Mono throws InvalidProgramException on calli+ExplicitThis

[steveharter]

While adding support for calli+ExplicitThis for CoreClr, the new tests for Mono are failing with:

System.InvalidProgramException : Invalid IL code in (wrapper dynamic-method) object:GetGuid (object,intptr): IL_0002: calli     0x00000001

The IL is basically:

ldarg.0 // the "this" pointer
ldarg.1 // function pointer to call obtained from methodInfo.MethodHandle.GetFunctionPointer()
calli explicit instance valuetype [System.Private.CoreLib]System.Guid(class object)

Tests affected:

• System.Reflection.Emit.Tests.DynamicILInfoTests.InstanceBasedFunctionPointer(useExplicitThis: true)
• System.Reflection.Emit.Tests.AssemblySaveAssemblyBuilderTests.AssemblyWithInstanceBasedFunctionPointer(useExplicitThis: true)

[steveisok]

@kg @lateralusX @BrzVlad thoughts on 'should we'? And if so, any guess on the size of work?

[lateralusX]

Don't think there is too much work implementing this but would need to explicitly debug around the actual implementation of MONO_CEE_CALLI with these tests to get a better idea. There might also be some special handling in interpreter that might need special attention.