Hangs when analyzing solution; sometimes provides results after, sometimes doesn't

[rjgotten]

Issue Description

Solution analysis hangs for a long time before finally providing Intellisense and listing open issues in the VSCode "Problems" panel.
Sometimes the issues do not fill out into the "Problems" panel until having open a .cs file in the editor or having flipped open a folder in the Explorer panel that holds .cs files.

Steps to Reproduce

1. Install version 1.23.3 of the C# extension
2. Open solution

Expected Behavior

The extension works without hangs, like 1.23.2 did.

Actual Behavior

The extension hangs for a long time and seems to only half-work afterwards.

Logs

OmniSharp log

[info]: OmniSharp.Roslyn.CSharp.Services.Diagnostics.CSharpDiagnosticWorkerWithAnalyzers
        Solution initialized -> queue all documents for code analysis. Initial document count: 885.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[warn]: OmniSharp.Roslyn.CSharp.Workers.Diagnostics.AnalyzerWorkQueue
        Timeout before work got ready for foreground analysis queue. This is assertion to prevent complete api hang in case of error.
[fail]: OmniSharp.Stdio.Host
        ************  Response ************ 
{
  "Request_seq": 25,
  "Command": "/v2/highlight",
  "Running": true,
  "Success": false,
  "Message": "\"System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.\\r\\nParameter name: line\\r\\n   at Microsoft.CodeAnalysis.Text.LinePosition..ctor(Int32 line, Int32 character)\\r\\n   at OmniSharp.Roslyn.CSharp.Services.SemanticHighlight.SemanticHighlightService.d__1.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\SemanticHighlight\\\\SemanticHighlightService.cs:line 36\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__19.MoveNext()\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__20.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:line 230\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__16.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:line 131\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Stdio.Host.d__13.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Stdio\\\\Host.cs:line 215\"",
  "Body": null,
  "Seq": 2951,
  "Type": "response"
}
[fail]: OmniSharp.Stdio.Host
        ************  Response ************ 
{
  "Request_seq": 29,
  "Command": "/v2/highlight",
  "Running": true,
  "Success": false,
  "Message": "\"System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.\\r\\nParameter name: character\\r\\n   at Microsoft.CodeAnalysis.Text.LinePosition..ctor(Int32 line, Int32 character)\\r\\n   at OmniSharp.Roslyn.CSharp.Services.SemanticHighlight.SemanticHighlightService.d__1.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\SemanticHighlight\\\\SemanticHighlightService.cs:line 36\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__19.MoveNext()\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__20.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:line 230\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Endpoint.EndpointHandler`2.d__16.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:line 131\\r\\n--- End of stack trace from previous location where exception was thrown ---\\r\\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   at OmniSharp.Stdio.Host.d__13.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Stdio\\\\Host.cs:line 215\"",
  "Body": null,
  "Seq": 2956,
  "Type": "response"
}

C# log

(empty)

Environment information

VSCode version: 1.50.0
C# Extension: 1.23.3

Dotnet Information

.NET Core SDK (reflecting any global.json): Version: 3.1.402 Commit: 9b5de826fd

Runtime Environment:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\3.1.402\

Host (useful for support):
Version: 3.1.8
Commit: 9c1330dedd

.NET Core SDKs installed:
2.1.505 [C:\Program Files\dotnet\sdk]
2.1.507 [C:\Program Files\dotnet\sdk]
2.1.508 [C:\Program Files\dotnet\sdk]
2.1.509 [C:\Program Files\dotnet\sdk]
2.2.107 [C:\Program Files\dotnet\sdk]
3.0.100 [C:\Program Files\dotnet\sdk]
3.1.402 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download

Visual Studio Code Extensions

Extension	Author	Version
alignment	annsk	0.3.0
csharp	ms-dotnettools	1.23.3
DocFX	ms-docfx	0.1.3
material-icon-theme	PKief	4.3.0
vetur	octref	0.28.0
vscode-eslint	dbaeumer	2.1.10