The code-completion is C/C++ only.
It might have worked in the past, because D looks like C/C++ (sometimes), but there is no guarantee that it will work in the future or for every project.
If you want to have CC for D in C::B the only solution is to step up and implement one.
If you use a existing parser it should not be that hard.
You only have to know to program in C++ and wxWidgets (this is not a requirement, because the lib is not that hard).