error: expected item, found keyword `where`
  --> $DIR/issue-17904-2.rs:1:24
   |
LL | struct Bar<T> { x: T } where T: Copy
   |                        ^^^^^ expected item
   |
   = note: for a full list of items that can appear in modules, see <https://doc.rust-lang.org/reference/items.html>

error: aborting due to 1 previous error