error[E0412]: cannot find type `__S` in this scope
 --> tests/ui/pin_project/unpin_sneaky.rs:9:16
  |
9 | impl Unpin for __S {} //~ ERROR E0412,E0321
  |                ^^^ not found in this scope

error[E0321]: cross-crate traits with a default impl, like `Unpin`, can only be implemented for a struct/enum type, not `[type error]`
 --> tests/ui/pin_project/unpin_sneaky.rs:9:1
  |
9 | impl Unpin for __S {} //~ ERROR E0412,E0321
  | ^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type