ILLink: argument exception in Cecil when writing assembly

[vitek-karas]

Repro:

dotnet new console

app.csproj:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <PublishTrimmed>true</PublishTrimmed>
        <WarningsAsErrors>false</WarningsAsErrors>
        <NoWarn>NU1605;NU1603;NU1701</NoWarn>
    </PropertyGroup>

    <ItemGroup>
        <TrimmerRootAssembly Include="Syncfusion.Maui.Gauges" />

        <PackageReference Include="Syncfusion.Maui.Gauges" Version="20.4.40" />
    </ItemGroup>
</Project>

dotnet publish

Stack trace from the output:

   ---> System.ArgumentException: Member 'Syncfusion.Maui.Graphics.Internals.IDrawableView' is declared in another modu
  le and needs to be imported
     at Mono.Cecil.MetadataBuilder.LookupToken(IMetadataTokenProvider provider)
     at Mono.Cecil.SignatureWriter.MakeTypeDefOrRefCodedRID(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteTypeSignature(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteGenericInstanceSignature(IGenericInstance instance)
     at Mono.Cecil.SignatureWriter.WriteTypeSignature(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeSpecSignature(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeSpecToken(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeToken(TypeReference type)
     at Mono.Cecil.MetadataBuilder.AddType(TypeDefinition type)
     at Mono.Cecil.MetadataBuilder.AddTypes()
     at Mono.Cecil.MetadataBuilder.BuildTypes()
     at Mono.Cecil.MetadataBuilder.BuildModule()
     at Mono.Cecil.MetadataBuilder.BuildMetadata()
     at Mono.Cecil.ModuleWriter.<>c.<BuildMetadata>b__2_0(MetadataBuilder builder, MetadataReader _)
     at Mono.Cecil.ModuleDefinition.Read[TItem,TRet](TItem item, Func`3 read)
     at Mono.Cecil.ModuleWriter.BuildMetadata(ModuleDefinition module, MetadataBuilder metadata)
     at Mono.Cecil.ModuleWriter.Write(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
     at Mono.Cecil.ModuleWriter.WriteModule(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
     at Mono.Cecil.ModuleDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Cecil.AssemblyDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory, WriterParameters writ
  erParameters)

/cc @LakshanF

Tagging subscribers to this area: @agocke, @sbomer, @vitek-karas
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Issue Details

---

Repro:

dotnet new console

app.csproj:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <PublishTrimmed>true</PublishTrimmed>
        <WarningsAsErrors>false</WarningsAsErrors>
        <NoWarn>NU1605;NU1603;NU1701</NoWarn>
    </PropertyGroup>

    <ItemGroup>
        <TrimmerRootAssembly Include="Syncfusion.Maui.Gauges" />

        <PackageReference Include="Syncfusion.Maui.Gauges" Version="20.4.40" />
    </ItemGroup>
</Project>

dotnet publish

Stack trace from the output:

   ---> System.ArgumentException: Member 'Syncfusion.Maui.Graphics.Internals.IDrawableView' is declared in another modu
  le and needs to be imported
     at Mono.Cecil.MetadataBuilder.LookupToken(IMetadataTokenProvider provider)
     at Mono.Cecil.SignatureWriter.MakeTypeDefOrRefCodedRID(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteTypeSignature(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteGenericInstanceSignature(IGenericInstance instance)
     at Mono.Cecil.SignatureWriter.WriteTypeSignature(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeSpecSignature(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeSpecToken(TypeReference type)
     at Mono.Cecil.MetadataBuilder.GetTypeToken(TypeReference type)
     at Mono.Cecil.MetadataBuilder.AddType(TypeDefinition type)
     at Mono.Cecil.MetadataBuilder.AddTypes()
     at Mono.Cecil.MetadataBuilder.BuildTypes()
     at Mono.Cecil.MetadataBuilder.BuildModule()
     at Mono.Cecil.MetadataBuilder.BuildMetadata()
     at Mono.Cecil.ModuleWriter.<>c.<BuildMetadata>b__2_0(MetadataBuilder builder, MetadataReader _)
     at Mono.Cecil.ModuleDefinition.Read[TItem,TRet](TItem item, Func`3 read)
     at Mono.Cecil.ModuleWriter.BuildMetadata(ModuleDefinition module, MetadataBuilder metadata)
     at Mono.Cecil.ModuleWriter.Write(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
     at Mono.Cecil.ModuleWriter.WriteModule(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
     at Mono.Cecil.ModuleDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Cecil.AssemblyDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory, WriterParameters writ
  erParameters)

