error[E0658]: use of unstable library feature 'ptr_internals': use NonNull instead and consider PhantomData<T> (if you also use #[may_dangle]), Send, and/or Sync
  --> $DIR/issue-49983-see-issue-0.rs:4:30
   |
LL | #[allow(unused_imports)] use core::ptr::Unique;
   |                              ^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(ptr_internals)]` to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.