Linker crashes on CustomAttribute with enum declared in generic class

[mrvoorhe]

Mono.Linker.LinkerFatalErrorException: ILLink: error IL1005: Mono.Linker.Tests.Cases.Attributes.GenericEnumInAttribute.Main(): Error processing method 'Mono.Linker.Tests.Cases.Attributes.GenericEnumInAttribute.Method()' in assembly 'test.exe'
 ---> System.NotImplementedException: GenericInst
   at Mono.Cecil.SignatureReader.ReadPrimitiveValue(ElementType type) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3643
   at Mono.Cecil.SignatureReader.ReadCustomAttributeElementValue(TypeReference type) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3611
   at Mono.Cecil.SignatureReader.ReadCustomAttributeElement(TypeReference type) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3591
   at Mono.Cecil.SignatureReader.ReadCustomAttributeElement(TypeReference type) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3591
   at Mono.Cecil.SignatureReader.ReadCustomAttributeFixedArgument(TypeReference type) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3526
   at Mono.Cecil.SignatureReader.ReadCustomAttributeNamedArgument(Collection`1& fields, Collection`1& properties) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3556
   at Mono.Cecil.SignatureReader.ReadCustomAttributeNamedArguments(UInt16 count, Collection`1& fields, Collection`1& properties) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 3534
   at Mono.Cecil.MetadataReader.ReadCustomAttributeSignature(CustomAttribute attribute) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\AssemblyReader.cs:line 2597
   at Mono.Cecil.CustomAttribute.<Resolve>b__35_0(CustomAttribute attribute, MetadataReader reader) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\CustomAttribute.cs:line 204
   at Mono.Cecil.ModuleDefinition.Read[TItem](TItem item, Action`2 read) in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\ModuleDefinition.cs:line 982
   at Mono.Cecil.CustomAttribute.Resolve() in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\CustomAttribute.cs:line 202
   at Mono.Cecil.CustomAttribute.get_HasConstructorArguments() in C:\Unity\dev\unity-monolinker-2\external\cecil\Mono.Cecil\CustomAttribute.cs:line 99
   at Mono.Linker.Steps.MarkStep.MarkCustomAttributeArguments(CustomAttribute ca) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 1284
   at Mono.Linker.Steps.MarkStep.MarkCustomAttribute(CustomAttribute ca, DependencyInfo& reason) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 1079
   at Mono.Linker.Steps.MarkStep.MarkCustomAttributes(ICustomAttributeProvider provider, DependencyInfo& reason) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 793
   at Mono.Linker.Steps.MarkStep.ProcessMethod(MethodDefinition method, DependencyInfo& reason, Scope& scope) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 2975
   at Mono.Linker.Steps.MarkStep.ProcessQueue() in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 513
   --- End of inner exception stack trace ---
   at Mono.Linker.Steps.MarkStep.ProcessQueue() in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 515
   at Mono.Linker.Steps.MarkStep.ProcessPrimaryQueue() in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 434
   at Mono.Linker.Steps.MarkStep.Process() in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 375
   at Mono.Linker.Steps.MarkStep.Process(LinkContext context) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker.Steps\MarkStep.cs:line 213
   at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker\Pipeline.cs:line 166
   at Mono.Linker.Pipeline.Process(LinkContext context) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker\Pipeline.cs:line 159
   at Mono.Linker.Driver.Run(ILogger customLogger, Boolean throwOnFatalLinkerException) in C:\Unity\dev\unity-monolinker-2\src\linker\Linker\Driver.cs:line 771

Here is a test case to reproduce

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using Mono.Linker.Tests.Cases.Expectations.Assertions;

namespace Mono.Linker.Tests.Cases.Attributes
{
	public class GenericEnumInAttribute
	{
		public static void Main ()
		{
			Method();
		}

		[Bar (Value = MyGenericClass<string>.MyEnum.One)]
		[KeptAttributeAttribute (typeof (BarAttribute))]
		static void Method ()
		{
		}

		[Kept]
		[KeptBaseType (typeof(Attribute))]
		class BarAttribute : Attribute
		{
			[Kept]
			public object Value { get;  [Kept] set; }
		}

		[Kept]
		[KeptMember ("value__")]
		[KeptBaseType (typeof (Enum))]
		class MyGenericClass<T>
		{
			[Kept]
			public enum MyEnum
			{
				[Kept]
				One,
			}
		}
	}
}

[mrvoorhe]

I created an issue for cecil as well to track this jbevain/cecil#804

[mrvoorhe]

@marek-safar or @vitek-karas Any chance I can pass this one off to you guys to handle? It's bug that could easily impact any assembly.

[vitek-karas]

I'll see if anybody on our end wants to dive deep into Cecil to fix this 😉

[vitek-karas]

I created jbevain/cecil#827 to fix this.

[vitek-karas]

The issue is fixed in Cecil and brought to linker with #2640.