/cc @LakshanF

Author:	vitek-karas
Assignees:	-
Labels:	area-Tools-ILLink
Milestone:	-

[vitek-karas]

Similar failure on a different package - worth validating on the same fix:

app.csproj:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <PublishTrimmed>true</PublishTrimmed>
        <WarningsAsErrors>false</WarningsAsErrors>
        <NoWarn>NU1605;NU1603;NU1701</NoWarn>

        <TargetPackageName>NewPlatform.Flexberry.ORM.ODataService</TargetPackageName>
        <TargetPackageVersion>7.0.0</TargetPackageVersion>
        <TargetAssemblyName></TargetAssemblyName>

        <TargetAssemblyName Condition="'$(TargetAssemblyName)' == ''">$(TargetPackageName)</TargetAssemblyName>
    </PropertyGroup>

    <ItemGroup>
        <TrimmerRootAssembly Include="$(TargetAssemblyName)" />

        <PackageReference Include="$(TargetPackageName)" Version="$(TargetPackageVersion)" />
    </ItemGroup>

    <Target Name="ConfigureTrimming"
            BeforeTargets="PrepareForILLink">
        <ItemGroup>
          <ManagedAssemblyToLink Condition="'%(Filename)' == '$(TargetAssemblyName)'">
              <TrimmerSingleWarn>false</TrimmerSingleWarn>
          </ManagedAssemblyToLink>
        </ItemGroup>
    </Target>
</Project>

Stack trace:

  Fatal error in IL Linker
  Unhandled exception. Mono.Linker.LinkerFatalErrorException: ILLink: error IL1011: Failed to write 'obj\Release\net8.0
  \win-x64\linked\Microsoft.AspNetCore.OData.dll'.
   ---> System.ArgumentException: Member 'Microsoft.AspNet.OData.Batch.ODataBatchMiddleware' is declared in another mod
  ule and needs to be imported
     at Mono.Cecil.MetadataBuilder.LookupToken(IMetadataTokenProvider provider)
     at Mono.Cecil.SignatureWriter.MakeTypeDefOrRefCodedRID(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteTypeSignature(TypeReference type)
     at Mono.Cecil.SignatureWriter.WriteGenericInstanceSignature(IGenericInstance instance)
     at Mono.Cecil.MetadataBuilder.GetMethodSpecSignature(MethodSpecification method_spec)
     at Mono.Cecil.MetadataBuilder.CreateMethodSpecRow(MethodSpecification method_spec)
   ...
     at Mono.Cecil.AssemblyDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory, WriterParameters writ
  erParameters)

[danmoseley]

is the bug here that it should not be dumping stack? or that it should not be failing? I was going to open a bug for the former, perhaps this covers it. dumping stack when it's not a bug on us is ugly.

