Given the GAsyncResult* parameter result I did:

auto resultData = ObjectG.getDObject!AsyncResultIF(result);
assert(resultData !is null);
writelnUt("@@@@@@  connectionCallback ", resultData.getSourceObject, ", ", resultData.getUserData);

which seems to work fine. :-) However when I call:

auto connection = client.connectFinish(resultData);

I am still getting a SIGSEGV. :-(

It seems that the AsyncResultIF generated from the GAsyncResult* is not a real AsynResultIF.