error[E0277]: `*const cxx::void` cannot be sent between threads safely
  --> $DIR/vector_autotraits.rs:20:5
   |
20 |     assert_send::<CxxVector<ffi::NotThreadSafe>>();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*const cxx::void` cannot be sent between threads safely
   |
   = help: within `CxxVector<NotThreadSafe>`, the trait `Send` is not implemented for `*const cxx::void`
   = note: required because it appears within the type `[*const cxx::void; 0]`
   = note: required because it appears within the type `cxx::private::Opaque`
note: required because it appears within the type `NotThreadSafe`
  --> $DIR/vector_autotraits.rs:7:14
   |
7  |         type NotThreadSafe;
   |              ^^^^^^^^^^^^^
   = note: required because it appears within the type `[NotThreadSafe]`
   = note: required because it appears within the type `PhantomData<[NotThreadSafe]>`
   = note: required because it appears within the type `CxxVector<NotThreadSafe>`
note: required by a bound in `assert_send`
  --> $DIR/vector_autotraits.rs:16:19
   |
16 | fn assert_send<T: Send>() {}
   |                   ^^^^ required by this bound in `assert_send`