CodeCompletion fails on intellisense on a 5 lines C# 9.0 code

[dodyg]

Please paste the output from your clipboard

Issue Description

A simple . to bring up inteliisense fails

Steps to Reproduce

Just copy and paste this code in Program.cs

var u = new Hero(new(new("Dr.Strange")));
public record Name(string Value);
public record Person(Name Name);
public record Hero(Person Person);

and MyProject.csproj

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <LanguageVersion>preview</LanguageVersion>
  </PropertyGroup>
</Project>

Expected Behavior

Intellisense works

Actual Behavior

It fails

Logs

OmniSharp log

Post the output from Output-->OmniSharp log here

```[warn]: OmniSharp.Stdio.Host ************ Request ************ { "Type": "request", "Seq": 2000, "Command": "/completion", "Arguments": { "FileName": "c:\\GitHub\\practical-aspnetcore\\projects\\net6\\hello-world\\src\\Program.cs", "Line": 2, "Column": 2, "CompletionTrigger": 2, "TriggerCharacter": "." } } [fail]: OmniSharp.Stdio.Host ************ Response ************ { "Request_seq": 2000, "Command": "/completion", "Running": true, "Success": false, "Message": "\"System.InvalidCastException: [A]System.Threading.Tasks.Task`1[System.ValueTuple`2[Microsoft.CodeAnalysis.Completion.CompletionList,System.Boolean]] cannot be cast to [B]System.Threading.Tasks.Task`1[System.ValueTuple`2[Microsoft.CodeAnalysis.Completion.CompletionList,System.Boolean]]. Type A originates from 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:\\\\WINDOWS\\\\Microsoft.Net\\\\assembly\\\\GAC_64\\\\mscorlib\\\\v4.0_4.0.0.0__b77a5c561934e089\\\\mscorlib.dll'. Type B originates from 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:\\\\WINDOWS\\\\Microsoft.Net\\\\assembly\\\\GAC_64\\\\mscorlib\\\\v4.0_4.0.0.0__b77a5c561934e089\\\\mscorlib.dll'.\\r\\n at OmniSharp.Roslyn.CSharp.Services.Intellisense.CompletionItemExtensions.GetCompletionsInternalAsync(CompletionService completionService, Document document, Int32 caretPosition, CompletionTrigger trigger, ImmutableHashSet`1 roles, OptionSet options, CancellationToken cancellationToken) in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\Intellisense\\\\CompletionItemExtensions.cs:line 65\\r\\n at OmniSharp.Roslyn.CSharp.Services.Completion.CompletionService.d__7.MoveNext() in D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\Completion\\\\CompletionService.cs:line 120\\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": 13061, "Type": "response" } [warn]: OmniSharp.Roslyn.CSharp.Services.Navigation.FindUsagesService No symbol found. File: c:\GitHub\practical-aspnetcore\projects\net6\hello-world\src\Program.cs, Line: 6, Column: 0.```

Environment information

VSCode version: 1.55.2
C# Extension: 1.23.11

Dotnet Information

.NET SDK (reflecting any global.json): Version: 6.0.100-preview.4.21229.17 Commit: f21e23699c

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19042
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100-preview.4.21229.17\

Host (useful for support):
Version: 6.0.0-preview.4.21222.10
Commit: bd2d701e75

.NET SDKs installed:
3.1.408 [C:\Program Files\dotnet\sdk]
5.0.100 [C:\Program Files\dotnet\sdk]
5.0.300-preview.21180.15 [C:\Program Files\dotnet\sdk]
6.0.100-preview.4.21229.17 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.4.21227.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.4.21222.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.4.21223.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

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

Visual Studio Code Extensions

Extension	Author	Version
csharp	ms-dotnettools	1.23.11
remote-wsl	ms-vscode-remote	0.54.6
svelte-vscode	svelte	104.10.3
vetur	octref	0.33.1
vscode-open-file-folder	auchenberg	0.0.4

[filipw]

Thanks for opening the issue. This is duplicate of #4090