error[E0119]: conflicting implementations of trait `cxx::memory::UniquePtrTarget` for type `here::C`
  --> $DIR/unique_ptr_twice.rs:16:5
   |
7  |     impl UniquePtr<C> {}
   |     ----------------- first implementation here
...
16 |     impl UniquePtr<C> {}
   |     ^^^^^^^^^^^^^^^^^ conflicting implementation for `here::C`