S1854 false positive in C# catch when variable used in finally with null-conditional

SonarQube for IDE Visual Studio
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1
  • Operating system: Windows 10 Pro 22H2
  • Visual Studio version: 18.0.2
  • SonarQube for Visual Studio plugin version: 9.1.0.15828
  • Programming language you’re coding in: C#
  • Is connected mode used: No

I get a false positive for S1854 in this code when setting myClassLocal = null in the catch block, even though the variable is used in the finally block after throwing. It seems that the null-conditional operator somehow causes it, because commenting out the line myClassLocal?.SetNumber(123); makes the report go away.

using static System.Console;

namespace Test;

internal static class Program
{
    class MyClass
    {
        public int Number { get; private set; }
        public void SetNumber(int value) => Number = value;
    }

    static MyClass myClassField;

    static void Main()
    {
        try
        {
            Do();
        }
        catch
        {
            // ...
        }

        WriteLine(myClassField.Number);
        ReadLine();
    }

    static void Do()
    {
        MyClass myClassLocal = new();
        myClassField = myClassLocal;

        try
        {
            // ...
        }
        catch
        {
            myClassLocal.SetNumber(0);
            myClassLocal = null;  // S1854 false positive
            throw;
        }
        finally
        {
            // Commenting this single line removes the S1854 report:
            myClassLocal?.SetNumber(123);

            if (myClassLocal != null)
            {
                myClassLocal.SetNumber(123);
            }
        }
    }
}
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