using System;

    using System.Collections.Generic;

    using System.Reflection;

​

    #nullable enable

​

    public class TestGNN<T>

    {

        public T this[string index] => default; // possible null ref that we'll ignore

    }

​

    public class TestGN<T>

    {

        public T? this[string index] => default;

    }

​

    public class TestNNS

    {

        public string this[string index] => index;

    }

​

    public class TestNS

    {

        public string? this[string index] => index;

    }

​

    public class TestNNI

    {

        public int this[string index] => 0;

    }

​

    public class TestNI

    {

        public int? this[string index] => null;

    }

​

    public class TestNNT

    {

        public Tuple<object, object> this[string index] => default;  // possible null ref that we'll ignore

    }

​

    public class TestNT

    {

        public Tuple<object, object>? this[string index] => null;

    }

​

    public class Program

    {   

        public static void Main()

        {

            List<object> cases =

            [

                new TestGNN<string>(),

                new TestGNN<string?>(),

                new TestGNN<int>(),

                new TestGNN<int?>(),

                new TestGNN<Tuple<object, object>>(),

                new TestGNN<Tuple<object, object>?>(),

                new TestGN<string>(),

                new TestGN<string?>(),

                new TestGN<int>(),

                new TestGN<int?>(),

                new TestGN<Tuple<object, object>>(),

                new TestGN<Tuple<object, object>?>(),

                new TestNNS(),

                new TestNS(),

                new TestNNI(),

                new TestNI(),

                new TestNNT(),

                new TestNT()

            ];

​

            NullabilityInfoContext context = new();

            foreach (var c in cases)

            {

                var t = c.GetType();

                foreach (var p in t.GetProperties(BindingFlags.Public | BindingFlags.Instance))

                {

                    var info = context.Create(p);

                    Console.WriteLine($"{c}: {info.ReadState}");

                }

            }

        }

    }