Determine nullability of list item type at runtime

[skrysmanski]

I'm currently writing a serializer and am looking at nullable reference types.

I'm using NullabilityInfoContext which works fine in most scenarios. However, there is one scenario where I don't know how to get the information I need.

I want to determine the nullability of the items in a collection.

Assume the following classes (with nullable reference types enabled):

public class TestClass
{
    public List<string> Value1 { get; set; }
    public List<string?> Value2 { get; set; }
    public TestList Value3 { get; set; }
}

public sealed class TestList : List<string> { }

For the first two properties, I can get the correct/desired nullability information like this:

var ctx = new NullabilityInfoContext();
Console.WriteLine("Value1: " + ctx.Create(value1PropertyInfo).GenericTypeArguments[0].ReadState); // NotNull
Console.WriteLine("Value2: " + ctx.Create(value2PropertyInfo).GenericTypeArguments[0].ReadState); // Nullable

But when I determine nullability info for Value3 I just get this:

I even tried this:

var getEnumeratorMethod = typeof(TestList).GetMethod("GetEnumerator");
var info = ctx.Create(getEnumeratorMethod.ReturnParameter);

But with this I get Unknown for info.GenericTypeArguments[0].ReadState.

Is there any way to get the information I'm looking for with NullabilityInfoContext (on .NET 8)?