warning: type alias is never used: `Z`
  --> $DIR/issue-37515.rs:14:1
   |
LL | type Z = for<'x> Send;
   | ^^^^^^^^^^^^^^^^^^^^^^
   |
note: lint level defined here
  --> $DIR/issue-37515.rs:12:9
   |
LL | #![warn(unused)]
   |         ^^^^^^
   = note: #[warn(dead_code)] implied by #[warn(unused)]