IL2CPP encountered a managed type which it cannot convert ahead-of-time

Hello,

I'm trying to use a library called Sprache to do some parsing in my game. However, when using IL2CPP, it fails at runtime with the following error:

Any usage of Sprache will cause this error, for example the following example snippet:

Code (CSharp):

1. Parser<string> identifier =
2.     from leading in Parse.WhiteSpace.Many()
3.     from first in Parse.Letter.Once().Text()
4.     from rest in Parse.LetterOrDigit.Many().Text()
5.     from trailing in Parse.WhiteSpace.Many()
6.     select first + rest;
7.  
8. var id = identifier.Parse(" abc123  ");

I have tried increasing the maximum depth of il2cpp.exe with the --maximum-recursive-generic-depth argument set all the way to 100, but it doesn't seem to work. This library heavily uses nested generics, so am I out of luck? I know Mono works fine with it, but I don't really want to use it if IL2CPP doesn't work with it considering Unity is moving towards that direction. If it's not possible to get it to work, are there any alternatives I could go to? I would rather not hand-write my own parser.

 

Okay...so I created a new project to reproduce the issue and it works completely fine now. Huh. I'll re-implement the parser I had in my main project and report back when I get the chance. I guess this rules out Sprache being the problem.

 

Alright, so I found the problematic parser in my project:

Code (CSharp):

1. public static readonly Parser<BeaverKeywordParameter> keywordParameter =
2.             from leading in Parse.WhiteSpace.Many().Optional()
3.             from key in Parse.CharExcept(": ").Many().Text()
4.             from delim in Parse.Char(':').Once()
5.             from value in Parse.CharExcept(": ").Many().Text()
6.             from ending in Parse.WhiteSpace.Many().Optional()
7.             select new BeaverKeywordParameter(key, value);

Which gives this error when playing the build:

Code (CSharp):

1. NotSupportedException: IL2CPP encountered a managed type which it cannot convert ahead-of-time. The type uses generic or array types which are nested beyond the maximum depth which can be converted.
2.   at Sprache.Parse.SelectMany[T,U,V] (Sprache.Parser`1[T] parser, System.Func`2[T,TResult] selector, System.Func`3[T1,T2,TResult] projector) [0x00000] in <00000000000000000000000000000000>:0
3.   at Beaver.Core.Dialogue.BeaverSpracheParser..cctor () [0x00000] in <00000000000000000000000000000000>:0

So it seems Sprache works fine unless the parser gets too big and hits the IL2CPP nested generic limit. Before I submit a bug report, is this the correct way to increase the maximum recursive generic depth for IL2CPP? Because I would think increasing the limit would fix it...

Code (CSharp):

1. using UnityEditor;
2. using UnityEditor.Build;
3. using UnityEditor.Build.Reporting;
4.  
5. public class IL2CPPOverride : IPreprocessBuildWithReport
6. {
7.     public int callbackOrder { get; set; } = 1;
8.  
9.     public void OnPreprocessBuild(BuildReport report)
10.     {
11.         PlayerSettings.SetAdditionalIl2CppArgs("--maximum-recursive-generic-depth=50");
12.     }
13. }

 

Hello Josh,

I created a reproducible project and submitted a bug report. The case is 1276405. Thank you!

 

That was quick Josh! Thank you so much for looking into this. You're a MVP.

 

Has this issue been resolved? I think I am running into the same thing still when trying to build a Hololens 2 app (Arm64) after importing the vrm-1.0 module (Releases · vrm-c/UniVRM (github.com)).

I get the following error:

Code (csharp):

1. Error: IL2CPP error for type 'VRMShaders.PathObject' in C:/Users/Admin/Dev/DoreiChan/Assets/VRMShaders/GLTF/IO/Runtime/PathObject.cs:22
2. System.NotSupportedException: The type 'VRMShaders.PathObject' contains a static field which has a type of 'System.Nullable`1<VRMShaders.PathObject>'. IL2CPP does not support conversion of this recursively defined type.
3.    at Unity.IL2CPP.TypeDefinitionWriter.VerifyTypeDoesNotHaveRecursiveStaticNullableFieldDefinitionRecusrive(TypeDefinition typeDefinition, HashSet`1 parentTypes)
4.    at Unity.IL2CPP.TypeDefinitionWriter.WriteTypeDefinitionFor(ReadOnlyContext context, TypeReference type, IReadOnlyContextGeneratedCodeWriter writer, TypeReference[]& typesRequiringInteropGuids)
5.    at Unity.IL2CPP.CppDeclarations.CppDeclarationDataModelInitializers.BuildCacheData(ReadOnlyContext context, TypeReference type)
6.    at Unity.IL2CPP.DataModel.TypeReference.Unity.IL2CPP.DataModel.InjectedInitialize.ITypeReferenceInjectedInitialize.GetCppDeclarationsData[TContext](TContext context, Func`3 initialize)
7.    at Unity.IL2CPP.CppDeclarations.CppDeclarationDataModelInitializers.GetCppDeclarations(ReadOnlyContext context, ITypeReferenceInjectedInitialize type)
8.    at System.Linq.Enumerable.SelectEnumerableIterator`2.ToArray()
9.    at Unity.IL2CPP.CppDeclarations.CppDeclarationsWriter.CollectDeclarations(SourceWritingContext context, ICppDeclarations declarationsIn, CppDeclarations& declarations)
10.    at Unity.IL2CPP.CppDeclarations.CppDeclarationsWriter.Write(SourceWritingContext context, ICodeStream writer, ICppDeclarations declarationsIn, Boolean addInteropGuids)
11.    at Unity.IL2CPP.CodeWriters.ManagedSourceCodeWriter.Dispose()
12.    at Unity.IL2CPP.SourceWriters.SourceWriterBase`2.FlushStream(GlobalWriteContext context, IGeneratedMethodCodeStream stream, NPath filePath)
13.    at Unity.IL2CPP.Contexts.Scheduling.Streams.FileLevelParallelStreamManager`3.WorkerWriteItemsToFile(WorkItemData`2 data)
14.    at Unity.IL2CPP.Contexts.Scheduling.PhaseWorkScheduler`1.WorkerLoop(Object data)
15.