ILLink : error IL1011: Failed to write 'obj\Debug\net8.0\linked\System.Private.CoreLib.dll'. [D:\a\aspire-samples\aspire-samples\samples\Metrics\MetricsApp.Client\MetricsApp.Client.csproj]
  Fatal error in IL Linker
  Unhandled exception. Mono.Linker.LinkerFatalErrorException: ILLink: error IL1011: Failed to write 'obj\Debug\net8.0\linked\System.Private.CoreLib.dll'.
   ---> System.IO.IOException: The process cannot access the file 'D:\a\aspire-samples\aspire-samples\samples\Metrics\MetricsApp.Client\obj\Debug\net8.0\linked\System.Private.CoreLib.dll' because it is being used by another process.
     at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
     at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
     at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
     at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
     at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
     at Mono.Cecil.ModuleDefinition.GetFileStream(String fileName, FileMode mode, FileAccess access, FileShare share)
     at Mono.Cecil.ModuleDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Cecil.AssemblyDefinition.Write(String fileName, WriterParameters parameters)
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory, WriterParameters writerParameters)
     --- End of inner exception stack trace ---
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory, WriterParameters writerParameters)
     at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory)
     at Mono.Linker.Steps.OutputStep.OutputAssembly(AssemblyDefinition assembly)
     at Mono.Linker.Steps.OutputStep.ProcessAssembly(AssemblyDefinition assembly)
     at Mono.Linker.Steps.BaseStep.Process(LinkContext context)
     at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step)
     at Mono.Linker.Pipeline.Process(LinkContext context)
     at Mono.Linker.Driver.Run(ILogger customLogger)
     at Mono.Linker.Driver.Main(String[] args)

[sbomer]

Confirmed the first repro provided. Here's what happens:

• Syncfusion.Maui.Core.dll defines a type SfDrawableViewHandler derived from ViewHandler<IDrawableView, object>.
• ViewHandler is defined in Microsoft.Maui, which is not referenced in the console app.
• When marking SfDrawableViewHandler we fail to resolve the base type so we don't mark IDrawableView (which is also defined in Syncfusion.Maui.Core.dll).
• SweepStep detaches all types from their modules, then never adds back IDrawableView because it wasn't marked.
• When writing the assembly, we try to write a typespec for ViewHandler<IDrawableView, object>, but at this point it fails because IDrawableView's Module is null.

For comparison, Native AOT fails on the same input with:

EXEC : error : Failed to load assembly 'Microsoft.Maui.Controls'
    Internal.TypeSystem.TypeSystemException+FileNotFoundException: Failed to load assembly 'Microsoft.Maui.Controls'
       at Internal.TypeSystem.ThrowHelper.ThrowFileNotFoundException(ExceptionStringID, String) + 0x30
       at Internal.TypeSystem.ResolutionFailure.Throw() + 0xfd
       at Internal.TypeSystem.Ecma.EcmaType.InitializeBaseType() + 0x1da
       at ILCompiler.DependencyAnalysis.TypeMetadataNode.GetStaticDependencies(NodeFactory) + 0x186
       at ILCompiler.DependencyAnalysisFramework.DependencyAnalyzer`2.GetStaticDependenciesImpl(DependencyNodeCore`1) + 0x3f
       at ILCompiler.DependencyAnalysisFramework.DependencyAnalyzer`2.GetStaticDependencies(DependencyNodeCore`1) + 0x33
       at ILCompiler.DependencyAnalysisFramework.DependencyAnalyzer`2.ProcessMarkStack() + 0xff
       at ILCompiler.DependencyAnalysisFramework.DependencyAnalyzer`2.ComputeMarkedNodes() + 0x4f
       at ILCompiler.ILScanner.ILCompiler.IILScanner.Scan() + 0x19
       at ILCompiler.Program.<Run>g__RunScanner|4_0(Program.<>c__DisplayClass4_0&) + 0x1fa
       at ILCompiler.Program.Run() + 0x29cc
       at ILCompiler.ILCompilerRootCommand.<>c__DisplayClass240_0.<.ctor>b__0(ParseResult result) + 0x35a

[sbomer]

The fundamental problem is that the input was missing a referenced assembly. This caused some inconsistent marking for generics, leading to downstream failures. I can see two solutions to this:

1. Make a best-effort attempt to be resilient to the missing reference. In this particular case that means marking the generic arguments even if we couldn't resolve the generic type definition.
2. Fail earlier and more predictably, like how Native AOT does it. (Whether it prints a stacktrace or logs an error is a separate question).

I opened #103831 for 2, but I don't think we should do that in .NET 9 so I am leaning towards 1 for a .NET 9 fix.