error[E0658]: use of unstable library feature 'ptr_internals': use `NonNull` instead and consider `PhantomData` (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 1 previous error For more information about this error, try `rustc --explain E0658`.