As the title says. Option<&mut _> currently gives an unsupported type error.

I have a T* argument that directly matches the semantics of Option<&mut T>, in that it must be a valid pointer or nullptr. Exposing it on the Rust side as Option<&mut T> would allow the Rust side of the shim to be completely safe. Currently I'm just using *mut T and then writing the final shim step manually.