I would like to switch to exhaustive switch in C# in .NET 8 so it will work similar way like some modern programing languages (Rust, ..), but I cannot make it work.

I try to replicate the answer here:

/a/68227845/518530

#pragma warning restore CS8509
#pragma warning disable CS8524

string SeverityToString(Severity severity)
{
    switch (severity)
    {
        case Severity.Error:
            return "Error";
        case Severity.Warning:
            return "Warning";
        //default: // default should be automatically generated by pragmas above, isnt it?
        //    throw new InvalidEnumArgumentException(severity.ToString(), (int)severity, severity.GetType());
    }
}

Console.WriteLine(SeverityToString(Severity.Error));

public enum Severity
{
    Warning,
    Error,
}

But anyway I still get compilation error, for some reasone, the compiler automatically does not generate the default statement if it should

  Program.cs(5, 8): [CS0161] 'SsverityToString(Severity)': not all code paths return a value

Why it does not work? Why the default statement is not generated by compiler?