Mosa Nullable Reproduction.cs

// Copyright (c) MOSA Project. Licensed under the New BSD License.

// #nullable disable
#nullable enable

using System;

// ReSharper disable all

namespace MOSANullReproduction;

public static class Program
{
    public static string String = null!;
    
    public static void Setup()
    {
        String = "Hello!";
        Console.WriteLine(String);
    }

    public static void Loop()
    {
    }
}

​Mosa Nullable Reproduction.decompiled.cs

using System;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Security;
using System.Security.Permissions;
using Microsoft.CodeAnalysis;

[assembly: CompilationRelaxations(8)]
[assembly: RuntimeCompatibility(WrapNonExceptionThrows = true)]
[assembly: Debuggable(DebuggableAttribute.DebuggingModes.Default | DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints | DebuggableAttribute.DebuggingModes.EnableEditAndContinue | DebuggableAttribute.DebuggingModes.DisableOptimizations)]
[assembly: SecurityPermission(SecurityAction.RequestMinimum, SkipVerification = true)]
[assembly: AssemblyVersion("0.0.0.0")]
[module: UnverifiableCode]
[module: System.Runtime.CompilerServices.RefSafetyRules(11)]

namespace MOSANullReproduction
{
    public static class Program
    {
        [System.Runtime.CompilerServices.Nullable(1)]
        public static string String;

        public static void Setup()
        {
            String = "Hello!";
            Console.WriteLine(String);
        }

        public static void Loop()
        {
        }
    }
}

namespace Microsoft.CodeAnalysis
{
    [CompilerGenerated]
    [Embedded]
    internal sealed class EmbeddedAttribute : Attribute
    {
    }
}

namespace System.Runtime.CompilerServices
{
    [CompilerGenerated]
    [Microsoft.CodeAnalysis.Embedded]
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Parameter | AttributeTargets.ReturnValue | AttributeTargets.GenericParameter, AllowMultiple = false, Inherited = false)]
    internal sealed class NullableAttribute : Attribute
    {
        public readonly byte[] NullableFlags;

        public NullableAttribute(byte P_0)
        {
            byte[] array = new byte[1];
            array[0] = P_0;
            NullableFlags = array;
        }

        public NullableAttribute(byte[] P_0)
        {
            NullableFlags = P_0;
        }
    }

    [CompilerGenerated]
    [Microsoft.CodeAnalysis.Embedded]
    [AttributeUsage(AttributeTargets.Module, AllowMultiple = false, Inherited = false)]
    internal sealed class RefSafetyRulesAttribute : Attribute
    {
        public readonly int Version;

        public RefSafetyRulesAttribute(int P_0)
        {
            Version = P_0;
        }
    }
}

​​.sharplab.json

{
    "version": 1,
    "target": "C#",
    "mode": "Debug"
}