MetadataLoadContext: IsValueType: NotSupportedException: Modified types do not support this member

[ericsink]

Description

I just updated some things to net8.0 preview 2 with System.Reflection.MetadataLoadContext preview 2. I'm using S.R.MDLC to load all the reference assemblies and process them.

There are several places now where I am now seeing the following exception:

Unhandled exception: System.NotSupportedException: Modified types do not support this member. Use the UnderlyingSystemType property to call this member.
   at System.Reflection.RoModifiedType.Equals(Type other)
   at System.Reflection.TypeLoading.RoType.ComputeBaseTypeClassification()
   at System.Reflection.TypeLoading.RoType.IsValueTypeImpl()
   at System.Reflection.NullabilityInfoContext.GetNullabilityInfo(MemberInfo memberInfo, Type type, NullableAttributeStateParser parser, Int32& index)
   at System.Reflection.NullabilityInfoContext.Create(ParameterInfo parameterInfo)

The exception is thrown when I try to retrieve nullability info for a parameter, but it can also be triggered by simply using IsValueType.

One place it happens is on the value parameter of System.Runtime.InteropServices.SequenceMarshal.TryRead. There are several others. The repro project will dump out a list of them.

I'm just coming up to speed on the new "modified types" stuff, and I see that they don't support equality, and that's what the exception is saying. What I cannot figure out is why a modified type is in play here. Or how I might detect that situation and use the APIs differently to avoid the problem.

Reproduction Steps

repro.zip

Run this console app with the path of the targeting pack as its first argument. For example:

dotnet run /usr/local/share/dotnet/packs/Microsoft.NETCore.App.Ref/8.0.0-preview.2.23128.3/ref/net8.0

Expected behavior

IsValueType on the parameter type should not throw.

Actual behavior

System.NotSupportedException: Modified types do not support this member.

Regression?

Yes, I think this is a regression of sorts.

The crash does NOT occur with System.Reflection.MetadataLoadContext 8.0.0-preview.1.23110.8

The crash DOES occur with System.Reflection.MetadataLoadContext 8.0.0-preview.2.23128.3

Known Workarounds

No response

Configuration

.NET 8 Preview 2

macOS arm64

I haven't tried this on Windows or Linux yet.

Other information

No response

[ghost]

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Issue Details

---

Description

I just updated some things to net8.0 preview 2 with System.Reflection.MetadataLoadContext preview 2. I'm using S.R.MDLC to load all the reference assemblies and process them.

There are several places now where I am now seeing the following exception:

Unhandled exception: System.NotSupportedException: Modified types do not support this member. Use the UnderlyingSystemType property to call this member.
   at System.Reflection.RoModifiedType.Equals(Type other)
   at System.Reflection.TypeLoading.RoType.ComputeBaseTypeClassification()
   at System.Reflection.TypeLoading.RoType.IsValueTypeImpl()
   at System.Reflection.NullabilityInfoContext.GetNullabilityInfo(MemberInfo memberInfo, Type type, NullableAttributeStateParser parser, Int32& index)
   at System.Reflection.NullabilityInfoContext.Create(ParameterInfo parameterInfo)

The exception is thrown when I try to retrieve nullability info for a parameter, but it can also be triggered by simply using IsValueType.

One place it happens is on the value parameter of System.Runtime.InteropServices.SequenceMarshal.TryRead. There are several others. The repro project will dump out a list of them.

I'm just coming up to speed on the new "modified types" stuff, and I see that they don't support equality, and that's what the exception is saying. What I cannot figure out is why a modified type is in play here. Or how I might detect that situation and use the APIs differently to avoid the problem.

Reproduction Steps

repro.zip

Run this console app with the path of the targeting pack as its first argument. For example:

dotnet run /usr/local/share/dotnet/packs/Microsoft.NETCore.App.Ref/8.0.0-preview.2.23128.3/ref/net8.0

Expected behavior

IsValueType on the parameter type should not throw.

Actual behavior

System.NotSupportedException: Modified types do not support this member.

Regression?

Yes, I think this is a regression of sorts.

The crash does NOT occur with System.Reflection.MetadataLoadContext 8.0.0-preview.1.23110.8

The crash DOES occur with System.Reflection.MetadataLoadContext 8.0.0-preview.2.23128.3

Known Workarounds

No response

Configuration

.NET 8 Preview 2

macOS arm64

I haven't tried this on Windows or Linux yet.

Other information

No response

Author:	ericsink
Assignees:	-
Labels:	area-System.Reflection
Milestone:	-

[steveharter]

@ericsink thanks for the wonderful repro.