Bug 3732 – Not all COM interfaces inherit from IUnknown.

Well this is rude. It turns out some COM interfaces - I specifically know of ID3D10Include (http://msdn.microsoft.com/en-us/library/ee419311%28VS.85%29.aspx) - do not inherit from IUnknown. Since inheritance from IUnknown is how DMD applies its magic, it means that such interfaces cannot be implemented directly from D. It would seem preferable to have a "pragma (COM)" or "pragma (com)" attribute to apply to an interface to cause it and its descendants to be understood to be COM participants than to inherit from IUnknown, which seems an outdated commonality, unfortunately. The justification from Microsoft's side seems to be that ID3D10Include objects should be lightweight, so removing IUnknown allows them to be stack objects since it's impossible for anyone to retain a living reference to them after returning.

Does the interface not have aquire, release, and queryinterface methods?

Nope. I've since found that this is also common to most of the interfaces used in the reflection API for DirectX 10 and 11, which you're not supposed to implement. I think the intent is the same, just the opposite direction - they're trying to serve objects whose lifetimes are completely dependent on the root object.

The correct solution would be to use extern(C++) interfaces. The bug is really in microsoft calling something a com class which isn't.