Invalid mock assembly produced

I'm generating mock assemblies and then inspecting them with ILSpy. I noticed that in some cases the generated assembly contains methods that can't be processed with ILSpy. I'm unsure if the problem lies in ILSpy or Refasmer. If I generate reference assemblies instead of the mocks, then I'm not facing the issue. Also, not all methods are impacted by the problem in a mock assembly.

The below commands

refasmer /usr/local/share/dotnet/packs/Microsoft.NETCore.App.Ref/7.0.2/ref/net7.0/System.Runtime.dll -v -c -O=out -p -n -m
ilspycmd -o X out/System.Runtime.dll

produce an exception:

 Processing 1 assemblies
 Processing /usr/local/share/dotnet/packs/Microsoft.NETCore.App.Ref/7.0.2/ref/net7.0/System.Runtime.dll
  [System.Runtime.dll] Using custom entity filter
 All done
Error decompiling @06000001 Microsoft.CodeAnalysis.EmbeddedAttribute..ctor
in assembly "out/System.Runtime.dll"
 ---> System.ArgumentNullException: Value cannot be null. (Parameter 'methodReference')
   at ICSharpCode.Decompiler.TypeSystem.MetadataModule.ResolveMethod(EntityHandle methodReference, GenericContext context) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\TypeSystem\MetadataModule.cs:line 421
   at ICSharpCode.Decompiler.IL.ILReader.DecodeCall(OpCode opCode) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\IL\ILReader.cs:line 1517
   at ICSharpCode.Decompiler.IL.ILReader.DecodeInstruction() in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\IL\ILReader.cs:line 926
   at ICSharpCode.Decompiler.IL.ILReader.ReadInstructions(CancellationToken cancellationToken) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\IL\ILReader.cs:line 443
   at ICSharpCode.Decompiler.IL.ILReader.ReadIL(MethodDefinitionHandle method, MethodBodyBlock body, GenericContext genericContext, ILFunctionKind kind, CancellationToken cancellationToken) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\IL\ILReader.cs:line 580
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileBody(IMethod method, EntityDeclaration entityDecl, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 1542
-- continuing with outer exception (ICSharpCode.Decompiler.DecompilerException) --
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileBody(IMethod method, EntityDeclaration entityDecl, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 1604
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DoDecompile(IMethod method, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 1478
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DoDecompile(ITypeDefinition typeDef, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 1318
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DoDecompileTypes(IEnumerable`1 types, DecompileRun decompileRun, ITypeResolveContext decompilationContext, SyntaxTree syntaxTree) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 574
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileWholeModuleAsSingleFile(Boolean sortTypes) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 610
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileWholeModuleAsSingleFile() in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 584
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileWholeModuleAsString() in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler\CSharp\CSharpDecompiler.cs:line 866
   at ICSharpCode.Decompiler.Console.ILSpyCmdProgram.Decompile(String assemblyFileName, TextWriter output, String typeName) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler.Console\IlspyCmdProgram.cs:line 234
   at ICSharpCode.Decompiler.Console.ILSpyCmdProgram.OnExecute(CommandLineApplication app) in D:\GitWorkspace\ILSpy_72\ICSharpCode.Decompiler.Console\IlspyCmdProgram.cs:line 153

From the below two commands, only the latter one is failing, so not all types are impacted:

ilspycmd out/System.Runtime.dll -t System.Security.Cryptography.CryptographicException
ilspycmd out/System.Runtime.dll -t Microsoft.CodeAnalysis.EmbeddedAttribute

Removing the -m works without any problem:

refasmer /usr/local/share/dotnet/packs/Microsoft.NETCore.App.Ref/7.0.2/ref/net7.0/System.Runtime.dll -v -c -O=out -p -n
ilspycmd -o X out/System.Runtime.dll

I'm running the above on MacOS. The input DLL is the dotnet 7 reference assembly System.Runtime.dll.

Start by reproducing the refasmer command with and without the -m option, then compare the generated out/System.Runtime.dll files. Use ilspycmd on Microsoft.CodeAnalysis.EmbeddedAttribute and System.Security.Cryptography.CryptographicException to isolate the failing method and verify whether the emitted mock assembly is valid. Done means the -m output can be processed without the reported ILSpy exception.