Confusing AOT IL3035 error regarding Enums during Source Generation

[thomhurst]

Heya, I don't know whether this falls under runtime or roslyn, but I'm a bit stuck on an issue.

When publishing an app in AOT, using the TUnit testing library, I get these warnings:

Build succeeded with 5 warning(s) in 38.2s
PS C:\Users\Tom\Downloads\TUnitTest\TUnitTest> dotnet publish -r win-x64
Restore complete (1.3s)
  TUnitTest succeeded with 5 warning(s) (46.7s) → TUnitTest\bin\Release\net9.0\win-x64\publish\
    C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\SourceGeneratedViewer\TUnit.Core.SourceGenerator\TUnit.Core.SourceGenerator.CodeGenerators.TestsGenerator\MyTestClass-accf4da59e2545048bac55da1cbd2b2c.Generated.cs(30): AOT analysis w
arning IL3050: TUnit.SourceGenerated.<MyTestClass_accf4da59e2545048bac55da1cbd2b2c_Generated>F029FFDF2C35D9CD904C997729B53179E6EE2A7FC3DDB5371A4DAD4DB33A86794__MyTestClass.Tests0(String): Using member 'System.Enum.GetValues(Type)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.
    C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\SourceGeneratedViewer\TUnit.Core.SourceGenerator\TUnit.Core.SourceGenerator.CodeGenerators.TestsGenerator\MyTestClass-accf4da59e2545048bac55da1cbd2b2c.Generated.cs(41): AOT analysis w
arning IL3050: TUnit.SourceGenerated.<MyTestClass_accf4da59e2545048bac55da1cbd2b2c_Generated>F029FFDF2C35D9CD904C997729B53179E6EE2A7FC3DDB5371A4DAD4DB33A86794__MyTestClass.<>c.<Tests0>b__2_1(): Using member 'System.Enum.GetValues(Type)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.   
    C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\SourceGeneratedViewer\TUnit.Core.SourceGenerator\TUnit.Core.SourceGenerator.CodeGenerators.TestsGenerator\MyTestClass-accf4da59e2545048bac55da1cbd2b2c.Generated.cs(74): AOT analysis w
arning IL3050: TUnit.SourceGenerated.<MyTestClass_accf4da59e2545048bac55da1cbd2b2c_Generated>F029FFDF2C35D9CD904C997729B53179E6EE2A7FC3DDB5371A4DAD4DB33A86794__MyTestClass.Tests0(String): Using member 'System.Enum.GetValues(Type)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.
    C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\SourceGeneratedViewer\TUnit.Core.SourceGenerator\TUnit.Core.SourceGenerator.CodeGenerators.TestsGenerator\MyTestClass-accf4da59e2545048bac55da1cbd2b2c.Generated.cs(80): AOT analysis w
arning IL3050: TUnit.SourceGenerated.<MyTestClass_accf4da59e2545048bac55da1cbd2b2c_Generated>F029FFDF2C35D9CD904C997729B53179E6EE2A7FC3DDB5371A4DAD4DB33A86794__MyTestClass.Tests0(String): Using member 'System.Enum.GetValues(Type)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.
    C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\SourceGeneratedViewer\TUnit.Core.SourceGenerator\TUnit.Core.SourceGenerator.CodeGenerators.TestsGenerator\MyTestClass-accf4da59e2545048bac55da1cbd2b2c.Generated.cs(74): AOT analysis w
arning IL3050: TUnit.SourceGenerated.<MyTestClass_accf4da59e2545048bac55da1cbd2b2c_Generated>F029FFDF2C35D9CD904C997729B53179E6EE2A7FC3DDB5371A4DAD4DB33A86794__MyTestClass.<>c__DisplayClass2_0.<Tests0>b__0(): Using member 'System.Enum.GetVa
lues(Type)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.

Build succeeded with 5 warning(s) in 48.5s

Now I've opened that exact file () and there is no usage of Enum.GetValues in the generated code. I have no idea how to proceed further. Obviously if there were calls using that method, I could just easily switch them out. But if it's not in the code, why is it flagging it up?

This is the generated code:

// <auto-generated/>
#pragma warning disable
using global::System.Linq;
using global::System.Reflection;
using global::TUnit.Core;
using global::TUnit.Core.Extensions;

namespace TUnit.SourceGenerated;

[global::System.Diagnostics.StackTraceHidden]
[global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
file partial class MyTestClass : global::TUnit.Core.Interfaces.SourceGenerator.ITestSource
{
	[global::System.Runtime.CompilerServices.ModuleInitializer]
	public static void Initialise()
	{
		global::TUnit.Core.SourceRegistrar.Register(new MyTestClass());
	}

	public global::System.Collections.Generic.IReadOnlyList<SourceGeneratedTestNode> CollectTests(string sessionId)
	{
		return Tests0(sessionId);
	}

