Why don't I get a warning about possible dereference of a null in C# 8 with a class member of a struct?

Question

In a C# 8 project with nullable reference types enabled, I have the following code which I think should give me a warning about a possible null dereference, but doesn\'t:

Answer 1

In the light of the excellent answer by @peter-duniho it seems that as of Oct-2019 it's best to mark all non-value-type members a nullable reference.

#nullable enable
public class C
{
    public int P1 { get; } 
}

public struct S
{
    public C? Member { get; } // Reluctantly mark as nullable reference because
                              // https://devblogs.microsoft.com/dotnet/nullable-reference-types-in-csharp/
                              // states:
                              // "Using the default constructor of a struct that has a
                              // field of nonnullable reference type. This one is 
                              // sneaky, since the default constructor (which zeroes 
                              // out the struct) can even be implicitly used in many
                              // places. Probably better not to warn, or else many
                              // existing struct types would be rendered useless."
}

public class Program
{
    public static void Main()
    {
        var instance = new S();
        Console.WriteLine(instance.Member.P1); // Warning
    }
}