error[E0658]: #[doc(alias = "...")] is experimental (see issue #50146)
  --> $DIR/feature-gate-doc_alias.rs:11:1
   |
LL | #[doc(alias = "foo")] //~ ERROR: #[doc(alias = "...")] is experimental
   | ^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(doc_alias)] to the crate attributes to enable

error: aborting due to previous error

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