	private global::System.Collections.Generic.List<SourceGeneratedTestNode> Tests0(string sessionId)
	{
		global::System.Collections.Generic.List<SourceGeneratedTestNode> nodes = [];
		var classDataIndex = 0;
		var testMethodDataIndex = 0;
		try
		{
			var testInformation = new global::TUnit.Core.SourceGeneratedMethodInformation
			{
				Type = typeof(global::TUnitTest.MyTestClass),
				Name = "MyTest",
				GenericTypeCount = 0,
				ReturnType = typeof(global::System.Threading.Tasks.Task),
				Attributes =
				[
					new global::TUnit.Core.TestAttribute()
				],
				Parameters = [],
				Class = global::TUnit.Core.SourceGeneratedClassInformation.GetOrAdd("global::TUnitTest.MyTestClass",
					() => new global::TUnit.Core.SourceGeneratedClassInformation
					{
						Type = typeof(global::TUnitTest.MyTestClass),
						Assembly = global::TUnit.Core.SourceGeneratedAssemblyInformation.GetOrAdd("TUnitTest", () =>
							new global::TUnit.Core.SourceGeneratedAssemblyInformation
							{
								Name = "TUnitTest",
								Attributes =
								[
									new global::System.Runtime.Versioning.TargetFrameworkAttribute(
										".NETCoreApp,Version=v9.0")
									{
										FrameworkDisplayName = ".NET 9.0",
									},
									new global::System.Reflection.AssemblyCompanyAttribute("TUnitTest"),
									new global::System.Reflection.AssemblyConfigurationAttribute("Release"),
									new global::System.Reflection.AssemblyFileVersionAttribute("1.0.0.0"),
									new global::System.Reflection.AssemblyInformationalVersionAttribute("1.0.0"),
									new global::System.Reflection.AssemblyProductAttribute("TUnitTest"),
									new global::System.Reflection.AssemblyTitleAttribute("TUnitTest"),
									new global::System.Reflection.AssemblyVersionAttribute("1.0.0.0"),
									new global::System.Reflection.AssemblyMetadataAttribute(
										"Microsoft.Testing.Platform.Application", "True")
								],
							}),
						Name = "MyTestClass",
						Namespace = "TUnitTest",
						Attributes = [],
						Parameters = [],
						Properties = [],
					}),
			};

			var testBuilderContext = new global::TUnit.Core.TestBuilderContext();
			var testBuilderContextAccessor = new global::TUnit.Core.TestBuilderContextAccessor(testBuilderContext);

			var resettableClassFactoryDelegate = () => new ResettableLazy<global::TUnitTest.MyTestClass>(() =>
					new global::TUnitTest.MyTestClass()
				, sessionId, testBuilderContext);

			var resettableClassFactory = resettableClassFactoryDelegate();

			nodes.Add(new TestMetadata<global::TUnitTest.MyTestClass>
			{
				TestId = $"TUnitTest.MyTestClass.MyTest:0",
				TestClassArguments = [],
				TestMethodArguments = [],
				TestClassProperties = [],
				CurrentRepeatAttempt = 0,
				RepeatLimit = 0,
				ResettableClassFactory = resettableClassFactory,
				TestMethodFactory = (classInstance, cancellationToken) =>
					AsyncConvert.Convert(() => classInstance.MyTest()),
				TestFilePath = @"C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\MyTestClass.cs",
				TestLineNumber = 12,
				TestMethod = testInformation,
				TestBuilderContext = testBuilderContext,
			});
			resettableClassFactory = resettableClassFactoryDelegate();
			testBuilderContext = new();
			testBuilderContextAccessor.Current = testBuilderContext;
		}
		catch (global::System.Exception exception)
		{
			nodes.Add(new global::TUnit.Core.FailedInitializationTest
			{
				TestId = $"TUnitTest.MyTestClass.MyTest:0",
				TestClass = typeof(global::TUnitTest.MyTestClass),
				ReturnType = typeof(global::System.Threading.Tasks.Task),
				ParameterTypeFullNames = [],
				TestName = "MyTest",
				TestFilePath = @"C:\Users\Tom\Downloads\TUnitTest\TUnitTest\TUnitTest\MyTestClass.cs",
				TestLineNumber = 12,
				Exception = exception,
			});
		}

		return nodes;
	}
}

[MichalStrehovsky]

Looks like some of the properties on SourceGeneratedMethodInformation are marked as [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]. My guess is that one of the types assigned to this property (on the line numbers reported by the analysis) are either enums, or have nested types that are enums (.All includes nested types).

This assignment then means that all methods on System.Enum should be considered targets of reflection (because .All also means all methods, including inherited). But that includes Enum.GetValues(Type) and this method is not safe to call in an AOT compiled app (it's marked as RequiredDynamicCode).

It's possible the app doesn't end up reflecting on that method, but the analysis doesn't try to prove things past what the annotation says. So a warning is generated.

[MichalStrehovsky]

Sample why this is a problem (this will throw "System.NotSupportedException: 'MyEnum[]' is missing native code or metadata. This can happen for code that is not compatible with trimming or AOT. Inspect and fix trimming and AOT related warnings that were generated when the app was published. For more information see https://aka.ms/nativeaot-compatibility" when AOT compiled):

using System.Collections;
using System.Diagnostics.CodeAnalysis;

class Program
{
    static void Grab([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] Type t)
    {
        var e = (IEnumerable)t.BaseType!.GetMethod("GetValues", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static, [typeof(Type)])!.Invoke(null, [t]);
        foreach (var a in e)
            Console.WriteLine(a);
    }

    static void Main()
    {
        Grab(typeof(MyEnum));
    }
}

enum MyEnum { }