyControllerWhenFinished>b__0(System.Threading.Tasks.Task`1<System.__Canon>)
at Roslyn.Utilities.TaskExtensions+<>c__DisplayClass14_0`2[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].<SafeContinueWithFromAsync>b__0(System.Threading.Tasks.Task)
at System.Threading.Tasks.ContinuationResultTaskFromTask`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].InnerInvoke()
at System.Threading.Tasks.Task.Execute()
at System.Threading.Tasks.Task.ExecutionContextCallback(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.Tasks.Task.ExecuteWithThreadLocal(System.Threading.Tasks.Task ByRef)
at System.Threading.Tasks.Task.ExecuteEntry(Boolean)
at System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
I think I was bringing up sig help. VS just disappeared. I pulled this out of the event log: