Should the safe query_interface return a Result<Interface, HResult> instead of a Option<Interface>?

[rylev]

We assume that if a call to QueryInterface doesn't return success, that the requested interface is not implemented for the backing class. But it is possible that some implementations may return non-standard errors. Should we provide the ability for the user to inspect the error to ensure that E_NOINTERFACE is returned and if not, do something else with the error?

[russcam]

I think Result<T,E> maps better to QueryInterface semantics than Option<T> does, and as you say, provides ability to make a decision on the error, or call .ok() to get an Option<T> to have current behaviour.