I feel like I might be doing something wrong as this part of the code has not been touched for the past 2 years according to GitHub and Windows is probably a well supported platform... But when I tried it on both mongo cxx 3.3.1 and 3.4.0, I'm getting the following when I run MSBuild:

This is what intellisense is saying:

I got the type by looking at the type definition and modified to this and it compiles:

_get_impl().chunks = stdx::optional<cursor>();

Am I doing something wrong? Would this be a valid temporary workaround?