Yep, replacing @property with auto did the trick.
The lack of error messages in opDispatch is frustrating. I realize that, due to tricks like __traits(compiles, Foo.testing_for_some_function), having opDispatch stop compilation if it fails is not going to work, but there's gotta be some way to expose what's going on with it when it fails. Maybe some kind of pragma to cause opDispatch to report its failures, I don't know.
