MTP produces IL2104 trim warning for test projects that target net8.0

[AArnott]

Describe the bug

When publishing a NativeAOT test project that targets net8.0, I get the following warning-as-error:

/Users/runner/work/Nerdbank.MessagePack/Nerdbank.MessagePack/.nuget/packages/microsoft.testing.platform/2.0.2/lib/net8.0/Microsoft.Testing.Platform.dll : error IL2104: Assembly 'Microsoft.Testing.Platform' produced trim warnings. For more information see https://aka.ms/dotnet-illink/libraries [/Users/runner/work/Nerdbank.MessagePack/Nerdbank.MessagePack/test/Nerdbank.MessagePack.TUnit/Nerdbank.MessagePack.TUnit.csproj::TargetFramework=net8.0]

Steps To Reproduce

git clone -b tunit-net8.0 git@github.com:AArnott/Nerdbank.MessagePack.git
cd Nerdbank.MessagePack
./init.ps1
dotnet publish .\test\Nerdbank.MessagePack.TUnit\ -f net8.0

Expected behavior

No warnings.

Actual behavior

A warning is produced:

e:.nuget\packages\microsoft.testing.platform\2.0.2\lib\net8.0\Microsoft.Testing.Platform.dll : warning IL2104: Assembly 'Microsoft.Testing.Platform' produced trim warnings. For more information see https://aka.ms/dotnet-illink/libraries

Additional context

dotnet --info

.NET SDK:
 Version:           10.0.101
 Commit:            fad253f51b
 Workload version:  10.0.100.1
 MSBuild version:   18.0.6+fad253f51

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26200
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\10.0.101\

.NET workloads installed:
 [ios]
   Installation Source: SDK 10.0.100
   Manifest Version:    26.1.10494/10.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.ios\26.1.10494\WorkloadManifest.json
   Install Type:              Msi

Configured to use workload sets when installing new manifests.

Host:
  Version:      10.0.1
  Architecture: x64
  Commit:       fad253f51b

.NET SDKs installed:
  9.0.205 [C:\Program Files\dotnet\sdk]
  9.0.307 [C:\Program Files\dotnet\sdk]
  9.0.308 [C:\Program Files\dotnet\sdk]
  10.0.100 [C:\Program Files\dotnet\sdk]
  10.0.101 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 10.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.21 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.21 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 10.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  DOTNET_CLI_DISABLE_PUBLISH_AND_PACK_RELEASE [true]
  DOTNET_SUGGEST_SCRIPT_VERSION            [1.0.2]

global.json file:
  E:\src\nerdbank.messagepack\global.json

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

[AArnott]

Here's a more concise repro, given in the form of a regression test you can merge into your repo!

Just run dotnet publish -c release -r win-x64 -warnaserror test\IntegrationTests\NativeAOTPublishTest -f net8.0 while my branch is checked out and you'll get the specific linker warning, which is:

ILC : Trim analysis error IL2041: Polyfills.Polyfill.GetMethod(Type,String,Int32,BindingFlags,Type[]): The 'DynamicallyAccessedMembersAttribute' is not allowed on methods. It is allowed on method return value or method parameters though.
e:.nuget\packages\polyfill\9.0.0-beta.19\contentFiles\cs\netstandard2.0\Polyfill\Polyfill_Type.cs(26): Trim analysis error IL2070: Polyfills.Polyfill.GetMethod(Type,String,Int32,BindingFlags,Type[]): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicMethods', 'DynamicallyAccessedMemberTypes.NonPublicMethods' in call to 'System.Type.GetMethod(String,Int32,BindingFlags,Binder,Type[],ParameterModifier[])'. The parameter 'target' of method 'Polyfills.Polyfill.GetMethod(Type,String,Int32,BindingFlags,Type[])' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.

This is in fact how I guard all my own NativeAOT libraries against such bugs as this.
You just need to add the dotnet publish command above (one for each TFM) to your pipeline/workflow so that any regressions get caught right away.