net8.0-android->net9-android linker error on publish

[DevronTLA]

Description

I've converted my project from net8-android to net9-android successfully. I was able to publish fine in net8, but on net9 the publish fails with a linker error:

 ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink
    Fatal error in IL Linker
    Unhandled exception. System.NotSupportedException: TypeDefinition cannot be resolved from 'Mono.Cecil.RequiredModifierType' type
       at Mono.Linker.LinkContext.Resolve(TypeReference typeReference)
       at MonoDroid.Tuner.FixAbstractMethodsStep.CompareTypes(TypeReference iType, TypeReference tType) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs:line 167
       at MonoDroid.Tuner.FixAbstractMethodsStep.HaveSameSignature(TypeReference iface, MethodDefinition iMethod, MethodDefinition tMethod) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs:line 215
       at MonoDroid.Tuner.FixAbstractMethodsStep.FixAbstractMethods(TypeDefinition type) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs:line 267
       at MonoDroid.Tuner.FixAbstractMethodsStep.ProcessType(TypeDefinition type) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs:line 86
       at MonoDroid.Tuner.FixAbstractMethodsStep.<Initialize>b__0_0(TypeDefinition type) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs:line 39
       at Mono.Linker.Steps.MarkStep.MarkType(TypeReference reference, DependencyInfo reason, MessageOrigin origin)
       at Mono.Linker.Steps.MarkStep.MarkField(FieldDefinition field, DependencyInfo& reason, MessageOrigin& origin)
       at Mono.Linker.Steps.MarkStep.MarkField(FieldReference reference, DependencyInfo reason, MessageOrigin& origin)
       at Mono.Linker.Steps.MarkStep.MarkFieldVisibleToReflection(FieldReference field, DependencyInfo& reason, MessageOrigin& origin)
       at Mono.Linker.Steps.MarkStep.MarkFieldsVisibleToReflection(TypeDefinition type, DependencyInfo& reason, MessageOrigin origin, Boolean markBackingFieldsOnlyIfPropertyMarked)
       at Mono.Linker.Steps.MarkStep.MarkEntireType(TypeDefinition type, DependencyInfo& reason, MessageOrigin origin)
       at Mono.Linker.Steps.MarkStep.MarkEntireAssembly(AssemblyDefinition assembly, MessageOrigin origin)
       at Mono.Linker.Steps.MarkStep.MarkAssembly(AssemblyDefinition assembly, DependencyInfo reason, MessageOrigin origin)
       at Mono.Linker.Steps.MarkStep.MarkModule(ModuleDefinition module, DependencyInfo reason, MessageOrigin origin)
       at Mono.Linker.Steps.MarkStep.ProcessMarkedPending()
       at Mono.Linker.Steps.MarkStep.Initialize()
       at Mono.Linker.Steps.MarkStep.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)

I'm not really sure where/what is causing this error, or the steps to narrow it down. Happy to provide more information with some guidance.

Reproduction Steps

convert csproj from:

 <TargetFramework>net8.0-android</TargetFramework>

to

 <TargetFramework>net9.0-android</TargetFramework>

and using:

<PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
    <Optimize>true</Optimize>
    <!-- <AndroidLinkMode>None</AndroidLinkMode> -->
    <AndroidLinkTool>r8</AndroidLinkTool>
    <PublishTrimmed>true</PublishTrimmed>
    <!-- <TrimMode>copy</TrimMode> -->
    <RunAOTCompilation>true</RunAOTCompilation>
  </PropertyGroup>

publish command line is: dotnet publish /bl -v diag -f net9.0-android

if I set config as:

<PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
    <Optimize>true</Optimize>
    <!-- <AndroidLinkMode>None</AndroidLinkMode> -->
    <AndroidLinkTool>r8</AndroidLinkTool>
    <PublishTrimmed>false</PublishTrimmed>
    <!-- <TrimMode>copy</TrimMode> -->
    <RunAOTCompilation>false</RunAOTCompilation>
  </PropertyGroup>

the publish succeeds but with very large aab files.

Expected behavior

publish command to successfully complete as per net8-android.

Actual behavior

dotnet publish fails with above error.

Regression?

yes, worked ok in net8-android.

Known Workarounds

none viable found.

Configuration

• net9.0-android
• windows 11
• android-arm;android-arm64;android-x86;android-x64
• no
• n/a

Other information

🤷

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[DevronTLA]

Any advise on this? is it something I can fix in my project or is an internal linker thing?

This is currently blocking my upgrade path to net9.

cheers

[agocke]

@sbomer can you take a look?

[DevronTLA]

@sbomer, any progress on this?

cheers

[sbomer]

@DevronTLA from the stacktrace I can't tell what the problem is. Would you be able to share a repro?

[DevronTLA]

@sbomer I'm having trouble reproducing this error in a basic project. Any clues on how to zero in on this error? The stack trace doesn't really offer any clues about where to look, and my project is quite large, so I don't really want to start dismantling it.