anchor.diff:              il.Emit(OpCodes.Ldarg_2)
               il.Emit(OpCodes.Stfld, argsField)
               il.Emit(OpCodes.Ldarg_0)
  +            il.Emit(OpCodes.Ldarg_3)
  +            il.Emit(OpCodes.Stfld, returnField)
  +            il.Emit(OpCodes.Ldarg_0)
               il.Emit(OpCodes.Newobj, typeof<Invocations>.GetConstructor([||]))
               il.Emit(OpCodes.Stfld, invocationsField)
               il.Emit(OpCodes.Ldarg_0)
  
positive.code:         /// Mock type
          let mockType = typeBuilder.CreateType()
          // Generate object instance
          let args = [|box (returnValues.ToArray());box (argsLookup.ToArray()); box args|]
          Activator.CreateInstance(mockType, args)
  
  /// Mock mode
  
negative.code:                     BindingFlags.Public ||| BindingFlags.NonPublic 
                  let ci = abstractType.GetConstructor(bindings, Type.DefaultBinder, argTypes, [||])
                  argTypes |> Array.iteri (fun i arg ->
                      il.Emit(OpCodes.Ldarg, 4) 
                      il.Emit(OpCodes.Ldc_I4, i) 
                      il.Emit(OpCodes.Ldelem_Ref)
                      il.Emit(OpCodes.Unbox_Any, arg)
  