Bug description

When running a xamarin forms app on an iOS device, while using pre-compilation, the MessagePackSerializer.Deserialize method throws an exception (System.NotImplementedException: byref delegate)

I've followed the readme https://github.com/neuecc/MessagePack-CSharp#aot-code-generation-support-for-unityxamarin and implemented the MS build task as described here https://github.com/neuecc/MessagePack-CSharp/blob/master/doc/msbuildtask.md to use pre-compiled types.

Repro steps

I've uploaded a small reproduction sample here: https://github.com/stefanbogaard86/MessagePack-iOS-sample,

this is the sample code:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using MessagePack;
using Xamarin.Forms;
using MessagePack.Resolvers;

namespace MessagePackSample
{
    [MessagePackObject]
    public class CustomObject
    {
        [Key(0)]
        public string Item1 { get; set; }

        [Key(1)]
        public DateTime Item2 { get;set; }

        public override string ToString()
        {
            return $"[{Item1} - {Item2.ToShortDateString()}]";
        }
    }
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        protected override void OnAppearing()
        {
            base.OnAppearing();
           
            MessagePackSerializerOptions generatedResolverOptions =
            MessagePackSerializerOptions.Standard
                .WithResolver(
                    CompositeResolver.Create(
                        GeneratedResolver.Instance,
                        StandardResolver.Instance
                    ));

            var customObjects = new List<CustomObject>
            {
                new CustomObject() {Item1 = "Yesterday", Item2 = DateTime.Today.AddDays(-1)},
                new CustomObject() {Item1 = "Today", Item2 = DateTime.Today},
                new CustomObject() {Item1 = "Next week", Item2 = DateTime.Today.AddDays(7)}
            };

            var serializedObj = MessagePackSerializer.Serialize(customObjects, generatedResolverOptions);

            try
            {
                var deserializedObj =
                    (IEnumerable<CustomObject>)MessagePackSerializer.Deserialize(typeof(IEnumerable<CustomObject>), serializedObj, generatedResolverOptions);

            }
            catch(Exception ex)
            {
                Debug.WriteLine(ex);
            }
        }
    }
}

Expected behavior

The serialized object is deserialized when running a xamarin forms app on iOS.

Actual behavior

When trying to deserialize on xamarin forms iOS, an exception is thrown.

{System.NotImplementedException: byref delegate at System.Linq.Expressions.Interpreter.LightLambda.CreateCustomDelegate (System.Type delegateType) [0x001cf] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Linq.Expressions/src/System/Linq/Expressions/Interpreter/LightLambda.cs:422 at System.Linq.Expressions.Interpreter.LightLambda.MakeDelegate (System.Type delegateType) [0x00012] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Linq.Expressions/src/System/Linq/Expressions/Interpreter/LightLambda.cs:446 at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate (System.Runtime.CompilerServices.IStrongBox[] closure) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Linq.Expressions/src/System/Linq/Expressions/Interpreter/LightDelegateCreator.cs:33 at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Linq.Expressions/src/System/Linq/Expressions/Interpreter/LightDelegateCreator.cs:28 at System.Linq.Expressions.Expression1[TDelegate].Compile (System.Boolean preferInterpretation) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs:211 at MessagePack.MessagePackSerializer+CompiledMethods..ctor (System.Type type) [0x0046d] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.MessagePackSerializer+<>c.<.cctor>b__45_0 (System.Type t) [0x00000] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.Internal.ThreadsafeTypeKeyHashTable1[TValue].AddToBuckets (MessagePack.Internal.ThreadsafeTypeKeyHashTable1+Entry[TValue][] buckets, System.Type newKey, MessagePack.Internal.ThreadsafeTypeKeyHashTable1+Entry[TValue] newEntryOrNull, System.Func2[T,TResult] valueFactory, TValue& resultingValue) [0x00045] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.Internal.ThreadsafeTypeKeyHashTable1[TValue].TryAddInternal (System.Type key, System.Func2[T,TResult] valueFactory, TValue& resultingValue) [0x000d2] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.Internal.ThreadsafeTypeKeyHashTable1[TValue].GetOrAdd (System.Type key, System.Func2[T,TResult] valueFactory) [0x0000d] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.MessagePackSerializer.GetOrAdd (System.Type type) [0x00000] in <e372d2478807460eabc86dc315aa3ac8>:0 at MessagePack.MessagePackSerializer.Deserialize (System.Type type, System.ReadOnlyMemory1[T] bytes, MessagePack.MessagePackSerializerOptions options, System.Threading.CancellationToken cancellationToken) [0x00000] in :0 at MessagePackSample.MainPage.OnAppearing () [0x000f5] in C:\Projects\MessagePack-iOS-sample\MessagePackSample\MessagePackSample\MessagePackSample\MainPage.xaml.cs:54 }

• Version used:
  Mono Framework MDK
  Runtime:
  Mono 6.12.0.140 (2020-02/51d876a041e) (64-bit)
  Package version: 612000140
  Xamarin.Forms 5.0.0.2125
  MessagePack 2.3.85
  MessagePack.MSBuild.Task 2.3.85

Additional context

It's working as expected on Android.