CS8618 Wrong identification of unassigned property

[JornWildt]

Analyzer

Diagnostic ID: [CS8618] Non-nullable property 'XXX' must contain a non-null value when exiting constructor. Consider declaring the property as nullable.

Analyzer source

.NET SDK:
Version: 8.0.304
Commit: 352dc5a01f
Workload version: 8.0.300-manifests.113cb230
MSBuild version: 17.10.4+10fbfbf2e

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\8.0.304\

.NET workloads installed:
[aspire]
Installation Source: VS 17.10.35201.131
Manifest Version: 8.1.0/8.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.1.0\WorkloadManifest.json
Install Type: FileBased

Host:
Version: 8.0.8
Architecture: x64
Commit: 08338fcaa5

.NET SDKs installed:
8.0.304 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.33 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Describe the bug

The analyzer identifies a member property Message as being not-set in the following constructor:

public class Test
{
  private string Message { get; set; }

  public Test()
  {
    Message = "";
    Console.WriteLine($"Message size: {Message?.Length}");
  }
}

Steps To Reproduce

Compile the above class.

Expected behavior

No warnings.

Actual behavior

The compiler (and VS2022 editor) complains with:

warning CS8618: Non-nullable property 'Message' must contain a non-null value when exiting constructor. Consider declaring the property as nullable.

Additional context

If Message?.Length is changed to Message!.Length then no warning is issued. But I would not expect the ?. operator to change the compiler warning - from my point of view, the property Message should have the same nullability whether ?. or !. is used - the code does assign Message a value in the constructor.