Function own_back 

pub unsafe fn own_back<T: 'static>(pointer: *mut T) -> Result<T, PointerError>

Opposite of raw<T>(), to use Rust’s ownership as usually.

drop(unsafe { opaque_pointer::own_back(pointer) });

Errors

The pointer must be not null as it is an obvious invalid pointer.

Also, the type must be the same as the original.

Safety

Invalid pointer or call it twice could cause an undefined behavior or heap error and a crash.