MessagePack.Generator.2.5.140 - Union metatag causes msc.exe error: Index was outside the bounds of the array

[Sean4572435243]

I believe this issue has come up before as shown in these unresolved issues
#922
#1146

This issue still exists in the latest exe version of MessagePack.Generator.2.5.140. For example, I have a .NET class library (target 7 or 8, doesn't matter) containing the github sample C# code here

using MessagePack;

namespace ClassLibrary1
{
    public class Class1
    {
        [MessagePack.Union(0, typeof(FooClass))]
        [MessagePack.Union(1, typeof(BarClass))]
        public interface IUnionSample
        {
        }

        [MessagePackObject]
        public class FooClass : IUnionSample
        {
            [Key(0)]
            public int XYZ { get; set; }
        }

        [MessagePackObject]
        public class BarClass : IUnionSample
        {
            [Key(0)]
            public string? OPQ { get; set; }
        }

    }
}

with a .csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net7.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="MessagePack" Version="2.5.140" />
  </ItemGroup>

  <Target Name="PreBuild" BeforeTargets="PreBuildEvent">
    <Exec Command="mpc.exe -i &quot;$(ProjectDir)$(ProjectName).csproj&quot; -o &quot;$(ProjectDir)MessagePackGenerated.cs&quot; -m&#xD;&#xA;" />
  </Target>

</Project>

running
mpc.exe -i "myProject.csproj" -o "MessagePackGenerated.cs" -m
generates

Fail in application running on MessagepackCompiler.RunAsync
System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.Collections.Immutable.ImmutableArray`1.get_Item(Int32 index)
   at MessagePackCompiler.CodeAnalysis.TypeCollector.<>c__DisplayClass20_0.<CollectUnion>g__UnionSubTypeInfoSelector|2(ImmutableArray`1 x) in D:\a\1\s\src\MessagePack.GeneratorCore\CodeAnalysis\TypeCollector.cs:line 399
   at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
   at System.Linq.OrderedEnumerable`1.ToArray()
   at MessagePackCompiler.CodeAnalysis.TypeCollector.CollectUnion(INamedTypeSymbol type) in D:\a\1\s\src\MessagePack.GeneratorCore\CodeAnalysis\TypeCollector.cs:line 408
   at MessagePackCompiler.CodeAnalysis.TypeCollector.CollectCore(ITypeSymbol typeSymbol) in D:\a\1\s\src\MessagePack.GeneratorCore\CodeAnalysis\TypeCollector.cs:line 375
   at MessagePackCompiler.CodeAnalysis.TypeCollector.Collect() in D:\a\1\s\src\MessagePack.GeneratorCore\CodeAnalysis\TypeCollector.cs:line 305
   at MessagePackCompiler.CodeGenerator.GenerateFileAsync(Compilation compilation, String output, String resolverName, String namespace, Boolean useMapMode, String multipleIfDirectiveOutputSymbols, String[] externalIgnoreTypeNames) in D:\a\1\s\src\MessagePack.GeneratorCore\CodeGenerator.cs:line 67
   at MessagePack.Generator.MessagepackCompiler.RunAsync(String input, String output, String conditionalSymbol, String resolverName, String namespace, Boolean useMapMode, String multipleIfDirectiveOutputSymbols, String[] externalIgnoreTypeNames) in D:\a\1\s\src\MessagePack.Generator\MessagepackCompiler.cs:line 66
   at ConsoleAppFramework.WithFilterInvoker.RunCore(ConsoleAppContext _)
   at ConsoleAppFramework.WithFilterInvoker.InvokeAsync()
   at ConsoleAppFramework.ConsoleAppEngine.RunCore(Type type, MethodInfo methodInfo, Object instance, String[] args, Int32 argsOffset)
   at ConsoleAppFramework.ConsoleAppEngine.RunCore(Type type, MethodInfo methodInfo, Object instance, String[] args, Int32 argsOffset)

Removing the

    [MessagePack.Union(0, typeof(FooClass))]
    [MessagePack.Union(1, typeof(BarClass))]

is successful, but obviously not a workaround, but it does isolate the problem exclusively to the Union metatag.

I am using

Microsoft Visual Studio Professional 2022
Version 17.8.6
VisualStudio.17.Release/17.8.6+34525.116
Microsoft .NET Framework
Version 4.8.09037

Installed Version: Professional

Visual C++ 2022   00483-00100-23601-AA172
Microsoft Visual C++ 2022

ASP.NET and Web Tools   17.8.358.6298
ASP.NET and Web Tools

Azure App Service Tools v3.0.0   17.8.358.6298
Azure App Service Tools v3.0.0

Azure Functions and Web Jobs Tools   17.8.358.6298
Azure Functions and Web Jobs Tools

C# Tools   4.8.0-7.23572.1+7b75981cf3bd520b86ec4ed00ec156c8bc48e4eb
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Common Azure Tools   1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

Extensibility Message Bus   1.4.39 (main@e8108eb)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

Microsoft JVM Debugger   1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Mono Debugging for Visual Studio   17.8.17 (957fbed)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager   6.8.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit https://docs.nuget.org/

Razor (ASP.NET Core)   17.8.3.2405201+d135dd8d2ec1c2fbdee220e8656b308694e17a4b
Provides languages services for ASP.NET Core Razor.

SQL Server Data Tools   17.8.120.1
Microsoft SQL Server Data Tools

Test Adapter for Boost.Test   1.0
Enables Visual Studio's testing tools with unit tests written for Boost.Test.  The use terms and Third Party Notices are available in the extension installation directory.

Test Adapter for Google Test   1.0
Enables Visual Studio's testing tools with unit tests written for Google Test.  The use terms and Third Party Notices are available in the extension installation directory.

Text Macros for Visual Studio 2012-2022   1.18
Brings back text-editing macro support in Visual Studio 2012-2022

TypeScript Tools   17.0.20920.2001
TypeScript Tools for Microsoft Visual Studio

Visual Basic Tools   4.8.0-7.23572.1+7b75981cf3bd520b86ec4ed00ec156c8bc48e4eb
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual F# Tools   17.8.0-beta.23475.2+10f956e631a1efc0f7f5e49c626c494cd32b1f50
Microsoft Visual F# Tools

Visual Studio IntelliCode   2.2
AI-assisted development for Visual Studio.

VisualStudio.DeviceLog   1.0
Information about my package

VisualStudio.Mac   1.0
Mac Extension for Visual Studio

VSPackage Extension   1.0
VSPackage Visual Studio Extension Detailed Info

Xamarin   17.8.0.157 (d17-8@8e82278)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   17.8.3.6 (remotes/origin/d17-8@eccf46a291)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Templates   17.8.16 (830b56a)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   13.2.2.0 (d17-5/45b0e14)
Xamarin.Android Reference Assemblies and MSBuild support.
    Mono: d9a6e87
    Java.Interop: xamarin/java.interop/d17-5@149d70fe
    SQLite: xamarin/sqlite/3.40.1@68c69d8
    Xamarin.Android Tools: xamarin/xamarin-android-tools/d17-5@ca1552d


Xamarin.iOS and Xamarin.Mac SDK   16.4.0.23 (9defd91b3)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

My system:

Processor	12th Gen Intel(R) Core(TM) i9-12900HX   2.50 GHz
Installed RAM	22.0 GB
System type	64-bit operating system, x64-based processor